Cattle Fever Tick Project

Research leaders: Marie-Claude Bon, Javid Kashefi

A   B 

A: Rhipicephalus microplus (Photo by Kashefi)
B: Infested cow in the native range (Photo by Kashefi)

Presentation & context

Cattle fever ticks (CFT), Rhipicephalus (Boophilus) annulatus and R. (B.) microplus are the vectors of Babesia bigemina and B. bovis, which cause bovine babesiosis, and Anaplasma marginale, which causes anaplasmosis in cattle, in addition to their direct impacts on livestock health as ectoparasites. Although CFT were eradicated from the USA in 1943 through efforts of the Cattle Fever Tick Eradication Program (CFTEP), and despite the maintenance of a permanent quarantine zone in south Texas along the Rio Grande to buffer CFT incursions from Mexico, where the tick vectors and bovine babesiosis remain endemic, CFT have again become a threat to the economic viability of the US livestock industry. Over decades, chemical control has been the main management strategy to regulate CFT populations, but CFT have developed resistance to the main classes of the acaricides that are used for their control. Acaricide resistance issues have led the cattle industry to conceive an integrated strategy based on an interdisciplinary systems approach that specifically includes classical biological control. Classical biological control which is a component of an integrated pest management strategy relies on the introduction of natural enemies originating from the native range of the pest to its invasive range in order to re-establish a natural equilibrium that was lost in the invasion process. Ticks have numerous natural enemies including parasitoid wasps, nematodes, Bacillus thuringiensis bacteria, and deuteromycete fungi (largely Metarhizium anisopliae and Beauvaria bassiana), but only a few species have been evaluated as tick biocontrol agents of CFT. To date, efforts to search for potential biological control agents are far from being made in the entire native range of R. microplus which extends across Southeast Asia from Indonesia to India and of R. annulatus which occurs in the Mediterranean Europe, northern Africa, and southwestern Eurasia.

Research components

Since 2016, EBCL USDA ARS has been involved in a research project on biological control of CFT together with USDA ARS Knipling Bushland U.S. Livestock Insects Laboratory and the National Institute of Veterinary Research in Hanoi, Vietnam. EBCL objectives were to conduct foreign exploration in the Balkans (Greece, Albania and Bulgaria) and Vietnam to find natural enemies of Cattle Fever Tick. Efforts were primarily focusing mainly on the parasitoid wasp, Ixodiphagus hookeri Howard (Hymenoptera: Encyrtidae ) which oviposits into nymphs, emerges from engorged adults, and has 1-2 generations per year.

Ixodiphagus hookeri and infested tick (Photo by Kashefi)

As parasitized ticks die prior to reproduction, I. hookeri is seen as a prime biological control agent candidate. So far, it has not been possible to identify any geographic area where the distribution of the parasitoid was not erratic and where its prevalence in tick populations was sufficient to conduct massive collections. In 2023, EBCL efforts in terms of exploration are being continued in Greece, Albania and Northern Vietnam to search not only for the parasitoid, but rather the assemblage of natural enemies associated with CFT including nematodes and pathogens which will be further characterized as well as the tick hosts using molecular barcoding and metabarcoding approaches.