A field study (February 2000 to August 2001) was conducted on communal and commercial farms in the Eastern Cape and North-West Provinces of South Africa to detect the levels of tick resistance to commonly used acaricides. The larvae obtained from engorged females of the one-host tick Boophilus decoloratus, the two-host tick Rhipicepalus evertsi evertsi and the three-host ticks Amblyomma hebraeum and Rhipicephalus appendiculatus were tested against various concentrations of amitraz, chlorfenvinphos and cypermethrin using the Shaw Larval Immersion Test method. Ticks from the communal farms showed higher levels of resistance to cypermethrin and some resistance to chlorfenvinphos whilst no resistance was detected against amitraz. However, ticks from commercial farms were equally resistant to amitraz, chlorfenvinphos and cypermethrin. The B. decoloratus populations tested were considerably more resistant to all the acaricides tested than the R. evertsi evertsi, A. hebraeum and R. appendiculatus populations. This supports the hypothesis that single-host ticks develop resistance faster than multi-host ticks. This trend was recorded on most of the farms where single- and multi-host ticks co-existed. It was concluded that the use of acaricides at high frequencies and high concentrations was one of the main causes of tick resistance in the study areas. Possible factors which caused the resistance problems are discussed and acaricide management strategies recommended.
Abstract Indoor residual spraying (IRS) is one of the key vector control tools with a long history of use in the world. Ethiopia has set a goal to eliminate malaria from selected districts mainly by applying IRS and the distribution of long-lasting insecticidal nets. IRS is applied in low malaria transmission districts which are epidemic prone and in districts with high malaria transmission. Ethiopia uses insecticides that are recommended by World Health Organization; these insecticides must also be registered in Ethiopia. The registration of new and potential products requires confirmatory, local efficacy trials to be performed. Actellic 300CS, now registered, is one of such potential product. Actellic 300CS showed average mortalities of 99.6%, 99.6%, and 99.0% on the sprayed surfaces in the experimental huts, the top, middle, and bottom sections, respectively during the first 6 mo of the study period. Beyond 6 mo, (7, 8, and 9 mo) follow-up, mortalities for the top, middle, and bottom sections were 85.2%, 86.3%, and 85.2%, respectively. The results showed that the residual efficacy of Actellic 300CS was up to 9 mo with the first 6 mo exhibiting mortalities of greater than 99% while the next 3 mo showed mortalities exceeding 85%. Actellic 300CS was effective against fully susceptible laboratory-reared Anopheles arabiensis on all four surface types (rough, smooth, dung, and painted surfaces) tested in this study and could be used as one of the chemical insecticides of choice for the ongoing IRS programs in Ethiopia.
The susceptibility of the larval offspring of engorged female Boophilus decoloratus, and of the engorged females, collected from cattle on the dairy farms Brycedale, Sunny Grove and Welgevind in the Eastern Cape Province, South Africa, was tested against the acaricides amitraz, chlorfenvinphos and cypermethrin. Resistance was determined by means of the Shaw Larval Immersion Test (SLIT) for larvae and the Reproductive Estimate Test (RET) and Egg Laying Test (ELT) for adults. At Brycedale the tests all indicated resistance to chlorfenvinphos, and RET and ELT indicated resistance to amitraz and emerging resistance to cypermethrin. At Sunny Grove, B. decoloratus was resistant to cypermethrin using SLIT and exhibited emerging resistance to chlorfenvinphos with SLIT and to cypermethrin with both RET and ELT. At Welgevind, resistance was recorded against chlorfenvinphos (SLIT) and against cypermethrin (ELT), and emerging resistance against permethrin (RET). The results obtained with RET and ELT were generally comparable, but often differed from those obtained with SLIT. Resistance could be detected within 7 days with ELT compared to 42 days with RET and 60 days with SLIT.
An aqueous emulsion of amitraz (Bovitraz, Bayer AH), prepared and applied according to the manufacturer's recommendations, was evaluated for its activity against cattle ticks on a dairy farm in Ethiopia. Eight crossbred heifer calves aged between 6 and 8 months and heavily infested with ticks were selected and divided into equal treatment and control groups. The calves in the treatment group were hand-sprayed with the amitraz emulsion while the control group was left untreated. Each calf was restrained and ticks were counted and identified in situ. One hundred percent tick control was achieved on Day 3 after acaricide application, and this was maintained for a further 18 days. The residual effect was long, and protected the animals from re-infestation for 21 days. There was a significant difference between the mean number of ticks on the control group compared to the treated group (P 0.05). An important finding in this trial was the rapid detachment of all tick instars from animals treated with the test acaricide.
Ixodid ticks were collected from domestic animals, mainly cattle, in 11 administrative zones covering 84 districts in central Ethiopia over a period of 2 years (July 1996 to June 1998). Nineteen tick species were identified. Four of these belonged to the genus Amblyomma, one to Boophilus, two to Haemaphysalis, three to Hyalomma and nine to Rhipicephalus. Amblyomma variegatum and Rhipicephalus evertsi evertsi were present in all 11 administrative zones and, with the exception of Afar, Boophilus decoloratus was present in nearly every district in which collections were made. These three species constituted more than 50% of all ticks collected. Amblyomma cohaerens and Rhipicephalus bergeoni were common in the west of the survey region and Rhipicephalus pulchellus in the east. Except for B. decoloratus, of which more females than males were collected, the numbers of male ticks recovered were equal to or exceeded those of females. Mortality in crossbred dairy cattle caused by heartwater (Cowdria ruminantium infection) was reported during the survey period. An integrated approach to tick control is suggested.
The efficacy of Deltamethrin 1% pour-on (Smash) and Deltamethrin 1% SC (Pali) against ticks was evaluated on cattle at private cattle farm (04053’03” N; 38008’31” E, altitude of 1620 masl), in Yabello district of Borena zone, Ethiopia. Experimental cattle were divided into three groups. Cattle in Group 1 were each treated with Deltamethrin 1% pour-on (Smash) and cattle in Group 2 were treated with Deltamethrin 1% SC (Pali) while the third group received no treatment and served as a control. During the experimental period (10 to 29 January 2011), the three groups of cattle were attended separately to avoid contacts. A high degree of efficacy of Deltamethrin 1% pour-on (Smash) and Deltamethrin 1% SC (Pali) against singleand multi-host ticks was achieved by a single application of each product. Deltamethrin 1% pour-on (Smash) controlled ticks for 15 days while Deltamethrin 1% SC (Pali) did for 13 days. Deltamethrin 1% pour-on (Smash) shown to be 97.3- 100% effective in the control of ticks from Day 2 to Day 14 post treatment. The percentage tick control achieved by Delthamethrin1% SC (Pali) ranged from 96.5-100% from Day 2 to Day 10 post treatment. The result demonstrated that Deltamethrin 1% when applied as pour-on effectively controlled ticks on cattle than when applied as spray form. Comparative advantage of pour-on application over spraying is that the pour-on application is relatively easier than the spraying when spraying facilities are not available. Pour-on application does not require specialized manpower to perform the operation and pastoralists can easily carry Deltamethrin 1% pour-on (Smash) and can apply while moving with their livestock. Key words : Deltamethrin, efficacy trial, Ixodid ticks, pour-on, synthetic pyrethroids
The efficacy of a flumethrin 1% pour-on (Bayticol, Bayer AH) was evaluated against natural infestations of ticks on cattle on a dairy farm in Ethiopia during 1997/98. The cattle, (n = 92), which were Friesian/ Zebu crosses, were heavily infested with Boophilus decoloratus. Dry cows (n = 8) were randomly selected and allocated either into a treatment or a control group. Flumethrin 1 % pour-on was applied to the treatment group according to the manufacturer's recommendation, i.e. along the dorsal mid-line from the head to the base of the tail. Ticks were counted and identified in situ on treated and control animals. When the total tick counts of the treated group were similar to those on the control, the trial was discontinued. Excellent results were achieved with flumethrin against heavy tick infestations. There was a rapid kill after 24 h post-treatment, and from day 4 onwards 100% control was achieved and maintained for a further 29 days. The results obtained indicate that there was a significant difference between the mean tick counts of the control group compared with those of the treatment group (P < 0,05). The evidence presented here suggests that the flumethrin 1 % pour-on may be applied at 45 day intervals and should provide effective protection against the economically important ticks if it is used at the recommended dosage rate and applied correctly.
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