Prevalence and abundance of tick genera and their control in Merino sheep in the four agro-ecological zones of Lesotho

Abstract

Ticks are blood sucking ecto-parasites that transmit haemoparasitic diseases and cause other ill-health problems such as traumatic dermatitis, anorexia and weight loss which leads to total loss in productivity of the sheep industry in Lesotho. In order to help farmers to control ticks infestation, a survey study was conducted with the following specific objectives: (i) to evaluate farmers’ demographic structure in different agro-ecological zones of Lesotho. (ii) to evaluate level of awareness of merino sheep farmers on ticks’ infestation in their flocks in different agro-ecological zones of Lesotho (iii) to determine commonly used control measures for ticks by merino sheep farmers in different agro-ecological zones of Lesotho (iv) to determine effect of agro-ecological zone and age of sheep in prevalence of tick genera in merino sheep of Lesotho and (v) to evaluate the efficacy of ivermectin in the control of ticks in different agro-ecological zones and sheep age groups of Lesotho. For the demographic study, a total of 403 respondents were interviewed using a structure questionnaire and a total number of 720 sheep were used for the remaining objectives. Ticks were collected and transferred into sample containers containing 70% ethanol kept in labelled screw-lid container before identification in the laboratory using a stereomicroscope. The efficacy of Ivermectin (1%) was determined using the following formula as prescribed by Abbott (1925): Efficacy % = 100 x (Mc – Mr)/Mc; Mc = mean number of live ticks on the host; Mr = mean number of live or dead ticks on host after treatment. Drug efficacy of 0.5 is threshold for medium tick response ratio. The data from 403 respondents was stored in Microsoft excel and analyzed using descriptive statistics. Binary logistic regression was used to analyse the data for ticks’ prevalence, age and ivermectin efficacy on ticks’ infestation. Data on ticks’ concentration was analyzed by Poisson model. The results showed that the majority of sheep farmers were males with a distribution of 67% in lowlands, 66% in foothills, 58% in highlands and 64% in Senqu River Valley (P > 0.05). Farmers in all four agro-ecological zones had very high level of awareness for ticks’ infestation - Lowlands (99.0%), Foothills (100.0%), Highlands (97.9%) and Senqu River Valley (97.3%) (P > 0.05).79%, 70%, 86% and 58% of farmers in Lowlands, Foothills, Highlands and Senqu River Valley, respectively used various drugs combinations (both traditional and conventional) to control ticks. Overall prevalence for different tick genera was 40% with Rhipicephalus having higher prevalence and abundance than other genera: Rhipicephalus (36%), Boophilus (0.7%), Amblyomma (0.4%), Hyalomma (0.2%) and Otobius (0.5%). Most ticks were in abundance under tail and around the anal region. The prevalence of ticks did not vary significantly (P > 0.05) with age of sheep. Ivermectin 1% subcutaneous injection overall efficacy was 28% and reduction percentages for major genera (Rhipicephalus) were as follows: Senqu River Valley (36%), Lowlands (46%), Foothills (70%) and Highlands (100%). In conclusion, the current study has established that (i) there are more male than female farmers in all agro-ecological zones (ii) farmers’ awareness of ticks infestation is very high in all the four agro-ecological zones (97-100%) (iii) All farmers routinely used both traditional and conventional drugs to control ticks (vi) Age of sheep did not significantly affect the prevalence of ticks in all agro-ecological zones and (v) The overall efficacy of 1% ivermectin was 28%.