Evaluation of noninvasive molecular monitoring for fecal pathogens among free-ranging carnivores

by Ballmann Acton, Anne Elaine

Abstract (Summary)
Disease surveillance in wildlife is limited by difficulties in obtaining ante-mortem diagnostic samples. Serologic surveys provide imperfect, retrospective measures of susceptible and immune subpopulations to pathogens that do not reveal which individuals are currently infectious. I examined fecal polymerase chain reaction (PCR) diagnostics as a noninvasive, alternative means of monitoring for pathogen presence among sympatric carnivores. PCR assays were evaluated for canine distemper virus (CDV) and canine parvovirus 2 (CPV2) by inoculating control feces with vaccines. Detection limits were below concentrations reported in clinically ill animals. The CPV2 assay amplified product from canine and feline vaccine strains while the CDV assay amplified 3 vaccine strains and neither cross-reacted with other vaccine viruses. Successful amplification, after 1 year, depended on the storage method and was robust in feces exposed to field conditions up to 2 to 3 weeks. Simulated infection, involving modified-live vaccination, investigated fecal virus shedding. Coyote pups shed CPV2 in their feces by Day 7 post-vaccination at levels below antigen-capture enzyme-linked immunosorbent assay (ELISA) sensitivity. Virus shedding ceased by Day 14 post-vaccination. Evaluation of vaccine-induced fecal shedding of CDV was complicated by co-amplification of bacterial contaminants; however, no virus was detected in the conjunctival epithelium on Day 7. Field viruses amplified from feces of animals showing clinical disease. Serologic and fecal PCR assays were deployed in eastern North Carolina where free-ranging bears, bobcats, gray foxes, raccoons, coyotes, and red wolves coexist and the viruses are endemic. All species had evidence of natural exposure to CDV and individuals of 5 species were actively shedding virus. Exposure to CPV2-like viruses occurred in 5 species, although overall fecal shedding of the virus was rare. Virus shedding occurred in both seropositive and seronegative individuals. Fecal PCR informs infectious disease models beyond the capabilities of serologic surveys. Identification of infected individuals, population density estimates, and spatial distributions allows more accurate estimation of contact rates within, and between, susceptible host populations, and thus, supports better understanding of disease ecology for multi-host pathogens.
Bibliographical Information:

Advisor:James S Guy; Michael K Stoskopf; Roger A Powell; George R Hess

School:North Carolina State University

School Location:USA - North Carolina

Source Type:Master's Thesis

Keywords:comparative biomedical sciences


Date of Publication:12/07/2007

© 2009 All Rights Reserved.