Molecular epidemiology of bovine anaplasmosis

Bovine anaplasmosis presents a worldwide distribution. However, specific models for studying the epidemiology of the disease are not available. Epidemiological modeling encounters some difficulties due to a lack of culturing techniques for Anaplasma marginale, the causative agent, as well as for the lack of typing techniques to characterize strains. The chronic carrier state and the population dynamics of mechanical and biological vectors also create difficulties. In addition, conventional serology and blood smear diagnostic techniques fail to detect all chronic carriers. Fortunately the needs for the accurate typing of isolates and for detecting chronic carriers made it possible to encourage the development of new tools based on molecular epidemiology principles. A. marginale isolates can now be typed by using panels of monoclonal antibodies, and the genes coding for some major surface proteins can be expressed or analyzed by looking at the nucleotide arrangement level. In the same manner, the latest techniques for detecting A. marginale chronic infections use DNA and RNA probes, and PCR-based methods to detect A. marginale DNA from bovine blood samples with extremely low rickettsaemias. Currently all these new epidemiological tools are being incorporated to experimental models to analyze their applicability for epidemiological studies in the near future.