Detection and risk factors associated with the transmission of Anaplasma marginale in dairy buffalo herds

Anaplasma marginale is an intracellular rickettsia transmitted by ticks and hematophagous insects that infect the mature erythrocytes of ruminants, being considered as the hemotropic of greater economic impact in the dairy farms of the world. The findings of A. marginale in buffalo (Bubalus bubalis) have shown that it is an important reservoir of the pathogen for cattle where they coexist. In order to detect A. marginale in lactating buffaloes as well as the risk factors (RF) associated with its transmission, twelve production units located in the Eje Panamericano, Sur del Lago de Maracaibo-Venezuela were visited. Collected 120 blood samples from the jugular vein using vacuum tubes with anticoagulant ethylenediamine tetraacetic acid (EDTA). The DNA obtained was purified according to the method of proteinase K and phenol-chloroform to identify by means of the Polymerase Chain Reaction (PCR) technique, a specific gene (msp1) for A. marginale. On the other hand, the presence of the pathogen was visualized through the blood smear under a microscope (100X) with Giemsa stain, and an epizootiological questionnaire was applied to register the epidemiological elements related to the transmission of the rickettsial microorganism. PCR revealed the presence of a specific amplicon for A. marginale of approximately 400 bp in 80% (96/120) of the total of buffaloes sampled; however, by extended blood only 30% (36/120) of the animals were diagnosed as positive. Among the FR studied, the presence of ticks (Rhipicephalus microplus) represented the highest negative impact (Odds ratio (OR) = 3.23), while the use of acaricide baths was a protection practice (OR = 0.83) for A. marginale. In conclusion, PCR proved to be a sensitive and specific diagnostic tool compared to the extended blood to find A. marginale. The high positivity among herds demand the adoption of sanitary strategies for the control of A. marginale in B. bubalis.