Dog Health

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The dog (Canis lupus familiaris), the first domesticated species, diverged from its main ancestor, the gray wolf [Canis lupus], as early as 32,000 years ago to become the most physically diverse species on earth.^1-3 Domestication has had a profound impact on the biology of “man’s best friend,” shaping its genetics, physiology, and behavior to adapt it to coexistence with humans.⁴

The current theory of dog domestication is that it occurred in two phases, beginning with familiarity between humans and wolves that allowed them to coexist in the same geographic environment. This was followed by domestication, which allowed the formation of individual human-animal bonds and human selection for desirable traits.⁵ As humans migrated, early dogs may have followed, and by 11,000 years ago, at least five genetically diverse ancient dog “breeds” could be found in the human-settled regions of Northern Europe, Central and Southeast Asia, and the Americas. DNA evidence from canid remains during these time periods suggests that genes continued to be transferred between these early dogs and wolves.¹ It is from these ancient breeds that modern dog breeds descended.

Although dogs still retain significant anatomical and physiological characteristics from their wolf relatives, selective breeding by humans has introduced significant changes, including variability in body size, conformation, gait, and lifespan; adaptation to starch-rich diets⁶; and tractable, individual, heritable behaviors. Many of these changes have been introduced relatively recently in canine evolution, such as by the establishment of dog clubs and breed standards during the late 1800’s which formed the basis for many modern Western breeds.⁷

Dog Lifespan

Over 400 dog breeds are recognized throughout the world, varying in appearance, behavior, genetic predisposition to disease, and lifespan. Although there are many factors affecting canine life expectancy (see section titled “Longevity Research in Dogs”), it is strongly influenced by breed size.⁸ Smaller breeds have average lifespans that exceed those of larger breeds, which, curiously, is the opposite of what is seen in other mammals.⁹ Median life expectancies for breeds of different sizes have been determined in several studies. The largest studies, which include millions of individual dogs,^10,11 have observed the following estimates:

Understanding Essential Nutrients for Dogs

Modern domesticated dogs are generally omnivorous, readily consuming animal products (including live prey), fruits, vegetables, and other plant materials depending on food availability.¹⁸ Modern dogs have developed the ability to digest starches more efficiently than their ancestors,¹⁹ likely as an adaptation to living in proximity to humans.

Nutritional requirements for dogs and several other domestic species have been established by the National Research Council (NRC) in the United States, and the European Pet Food Industry (Fédération Européenne de l'industrie des Aliments pour Animaux Familiers [FEDIAF]) in Europe.^20,21 These organizations update their recommendations periodically based on ongoing canine nutritional research. This is similar to the evolving Reference Daily Intakes (RDIs) and percent Daily Values (% DV) established by the Food and Drug Administration through human nutrition research. Due to the variability in the size of dogs, nutritional recommendations by these organizations are expressed in terms of body weight, intake per 1,000 kilocalories, and amount per kilogram of food (excluding water content). There are separate recommendations for adult dogs, growing puppies, and dogs during pregnancy/lactation.

Essential nutrients in the canine diet include:

• Macronutrients: amino acids (total protein) and essential fatty acids (fat)
• Amino acids: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine
• Essential fatty acids: omega 6 (linoleic acid) and omega-3 (alpha linolenic acid [ALA], eicosapentaenoic acid [EPA], and docosahexaenoic acid [DHA]) fats
• Macrominerals: calcium, phosphorous, sodium, potassium, chloride, and magnesium
• Trace elements: iodine, iron, manganese, selenium, zinc, and copper
• Vitamins: Vitamins A, D, E, and K; B vitamins; and choline

To facilitate evaluation and selection of appropriate commercial diets by consumers, FEDIAF (in Europe) and the American Association of Feed Control Officials (AAFCO, in the United States) have developed nutrition labeling standards. AAFCO is an independent organization that evaluates commercial diet formulas for adherence to current nutritional guidelines and makes recommendations to pet food safety regulators; however, they do not regulate, test, approve, or certify pet foods. AAFCO statements of nutritional adequacy or purpose can be found on commercial pet food labels and identify the dog’s life stage and/or lifestyle for which the food is nutritionally complete. The four current AAFCO statements include²²:

• This diet is formulated to meet the nutritional levels established by the AAFCO Dog Food Nutrient Profiles for [gestation/lactation/growth/maintenance/all life stages].
  • It may also contain statements about nutritional adequacy for large breed dogs (>70 lbs. as adults), as these breeds require lower calcium levels in their diets.
• Animal feeding tests using AAFCO procedures substantiate that this diet provides complete and balanced nutrition for [gestation/lactation/growth/maintenance/all life stages].
• This diet provides complete and balanced nutrition for [gestation/lactation/growth/maintenance/all life stages] and is comparable in nutritional adequacy to a product that has been substantiated using AAFCO feeding tests.
• This product is intended for intermittent or supplemental feeding only.
  • These diets or other pet food products may not meet AAFCO Dog Food Nutrient Profile requirements, but in some instances, can be recommended to help treat specific disease processes.

These statements are intended to help consumers choose a diet with a nutrient profile that has been recommended for their dog based on its life stage (puppy, adult, pregnancy/lactation) and body conformation (large vs. medium/small breed). It also indicates whether the food is determined to be nutritionally complete by feeding trials or diet composition.

Types of Dog Diets

There are several options for feeding dogs, including traditional commercial diets (dry and canned), commercial fresh/refrigerated products, and non-traditional diet options (commercial and homemade raw, vegan/vegetarian, and cooked homemade diets). The merits of different diet types have been a source of debate, with the popularity of non-traditional diets increasing among consumers due to ethical, nutritional, and numerous other concerns. Raw diets have been touted by some as having health benefits, such as higher digestibility, more diverse gastrointestinal microbiomes, and better owner-perceived health; however, these claims have not been substantiated in modern research. Moreover, raw diets have been associated with an increased risk of harmful bacterial infections (eg, Escherichia coli [E. coli], Salmonella spp., Campylobacter spp., Listeria spp., etc.) for both humans and animals in raw-fed households.^23-25 Another non-traditional diet variety in canine nutrition is the vegan/vegetarian diet. Vegan/vegetarian diets have the potential for being deficient in several key essential nutrients unless properly formulated. Studies of nutritionally complete vegan diets (ie, those meeting NRC/AAFCO/FEDIAF nutrient requirements for dogs) suggest that properly formulated vegan diets appear to be safe for dogs and may offer some health benefits over traditional commercial diets.^24,26 While more research is needed into the merits of non-traditional commercial diets, the choice to feed them should be based on established nutritional recommendations to minimize the risk of negative health consequences.²⁷

Homemade diets are increasing in popularity and are a valid diet option when properly formulated to meet the dog’s individual nutrient requirements. This requires designing the diet based on validated recipes or the expertise of a specially trained veterinary professional, and in many cases requires additional vitamin and mineral supplementation to ensure nutritional completeness. Customized diets are available through consultation with a board-certified veterinary nutritionist (DACVIM-Nutrition), and several free recipe calculators are available online (eg, https://balance.it).

Therapeutic Diets

Diet therapy is more common in veterinary medicine than human medicine. It can be used as a sole therapy or in conjunction with other medical interventions. Therapeutic diets are formulated based on current research into the effect of dietary ingredients or nutrient compositions that may affect disease progression.

Canine conditions or diseases in which diet composition may have an effect on disease progression or outcome include kidney disease, foodborne and environmental allergies, neurologic conditions, pancreatitis, bladder stones, dysbiosis/chronic inflammatory intestinal disease, metabolic diseases (eg, diabetes mellitus), liver disease, joint disease, and dental disease.²⁸ Examples of therapeutic diets include those limiting protein sources or using hydrolyzed (significantly broken down) protein sources for dogs with a history of food allergy, or diets with reduced protein and copper content and increased branched-chain amino acids for dogs with liver disease. Commercial therapeutic diets are available for a variety of health conditions through several manufacturers. Most are currently available only by prescription to prevent the misuse of these diets, but non-prescription commercial versions are becoming more widely available.

Feeding Guidelines and Portion Control

Pets need appropriate amounts of calories and nutrients to enjoy optimal health. Calorie and nutrient requirements vary depending on the dog’s age, intact/neutered status, and lifestyle, and overfeeding can result in obesity and related health problems.¹⁶ Canine obesity is an epidemic similar to that seen in humans: approximately 50% of pet dogs have been estimated to be obese based on several epidemiological studies.²⁹ Determining a dog’s optimal daily food intake can be done in several ways, with varying degrees of accuracy:

• Feeding recommendations on dog food labels. These are expressed in terms of volume (eg, cups) per pound of body weight. They are the easiest to understand and provide a good general recommendation for most healthy, non-overweight dogs; however, they may not be precise enough in all cases. They can be overly broad, and do not account for a dog’s body composition if overweight or underweight. Note that caloric content varies between different commercial food products, so it is important to follow the feeding instructions specific to the product.
• Feeding recommendations based on energy requirement. A dog’s estimated ideal caloric intake can be calculated using their body weight, life stage, and activity level. These equations have been validated through nutrition research, and several online calculators exist to facilitate the process.^30,31 For example, The Ohio State University Veterinary Medical Center provides an overview on its website, and the Pet Nutrition Alliance provides an interactive calculator. While this approach is more accurate than using feeding instructions, it is still an estimation.
• Feeding according to body condition score. Body condition scoring (BCS), a method for assessing body composition in several domestic animal species,³² is akin to body mass index (BMI) or central adiposity measurements in humans. This method is commonly used by veterinary professionals and researchers. The most common and accurate BCS scoring system uses a 9-point scale in which a visual and tactile evaluation of fat and muscle coverage on the dog is made over several areas of its body. Based on the observer’s evaluation of these areas of the dog’s body, a score is assigned from 1 (very emaciated) to 9 (obese), with a score of 4–5 being considered ideal body condition. Visual comparison charts are available to facilitate scoring. BCS scoring eliminates the reliance on weight for determining if a dog is overweight or underweight, instead providing an accurate estimate of a dog’s total body fat percentage to determine an ideal body weight when performed correctly. When feeding a dog to maintain ideal BCS, an initial daily caloric intake is determined by using one of the methods above (food labels or calculation) in combination with a dog’s previous diet history, with the amount of food then adjusted to keep the dog at an ideal body condition score.^28,33

Feeding Frequency

There is no consensus as to the number of meals per day all adult dogs should be fed. Once the total daily intake requirement of food is determined for a dog (as described above), it can be provided in one or more meals over the course of the day. For otherwise healthy adult dogs, two meals per day is common. Animals with existing health conditions or predispositions may require different feeding frequencies, and it is not uncommon for veterinarians to recommend three to four meals per day for sick, at-risk, growing, or pregnant/lactating dogs. Smaller, more frequent meals can be helpful for increasing food intake without overfilling the stomach, while also potentially reducing the metabolic burden placed on the body at a given point in time when compared to a single, large meal each day.^134,135,136

While dividing the daily caloric intake between two meals per day is a common practice for healthy adult dogs, recent data observed that once-daily feeding of dogs was associated with a lower incidence of cognitive dysfunction, and lower odds of having gastrointestinal, dental, orthopedic, kidney/urinary, and liver/pancreas disorders. It is unclear whether this observation was due to the effects of time-restricted feeding (ie, intermittent fasting), a lower overall caloric intake with once-daily feeding (ie, caloric restriction), or whether pre-existing health conditions in the dogs may have affected how frequently they were fed.³⁴ Nonetheless, it presents an interesting avenue for further research.

Dog Health

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Several commercial dietary supplements are available for dogs. Supplemental ingredients that have been the subject of clinical research in dogs are discussed in this section.

When considering any supplements for your pet, please be sure to consult with your primary care veterinarian before starting, as supplements can be harmful when consumed inappropriately and may interact with medications, diets, and other therapies your pet is using.

Skin & Coat Health

Omega-3 fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are omega-3 polyunsaturated fatty acids (PUFAs) that can be obtained through diet or via conversion from dietary alpha-linolenic acid (ALA); however, since this conversion is limited in dogs, EPA and DHA need to be supplied through the diet.⁴² EPA and DHA are considered essential nutrients for dogs by the NRC and FEDIAF, two scientific bodies that set nutritional guidelines for domestic animals.^20,21 Human studies have implicated numerous health benefits for EPA and DHA in inflammatory diseases. In dogs, studies of EPA and DHA supplementation on inflammatory skin conditions have reliably shown benefits. A meta-analysis that included nine studies of EPA/DHA in dogs with various skin diseases found consistent reductions in itchiness, inflammation, and secondary skin problems (redness, hair loss, rash) after at least two months of treatment with EPA (daily doses ranging from 16 to 88.5 mg/kg body weight) plus DHA (daily dosages ranging from 10 to 91 mg/kg body weight).⁴²

In addition to its benefits on skin, these omega-3 fatty acids are among the best studied supplements for addressing osteoarthritis in dogs, with 18 out of 20 clinical trials included in a systematic review showing an overall benefit in mobility and reduction of pain scores after three to six months.^42,43

Vitamin E. Inflammatory skin diseases in dogs have been associated with oxidative stress and reduced levels of the fat-soluble antioxidant vitamin E. In a study of 29 dogs with allergic dermatitis being treated with an antihistamine, those supplemented with 8.1 IU/kg of vitamin E daily (form not specified) showed a lower intensity of itching than dogs given a placebo,⁴⁴ supporting a possible role for this nutrient alongside conventional drug therapies.

Bone & Joint Health

Green-lipped mussel. Marine-derived omega-3 fatty acids are among the most clinically validated nutrients for improving joint health in dogs.⁴³ Green-lipped mussel (Perna canaliculus) is a source of several long-chain omega-3 fatty acids and other nutrients that are potentially beneficial for joint health.⁴⁵ Investigations of green-lipped mussel preparations on subjective measures of pain in dogs with joint conditions have been positive. Adding 450 mg, 750 mg, or 1,000 mg (depending on body weight) of green-lipped mussel powder per day to dog food or treats for six weeks has been reported to improve subjective pain, joint swelling, and overall arthritis scores in dogs with osteoarthritis.^46,47 In one study, 2–3 grams (depending on body weight) of green-lipped mussel for 10 days, followed by 1–1.5 grams daily for 46 days, reduced the amount of carprofen required to maintain comfort and mobility in dogs with osteoarthritis.⁴⁸ Another study found 23 osteoarthritic dogs had increased mobility after 60 days of eating a dry dog food enriched with green-lipped mussel, as well as fish oil, glucosamine, chondroitin, and other joint-supportive nutrients.⁴⁹

Palmitoylethanolamide. Palmitoylethanolamide (PEA) is a member of a family of endocannabinoid-like fatty acids that are produced by cells to control inflammation and limit tissue damage. Decreased levels of PEA may contribute to the progression of inflammatory diseases. Laboratory research and clinical studies in dogs have investigated the potential role of supplemental PEA and other similar compounds in treating inflammatory skin, skeletal, gastrointestinal, and dental diseases.⁵⁰ It has also been proposed for reducing neuroinflammation in canine cognitive decline.⁵¹ Studies of dogs with osteoarthritis have shown that treatment with PEA plus quercetin, at a daily dose of 24 mg/kg body weight for four weeks, or a PEA derivative called palmitoyl-glucosamine plus curcumin for 1–2 months led to improvements in dog mobility and function and reductions in pain and lameness.^50,52

Curcumin. Curcumin is the major component of turmeric, the yellow spice derived from the rhizomes of the plant Curcuma longa. It has been investigated in several human studies for its effect on multiple inflammatory diseases. While curcumin supplementation in dogs appears to significantly reduce the expression of genes associated with inflammation,⁵³ its overall effect on pain and mobility in dogs with osteoarthritis has produced variable results, exhibiting improvements in subjective pain assessments in some cases of dogs with osteoarthritis, but not exhibiting reliable objective improvements in mobility.^52,54-56

A three-month study of a supplement containing a mixture of curcuminoids (at 0.43 mg per 1,000 kilocalories in the diet) plus hydrolyzed collagen and green tea extract in 42 adult dogs with osteoarthritis found the supplement did not improve lameness or owners’ subjective assessment of mobility, but significantly reduced veterinarians’ subjective assessment of pain upon movement of affected limbs.⁵⁴ Similar findings were reported for a mixture of curcuminoids from Indian (Curcuma domestica) and Javanese (Curcuma xanthorrhiza) turmeric (P54FP).⁵⁷ When combined with the non-steroidal anti-inflammatory drug (NSAID) meloxicam (Vivlodex), a micronized curcumin/palmitoyl-glucosamine complex that provided 266–798 mg palmitoyl-glucosamine plus 133–399 mg curcumin per day, depending on body weight, allowed for the reduction of meloxicam dose (by up to 25%) while maintaining the same degree of pain mitigation based on veterinarian evaluations.⁵⁶

Collagen. Supplemental collagen, which may provide building blocks for or stimulate the production of joint matrix, has been investigated in several studies for its potential role in the maintenance of canine joint health with mixed results. One review that included nine studies of collagen supplementation in dogs with osteoarthritis found collagen was unable to improve objective measures of joint mobility or subjective measures of pain.⁴³ On the other hand, another review of 26 studies in osteoarthritic dogs found undenatured type II collagen supplementation, at a typical dose of 10 mg per day for one to five months, increased mobility and physical activity, and reduced lameness.⁵⁸

Oral hyaluronic acid. Hyaluronic acid, a component of joint fluid, provides cushioning and lubrication to joints, and has been investigated as an oral chondroprotective (cartilage-protecting) nutrient for dogs. A supplement providing 18 mg hyaluronic acid per 10 kg body weight per day, along with 500 mg glucosamine hydrochloride, 300 mg chondroitin sulfate, 4 mg non-hydrolyzed type II collagen, and 70 mg of an anti-inflammatory herbal combination per 10 kg body weight per day, improved subjective pain measures and clinical status in dogs with osteoarthritis after 60 days of treatment.⁵⁹ In another study of 105 dogs, a chondroprotective combination (Hyaloral) providing 10 mg hyaluronic acid, 1.1 grams hydrolyzed collagen, 156.3 mg glucosamine, 100 mg chondroitin sulfate, and 50 mg gamma oryzanol per 10 kg body weight per day reduced the risk of developing elbow dysplasia (a type of degenerative joint disease) and slowed progression of the disease compared with no supplementation during 20 months of monitoring.⁶⁰ On the other hand, a study in working dogs with osteoarthritis compared hyaluronic acid plus chondroitin sulfate and glucosamine hydrochloride to conventional NSAID therapy (carprofen [Rimadyl]) and found neither treatment significantly reduced pain scores over the six-month study.⁶¹

Glucosamine and chondroitin. Sulfated glucosamine and chondroitin are building blocks of cartilage, and as such have long been investigated as nutritional therapies for joint disorders in both humans and domestic animals. Studies of their effectiveness in mitigating osteoarthritis pain and improving mobility in dogs have been inconclusive. A 2022 meta-analysis of nine clinical trials of glucosamine-chondroitin combinations in animals with osteoarthritis did not observe any effect on improving joint health.⁴³ A 2017 review similarly concluded glucosamine plus chondroitin, at daily doses of 1–2 grams glucosamine hydrochloride and 800–1,600 mg chondroitin sulfate, depending on body weight, for one to five months did not consistently alleviate osteoarthritis symptoms in dogs, although some small trials have found benefits.⁶² One trial that included 40 dogs compared a combination product providing 500 mg glucosamine hydrochloride and 300 mg chondroitin sulfate per 10 kg body weight, along with 70 mg of an anti-inflammatory herbal combination, 4 mg non-hydrolyzed type II collagen, and 18 mg hyaluronic acid per 10 kg of body weight, to placebo daily for 60 days; the supplement improved some measures of chronic pain as assessed by owners and veterinarians.⁵⁹ More research is needed to clarify the potential utility of glucosamine and/or chondroitin in dogs with joint health concerns.

Stress & Behavioral Health

L-theanine. Theanine, an amino acid found in green tea leaves, can compete with the excitatory neurotransmitter glutamate in the brain, exerting an anti-stress effect. A commercial chewable theanine product (Anxitane) has been evaluated in an open-label study in dogs with a history of noise phobias. Dogs were treated with 25 mg, 50 mg, or 100 mg (depending on body weight) of theanine twice daily through five thunderstorms and their stress responses were evaluated by questionnaire. At study end, the dogs showed a decrease in overall storm-related anxiety, as well as reductions in stress-related behaviors.⁶³ Another study in 20 dogs with various noise phobias found 63 days of treatment with the same doses of L-theanine, along with behavioral therapy, led to a larger decrease in phobia symptoms than behavioral therapy alone.⁶⁴ Theanine, in these standard doses, was also found to reduce anxiety-related behaviors around unfamiliar humans in a small controlled study involving 17 dogs that had previously demonstrated fear of human strangers.⁶⁵

Tryptophan. Tryptophan is the precursor for the synthesis of the neurotransmitter serotonin, which acts in the central nervous system to modulate fear and anxiety and decrease stress responses. A small controlled study involving 16 Siberian husky sled dogs under intense exercise stress found those fed a tryptophan-enriched dog food (with a ratio of tryptophan to large neutral amino acids [LNAA] of 0.075:1) for 11 weeks had better stool consistency than those fed standard food (with a ratio of tryptophan to LNAA of 0.047:1).⁶⁶ In 53 sheltered dogs exhibiting high anxiety levels, eating food with nearly four times more tryptophan than standard food for six weeks reduced abnormal social behaviors associated with stress; levels of cortisol (a stress hormone) were also reduced after six weeks, but this effect was not statistically significant.⁶⁷

Melatonin. This hormone from the pineal gland in the brain is responsible for light/dark cycle control in many animals and is most frequently used for adjusting sleep cycles in humans. Melatonin may sometimes be combined with the anti-anxiety drugs gabapentin (Neurontin) plus acepromazine or trazodone as part of a protocol to address severe anxiety in dogs prior to veterinary visits.⁶⁸ In a study in 50 healthy client-owned dogs scheduled for elective surgery, administration of melatonin, at 5 mg/kg body weight two hours prior to anesthesia, produced a calming effect and reduced the amount of anesthesia needed.⁶⁹ One controlled study involving 14 healthy puppies found treatment with melatonin at 10 mg/kg body weight before being transported by road during hot, dry weather conditions reduced levels of markers of physiologic stress.⁷⁰ Studies of its efficacy as a sole treatment for general stress in otherwise healthy dogs is lacking. However, in a single case report of a 7.8 kg terrier mixed breed dog with compulsive disorder, five months of treatment with 5 mg melatonin twice daily along with a combination of cannabinoids and behavioral therapy reduced compulsive behavior and led to easier management by the owner.⁷¹

Medium-chain triglycerides. Medium-chain triglycerides (MCTs), which are made up of intermediate-length fatty acids, are absorbed intact in the intestines and readily converted into ketone bodiesby the liver. Ketone bodies can be used by tissues throughout the body, especially the brain, as an alternative to glucose for generating cellular energy. Glucose metabolism may become impaired in humans and canines because of aging or neurologic diseases, and ketone bodies created from MCTs may help supply the energy needed for healthy brain function in the context of these conditions.⁷² Studies have shown MCT-enriched diets, with 9–10% of daily calories as MCTs for three months, may augment conventional therapies in dogs with epilepsy by improving spatial-working memory, problem-solving ability, and owner-reported trainability⁷³; reducing ADHD-like behavior⁷⁴; and decreasing seizure frequency.⁷⁵

Gut & Digestive Health

Probiotics. The importance of the gut microbiome for health is well documented across several species. Beneficial bacteria have long been studied in dogs and are routinely used in the treatment of gastrointestinal diseases. Several studies have investigated the role of a variety of probiotic strains on gastrointestinal health in dogs.⁷⁶ In particular, evidence suggests probiotics may be helpful in acute (sudden-onset) or infectious gastrointestinal conditions. Probiotics also appear promising as supportive treatments for inflammatory bowel disease in dogs.⁷⁷

Data from studies using various strains of probiotics indicate probiotics can reduce diarrhea and improve stool quality, increase short-chain fatty acid production (a fuel source for intestinal cells), reduce gastrointestinal infections and numbers of disease-causing bacteria, lower blood sugar levels, and improve immune function.⁷⁶ Probiotics may decrease clinical severity of inflammatory bowel disease in dogs as well. In a trial that enrolled 20 pet dogs with idiopathic inflammatory bowel disease, administration of a commercially available probiotic (VSL#3) in amounts providing 112.5–125 billion colony forming units (CFUs) per 10 kg body weight per day for 60 days led to a significant decrease in clinical and histological scores. Favorable changes of some immune system parameters, particularly an increase in regulator T cells, were observed and gut microbiome composition was normalized after probiotic treatment.⁷⁸ In another trial, 20 dogs aged 1–6 months with canine parvovirus (CPV) infection were treated with standard treatment plus VSL#3, providing 450 billion CFUs per day, or standard treatment alone for one to three weeks. Dogs receiving the probiotics were in better clinical condition than those not receiving probiotics three and five days after treatment initiation. Moreover, survival was better in the group receiving the probiotics than the group not receiving them (90% vs. 70%, respectively), although it was not clear whether this difference was statistically significant.⁷⁹ (Note that the formula for VSL#3 changed in 2016 and the original, studied formula is now available in a commercial product called Visbiome).⁸⁰

Animal and human studies have also shown that gut microbiota can be involved in the regulation of chemical signals involved in stress and anxiety (eg, serotonin and cortisol), which implicate a role for probiotics in managing these conditions.⁸¹ A study in anxious dogs showed treatment with the probiotic yeast Saccharomyces boulardii, at 1 billion CFUs per kg of dog food daily for 35 days, decreased levels of cortisol, suggesting stress reduction.⁸² In another study, six weeks of supplementing anxious dogs with Bifidobacterium longum BL999 decreased stress behaviors, lowered salivary cortisol levels, decreased heart rate, and increased heart rate variability.⁸³ With the sequencing of several canine microbiomes (gastrointestinal, oral, nasal, urogenital) completed, other applications for probiotics may be found in the future.

S-adenosylmethionine and milk thistle compounds. S-adenosylmethionine (SAMe), an amino acid derivative important in liver metabolism, and extracts from milk thistle (Silybum marianum), have been investigated (alone and in combination) in dogs for their liver-protecting properties and are currently used as part of treatment for a variety of liver diseases in dogs. In studies in dogs with liver disease, supplementation with 12.75–15 mg silybin (a flavonoid from milk thistle) per 10 kg body weight per day for 28–60 days reduced biomarkers of liver damage and improved liver function tests.^84,85 In a crossover study of healthy dogs taking the steroid prednisolone, SAMe supplementation at 10 mg/kg body weight twice daily for 42 days was found to reduce blood markers of liver oxidative damage, although the dogs still developed signs of steroid-induced liver disease.⁸⁶ A combination of SAMe and silybin (Denamarin) was used in one study as a liver protectant in dogs receiving chemotherapy. Dogs taking the supplement, which provided 225 mg of SAMe and 82 mg of silybin-phosphatidylcholine complex (24 mg of silybin) per day, throughout chemotherapy were less likely to exhibit increased biomarkers of liver damage and were less likely to have their chemotherapy treatments delayed due to increased liver enzyme activity.⁸⁷

General Health – Multi-nutrient Supplements

Multivitamin/multimineral supplements. Multivitamin and multimineral supplements are one of the most common dietary supplements administered to dogs.⁸⁸ As most properly formulated commercial dog foods are fortified to include the recommended levels of vitamins and minerals for healthy dogs at different life stages, supplementation is not necessary for most pets, and in some cases, can be harmful. As seen above, supplemental vitamins, amino acids, and essential fatty acids may have roles in optimizing nutrition for disease states such as skin disease, joint disease, or stress. One recognized role for multivitamin/multimineral supplementation is for dogs fed homemade diets formulated by board-certified veterinary nutritionists, as a complete and balanced diet may not be achievable through such diets.⁸⁹ In these cases, appropriate multivitamin and multimineral supplements, if needed, should be included in the recipe with the guidance of a veterinary nutritionist.

Regular physical exercise is as important for dogs as it is for humans. Studies of physical activity in dogs have associated regular exercise with several positive health outcomes, including maintenance of healthy weight and lean body mass, increased energy expenditure, improved glucose metabolism, and strengthening of the human-animal bond.²⁸ Owners whose dogs engage in regular exercise can also see health benefits, as studies have shown that adults and children with dogs are more likely to be physically active themselves.⁹⁰ Moreover, older dog owners who exercise with their dogs tend to have lower BMIs and make fewer visits to the doctor.⁹¹ Owners who habitually exercise are more likely to have dogs with regular exercise schedules.⁹²

Recommendations for activity in dogs have been proposed by both the United States Department of Agriculture (USDA) and American Animal Hospital Association (AAHA), and range from 30–60 minutes of walking/trotting three times per week (AAHA) to a minimum of 30 minutes of exercise daily (USDA).^28,93 Breed-specific exercise requirements have been proposed, but these recommendations are generally not taken from scientific evidence and are based on opinions from the breed clubs.^94,95

Aside from leash walking, examples of exercise activities include jogging, hiking, interactive play like fetch or agility training, and off-leash activities at dog parks. Safe exercise involves avoiding temperature extremes and choosing appropriate activities based on age and health status. Growing dogs risk bone damage with rough play or extremely vigorous exercise.⁹⁶ Older dogs and dogs with certain health conditions, such as cardiovascular, respiratory, or musculoskeletal disease, may not have the exercise tolerance of younger and healthier dogs. It is important to change exercise routines gradually and tailor exercise to the individual dog.

The Impact of Environmental Enrichment on Dog Health

Mental and sensory stimulation (environmental enrichment) has an important role in canine health; environmental enrichment promotes relaxation, and reduces alertness and stress behaviors, the widely used indicators of canine well-being.^97,98

Benefits of environmental enrichment for dogs include:

• Reduced stress and anxiety
• Decreases in stereotypic behaviors (tail chasing, surface licking, pacing, etc.)
• Increased relaxation
• Improved cognitive abilities
• Reduced vocalization (crying/barking)

Examples of environmental enrichment include: bonding with owners (petting, grooming), food-based activities (food puzzles, food-stuffed toys), interactive toys and play, investigating new areas, and social interactions with other humans and dogs.⁹⁷ Auditory (human conversation, music) and olfactory (dog pheromone, lavender oil) enrichment also have beneficial effects on relaxation.⁹⁹ Studies indicate social activities result in the most positive behavioral effects, while food-based activities have the least effect on behavior, although an effective environmental enrichment plan should utilize multiple different types of activities and stimuli.⁹⁷

Bonding and Socialization with Humans and Other Dogs

Bonding and socialization are both important components of environmental enrichment, and early socialization can reinforce future desirable behavior. The critical socialization period in developing dogs is 3–12 weeks of age, when puppies show increased interest in social interactions with both dogs and humans and a reduced fear and avoidance of new situations and environments.¹⁰⁰ For many puppies, this period begins before they transition to their permanent homes. Benefits of socialization include less reactivity and more playfulness when exposed to new auditory and visual stimuli, less separation and general anxiety, less alertness around strangers, and less aggression toward children or owners.^100,101 Socialization can include puppy classes; organized play sessions; and exploration of new people, dogs, and environments.

There have been concerns that the critical period for puppy socialization occurs prior to the completion of a full vaccination schedule. At least one study provides reassurance that this need not be a major concern. Researchers assessed whether puppies that attended socialization classes and had been vaccinated at least once were at an increased risk of CPV compared with those that did not attend classes. The study encompassed information from 21 clinics across four U.S. cities, including details on demographics, vaccination status, CPV diagnosis, and class attendance for puppies aged 16 weeks or younger. Additionally, information was collected from 24 trainers in these cities about puppies attending their classes. Researchers found that among the 279 puppies that attended socialization classes, none were suspected of or diagnosed with CPV infection. This led to the conclusion that puppies that had started vaccinations and were attending socialization classes were at no greater risk of CPV infection than vaccinated puppies that did not attend these classes. These findings suggest that, with at least one round of vaccination, the benefits of socialization may outweigh the risks of contracting certain infectious diseases like CPV.¹⁰² In line with the findings of this study, authoritative veterinary and dog organizations generally suggest that puppy socialization via puppy classes can (and should) begin once puppies have started their vaccination schedules.^103-105

Managing Stress and Anxiety in Dogs

Fear and anxiety can be common in dogs, and stressful stimuli can have negative impacts on health, welfare, and lifespan.^106,107 Behaviors associated with stress and anxiety include: destructive behavior, fear aggression, inappropriate urination/defecation, vocalization, vomiting, salivation, panting, increased heart rate and stress hormone production, hiding, pacing, cowering/lowered body posture, shaking/trembling, escape attempts/retreating, and seeking out familiar people.^106,108

Separation anxiety and noise phobias are two of the most common causes of stress in dogs. As many as 50% of dogs may have phobias to loud, unfamiliar noises (fireworks, thunderstorms, smoke alarms, household appliances).¹⁰⁶ Separation anxiety, the physical or behavioral signs of stress during the actual or perceived absence of the dog’s owner, is one of the most common behavioral problem in dogs besides aggression.¹⁰⁹ Several studies estimate the prevalence in the overall canine population to be as high as 20%, with possibly increased prevalence in some breeds.^108,110 Studies have shown that separation anxiety is associated with changes in owner routine, addition of people to the household, and traumatic events that have happened when the owner was away. It appears to be increased in mixed breed dogs—although it is unclear if this could be due to mixed breed dogs being overrepresented in shelters—as well as dogs adopted at a young age and dogs that are hyper-attached to their owners.¹⁰⁸

Factors that have been associated with reduced separation anxiety include attending obedience training; adequate exercise; and socialization at a young age (6–9 months) with other people, dogs, and environments.¹⁰⁸ Environmental enrichment, especially auditory and olfactory stimulation, can have positive effects.^99,111

In additional to socialization, behavior modification training, and environmental enrichment, some cases of situational stress and anxieties (noise phobias, fear of travel) and long-term anxiety are also commonly treated with anti-anxiety medications, pheromones, supplements, and therapeutic diets.^81,112-114

Preventive care or preventive medicine is the anticipation of health risks and recommendations for reducing these risks prior to emergence of overt medical problems. Several diseases (eg, heartworm disease; some bacterial, parasitic, and viral diseases; dental disease; nutritional deficiencies) can be avoided with proper preventive care. Additionally, the progression of some debilitating chronic diseases (eg, chronic kidney disease, endocrine diseases including diabetes and hypothyroidism, heart disease, osteoarthritis) can be significantly reduced in dogs with early diagnosis and proper medical care. Central to a preventive medicine plan for dogs are routine veterinary visits, during which lifestyle, behavior, and diet are evaluated, physical examination is performed, and appropriate disease screening tests are completed.

Dog Health

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Vaccination

The intention of vaccination is to train the immune system to respond to a particular disease-causing organism (pathogen), so that when infection occurs, the immune system can fight the pathogen before serious disease arises. While the immune system is very robust, the aspect of immunity that gives rise to specific and long-lasting protection (the adaptive immune system; antibodies) can only effectively fight diseases it has seen before. When a dog becomes infected with a particular bacteria or virus for the first time, its immune system must “learn” to produce antibodies to neutralize the threat; and this training process takes time. In this scenario, a highly virulent disease (like rabies) may be able to cause significant damage or death before the immune system has learned how to effectively fight it.

To reduce the risk of serious disease or death, a vaccine provides an initial first exposure to a weakened pathogen that cannot cause disease, but can still train the adaptive immune response to fight that particular pathogen. The next time that pathogen is encountered, the trained adaptive immune response will be swift and more robust, reducing the risk that infection and serious disease might occur. Appropriate vaccination can reduce the incidence, intensity, and mortality of a disease, and reduces the disease reservoir (ie, the concentration of pathogens in the environment).

The AAHA publishes vaccine recommendations that are updated periodically to reflect the evolving knowledge of disease prevalence and vaccine effectiveness.¹¹⁵ Canine vaccinations are divided into “core vaccines” (rabies, distemper virus, parvovirus, adenovirus, parainfluenza) and “lifestyle vaccines” (Leptospira, Bordetella, influenza, Lyme disease).

Core vaccines are recommended for all dogs (or, in the case of rabies, required by many state/local laws) due to the severity of the diseases they prevent. Lifestyle vaccines also protect against serious diseases, but ones that not all dogs are at risk of contracting. Vaccines against other diseases (Giardia, coronavirus) are commercially available but not recommended, as some have questionable effectiveness or protect against diseases that are considered mild. Owners are encouraged to consult a veterinary professional to determine the appropriate vaccination plan for their pets.

Parasite Prevention (Fleas, Ticks, Heartworms, Intestinal Worms)

There are a variety of parasites that can affect dogs, both internally (intestinal worms, intestinal protozoa, heartworms) and externally (fleas, ticks, lice, mites). The nature and severity of the diseases caused by these parasites varies. Some parasites cause no or mild disease, while other parasitic diseases (eg, certain tickborne diseases and heartworm disease) have the potential to be life-threatening. Additionally, several of these parasites have the potential for transmission to humans. While many of these diseases were once localized to specific geographical regions, recent expansion of the causative agents (ticks, mosquitos, etc.) has resulted in an increased incidence of diseases in areas once considered low-risk.⁹⁶ If you are curious about the risk of these infections in your area, information can be found on the Companion Animal Parasite Council website

Canine parasites of medical interest include:

• Intestinal worms (hookworms, roundworms, whipworms): Hookworms, roundworms, and whipworms spread through feces and can cause gastrointestinal illness, poor growth, and anemia in extreme cases. These types of intestinal worms are of primary concern in puppies, as they can be spread through the placenta in utero or through colostrum. Many monthly preventative therapies are available to reduce the risk of infection with these parasites.
• Tapeworms: The most common tapeworms in dogs are spread through fleas. They generally cause no or mild gastrointestinal disease. The egg sacks from tapeworms can often be visualized in an infected dog’s stool, appearing like small grains of rice. Some monthly preventatives are available that include coverage against tapeworm infections.
• Coccidia and Giardia: Coccidia and Giardia are two single-celled parasites, spread through feces, which can cause illness with diarrhea and vomiting. Coccidia is more common in puppies, while Giardia can infect dogs of any age. Effective treatments are available, but no preventatives are available.
• Heartworm: Heartworm is a worm spread between dogs through mosquito bites. Larvae develop into mature worms that live in the heart and great vessels and can lead to severe respiratory and cardiovascular disease and death. Treatment is lengthy, complex, and comes with potentially serious side effects, including death. Many effective preventatives are available.
• Fleas, ticks, and mites: Fleas, ticks, and mites are external parasites that can cause a variety of skin diseases. Flea bites in susceptible dogs can cause severe allergic reactions and result in large areas of inflamed, itchy skin (flea allergy dermatitis). Fleas can also spread the most common type of canine tapeworm. Mites, while uncommon, can also lead to similar severe skin disease (mange). Several species of ticks can parasitize dogs. While tick bites themselves are usually harmless, ticks can carry and transmit serious bacterial diseases (Anaplasmosis, Ehrlichiosis, Lyme disease, Rocky Mountain Spotted Fever) to dogs and people. Preventative medications for fleas, mites, and ticks are effective against each of these external parasites.

To reduce the risk of serious parasitic disease, several preventative treatments and screening tests have been developed. Current recommendations include year-round protection from internal and external parasites using an appropriate preventative medication, even during winter and for indoor-only pets.^96,116 Individual preventatives are available for intestinal parasites, heartworm, and external parasites (fleas/ticks/mites). There are also newer, broad-spectrum medications that cover all these groups in a single product. An appropriate risk-based plan should be developed with a veterinarian to account for the dog’s age, lifestyle, breed, and existing health conditions, as not all parasite preventative programs will be suitable for all dogs. Parasite screening tests for intestinal parasites and heartworm, as well as screening for tickborne diseases, are available through most clinics and have been recommended as part of a comprehensive parasite prevention strategy to assess risk and confirm efficacy of preventive treatments.

Dental Care for Dogs

Dental diseases are common in dogs, and dental care is a recommended part of any preventive care program.⁹⁶ Common dental diseases include periodontal disease/gingivitis, tooth fracture or loss, oral masses, and retained deciduous (baby) teeth. Dental disease has been associated with decreased overall health and can be a significant source of pain or discomfort in affected animals. Particular attention should be paid to small breeds, brachycephalic (flat-faced) breeds, and dogs with overbite or underbite, in which dental diseases are more common.¹¹⁷ Recommended care plans for dental health include routine oral examination at veterinary visits, dental cleanings , and home care, like brushing or use of home dental treats and treatments.¹¹⁶

Dental cleanings for dogs are typically performed under anesthesia, although non-anesthetic dental procedures are available. Anesthetic dental cleanings have the advantages of allowing for better assessment of the dog’s teeth and more thorough cleaning with less risk of injury, lower stress and pain levels, and the ability to safely perform additional procedures if necessary. Because of these advantages, anesthetic dental cleaning is the current recommended method for teeth cleaning in dogs. Non-anesthetic procedures, while not shown to be safer or as thorough as anesthetized cleaning,¹¹⁷ may be more appropriate in animals for which anesthesia may pose increased risk.

Grooming Needs

A comprehensive grooming plan should include attention to coat, skin, ears, and nails. While there are professional services for most grooming needs, many can be performed by dog owners with minimal equipment. Breed-specific grooming frequency recommendations have been proposed based on opinions from breed clubs.^94,118 Acclimating dogs to grooming at a young age may alleviate some of the stresses associated with these procedures.

Long-coat breeds require more frequent attention to their coats to reduce the risk of matting and accumulation of debris, as well as to assess skin for signs of disease or external parasites.

Bathing with dog-appropriate shampoos need only be performed when necessary; excessive bathing can reduce the natural oils from the skin and promote dry skin and irritation. Puppies under 4 months of age should not be submerged in water when bathing and should be hand-dried promptly, as they have a difficult time regulating their body temperature at this age and risk overexposure from a bath that is too hot or cold.

Brachycephalic breeds (eg, pugs, Boston terriers, English and French bulldogs) and Shar-peis have excessive skin folds, especially on the face, that can trap moisture and predispose these breeds to fungal or bacterial skin infections. These folds should be kept clean and dry using appropriate gentle cleansers, and irritation or discharge in these areas addressed through veterinary care.

In breeds with long pendulous ears (eg, beagles, basset hounds) or heavily haired ears (eg, spaniels, poodles and poodle mixes), special attention should be paid to ear hygiene in order to remove wax or pluck excess hair that can trap moisture and become a favorable environment for the growth of fungi and bacteria that can cause external ear infections.

Dog nails should be inspected and trimmed regularly, and overgrowth or damage addressed to avoid injury or self-trauma.

Some of the more common acute (suddenly arising) health conditions include¹¹⁹:

• Dermatitis: Dermatitis is inflammation or infection of the skin that can result from bacterial infections; fungal infections; or environmental, food, and flea bite allergies.
• Allergy: Food, flea bite, and environmental allergies are common, and can lead to dermatitis, conjunctivitis (inflamed eyes), ear infection, or gastrointestinal problems.
• Dental diseases: Common dental diseases in dogs include gingivitis, periodontal disease, and tooth fracture or loss.
• Ear infections: Ear infections are often a result of allergy, but can also be due to bacterial, fungal, or parasitic infection.
• Diarrhea/vomiting/gastrointestinal upset: These are not diseases themselves, but common symptoms of other health conditions.
• Eye problems: Dogs may develop conjunctivitis (inflamed eyes) due to infection or allergy, and may experience corneal ulceration (scratches in the cornea) due to trauma.
• Traumatic injury: These include lacerations, punctures from animal bites, and fractured bones or nails.
• Intestinal parasites: These include roundworms and tapeworms.

Some of the more common chronic (developing over a long time) health conditions include¹¹⁹:

• Obesity
• Endocrine diseases: Canine diabetes (similar to Type I diabetes in humans), hypothyroidism, and diseases of the adrenal glands
• Heart disease: Heartworm disease and diseases of the heart valves, which can lead to heart failure if untreated
• Skeletal diseases: Osteoarthritis and patellar luxation (displacement of the kneecap, which is common in smaller breeds)
• Kidney disease: Age-related decreases in kidney function
• Cancer
• Eye conditions: Nuclear sclerosis (a very common, age-related diffuse clouding of the lens of the eye) and cataracts (opaque deposits in the lens)
• Periodontal disease: Inflammation and degeneration of the gums, which may lead to tooth loss

Do dogs eat grass when they are sick?

Eating grass is likely not related to sickness. Its biological role in dogs remains a mystery, but it appears to be a behavior passed down from their ancestors. One of the few scientific assessments of grass eating investigated this behavior in over 1,500 dogs.¹²⁰ It determined that grass eating is likely a common, normal behavior in healthy dogs, as nearly 80% of dogs eat grass. Grass eating is common in dogs eating nutritionally complete diets and is not associated with vomiting.

There have been many other theories as to why dogs eat grass and other plants: nutrient deficiencies or lack of fiber; pica (a compulsive ingestion of non-food items); boredom; anxiety; or they enjoy the taste. Grass has been found in wolf droppings in the wild; in some cases these were observed in conjunction with parasites and has led to speculation that grass eating in wild canids serves as a way for these species to self-treat for intestinal parasitism.¹²⁰

Does a warm, dry nose signal a fever?

On its own, not necessarily. While a warm, dry nose can be a non-specific sign of fever, it can result from several common (warm weather, dry skin, dehydration, sunburn) and uncommon (hyperkeratosis, dysfunction of tear production, autoimmune disease) conditions.¹²¹ By itself, the temperature and moisture of a dog’s nose does not provide much insight into a dog’s overall health. The most reliable way to assess a dog’s temperature is with a thermometer, which is part of a routine veterinary visit. The normal temperature range for dogs is 99°F–102.5°F.

Are all dogs colorblind?

The dog’s eye anatomy suggests they have a more limited ability to detect colors compared with humans, but what range of color they can detect is still debated.¹²² They have fewer cone (color-sensing) cells than humans, and the light receptors in these cells differ from humans. Dogs contain two types of light receptors that detect blue and yellow light, while humans detect red, green, and blue. This suggests that dogs see the world as shades of blue and yellow (also known as “dichromatic vision,” similar to red-green color blindness in humans). Attempts to directly test the dog’s color vision have had mixed results; some studies determined dogs could not distinguish between shades of red, yellow, and green, while others have shown the opposite result.

Additional differences in vision between dogs and humans include¹²²:

• Dogs have less visual acuity than humans.
• A dog’s depth perception is variable and depends on their facial conformation.
• Dogs have better low-light vision than humans. There are more light-gathering rod cells in the retina, and a reflective surface (tapetum lucidum) in the retina to enhance vision in low light. The tapetum produces the “green eye” in dogs when a light is directed into their eyes.

Is it ok to give your dog table scraps?

Although feeding table scraps or human food to dogs is common practice, it has been linked to some negative health consequences.^123,124 Feeding table scraps has been associated with canine obesity,¹²⁴ a greater than 3-fold increased risk of canine diabetes,¹²⁵ and a 2–6-fold increased risk of pancreatitis (inflammation and self-destruction of the pancreas that can range in severity from mild to fatal).¹²⁶ Exposure to different dietary ingredients also increases the risk of allergic reactions and gastrointestinal upset.

Select human foods can be used to supplement diets as treats, as long as the dog’s overall diet is taken into account to ensure that caloric intake is appropriate. A dog-safe food list is available on the Tufts Veterinary School website. As a general rule of thumb, treats should make up no more than 10% of a dog’s total caloric intake to help reduce the risk of nutrient deficiencies and excesses. Human foods can also be used in the context of complete and balanced homemade diets, provided that the diet is properly formulated to contain an appropriate nutrient profile. Customized diets are available through consultation with board-certified veterinary nutritionists.

Are dog illnesses contagious to humans?

Some dog illnesses can be transmitted to humans. Examples of infectious diseases that can be spread from dogs to humans (zoonotic diseases) include¹²⁷:

• Viral diseases: Rabies, noroviruses, monkeypox
• Bacterial diseases: Salmonella and Campylobacter (gastrointestinal infections), Pasteurella and Bordetella (respiratory infections), Leptospira, methicillin-resistant Staphylococcus aureus (MRSA)
• Fungal diseases: Ringworm
• Parasites: Giardia and cryptosporidium (gastrointestinal infections), intestinal roundworms and tapeworms, mange, and ticks that can transmit diseases like Lyme disease to humans

The Centers for Disease Control and Prevention maintains a list of common zoonotic diseases and recommendations for minimizing their spread. Routine deworming treatments, parasite preventatives (see section on Preventive Care), and prompt veterinary care for sick dogs can reduce the probability of spread of these diseases.

What should healthy dog poop look like?

Normal dog stool should be firm/formed, hydrated, and brown in color. The amount produced can vary based on diet (dry, wet, or fresh). Small amounts of other ingested matter like hair and small amounts of undigested fibrous plant matter can be normal. Abnormalities include:

• Loose stool or diarrhea
• Very dry/hard stool
• Bright red blood in the feces; or black, tarry stools (digested blood)
• Tan, greasy, oily stools
• Worms or tapeworm segments (appear like small grains of rice)
• Large amounts of undigested food or non-food items (fabric, fragments of toys, etc.)

Any of these findings should be investigated by a veterinarian.

How can I tell if my dog has a fever?

The most reliable way to determine if a dog has a fever is to have its temperature taken with a thermometer. A normal temperature range for dogs is 99°F–102.5°F.

There are several clinical signs that have been associated with fever:

• Red eyes
• Lethargy, lack of energy, depression
• Warm ears
• Warm, dry nose
• Shivering
• Loss of appetite
• Nasal discharge
• Coughing
• Vomiting

However, the above-mentioned signs are non-specific signs of possible illness, and are not always associated with a fever. It is important to remember that over-the-counter fever reducers for humans (Tylenol, Ibuprofen) can be toxic to dogs and should not be used without consultation with a veterinarian.^35,36

A final note: An elevated temperature in dogs can be a result of fever (associated with infection or inflammation) or can be due to hyperthermia (an elevated temperature due to activity, anxiety, excitement, or overexposure to a hot environment).¹²⁸

How long do dog illnesses last?

Diseases in dogs have a variable duration that depends primarily on the disease itself. These can range from acute infectious diseases with short durations of days to weeks (depending on severity and location of the infection) to chronic diseases (eg, kidney or heart disease) that cannot be cured but can be managed and last the duration of the pet’s lifetime.

Aside from the nature of the disease, other factors that influence the duration of an illness include:

• The age of the animal (very young and older animals may have weaker immune systems and slower rates of healing)
• Existing health conditions that may delay healing or suppress immunity
• The type of treatment used
• Animal and owner compliance with medical recommendations

What are the healthiest dog breeds?

This is a difficult question to answer. While there is evidence gathered from millions of dogs that breed size influences lifespan,^10,11 rigorous, large-scale comparisons between the health of individual breeds are lacking.

Some general observations of the effects of breed on health include:

• Breeds with certain anatomical features can be associated with a higher risk of certain diseases. Examples include:
  • Brachycephalic breeds (short-faced breeds including pugs, Boston terriers, English and French bulldogs) have a higher degree of eye and upper airway concerns due to their compressed upper airways.¹²⁹
  • Chondrodysplastic breeds (short-legged breeds including basset hounds, corgis, and dachshunds) have higher risks of intervertebral disc diseases due to their proportionally longer backs.¹³⁰
  • Small/toy breeds have an increased risk of dental disease and patellar luxation (displacement of the kneecaps).¹³¹
  • Giant breeds have a larger risk of developmental joint diseases due to their rapid growth as puppies.¹³²

Even within a breed that may be considered “healthy,” inbreeding (mating of closely related animals) is associated with an increased risk of the development of genetic diseases. Hundreds of genetic disorders have been identified in dogs, many of which are more common in certain breeds.¹³⁰ Inbreeding increases the risk of these genetic disorders being passed down to offspring. Inbreeding can result from the repeated breeding of specific animals to preserve certain desirable characteristics of a particular breed. By the same reasoning, mixed-breed dogs may have a lower chance of retaining and propagating certain traits associated with disease. This has been termed hybrid vigor.¹³³

For any breed, maximizing the chances of selecting a healthy dog includes:

• Choose a dog from a breeder that tracks the overall health of all their dogs and uses this health data to select individuals for their breeding programs with the lowest probability of passing down undesirable genetic traits to their offspring.
• Genetic testing in recent years has become accessible to most dog owners and is routinely used by reputable breeders to ensure the health of their bloodlines. Genetic tests (eg, Wisdom Panel, Embark) test for hundreds of genetic disorders, are inexpensive, and can be performed by owners at home using a swab of cheek cells.
• Appropriate diet, preventive medicine, and timely treatment of medical concerns benefits individual dogs regardless of breed.