Epidemiology and ecology of H3N8 canine influenza viruses in US shelter dogs.
BACKGROUND
H3N8 canine influenza virus (CIV) infection might contribute to increased duration of shelter stay for dogs. Greater understanding of factors contributing to CIV within shelters could help veterinarians identify control measures for CIV.


OBJECTIVE
To assess community to shelter dog CIV transmission, estimate true prevalence of CIV, and determine risk factors associated with CIV in humane shelters.


METHODS
5,160 dogs upon intake or discharge from 6 US humane shelters, December 2009 through January 2012.


METHODS
A cross-sectional study was performed with prospective convenience sampling of 40 dogs from each shelter monthly. Nasal swabs and serum samples were collected. Hemagglutination inhibition and real-time reverse transcriptase-polymerase chain reaction assays were performed for each nasal and serum sample. True prevalence was estimated by stochastic latent class analysis. Logistic regression was used to identify risk factors associated with CIV shedding and seropositivity.


RESULTS
Nasal swabs were positive from 4.4% of New York (NY), 4.7% of Colorado (CO), 3.2% of South Carolina, 1.2% of Florida, and 0% of California and Texas shelter dogs sampled. Seropositivity was the highest in the CO shelter dogs at 10%, and NY at 8.5%. Other shelters had 0% seropositivity. Information-theoretic analyses suggested that CIV shedding was associated with region, month, and year (model weight = 0.95) and comingling/cohousing (model weight = 0.92).


CONCLUSIONS
Community dogs are a likely source of CIV introduction into humane shelters and once CIV has become established, dog-to-dog transmission maintains the virus within a shelter.
Departments of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO.
H L
HL
Pecoraro
S
S
Bennett
K P
KP
Huyvaert
M E
ME
Spindel
G A
GA
Landolt
D000827:Animal Welfare / Q000706:statistics & numerical data; D000818:Animals; D003430:Cross-Sectional Studies; D004285:Dogs / Q000821:virology; D004463:Ecology; D005260:Female; D006385:Hemagglutination Inhibition Tests / Q000662:veterinary; D006799:Housing, Animal / Q000706:statistics & numerical data; D053123:Influenza A Virus, H3N8 Subtype; D016015:Logistic Models; D008297:Male; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D017201:Virus Shedding
Akaike; Canine infectious respiratory disease; Humane shelter; Information-theoretic approach