The epidemiology of anaplasmosis: Geographic and risk factor analyses for Illinois cattle and white-tailed deer
Hungerford, Laura L.
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Permalink
https://hdl.handle.net/2142/23168
Description
Title
The epidemiology of anaplasmosis: Geographic and risk factor analyses for Illinois cattle and white-tailed deer
Author(s)
Hungerford, Laura L.
Issue Date
1989
Department of Study
Pathobiology
Discipline
Pathobiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Pathology
Biology, Veterinary Science
Language
eng
Abstract
Three data sources were combined to examine spatial and individual risk factors for anaplasmosis, an economically significant, blood-borne infection of ruminants. A survey of 220 Illinois veterinarians identified a significantly clustered pattern of infection (p $<$.05) with two endemic clusters; in southern and in west-central Illinois. This pattern showed spatial codistribution with wooded areas, a marker for vector habitat. Temporal analysis revealed large summer and small winter outbreak peaks.
A serological survey of 5000 market cattle identified clustering of county prevalence levels (p $<$.01). Areas with high prevalence showed significant codistribution with areas classified as endemic by surveyed veterinarians and with the vector habitat marker. County adjacency, as a measure of shared ecologic factors showed significant spatial autocorrelation (z = 7.2, p $<$.01). Prevalence in counties linked by cattle markets but not borders, representing cattle movement between diverse areas, was also highly autocorrelated (z = 6.7, p $<$.01).
For individual cattle, the risk of having anaplasmosis increased with age (p$\sb{\rm trend}$ $<$.01). In high prevalence counties, this trend was accentuated while in low prevalence areas, prevalence did not increase with age. Risk was decreased for Holsteins (p $<$.01) but increased for Angus and crossbreds (p $<$.01). Risk was dissimilar for the same breed in different areas. There were no sex differences. When age, sex and breed were analyzed simultaneously using logistic regression with prevalence as a covariate, females, Angus and Holsteins were at decreased risk while crossbreds and older animals remained at increased risk.
Sera from cattle and white-tailed deer in a refuge in southern Illinois and deer samples from hunters throughout Illinois were tested for antibodies to Anaplasma. Epidemiologic and geographic analyses revealed no spatial, temporal or demographic risks for anaplasmosis in either deer population. Seroprevalence had a completely random spatial distribution.
These results provide etiologic data and important management information for cattle producers and veterinarians about endemic areas and risk factors for individual animals. The lack of significant risk patterns for deer, as were identified for cattle, suggests that though seropositive individuals were present, anaplasmosis is not established in deer and they are not a major factor in the epidemiology of bovine anaplasmosis in Illinois.
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