Incidence of the brown dog tick, Rhipicephalus sanguineus and its parasitoid, Ixodiphagus hookeri on dogs in South Texas

Authors: VASQUEZ, ALEJANDRO - University Of Texas; Goolsby, John; VACEK, ANN - University Of Texas; RACELIS, ALEXIS - University Of Texas; KARIYAT, RUPESH - University Of Texas

Submitted to: Subtropical Agriculture and Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2019
Publication Date: 8/29/2019
Citation: Vasquez, A., Goolsby, J., Vacek, A.T., Racelis, A.E., Kariyat, R.R. 2019. Incidence of the brown dog tick, Rhipicephalus sanguineus and its parasitoid, Ixodiphagus hookeri on dogs in South Texas. Subtropical Agriculture and Environments. 70:6-10.

Interpretive Summary: Cattle fever ticks (CFT) Rhipicephalus (=Boophilus) microplus and Rhipicephalus annulatus are invasive livestock pests that are endemic to Mexico and invasive along the Texas – Mexico border. Acaricide resistance, alternate wildlife hosts, and pathogenic landscape forming weeds present challenges for sustainable eradication of this pest in the U.S. CFT are the vectors of single-celled blood parasites causing bovine babesiosis, a lethal disease causing high mortality particularly in susceptible European breeds of cattle and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful; however, a permanent quarantine zone (PQZ) is maintained between Texas and Mexico to prevent incursions of CFT from wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the PQZ in Texas. One of the alternate wildlife hosts for CFT in South Texas are nilgai (Boselaphus tragocamelus), an exotic Asian antelope. Nilgai are highly mobile with large home ranges and are implicated in the spread of CFT, through the landscape. Currently, there are no methods for control of CFT on nilgai other than culling. Specialist, biological control agents (tick parasitic wasps) from the native range of the cattle fever tick in Southeast Asia are under investigation as control method for CFT, especially on wildlife hosts such as nilgai that cannot be gathered for treatment. Tick parasitoids were collected in 1911 at multiple sites South Texas from the brown dog tick, Rhipicephalus sanguineus, which is a closely related tick to R. microplus and R. annulatus. Knowledge of how to rear the local tick parasitoids will be valuble, if specialized cattle fever tick parasitoids are imported from Asia. In this study in Hidalgo Co. we attempted to collect the parasitoid from brown dog ticks at a local animal shelter. Although we collected over 200 nymphal brown dog ticks, no parasitoids emerged from the ticks. Changes in land and pesticide use, especially in Hidalgo Co. may have effected local populations of the tick parasitoid, Ixodiphagus hookeri. Methods for holding ticks for emergence of parasitoids were evaluated, which will be useful when specialist cattle fever tick parasitoids are discovered and shipped to the US for evaluation. Tick parasitoids could play an important role in the integrated pest management program being developed to support cattle fever tick eradication program.

Technical Abstract: The southern cattle fever tick, Rhipicephalus microplus, is a livestock pest worldwide, including South Texas, and can vector the Babesia spp. the causal agent of bovine babesosis. Its congener, the brown dog tick, Rhipicephalus sanguineus, is common on dogs worldwide and is frequently parasitized by the parasitic wasp, Ixodiphagus hookeri. To better understand the life history and host location cues of parasitic wasps of ticks to support the cattle fever tick eradication program for R. microplus, we examined the incidence of R. sanguineus and its parasitoid I. hookeri, on dogs in Hidalgo County, TX from Oct 2018 to April 2019. Our results show that the sampled dogs had very low levels of R. sanguineus (1.89%), with 219 nymphs, and no parasitoids were recovered. We also found that R. sanguineus nymph incidence is significantly higher on female dogs and puppies from the 624 dogs examined.