PCR identification of Trypanosoma lewisi , a common parasite of laboratory rats

Trypanosoma (Herpetosoma) lewisi is a trypanosome of the sub-genus Herpetosoma (Stercoraria section), parasite of rats (Rattus rattus and Rattus norvegicus) transmitted by fleas. T. lewisi has a stringent species specificity and cannot grow in other rodents such as mice. Rats are infected principally by oral route, through contamination by flea faeces or ingestion of fleas. Trypanosoma lewisi infections in rat colonies can interfere with research protocols and fleas of wild rats are often the source of such infections. Currently, diagnosis of T. lewisi in rats is performed by microscopic observation of stained blood smears. In the course of a research project at CIRDES, a T. lewisi infection was detected in the rat colony. In this study we evaluated PCR primer sets for their ability to diagnose multiple species of trypanosomes with a single amplification. We show that the use of ITS1 sequence of ribosomal DNA provides an efficient and sensitive assay for detection and identification of T. lewisi infection in rats and recommend the use of this assay for monitoring of T. lewisi infections in rat colonies. Background Trypanosoma (Herpetosoma) lewisi was first reported by Kent in 1880 and subsequently by Laveran and Mesnil in 1901. It is a trypanosome of the sub-genus Herpetosoma (Stercoraria section). A parasite of rats (Rattus rattus and Rattus norvegicus), that is transmitted by fleas: Nosopsyllus fasciatus, in temperate countries, and Xenopsylla cheopis in inter-tropical areas [1]. T. lewisi can also develop in Ctenocephalides canis (dog flea), Leptopsylla segnis (mouse flea) and Pulex irritans (human flea) which can act as reservoirs [1]. As T. lewisi is specific to rats, it cannot grow in mice. Rats are infected principally by oral route, through contamination by flea faeces or ingestion of fleas [2]. Some Herpetosoma, like the mouse trypanosome Trypanosoma musculi, have a similar strict host specificity, but others, like Trypanosoma rangeli, can infect a wide range of hosts [1]. All trypanosomes of the sub-genus Herpetosoma are non-pathogenic to their vertebrate host, it has even been reported that rats infected by T. lewisi, and mice infected by T. musculi have a quicker growth-rate and reach a heavier weight than those which are not infected [1]. However, it has been suggested that infection of rats by T. lewisi can increase their sensitivity to other parasites [3]. We have found that serial passages from mixed infections of rats with T. vivax and T. lewisi leads to the apparent elimination of T. vivax over 5 passages (unpublished data). Obviously, in using rat models to research trypanosomosis, it is important to confirm that rats used are free of infection Published: 29 May 2002 Kinetoplastid Biology and Disease 2002, 1:2 Received: 8 April 2002 Accepted: 29 May 2002 This article is available from: http://www.kinetoplastids. com/content/1/1/2 © 2002 Desquesnes et al; licensee BioMed Central Ltd. Verbatim copying and redistribution of this article are permitted in any medium for any purpose, provided this notice is preserved along with the article's original URL.