Susceptibility of adult engorged ticks, rhipicephalus microplus (Acari: Ixodidae) to a native heterorhabditid isolate (nematoda: Heterorhabditidae) in Colima, Mexico

Abstract

A survey of entomopathogenic nematodes (EPNs) belonging to the families Steinernematidae and Heterorhabditidae was conducted in the municipality of Tecomán, Colima, Mexico in an effort to obtain alternative controls for cattle ticks. Soil cores from grasslands were baited with last instars of the great wax moth (GWM), Galleria mellonella L., and an EPN isolate was obtained, it belonged to the genus Heterorhabditis and identified as JMO71. The nematodes were cultivated in GWM larvae, and the emerging infective juveniles (IJs) were collected from White traps, and pooled in canted neck vented plastic flasks. The susceptibility of an important livestock arthropod, the cattle tick, Rhipicephalus microplus Canestrini to JMO71 was determined. Ticks were manually collected from cross-bred beef cattle, and then the heterorhabditid nematodes assayed against these ticks using the Petri dish assay. Concentrations of 0, 500, 1000, 2000, 4000 and 8000 IJs were applied in 1 mL of sterile distilled water dispensed on the surface of a couple of moistened filter papers. For each treatment concentration, 10 adult engorged ticks were placed in the Petri dishes, and each treatment was replicated four times; the experiment was replicated two times. Tick mortality was recorded daily for 9 days. Our EPNs were able to parasitize engorged ticks, and tick mortality ranged between 70-100% after 9-d post-exposure. The faster and higher tick mortality was obtained with the concentration of 2000 IJs causing 100% mortality after 3 days post-exposure. This is the first report of a native Mexican heterorhabditid nematode causing cattle tick mortality.