Colin Parrish, PhD
John M. Olin Professor of Virology
Albert C. Bostwick Laboratory of Molecular Biology
We study viruses that infect our animals, and focus on those viruses that have the ability to transfer from one animal host to another to cause large outbreaks of disease. In our recent work we are examining several different viral diseases of dogs, cats, and horses, particularly the canine and feline parvoviruses, as well as the equine and canine influenza viruses. In each case the viruses have transferred from one host to another to cause an epidemic of disease in the new host.
Canine and feline parvoviruses: Parvoviruses are very small and robust viruses, and contain a short length of single stranded DNA as their genome. They can persist in the environment and infect animals by entering the mouth or nose. A parvovirus that infects cats has been known at least since the 1920s, and that causes a disease called feline panleukopenia (panleukopenia means a reduction in the number of all of the white blood cells in infected animals). That virus was called feline panleukopenia virus (FPV), and it also infected mink and raccoons, as well as many other hosts including wild cats such as leopards and lions. However, dogs were not infected by these viruses until around 1978, when the canine parvovirus (CPV) emerged and quickly spread worldwide, causing disease in dogs, wolves and coyotes. We showed in our work that the CPV is a mutant of a virus like FPV, which gained a small number of mutations that gave it the ability to infect dogs. Since CPV emerged it has also been found to infect other wild animals, including raccoons, mink, foxes, mountain lions, and the giant panda.
Host Range and other changes in parvoviruses – how the virus jumped from one host to another:The studies in the Parrish laboratory have been seeking to understand how the parvoviruses function and change in nature.In particular we are explaining how the feline virus was able to change its host range to infect dogs leading to the emergence of CPV. We are also examining the ways in which the viruses interact with the host immunity, so that we can determine whether there is a need for new or improved vaccines. We have shown that the changes in the viruses that control their host ranges alter the way in which the viruses recognize the receptors on the surface of host cells – in particular a protein on the surface of cells called the transferrin receptor, which the viruses use to infect cells.Differences in the ability of the viruses to recognize the transferrin receptors on dog and cat cells are critical in the specific recognition and the control of host range. Another major aim is to develop better and more effective methods for vaccinating dogs or cats against these viruses, in particular by monitoring the changes in the viruses that result in alteration of their antigenic structure as recognized by protective host antibodies.
Equine and canine influenza viruses: In this study we are also interested in finding out how the virus was able to transfer from horses to dogs, and whether there are changes in the virus that are causing it to become better adapted to dogs.While the results are giving us important information about the viruses in dogs, they will also likely inform us about how influenza can shift between other hosts, including to humans.These studies involve examining the sequences of the viral RNA genome, to see whether there are any changes that are found in the viruses from dogs that are not present in the horse viruses.Those are candidates for changes that are involved in the adaptation of the viruses to the new host.The sequence changes in the different viruses from dogs also tell us how the viruses are spreading in the dog population, which allows us to devise improved strategies for controlling them in the future.