Detection of high levels of congenital transmission of Toxoplasma gondii in natural urban populations of Mus domesticus

Abstract

The relative importance of different transmission routes of Toxoplasma gondii has been a matter for debate. This ubiquitous parasite is generally thought to be transmitted by infective oocysts excreted by the definitive host, the cat. Ingestion of undercooked meat has also been considered an important route of transmission in many mammals while congenital transmission has generally been considered relatively rare. Experimental studies demonstrate the ability of T. gondii to be transmitted congenitally, but few studies have investigated the frequency of this transmission route in natural populations. We use PCR amplification of the SAG1 gene to investigate the frequency of congenital transmission in a wild population of mice (Mus domesticus) and show that congenital transmission is occurring in 75% of pregnancies in this population. Furthermore, for infected pregnant mice, transmission occurs to at least one foetus in 100% of cases while variable penetrance of congenital infection is observed. These high levels of congenital transmission in this wild population of mice, taken together with other recent data on congenital transmission in sheep, suggests that this phenomenon might be more widespread than previously thought.

Significant familial differences in the frequency of abortion and Toxoplasma gondii infection within a flock of Charollais sheep

“…over several generations) is still to be established. Similar high levels of congenital transmission have recently been reported in other mammals (Mus domesticus and Apodemus sylvaticus) (Owen &Trees, 1998 ;Marshall et al 2004). Furthermore, it is well understood that serial vertical transmission of the closely related parasite Neospora caninum occurs in cattle families (Schares et al 1998 ;Davison, Otter & Trees, 1999) and congenital transmission has been demonstrated in sheep (McAllister et al 1996).…”

The Life Cycle of Toxoplasma gondii in the Natural Environment

“…In rodents, prevalence is generally low (0 -10% [47,46]), which renders comparisons difficult. High seroprevalences have been occasionally reported in brown rats (70% in Italy [48]) and in house mice (59% in rural and sub-urban areas in England [49]). However, these limited data do not permit to draw a clear pattern among environments in rodents.…”

The prevalence ofNeospora caninumand co-infection withToxoplasma gondiiby PCR analysis in naturally occurring mammal populations

“…Collection of samples and DNA extraction House mice (Mus domesticus) used in this study were captured within domestic dwellings in the Cheetham Hill area of Manchester, UK as part of a pest control programme (Marshall et al 2004), brown rats (Rattus norvegicus) were captured in urban areas of Manchester. Tissue was obtained from lambs (Ovis aries) which were either aborted, dead at birth or died shortly after birth from 2 farms and contained individuals from 3 breeds, Suffolk cross, Charolais and Lleyns as described by Duncanson et al (2001), Williams et al (2005) and Morley et al (2005).…”