Molecular detection of Anaplasma marginale in stable flies Stomoxys calcitrans (Diptera: Muscidae) feeding on a tick-free bovine herd

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Bautista-Garfias CR, Rodriguez T, Rojas C, Lira JJ, Alvarez JA, Polanco D. Molecular detection of Anaplasma marginale in stable flies Stomoxys calcitrans (Diptera: Muscidae) feeding on a tick-free bovine herd. Veterinaria Mexico OA. 2018;5(1). doi: 10.21753/vmoa.5.1.436 . Data on the implication of the stable fly ( Stomoxys calcitrans , Diptera: Mus­cidae), in the transmission of Anaplasma marginale in tick-free cattle is scarce. Hence, the objective of this investigation was to detect the presence of DNA from A. marginale in stable flies caught near a bovine herd, which has been maintained free of ticks for 40 years, and occasionally presents some clinical cases of anaplasmosis. Twenty-four batches of S. calcitrans (15 flies each) were collected in the morning and in the afternoon twice a week (except for one catch in one week of September and one catch in one week of December) during 12 catching days in a period of four months. Their DNA was obtained and analysed by nested PCR (nPCR) to identify the presence of A. marginale DNA. Seven of the batches (29.16 %) were pos­itive for A. marginale , as detected by an nPCR that targets the A. marginale msp5 gene. Similarly, in two out of 12 catching days (16.66 %), those S. calcitrans batches collected in the morning and in the afternoon, were pos­itive for A. marginale , while those S. calcitrans groups collected in three out of 12 catching days (25 %), were positive for the rickettsia. The obtained re­sults suggest that A. marginale transmission is carried out mechanically by S. calcitrans , favouring the circulation and maintenance of the microorganism in this particular bovine herd. Figure 1. A. Example of a stable fly Stomoxys calcitrans caught in this study (photograph: Carlos R. Bautista).