Microsatellite diversity of isolates of the parasitic nematode Haemonchus contortus

The alarming development of anthelmintic resistance in important gastrointestinal nematode parasites of man and live-stock is caused by selection for specific genotypes. In order to provide genetic tools to study the nematode populations and the consequences of anthelmintic treatment, we isolated and sequenced 59 microsatellites of the sheep and goat parasite Haemonchus contortus. These microsatellites consist typically of 2-10 tandems CA/GT repeats that are interrupted by sequences of 1-10 bp. A predominant cause of the imperfect structure of the microsatellites appeared mutations of G/C bp in the tandem repeat. About 44% of the microsatellites were associated with the HcREP1 direct repeat, and it was demonstrated that a generic HcREP1 primer could be used to amplify HcREP1-associated microsatellites. Thirty microsatellites could be typed by polymerase chain reaction (PCR) of which 27 were polymorphic. A number of these markers were used to detect genetic contamination of an experimental inbred population. The microsatellites may also contribute to the genetic mapping of drug resistance genes.