A pilot study on screening for gestational/congenital toxoplasmosis of pregnant women at delivery in the Eastern Province of Saudi Arabia

This prospective study measured the overall incidence of congenital Toxoplasmosis, both patent and ‘silent’ infection, among pregnant women in the Eastern Province of Saudi Arabia.
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Toxoplasmosis is an endemic zoonotic disease caused by the protozoan parasite Toxoplasma gondii (T. gondii) that infects all warm-blooded animals (e.g. members of the cat family Felidae) and humans, who serve as intermediate hosts. The parasite T. gondii can persist in humans (and other animals) for long periods of time, possibly even throughout life. The parasite can cross the intestinal epithelial barrier, disseminate throughout the body, and localize in the placenta, causing increasingly large focal lesions. 

Toxoplasmosis remains a significant cause of morbidity and mortality, and outbreaks of T. gondii infection pose a serious public health threat, particularly in developing countries. Toxoplasma can be transmitted from mother to fetus in approximately 40% of cases when pregnant women become infected with T. gondii during pregnancy, resulting in abortion or fetal abnormalities.

Approximately 25–30% of the world's population is infected with Toxoplasma, with rates varying widely between countries (10–80%) and often between different communities in the same region. In Saudi Arabia, prevalence studies have shown that 29.5–35.6% of pregnant women were infected with T. gondii during pregnancy.

Until recently, only a few studies have been conducted on the incidence of maternal and congenital Toxoplasmosis in Saudi Arabia. This prospective study aimed to measure the overall incidence of congenital Toxoplasmosis, both patent and ‘silent’ infection, among pregnant women in the Eastern Province of Saudi Arabia. Furthermore, the study attempted to relate the cord blood results with the time of seroconversion in the mother, underlining the importance of early intervention in such cases. Since the detection of parasites in cord blood by PCR is a practical and cost-effective approach to the early neonatal diagnosis of congenital Toxoplasmosis.  A sample, which is often obtained either at the end of the first trimester or in the second or third trimester, is the only source of information about whether a fetus is at risk. It was further hypothesized that this pilot study would serve as a basis for developing a neonatal screening policy in the Eastern Province of Saudi Arabia, as the Kingdom lacks a newborn screening strategy for early diagnosis and treatment of infected infants. 

Five hundred paired maternal/cord blood samples were tested for the presence of IgG or IgM antibodies to Toxoplasma. Samples were collected at the time of delivery from the mother (age ranged from 16 to 45 years) and the neonate (cord blood). Only positive cord blood samples with IgG and/or IgM antibodies to Toxoplasma were processed for confirmation by real-time PCR.

The results showed that 21.0% (n = 105) of mother/child pairs were serologically positive for IgG antibodies to Toxoplasma. Maternal seropositivity for Toxoplasma IgM antibodies was found in 4 participants (0.8%) who were also seropositive for Toxoplasma IgG antibodies. No children tested positive for Toxoplasma IgM antibodies, even those born to IgM-positive mothers. All 105 cord blood tests in the study sample were confirmed negative by real-time PCR. Seroprevalence of IgG antibodies to Toxoplasma increased with maternal age, parity, and was significantly higher in women who gave birth to children with congenital anomalies.

The cumulative findings of this pilot study indicate that detection of parasite DNA in cord blood by PCR is an important and cost-effective tool for diagnosing neonates likely to be infected with T. gondii. This test has better sensitivity and is relatively inexpensive compared to serologic tests currently used in Saudi diagnostic laboratories. However, the benefits of early treatment using currently available regimens have not been evaluated in a randomized controlled trial, and the optimal duration of treatment is unknown. Alas, since there is no official notification of congenital Toxoplasmosis infections in Saudi Arabia, the true number of cases is unknown. If national prenatal antibody screening programs were introduced in Saudi Arabia, 79% of non-immune pregnant women would need to be serologically monitored before delivery. In essence, the potential benefit relates not only to the initiation of specific treatment for Toxoplasmosis but, importantly, to the identification of this susceptible group of infants who require a full clinical assessment and facilitating their inclusion in early intervention services as needed.

Finally, it was also suggested that preventive programs against T. gondii infection, a health education program on how to avoid Toxoplasmosis for all seronegative women during pregnancy, and screening of all newborns for congenital Toxoplasmosis by the Saudi National Board of Health could theoretically be a cost-effective approach to the prevention and treatment of this health condition.

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