Use of molecular tools to investigate the prevalence and transmission routes of Toxoplasma in woodmice and humans

Toxoplasma gondii is an important pathogen of humans and domestic livestock and isa major cause of abortion. It is widely distributed amongst mammals and birds and theepidemiology of human disease is complex due to the interactions between humanand animal hosts. Cats are the definitive host for the parasite and rodents are believedto be involved in propagation of the parasite in cat populations. The aims of this studywere to use molecular biological methods to investigate parasite transmission in wildrodents and humans.In this study, the prevalence of Toxoplasma was determined in a natural population ofwoodmice (Apodemus sylvaticus) which probably have infrequent interaction withcats. The prevalence (49%) was compared with an urban rodent population (59%)which definitely does interact with cats. No significant difference in prevalence wasfound.Toxoplasma gondii is found as three major clonal lineages - type I, II and III.Although several methods exist for typing strains, these were not always found to besensitive enough to detect the parasite in infected tissue samples. In this study animproved test for determining the strain types of Toxoplasma was developed based onthe "rep" DNA elements. This method could distinguish type I and II strains but couldnot distinguish type III. As a more effective method for typing was published duringthe course of this study, it was decided that no further effort would be invested inattempting to modify the technique to work with type HI strains.To investigate transmission routes for Toxoplasma in humans, a study was designedto specifically measure vertical transmission. A collection of human DNA sampleswas made from subjects in Miserata hospital in Libya. Following ethical consent procedures, DNA was extracted from foetal (umbilical cord) tissue discarded at birthand transported to the UK for testing for Toxoplasma. One hundred and twenty threesamples were collected from 121 mothers. With the exception of two mothers, all ofthe pregnancies were successful. Clinical records were obtained at the time of birth,analysed and showed that the sample characteristics (eg birth rate, sex ratio etc)appeared to be representative of the Libyan population in general. These sampleswere tested for Toxoplasma, using the SAG-1 PCR system to determine the rate ofvertical transmission. The rate of vertical transmission in this cohort was found to be20.1% which is very high compared to many published studies using serology. Noassociation of Toxoplasma infection was found with intra uterine foetal death(abortion), previous abortion or pre-eclampsia toxaemia. The results are discussed inthe light of other published literature.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2007

Author dc:creator

• Gerwash, OM

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1337159

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1337159