الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
Toxoplasma gondii is one of the most prevalent chronic infections, affecting one third of the world’s human population. Infection with T. gondii is usually asymptomatic; however congenital transmission of the parasites in pregnant women can produce serious complications in the fetus. Health education and systematic serological screening of pregnant women are the most reliable and currently available strategies for the prevention, diagnosis, and early treatment of the infection in the offspring; this is largely because toxoplasmosis in pregnant women most often goes unrecognized.
Meanwhile, studying the genetic diversity of T. gondii is of a considerable medical importance for understanding epidemiological patterns as well as heterogeneity in disease manifestations or for developing new strategies for vaccination, treatment and diagnosis.
This study was designed to detect the prevalence of T. gondii infection, with reference to some relevant risk factors, in high risk pregnant women with complicated pregnancy outcomes attending Women’s Health Hospital at Assiut University. Also, the study aimed to confirm recent Toxoplasma infection in some selected cases in a trial to characterize the infecting Toxoplasma strain.
In the present study, 182 pregnant women were screened by ELISA test to detect anti-Toxoplasma specific IgG and IgM antibodies in the participants’ sera. Forty-two seropositive cases were randomly selected to be diagnosed by IgG avidity test and conventional PCR technique on the trophoblastic and/ or placental tissues. Then, a multiplex nPCR-RFLP technique was used to characterize Toxoplasma genotype in 29 PCR-positive cases.
T. gondii infection showed high prevalence rate (68.7% of cases). 40.1% of subjects were IgG seropositive indicating that they were immune to Toxoplasma infection. On the other hand, 31.3% of subjects were seronegative meaning that they were susceptible to primary infection. With respect to Toxoplasma risk factors, significant relationships were found between Toxoplasma seropositive cases and residency in rural areas, consumption of milk or dairy products, contact with soil, and eating undercooked meat or viscera.
The rate of probable acute Toxoplasma infection was 28.6% in all participants. The IgG avidity test confirmed recent infection in 66.7% of the selected 42 cases. PCR analysis showed higher positivity rate of these selected cases to be 78.5%. The sensitivity and specificity of avidity test in comparison with PCR test were 72.7% and 55.6%, respectively, indicating that IgG avidity test could be used as a valuable tool in diagnosis of recent T. gondii infection in conjunction with other screening tests. However, PCR analysis is a superior test in postnatal diagnosis of congenital toxoplasmosis.
On genotype analysis, all samples were successfully amplified at (5’- 3’ SAG2) and SAG3 genes except 41.4% and 79.3% of samples failed to be amplified with GRA6 and BTUB genes, respectively. The genotype analysis of restriction pattern of the amplified genes revealed the presence of genotype I in all restricted samples and one sample with atypical restriction pattern.
In conclusion, we report high prevalence for T. gondii infection among pregnant women with adverse pregnancy outcomes in Assiut Governorate. The significant risk factors presented herein might represent potential sources of infection to seronegative women. This study also highlights the need for combining specific serology with confirmatory tests as IgG avidity test or PCR to formulate a specific approach for diagnosis, effective treatment and prevention of fetal complications. Also, type I strain was found to be responsible for severe cases of congenital toxoplasmosis with bad obstetric outcomes mostly abortion cases. Besides, the absence of amplification products or restriction pattern with certain genes in some samples may be attributed to the presence of mutations or polymorphisms in the primers’ binding site of these isolates, raising the possibility of mixed or recombinant genotypes. It is recommended to perform further sequencing of these genes to detect such genetic polymorphism in future studies.
To the best of our knowledge, this is the first time to perform genotype analysis study based on Multiplex nPCR- RFLP technique for genetic characterization of congenital T. gondii infection in Egypt. Not only but also, it is the first time to prove that the most prevalent strain of T. gondii, responsible for congenital toxoplasmosis in Assiut governorate, is the highly virulent type “I”.