The Houghton strain of Eimeria tenella:: a review of the type strain selected for genome sequencing

A landmark decision was taken in 2002 by the Biotechnology and Biological Sciences Research Council ( BBSRC) in the UK to fund the genome sequencing of an eimerian (apicomplexan) parasite from the fowl. The project is a joint collaboration between the Institute for Animal Health (IAH) at Compton, UK and the Wellcome Trust Sanger Institute, Cambridge, UK ( see http:// www. sanger.ac.uk/Projects/E_tenella/ and http:// www.iah.bbsrc.ac.uk/eimeria/). The species chosen, Eimeria tenella, is the best known member of the genus and the Houghton ( H) strain is one of the most widely studied. The H strain was isolated in 1949 in the UK. It was maintained initially at the Houghton Poultry Research Station ( HPRS), Houghton, and, following closure of that laboratory in 1992, thereafter at the IAH in Compton. At various times the parasite has been provided to other institutions and research groups carrying out coccidiosis research in the fowl. The H strain has been utilised in many fundamental studies on the eimerian life cycle and its relationship with the host. It has also been used to investigate the nature of drug resistance, and to derive attenuated lines-one of which, a "precocious line'', is a component of a multivalent live attenuated coccidiosis vaccine (Paracox(R) vaccine, Schering-Plough Animal Health). In this article, some immunological, epidemiological, genetic, and chemotherapeutic investigations with the H strain are reviewed, a summary is provided of the biological characteristics of the parasite and some of the core methods used to prepare purified extracellular life cycle stages for experimental studies or passage are given.