PhD Defence: Coronavirus and influenza A virus infections in dogs and cats

Summary of dissertation

The Netherlands is a vulnerable country for the introduction and spread of zoonotic pathogens due to a high human and livestock population density, a diverse wildlife population, and a water- rich landscape that attracts migratory birds and vectors. In this setting, 1.8 million dogs and 3.2 million cats live close to humans and may also interact with wildlife. This raises concerns for a potential role of dogs and cats as a source of pathogens to humans, such as respiratory coronaviruses (CoVs) and influenza A viruses (IAVs), which can easily adapt to new hosts and may spread through the air.

This thesis investigated the role of dogs and cats as potential hosts, sources, or reservoirs of CoVs and IAVs of animal and human origin through virus detection and antibody detection, to capture both active and past infections. 

Rural stray cats living in groups were studied to assess whether they could form a reservoir for severe respiratory coronavirus-2 (the virus that caused the Covid-19 pandemic), but no evidence indicating towards this was found. Seropositivity to feline coronavirus was high in dense cat groups with indoor access, and feline immunodeficiency virus was more common in older, male and unhealthy cats, underlining the importance of including habitat and lifestyle when evaluating the risk for exposure to specific pathogens.

Across multiple dog and cat cohorts with different lifestyles and habitats, about one in twenty dogs and cats had antibodies to human H1N1 influenza virus, suggesting frequent spillover from infected owners or caretakers. Up to one every eight hunting-training dogs and stray cats had antibodies to H5 avian influenza virus, but antibodies were also, but less frequently, present in companion dogs and outdoor cats. It is therefore plausible that dogs and cats in the Netherlands are regularly exposed to avian influenza viruses through contact with infected wild birds or a contaminated environment. Because dogs and cats live close to humans, these animals could introduce such viruses into the household, and it is important to investigate whether dogs and cats can contribute to further spread to animals or even to humans.

In a follow-up study, potential attachment sites for both human and avian influenza viruses were detected in the nasal, tracheal and conjunctival epithelia of dogs and cats. This suggests that these animals may be infected with both viruses simultaneously and dogs and cats could play a role in virus evolution.
The thesis highlights the value of integrating dogs and cats into “One Health” surveillance—an interdisciplinary collaboration aiming to improve the health of humans, animals and ecosystems. This could improve early detection, understanding of transmission between wildlife, pets and humans, and strengthen pandemic preparedness.

The ceremony will begin with a short layman’s talk. The livestream will therefore start 15 minutes earlier.