Water quality effects on organophosphate acaricidal efficacy against the Rhipicephalus appendiculatus ticks. A case of Glenlussa and Sunnyside, Zvimba East District, Mashonaland West Province, Zimbabwe

Cattle losses due to January disease caused by the vector, Rhipicephalus appendiculatus , which transmits Theileria parasite, is a major constraint to livestock productivity. Farmers in Glenlussa and Sunnyside rely on scarce water and mostly organophosphate based acaricides for the vector control. Tick persistence post-dipping using recommended dose sparked interest to investigate effect of water quality on organophosphate acaricidal activity against Brown-ear ticks. Water was analysed at EMA laboratories. Susceptible ticks were collected from Southern-side Lake Chivero Recreational Park. A RCBD was used with two factors, water and acaricide concentration, each at four levels, and treatments replicated in 3 blocks. Engorged adult female ticks were immersed for 30 minutes in serial dilutions at 25 o C of organophosphate (3.75, 5, 5.75 and 6.25% m/v), with open-well, pond, weir + stream and borehole water. Ticks, incubated at 27 o C and 80% RH to oviposition (7 days), had mortality recorded at varying post-exposure times. Results were analysed using Excel and SAS two-way analysis of variance (ANOVA). At 5% m/v recommended dose, July open-well water had highest mortality (73.3%) and no significant difference (p>0.05) in mortality observed among the four water sources. January borehole water recorded highest mortality (73%). Ca, Mg, NO3- and carbon waste effluent contributed to water hardness which, though not always, resulted in significant difference (p0.05). LC99.9 was >6.25% m/v concentration. Water quality influenced organophosphate efficacy. The study suggested need to vary acaricide concentration with season for higher tick mortality. Keywords: acaricide; January disease; pollution; susceptible; water quality DOI: 10.7176/JAAS/85-01 Publication date: January 31 st 2026