How Dogs Help with Diagnosis and Treatment of Human Diseases

Black Poodle Laying on the Grass Looking into the Camera

Of all the ways dogs are humankind’s best friends, none may be more important than the contribution canines make to the research, diagnosis, and treatment of serious human diseases.

We don’t just share our lives with our canine companions; we also share vulnerabilities to many common and often serious pathologies. Like us, dogs suffer from:

• Mammary tumors.

• Cardiac conditions.

• Deafness.

• Epilepsy.

• Muscular dystrophy and other health challenges.

Many of these disorders are inherited through genetic combinations, while others have an environmental component. While we do not share genes with dogs, we do share our environments, and studying how genetic and environmental risk factors interact to produce disease in dogs can be enlightening in human illness.

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Why Do Dogs Experience So Many Health Conditions?

Many of the canine groupings we recognize as breeds were engineered to have specific desired sizes, physical features and abilities. Along with these positive traits, however, the closed gene pools resulting from aggressive breeding can lead to pathologic vulnerabilities. Any inbreeding permits recessive gene combinations to emerge, which can lead to negative effects. By one estimate, almost half of inherited diseases in dogs are breed-specific.

Why Study Dog Diseases?

• Compared with many lab animals, dogs are closer to human size, which makes them biologically more similar to us than rats and mice.

• For many conditions, clinical disease progression is similar in dogs and humans.

• Also, as noted, we share our environments, so studying disease causation in dogs can be instructive for scientists analyzing conditions with environmental causes.

• Moreover, dogs metabolize and respond to drugs in comparable ways to how humans react.

• Also, dogs don’t drink alcohol or smoke (except passively) and most have a largely non-varying diet. These factors can confound diagnosis in humans but make assessments simpler in canines.

The Value of Pedigree Mapping

Dog registries detail an animal’s ownership, pedigree and medical history. Even before gene mapping, this information helped to identify disease-affected and disease-carrying individuals in a dog’s family. These data gave geneticists a head start in predicting modes of inheritance. With dogs, it’s also possible to collect DNA samples from three generations and correlate genetic effects, a task much more difficult in human families.

Sequencing the Canine Genome

In 2001, a proprietary genome sequence of Shadow, a Standard Poodle, was generated by Celera Genomics. In 2003, the Broad Institute and Agencourt Biosciences Corp. sequenced the genome of a Boxer named Tasha. In parallel, analysis of the genomes of nine other breeds were generated to compare with the Boxer genomic sequence. Among the huge number of canine genes sequenced, scientists identified orthologs for about 75 percent of human genes. (Orthologs are genes evolved from a common ancestral gene across multiple species. Orthologs generally retain the same function during the course of evolution.) 

Two Poodles Cuddling

Treatments Emerging

What has the science of canine-human disease study produced? Below are a few examples.

• Many degenerative retinal conditions are being eliminated from dog breeds that have historically had a vulnerability to these conditions. Gene therapy trials in dogs may produce results that can apply to similar human optic pathologies.

• Like humans, dogs get cancer. Studying breed-specific predispositions to certain tumor types can help identify gene-related carcinogenic pathways in humans and possibly lead to vaccines or other treatments.

• Joint canine-human research has led to the identification of a gene associated with a form of canine epilepsy similar to Lafora disease, the most severe teenage-onset form of human epilepsy. Research leading to better response to Lafora would be a major breakthrough in treating a devastating malady.

These are just a few instances of how joint canine-human research can improve the quality of life for both species. Cooperative science is one more way our dogs remain indispensable partners, further deepening and enriching our eons-old connection.

All Images Courtesy of MobilityDog.org.