Resistance to benzimidazoles and levamisole in nematode parasites of sheep in Nyandarua district of Kenya

• Published in: Acta tropica Vol. 69; no. 1; pp. 31 - 40
• Main Authors: Maingi, N, Bjørn, H, Gichohi, V.M, Munyua, W.K, Gathuma, J.M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-1998; Elsevier
• Subjects: Animals; Anthelmintic resistance (AR); Antibiotics. Antiinfectious agents. Antiparasitic agents; Antinematodal Agents - pharmacology; Antinematodal Agents - therapeutic use; Antiparasitic agents; Benzimidazoles - pharmacology; Benzimidazoles - therapeutic use; Biological and medical sciences; Drug Resistance; Egg hatch assay (EHA); Faecal egg count reduction test (FECRT); Haemonchus - drug effects; Kenya; Larval development assay (LDA); Levamisole - pharmacology; Levamisole - therapeutic use; Medical sciences; Nematodes; Pharmacology. Drug treatments; Sheep; Sheep - parasitology; Tropical medicine; Kenya; Africa; Nematodes; Sheep; Anthelmintic resistance (AR); Larval development assay (LDA); Faecal egg count reduction test (FECRT); Egg hatch assay (EHA); Anthelmintic; Levamisole; Parasitosis; Helminthiasis; Infection; Vertebrata; Chemotherapy; Mammalia; Sensitivity resistance; Treatment; Animal; Benzimidazole; Nematode disease; Digestive diseases; Artiodactyla; Clinical isolate; Ungulata
• ISSN: 0001-706X; 1873-6254
• DOI: 10.1016/S0001-706X(97)00109-5

The occurrence of anthelmintic resistance on 25 sheep farms in the Nyandarua District of Kenya was investigated, using the faecal egg count reduction test (FECRT), the egg hatch assay (EHA) and a larval development assay (LDA). In the FECRT, resistance to both benzimidazoles (BZs) and levamisole (LEV) was detected on four farms, resistance to LEV only on three farms and to BZs, only on two farms.
Haemonchus contortus was the predominant nematode species in both pre-treatment and post-treatment faecal cultures. Out of the six farms where BZ resistance was detected in the FECRT, only isolates from one farm had an LD
50 value higher than 0.5
μM thiabendazole (TBZ) (0.1
μg TBZ/ml) in the EHA indicating resistance. Isolates from three other farms, where susceptibility to BZs was detected and four with suspected BZ resistance in the FECRT, had LD
50 values higher than 0.5
μM TBZ in the EHA. The LD
50 values for TBZ in the LDA for four of the six isolates with BZ resistance in the FECRT were higher than 0.5
μM (0.59–2.07) TBZ. There were disagreements in ascribing resistance for various farms, between methods of calculating and interpreting the faecal egg count reduction percentages (FECR%) based on the arithmetic mean, and those where the geometric mean eggs per gram (EPG) of faeces are used. Inclusion of pre-treatment EPG or control group EPG in the calculation of FECR% resulted in similar variations.