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During the summer of 2015, I mentored a group of undergraduate researchers at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee. We studied canine distemper virus (CDV), which is a highly infectious disease that affects a variety of animals. Common symptoms in canines include sinus discharge, gastrointestinal unrest, and neurological ailments, often resulting in death.
A vaccine for the disease was developed for domestic dogs in the 1950s and resulted in near elimination of CDV from pets in the United States. However, wild animals remain a reservoir for the disease and a lapse in vaccinations lead to several recent outbreaks of CDV in animal shelters in Tennessee. The local resurgence of CDV inspired work between mathematicians and veterinarians to create a compartmental model with ordinary differential equations (ODEs) for the disease in a general shelter environment.
After visiting a local animal shelter, we reduced our general model to more accurately model an outbreak in a local shelter. Upon admittance to the shelter, all dogs are vaccinated for CDV and are administered a booster after two weeks. If CDV is suspected in an animal the shelter runs tests in house with a PCR machine. We used data from the shelter to estimate parameters including the dog drop-off rate, adoption rate, vaccination rate, and CDV test turn-around rate. Data from local outbreaks was used to estimate transmission rates and the disease progression rate. We then considered intervention strategies that would avoid depopulation of the shelter if CDV were to be introduced to the system.
Similar to local events, we found that delayed test results or failing to recognize cases of CDV quickly leads to a severe outbreak in a shelter environment. Our analysis also indicates that access to rapid diagnostic tests and a policy to quickly euthanize confirmed cases are paramount in preventing outbreaks and limiting the number of deaths.
The following figure shows an outbreak that takes place in a shelter that does not quickly euthanize dogs (d=1/7).