A field study to estimate tick attachment rate (TAR) and duration of feeding period (FD) of Rhipicephalus appendiculatus ticks was carried out in Endulen (Ngorongoro Conservation Area, Arusha Region, Tanzania) between February-April 2002. In the study area, East Coast fever (ECF), caused by Theileria parva, is known to cause high mortality in calves less than 6 months of age. The study was conducted on sentinel calves (age: <3 months) in 3 Maasai herds (bomas), characterised by different tick-control regimes: Boma1, weekly treatment (n=40 calves); Boma2, no-treatment (n=5); Boma3, threshold treatment (n=17). At the beginning of the trial, calves did not show any signs of ECF, neither had they been reported sick nor treated by the owners. Health status of cattle herds was closely monitored to estimate the incidence of tick-borne diseases. ECF diagnosis was made by clinical examination and laboratory confirmation. TAR (mean number of new ticks attaching on each animal/day) and FD (mean number of days each attached tick fed before dropping) were evaluated by using a “tick-painting” technique on 3 calves randomly selected from each boma. Differences in TAR were observed [Boma1: mean 17.5 (range14.7-21.3); Boma2: 21.5 (17.4-21.4); Boma3: 4.3 (4.1-4.5)]. Although Boma2 (no acaricide treatment) had the highest TAR, no clinical cases of ECF were reported during the study period. Cases of ECF were reported in Boma1 (n=21) and Boma3 (n=4). Mean FD was 1.3 days (range 1.25-1.44), but no significant differences were observed amongst bomas. Infection prevalence by T. parva sporozoites in R.appendiculatus salivary glands was assessed using standard staining methods; only one out of 123 ticks examined was positive (0,8%). The results obtained seem to be somehow contradictory as to the ECF epidemiological state in the area (endemic stability in cattle above 6 months of age). Further studies to better elucidate the above findings are needed.
Estimation of attachment rate and infection prevalence by Theileria parva in Rhipicephalus appendiculatus as a measure of biological risk of East Coast Fever in a traditional pastoralist production system in Northern Tanzania
TOMASSONE, Laura;DE MENEGHI, Daniele
2005-01-01
Abstract
A field study to estimate tick attachment rate (TAR) and duration of feeding period (FD) of Rhipicephalus appendiculatus ticks was carried out in Endulen (Ngorongoro Conservation Area, Arusha Region, Tanzania) between February-April 2002. In the study area, East Coast fever (ECF), caused by Theileria parva, is known to cause high mortality in calves less than 6 months of age. The study was conducted on sentinel calves (age: <3 months) in 3 Maasai herds (bomas), characterised by different tick-control regimes: Boma1, weekly treatment (n=40 calves); Boma2, no-treatment (n=5); Boma3, threshold treatment (n=17). At the beginning of the trial, calves did not show any signs of ECF, neither had they been reported sick nor treated by the owners. Health status of cattle herds was closely monitored to estimate the incidence of tick-borne diseases. ECF diagnosis was made by clinical examination and laboratory confirmation. TAR (mean number of new ticks attaching on each animal/day) and FD (mean number of days each attached tick fed before dropping) were evaluated by using a “tick-painting” technique on 3 calves randomly selected from each boma. Differences in TAR were observed [Boma1: mean 17.5 (range14.7-21.3); Boma2: 21.5 (17.4-21.4); Boma3: 4.3 (4.1-4.5)]. Although Boma2 (no acaricide treatment) had the highest TAR, no clinical cases of ECF were reported during the study period. Cases of ECF were reported in Boma1 (n=21) and Boma3 (n=4). Mean FD was 1.3 days (range 1.25-1.44), but no significant differences were observed amongst bomas. Infection prevalence by T. parva sporozoites in R.appendiculatus salivary glands was assessed using standard staining methods; only one out of 123 ticks examined was positive (0,8%). The results obtained seem to be somehow contradictory as to the ECF epidemiological state in the area (endemic stability in cattle above 6 months of age). Further studies to better elucidate the above findings are needed.
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