Specificity of four Serologic Assays for Mycobacterium Avium ss Paratuberculosis in Llamas and Alpacas: A Single Herd Study

Abstract

Abstract. An investigation was conducted for Mycobacterium avium ss paratuberculosis infections in a research herd of llamas and alpacas. Herd culture-negative status was established over a 23-month period by screening any individuals with any signs compatible with paratuberculosis (n ϭ 1), high serology values (n ϭ 8), or other health and research related reasons (n ϭ 24). There were no M. avium ss paratuberculosis isolates from radiometric cultures of multiple tissue and fecal samples from these individuals and no known sources of exposure. Paratuberculosis is uncommon in North American llamas and alpacas: only 5 cases were identified after an extensive search of the Veterinary Medical Data Base, diagnostic laboratory records, publication databases, and personal communications. Therefore, serum samples from llamas (n ϭ 84) and alpacas (n ϭ 16) in the culture-negative herd were used to obtain preliminary estimates of test specificity for 3 enzyme-linked immunoassays (ELISAs) and an agar gel immunodiffusion (AGID) assay kit for detecting serum antibodies to M. avium ss paratuberculosis in South American camelids. The ELISAs were modifications of established bovine assays for antibody detection. With provisional cutoffs, ELISA-A had 52 false positives (specificity 48%), ELISA-B had 8 false positives (specificity 92%), ELISA-C had two false positives (specificity 98%), and the AGID had 0 false positives (specificity 100%). The range of ELISA values for culture-positive llamas and alpacas (n ϭ 10) from other herds overlapped the range of values for culture-negative llamas and alpacas. The accuracy of the ELISAs may be improved by using age-and sex-specific cutoffs because uninfected male llamas and alpacas that were older than 1 year had higher values for some tests. These tests can be used for either llamas or alpacas; the protein-G conjugate ELISA (ELISA-B) may be useful for multispecies applications. These assays are best used for rapid presumptive diagnoses of llamas and alpacas with diarrhea and weight loss and as a screening tool for herds known to be exposed to infection. All seropositive results should be confirmed with culture.Recent reports have demonstrated that paratuberculosis is a potential health risk for South American camelids. 2,13 An ongoing outbreak in Australian alpacas (Lama paca) 13 has illustrated that, as in bovine herds, 8 when paratuberculosis is introduced into a previously unexposed herd, much of the herd can become infected prior to any animals showing clinical signs of disease. North American llamas (Lama glama) have been reported with culture-confirmed infections. 2 Because llamas and alpacas constitute a significant industry worldwide and because the value of individual animals can be substantial, paratuberculosis could cause severe economic losses if the disease becomes Received for publication September 29, 1998. established in the industry. Because llama and alpaca importations and animal transfers among herds are important to the genetic and economic health of the llama and a...

Disorders of the Digestive System

“…157,158,164,168 Diarrhea is often a near-terminal finding and only seen in about half the cases. 157,158,164,168 Diarrhea is often a near-terminal finding and only seen in about half the cases.…”

Prevalence ofMycobacterium aviumsubsp.paratuberculosisFecal Shedding in Alpacas Presented to Veterinary Hospitals in the United States

“…Serum tests (ELISA) for antibodies to MAP have been adapted for use in camelids . However, the sensitivity of these tests to detect MAP infection is between 50 and 70%, which is most likely explained by the fact that as an intracellular pathogen, MAP might not induce a strong humoral immune response until late in the infection . Similar to cattle, tests relying on the detection of antibodies could be more useful at the herd level, and not for individual animal diagnosis.…”

Serosurvey of zoo ungulates in central Europe

“…burnetii and M. pt was performed using an indirect ELISA [CHEKIT-Chlamydia, CHEKIT-Q-Fever, CHEKIT-M. pt (IDEXX)]. These assays use a monoclonal anti-ruminant-IgG conjugate (Miller et al, 2000;Kramsky et al, 2003). The ELISA was performed following the manufacturer's protocol.…”