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The efficacy of strategic anthelmintic control of liver flukes (Fasciola) and gastrointestinal (GI) nematodes on the performance of ewes and lambs on pasture was assessed on a farm in the highlands of Kenya. In May 1999, 45 Corriedale ewes, aged between 2 and 3 years, were ear-tagged, weighed and allocated randomly to three equal treatment groups based on body weight. Faecal samples taken at this time revealed low levels of strongyle-type eggs per gram of faeces (EPG) and the presence of liver fluke eggs in only a few of the animals. All the animals were then set stocked for 12 months on separate paddocks in an area endemic for both Fasciola and GI nematodes. The ewes in group 1 were given a combined anthelmintic treatment against Fasciola and GI nematodes during the periods recommended for the control of Fasciola in the area (February, June and October). The ewes in group 2 were given the combined treatments 3 weeks after the onset of both the short and long rainy seasons (November and April, respectively). Those in group 3 were given separate treatments for Fasciola (February, June and October) and nematodes (3 weeks after the onset of the rainy seasons). The anthelmintic treatment against Fasciola consisted of triclabendazole at 10 mg per kg body weight, and that against nematodes was levamisole at 10 mg per kg body weight. The nematode EPG for the ewes in group 1 were higher than in groups 2 and 3 during both rainy seasons. The nematode EPG did not differ significantly between groups 2 and 3. The prevalence of Fasciola eggs (number of ewes shedding eggs in a group) in the ewes in groups 1 and 3 remained very low throughout the study period compared to those in group 2. The highest birth weights and the weight gains of lambs were recorded for the group of ewes given separate anthelmintic treatments for Fasciola and nematodes (group 3). The results of this trial indicated that, in an area like Nyandarua District, where liver flukes and GI nematodes are important constraints to sheep production, the best practice is to give separate treatments for the two groups of parasites at the recommended times.

The anthelmintic efficacy of benzimidazoles, levamisole, rafoxanide and ivermectin was evaluated on an institutional farm in Kenya using faecal egg count reduction test, larval cultures and a controlled slaughter trial. The results of this study indicated simultaneous resistance of Haemonchus contortus against benzimidazoles, levamisole and rafoxanide and Trichostrongylus columbriformis and Oesophagostomum sp. against levamisole on the same farm. Injectable and orally administered ivermectin was effective against the benzimidazole and levamisole resistant H. contortus.

The efficacy of morantel sustained release trilaminate (MSRT) bolus against gastrointestinal nematodes was evaluated under field conditions over a 10-month period. Twenty weaner calves were randomly divided into 2 groups of 10 calves each and grazed from March to December on adjacent, similarly contaminated paddocks. Group 1 calves (T-1) served as untreated controls while group 2 calves (T-2) were dosed at turnout with MSRT bolus designed to release morantel tartrate continuously for 90 days. The efficacy of MSRT was assessed by comparison of parasitological data (faecal worm egg counts, herbage larval counts, worm counts from tracer calves and set-stocked trial calves, determination of haematological parameters and pepsinogen levels), weight gains and clinical status of the animals. Faecal egg counts from the treated group (T-2) were reduced by 100% (P < 0.001) following treatment and remained significantly (P < 0.05) lower than counts from T-1 calves up to trial termination. The use of MSRT bolus resulted in a reduction of 92% (P < 0.001) in the number of gastrointestinal nematodes in set-stocked calves at the end of the study and a 55 to 85.7% reduction in herbage larval infectivity as reflected in lowered parasite burdens in tracer calves. At the trial termination, the control calves had gained on average (+/- s.d.) 59.4 +/- 4.8 kg (200.0 +/- 7.4 g day-1) and the treated ones on an average 128.6 +/- 10.5 kg (530.0 +/- 13.1 g day-1).

Forty-nine sheep artificially exposed to a thiabendazole (TBZ) resistant isolate of Haemonchus contortus were assigned to 7 groups of 7 animals each and used to conduct a controlled anthelmintic trial. One group of sheep served as untreated infected controls and 6 groups were treated as follows: closantel, 5.0 mg kg-1; ivermectin, 0.2 mg kg-1; oxfendazole, 5.0 mg kg-1; thiophanate, 50 mg kg-1, levamisole, 7.5 mgkg-1 and thiabendazole, 66 mg kg-1. Eggs per gram of faeces were determined on days 21, 24 and day 34 (10 days post-treatment) after infection and all animals were necropsied for residual worm counts. The calculated efficacies of the treatments against H. contortus as indicated by worm reduction were closantel (100%), ivermectin (99.3%), oxfendazole (35.2%), thiophanate (56.7%), levamisole (98.6%) and thiabendazole (24.3%). The data therefore indicate that the TBZ-resistant isolate of H. contortus used was highly resistant to the 2 benzimidazole (BZ) anthelmintics, oxfendazole and thiophanate. This is the first report in Kenya of a field strain of H. contortus resistant to thiophanate.

Une etude preliminaire a ete menee entre janvier et mai 2006 pour enqueter sur la prevalence des helminthes et leurs lesions pathologiques chez quatre especes de poisson. Au total, 43 poissons frais de la riviere Tana, vendus au marche de Gikomba, ont ete achetes et autopsies. Ces poissons etaient 15/43 (34,9%) de l'espece Oreochromis, 11/43 (25,6%) Clarias spp., 10/43 (23,2%) Cyprinus carpio et 7/43 (16,3%) Barbus spp. A l'autopsie, on a trouve plusieurs vers Contraceacum au troisieme stade larvaire dans la cavite abdominale, les muscles et derriere les branchies. Au total, 91% des poissons-chats (Clarias spp.) et 20% des tilapias (Oreochromis spp.) avaient une infestation « moderee a grave » de vers Contraceacum. L'intensite de l'infestation variait entre 1 et 593 helminthes par poisson, ce qui a provoque une grave peritonite et l'adherence sur les organes visceraux. Au microscope, les helminthes causaient une forte infiltration des heterophiles, des macrophages, des plasmocytes et la fibrose des organes. Il y avait une atrophie de la pression de l'epithelium du canal biliaire chez un tilapia, qui a ete causee par un tenia migrateur pleurocercoide, un protozoaire Cryptocotyle incruste sur l'arc branchial, et des lesions parasitaires granulomateuses sur les parois des intestins. Les autres lesions observees etaient des hemorragies, des ulceres et des blessures sur les nageoires, autour de la bouche et sur la peau. Les resultats de cette etude montrent que les poissons de la Riviere Tana sont infestes par les helminthes qui provoquent de graves lesions pathologiques chez les poissons affectes. Ces poissons peuvent aussi servir de reservoirs de ces parasites pour les poissons d'aquaculture. Bulletin of Animal Health and Production in Africa Vol. 56 (1) 2008: pp. 38-46