01105: Understanding the Dynamics of Canine Influenza Virus Transmission in Dog Populations and Intervention Strategies for Reducing Transmission
Grant Status: Closed
Canine influenza is a highly contagious respiratory infection of dogs caused by a novel influenza A virus of the subtype H3N8. H3N8 canine influenza virus (H3N8 CIV) has caused respiratory disease outbreaks in thousands of dogs located in 38 states in the U.S. Although most dogs recover from an influenza-like illness, many develop a debilitating pneumonia that can be fatal if not treated under hospital care. There is little information on risk factors for canine influenza, either for individual dogs or for facilities that house dogs. In our first epidemiological study, location in the Northeast and West regions of the country and housing in animal shelters and boarding facilities were identified as risk factors for H3N8 CIV infection of dogs. We are currently completing a second epidemiological study focused on identifying kennel facility parameters such as population density, source and frequency of introduction of new dogs, sanitation practices, disease surveillance and infection control protocols that may increase the risk for canine influenza outbreaks. Since shelters are a risk factor for virus exposure, we constructed a mathematical model to simulate H3N8 CIV transmission in shelters to determine factors important to development of outbreaks and establishment of endemic infection. This study identified indirect virus transmission by contaminated fomites and the number of dogs housed in the shelter as the most important factors promoting canine influenza outbreaks. Isolation of sick dogs, vaccination against canine influenza, vaccination and isolation combined, and stopping admission of new dogs were four common intervention strategies applied to the model to determine their effect in reducing or preventing virus transmission. Analyses indicate that neither isolation nor vaccination alone or in combination can completely eliminate virus transmission in a shelter under the modeling conditions employed. However, these strategies can reduce the number of infected dogs during outbreaks. While stopping admissions of new dogs did not prevent outbreaks, this intervention strategy prevented establishment of endemic infection in the shelters. An individual-based model to simulate H3N8 CIV virus transmission in dog shows was also developed. Overall, the model as constructed had an excess of infectious contacts, thus reducing any one mode of virus transmission did not necessarily have a strong effect on the number of infected dogs leaving the show. The number of infected dogs leaving the show was most affected by the probability of contact between all dogs, either by direct transmission of virus between dogs or indirect virus transmission by fomites, including contaminated judges. Increased efforts to decontaminate judges only caused a slight reduction in the number of infected dogs. However, there was a dramatic decrease in the number of infected dogs when at least 90% of the dogs were vaccinated against canine influenza prior to the show. The overall results of these studies provide valuable information to dog show organizers and kennel facility managers for guiding the formulation of policies for prevention and control of canine influenza.
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