Anaplasmosis: Practical principles for the diagnosis, treatment and control of field cases and outbreaks

Abstract

Anaplasmosis, caused by the rickettsial hemoparasite Ana­plasma marginale (Am), is the most prevalent tick-transmitted disease of cattle worldwide and a major obstacle to profitable beef production in the continental United States. Anaplasmosis is readily transmitted through biological and mechanical vec­tors such as ticks and biting flies and iatrogenically through needles and equipment contaminated with infected blood. Clinical anaplasmosis, characterized by anemia, icterus and fever, is associated with significant production losses, abor­tions and mortalities in cattle. It is estimated that the introduc­tion of anaplasmosis into a previously naïve herd can result in a 3.6% reduction in calf crop, a 30% increase in cull rate and a 30% mortality rate in clinically infected adult cattle. Further­more, a study has shown that 16% of pregnant carrier cows will transmit anaplasmosis in utero producing persistently infected offspring. The existence of both horizontal and vertical ana­plasmosis transmission has important implications for disease control in endemic areas. In this presentation, we will use case studies to examine strategies to treat and control anaplasmosis in beef and dairy herds.