Epidemiologic evaluation of encephalitic listeriosis in goats

Objective - To evaluate host and environmental factors associated with the development of encephalitic listeriosis in goats. Design - Retrospective analysis of diagnostic laboratory records and survey of veterinarians and goat producers. Sample Population - 355 goat herds accessible through laboratory records; 38 veterinarians who treated goats and 76 goat producers. Procedure - Data regarding breed and use for goats affected with encephalitic listeriosis were obtained from surveys and case follow-up information. Listeria monocytogenes isolates from the brains of 7 affected goats were serotyped and subjected to DNA restriction analysis. Results - Odds ratio for the development of encephalitis listeriosis in Angora (mohair-producing) goats was 22.9 by use of diagnostic laboratory records. Surveys also revealed a high prevalence in herds of Angora and other breeds that subsisted on woody browse, although Angora goats feeding predominantly on hay or pasture were not affected. Listeria monocytogenes isolates from 4 Angora goats in 3 herds differed in DNA restriction patterns, although the pattern was identical in 3 other goats from another herd. Clinical Implications - Encephalitic listeriosis can be observed in all goat breeds, but a lifestyle of heavy browse consumption seems important to the development of disease in some herds.