|Knowles, Donald - Don|
Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2004
Publication Date: 11/1/2004
Citation: Palmer, G.H., Knowles, D.P., Rodriguez, J-L., Gnad, D.P., Hollis, L.C., Marston, T., Brayton, K.A. 2004. Stochastic Transmission of Multiple Genotypically Distinct Anaplasma marginale Strains in a Herd with High Prevalence of Anaplasma Infection. Journal of Clinical Microbiology. 42(11):5381-5384. Interpretive Summary: This study investigated the potential role of strain genetics in contributing to transmission patterns of Anaplasma marginale. We utilized a current cattle herd with an infection prevalence of 29% based on the presence of anti-A. marginale antibody. Strain typing was based on our previous data concerning genotyping using the major surface protein MSP1a. Two important outcomes of this study are that preferential transmission of a given strain defined by MSP1a genotyping does not occur and importantly superinfection (reinfection of a persistently infected cow with a new strain) does occur. This has important implications for vaccine development.
Technical Abstract: Multiple genotypically unique strains of the tick-borne pathogen Anaplasma marginale occur and are transmitted within regions where the organism is endemic. In this study, we tested the hypothesis that specific A. marginale strains are preferentially transmitted. The study herd of cattle (n 261) had an infection prevalence of 29% as determined by competitive inhibition enzyme-linked immunosorbent assay and PCR, with complete concordance between results of the two assays. Genotyping revealed the presence of 11 unique strains within the herd. Although the majority of the individuals (70 of 75) were infected with only a single A. marginale strain, five animals each carried two strains with markedly distinct genotypes, indicating that superinfection does occur with distinct A. marginale strains, as has been reported with A. marginale and A. marginale subsp. centrale strains. Identification of strains in animals born into and infected within the herd during the period from 1998 to 2003 revealed no significant difference from the overall strain prevalence in the herd, results that do not support the occurrence of preferential strain transmission within a population of persistently infected animals and are most consistent with pathogen strain transmission being stochastic