Efficacy of entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae) against engorged females of the cattle fever tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Authors: SINGH, NIRBHAY - Guru Angad Dev Veterinary & Animal Sciences University; Goolsby, John; Shapiro Ilan, David; Miller, Robert; Thomas, Donald; KLAFKE, GUILHERME - Desiderio Finamore Veterinary Research Institute (FEPAGRO); Tidwell, Jason; RACELIS, ALEX - University Of Texas Rio Grande Valley; GREWAL, PARWINDER - University Of Texas Rio Grande Valley; Perez De Leon, Adalberto - Beto

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2017
Publication Date: 3/1/2018
Citation: Singh, N., Goolsby, J., Shapiro Ilan, D.I., Miller, R., Thomas, D.B., Klafke, G., Tidwell, J.P., Racelis, A., Grewal, P., Perez De Leon, A.A. 2018. Efficacy of entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae) against engorged females of the cattle fever tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae). Southwestern Entomologist. 43(1):1-17. https://doi.org/10.3958/059.043.0119.
DOI: https://doi.org/10.3958/059.043.0119

Interpretive Summary: Six species of parasitic round worms, called entomopathogenic nematodes (EPNs) were tested for their effects using an exposure of adult CFT on filter paper. Three of the nematode species showed effectiveness against CFT. One of the species, Steinernema riobrave is native to the the Rio Grande Valley of Texas and has special utility in protected natural areas where conventional acarcides may not be appropriate. S. riobrave is also commericially produced, which is an important factor in the implementation of EPN for use in the USDA-APHIS Cattle Fever Tick Eradication Program.

Technical Abstract: The southern cattle fever tick, Rhipicephalus (Boophilus) microplus, has a wide geographic distribution across tropical and subtropical regions causing huge economic losses to bovine milk and meat production. Presently, application of chemical acaricide is the most widely used control strategy but due to growing evidence of acaricide resistance, contamination of environment and animal products, novel strategies are needed. Entomopathogenic nematodes (EPNs) represent a promising alternative to develop tick control strategies. Six species of EPNs, Steinernema riobrave (355 strain), S. carpocapsae (All strain), S. feltiae (SN strain), Heterorhabditis bacteriophora (VS strain), H. indica (HOM1 strain), and H. floridensis (K22 strain) were tested for their pathogenicity against R. (B.) microplus (Deutch strain). Engorged female ticks were exposed to 1,250, 2,500, and 5,000 infective juvenile (IJ) nematodes for 24, 48 and 72 h on Petri dishes and tick mortality over time, pre-oviposition period, egg mass weight, reproductive index, percentage inhibition of oviposition and hatching percentage were monitored. A dose-dependent mortality was recorded in all Heterorhabditis species, S. riobrave and S. carpocapsae which increased with exposure time. Minimum LC50 (95% CL) values of 1999 (1947-2052) and 69 (63-75) IJs per dish were estimated for S. riobrave and H. floridensis, respectively upon 72 h exposure. IJ concentration and exposure time did not influence pre-oviposition period. Differences in egg mass weight and reproductive index among the treatments and control group were observed with respect to concentration and exposure time. Reduction in hatchability was recorded only in S. riobrave exposed ticks. Overall, H. floridensis, followed by S. riobrave and S. carpocapsae were found to be the most virulent species against engorged R. (B.) microplus engorged females, adversely impacting most biological parameters. Future studies are warranted to explore the potential of these new nematode species for biological control of the cattle fever tick.