Transovaric transmission of Anaplasma marginale in Rhipicephalus microplus ticks and evaluation of their capacity to infect a susceptible bovine

DE LA FOURNIERE S; GUILLEMI E; JARAMILLO ORTIZ J; SOSA C; SARMIENTO N; WILKOWSKY S. E; FARBER M

Cairns

Congreso; 9th Tick and Tick Borne Pathogen Conference & 1st Asia Pacific Rickettsia Conference; 2017

In Argentina the transmission of Anaplasma marginale is mainly related to the bovine tick, Rhipicephalus microplus.Despite being considered an important factor in the spread of the disease, to date, there is no evidence of vertical transmission of A. marginale in this tick. Therefore, its role as a biological vector has not been demonstrated. The aim of this work was to evaluate the presence of A. marginale in R. microplus larvae obtained from adult engorged females and use these larvae to reproduce the infection cycle in cattle. R. microplus engorged females were collected from cattle naturally infected and confirmed positive for A. marginale. Ticks were incubated for spawning and a fraction of the emergent larvae was isolated for PCR detection of A. marginale msp5 and msp1 genes. Results were positive in all the engorged ticks and also in their respective larvae. Thus, new fractions of the same pool of positive larvae were used to infest a healthy splenectomized calf. Twenty two days after infestation, the calf showed clinical signs of anaplasmosis together with both blood smears and msp1- PCR positive for A. marginale. Overall, the results reveal the central role of R. microplus in the transmission of A. marginale, through the first experimental demonstration of the complete cycle of the bacteria in the tick, analyzing its presence in the adult and larval stages, and the capacity of the latter to transmit the infection of A. marginale into a healthy bovine host.