Rearing of Rhipicephalus annulatus ticks on rabbits for the biological transmission of Anaplasma marginale.

Background and aim: Anaplasma marginale is an obligate intraerythrocytic rickettsial parasite that infects cattle in tropical and subtropical regions. There is no evidence that A. marginale inoculation can be used to culture Rhipicephalus annulatus in rabbits. This study aimed to determine the molting of R. annulatus larvae, nymphs, and adults on rabbits as well as nymphs and adults of R. annulatus on calves with or without A. marginale. Transstadial, horizontal, and transovarial transmissions of A. marginale in R. annulatus reared on rabbits and calves were evaluated.

Materials and methods: Engorged female ticks were collected from field samples of A. marginale-infected and non-infected cattle. We divided the eight rabbits into two groups: A and B. Group A rabbits were infected with A. marginale through parenteral inoculation, whereas Group B rabbits were kept as a control. The "clean rabbits" in Group B were observed for tick rearing without A. marginale. Polymerase chain reaction was used to screen A. marginale in rabbits and stages of tick. The complete life cycle of R. annulatus with or without A. marginale was observed on rabbits.

Results: A 6.5-day longer life cycle was observed in ticks harboring A. marginale than in ticks without A. marginale. To observe transstadial transmission, transstadial, horizontal, and transovarial transmissions of A. marginale in R. annulatus ticks were experimentally observed in one clean calf fed separately with infected nymphs and female adult ticks.

Conclusion: We experimentally observed transovarian, transstadial, and transovarial transmission of A. marginale in R. annulatus ticks as a biological vector reared on calves and rabbits. We used rabbits as a model animal for rearing R. annulatus ticks and culture of A. marginale.