Originally published as Genetics Published Articles Ahead of Print on October 14, 2008.

Genetics, Vol. 180, 1877-1887, December 2008, Copyright © 2008
doi:10.1534/genetics.108.094623

Genetics of Mating and Sex Determination in the Parasitic Nematode Haemonchus contortus

Elizabeth Redman*, Victoria Grillo*,1, Gary Saunders*, Erica Packard*, Frank Jackson{dagger}, Matt Berriman{ddagger} and John Stuart Gilleard*,2

* Division of Infection and Immunity, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, United Kingdom, {dagger} Moredun Research Institute, Pentlands Science Park, Midlothian EH26 0PZ, United Kingdom and {ddagger} The Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, United Kingdom

2 Corresponding author: Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, 3330 Hospital Dr. NW, University of Calgary, Calgary, AB T2N 4N1, Canada.
E-mail: jsgillea{at}ucalgary.ca

Genetic analysis of parasitic nematodes has been a neglected area of research and the basic genetics of this important group of pathogens are poorly understood. Haemonchus contortus is one of the most economically significant livestock parasites worldwide and is a key experimental model for the strongylid nematode group that includes many important human and animal pathogens. We have undertaken a study of the genetics and the mode of mating of this parasite using microsatellite markers. Inheritance studies with autosomal markers demonstrated obligate dioecious sexual reproduction and polyandrous mating that are reported here for the first time in a parasitic helminth and provide the parasite with a mechanism of increasing genetic diversity. The karyotype of the H. contortus, MHco3(ISE) isolate was determined as 2n = 11 or 12. We have developed a panel of microsatellite markers that are tightly linked on the X chromosome and have used them to determine the sex chromosomal karyotype as XO male and XX female. Haplotype analysis using the X-chromosomal markers also demonstrated polyandry, independent of the autosomal marker analysis, and enabled a more direct estimate of the number of male parental genotypes contributing to each brood. This work provides a basis for future forward genetic analysis on H. contortus and related parasitic nematodes.