EFFICACIES OF CHLORFENVINPHOS, AMITRAZ AND ALPHACYPERMETHRIN AND THEIR COMBINATIONS ON RHIPICEPHALUS (BOOPHILUS) DECOLORATUS TICKS FROM CATTLE IN NANDI COUNTY, KENYA

Abstract

The one-host tick, Rhipicephalus (Boophilus) decoloratus, is a ubiquitous ectoparasite of cattle in Nandi County, Kenya. For more than one decade, the County has used plunge dips to apply, either chlorfenvinphos, amitraz and alphacypermethrin acaricides on the cattle, to control the tick. Farmers, reportedly combine different classes of acaricides for use too. This study was designed to examine the dipping performance in the years 2000 – 2012, assess the efficacies of the acaricides and their binary combinations on the adult female R. (B). decoloratus ticks and larvae. Visibly engorged ticks that persisted dipping with the acaricides were collected from cattle and subjected to the Adult Immersion Test (AIT) using the acaricides, at recommended dipping concentrations. Larvae from the ticks were tested with similar acaricide preparations through the Larval Packet Test (LPT). The ticks were also tested with binary combinations of the acaricides, mixed at 50:50mls. The study showed that the majority of the farmers in the County used an average of 286 communally-managed plunge dips (84.11%) while others used 48 private dips (15.89%). Irregular numbers of cattle were presented for dipping annually (266,178.3±30,963), with anaplasmosis being the most prevalent tick-borne disease (47.74%), followed closely by East Coast Fever (47.08%). Over half of the dip-wash used in the period (56.36%) had the recommended acaricide concentrations, while 38.81% were under-strength and 4.83% over-strength. Viable ticks, whose weights ranged between 0.114 – 0.124g, with capacity to lay eggs that had visually 100% hatchability, were recovered from the cattle. The single acaricides had slow action on adult ticks, with 66.67 – 91.67% mortalities occurring after 96 hours from immersion, while combinations containing chlorfenvinphos had 83.33% and 100% efficacies on those collected from cattle dipped in alphacypermethrin and amitraz, respectively, at the same time interval. The single acaricides produced 75 - 100% efficacies on larvae in LPT, while combinations had 95 -100% in 24 hours (F = 0.000). In conclusion, irregular numbers of cattle were dipped with varying concentrations of acaricides, mostly in communal dips, in the County. The acaricides used were still efficacious, especially on larval stages of R. (B). decoloratus, with their combinations having improved efficacies against the adult and larval stages of the tick