National Cat & Dog Gut Health Awareness Day – September 21, 2026

History of National Cat & Dog Gut Health Awareness Day

Dutch businessman and self-taught scientist Antonie van Leeuwenhoek discovered bacteria in the late 17th century, using powerful, single-lens microscopes he made himself. Leeuwenhoek considered these “animalcules,” as he termed them, to be the most marvelous of all of his discoveries. Leeuwenhoek’s work opened the door for studies on the relationships between bacteria and human health and disease.

In 1842, Edinburgh surgeon John Goodsir made one of the first descriptions of gastrointestinal bacteria, discovering a bacterium he named Sarcina ventriculi from the stomach and implicating it as a cause of vomiting. Also around this time, French chemist and microbiologist Louis Pasteur postulated that microorganisms known as pathogens or “germs” can lead to disease. A few decades later, German physician and microbiologist Robert Koch extended these earlier studies with the development of a set of scientific rules termed “Koch’s postulates.” Based on the isolation and culture of bacteria from people or animals with the disease, and subsequent inoculation of healthy individuals with the isolated organism to reproduce the disorder, Koch’s postulates provided unequivocal links between specific pathogens and disease.

The relationship between gut bacteria and health and disease was further advanced by the German pediatrician, Theodor Escherich in the late 1880s.  Escherich theorized that microorganisms living in the intestine, including Escherichia coli (E. coli), which he discovered,  were crucial to comprehending the physiological and pathophysiological processes of the gut. 

Almost a century later (in the 1970s), Carl Woese and George Fox revealed the deep evolutionary history shared by all living organisms using molecular sequencing techniques. This led to a new understanding of animal biology, reflecting the strong interdependencies between complex multicellular organisms, their associated commensal or “friendly” microorganisms, and the impact of these relationships on animal physiology.

To further our understanding of these interdependent relationships, the National Institutes of Health (NIH) Human Microbiome Project (HMP), initiated in 2007, examined microbial communities from 300 healthy human individuals across several different body sites. The complexity of microbial communities at each body site was examined using molecular sequencing techniques, facilitating investigations on the existence of a core healthy microbiota (also referred to as the microbiome) across individuals. Perturbations disrupting the balance of a healthy gut microbiome are considered to be indicative of dysbiosis. In studies of human health, many diseases have been reported to be associated with dysbiosis of the gut microbiome, including inflammatory bowel disease, diabetes (types 1 and 2), multiple sclerosis, autism, allergies, asthma, and cancer. 

Ongoing research has also shown that the gut microbiome plays a significant role in our pets’ overall health and well-being. Testing pet microbiomes began in 2015. A report showed that 58% of pets experience at least one symptom, every month, that could be related to an imbalance in their gut microbiome. So it’s more important than ever for pet parents to understand how the bacteria in the gut influence an animal’s digestion, immune functions, skin health, longevity, and other aspects of their well-being.

By learning how to support and improve your cat’s or dog’s gut microbiome, you can help your pet stay healthy and happy for a long time.