Schistosoma mansoni and Soil Transmitted Helminth (STH) Infections among Pregnant Women Attending Primary Health Care Facilities in Lagos Mainland, Nigeria

In a cross-sectional survey among consented pregnant women, rapid diagnostic test (RDT) for malaria was carried out and stool examination was done to detect the presence of Schistosoma mansoni and soil transmitted helminthes using Kato-Katz technique. Intensity of infection was expressed as the number of eggs per gram (epg) of faeces. Prevalence of soil transmitted helminthes was 8.3% and 0.83% for Schistosoma mansoni while none was positive for malaria infection. Lack of co-infection with malaria could be connected with the intermittent preventive treatment with sulphadoxine pyrimethamine (IPTp-SP). Public health impact of soil transmitted helminthes and schistosomiasis infections in pregnancy may necessitate initiation of preventive treatment of helminth infections during pregnancy.


Introduction
Approximately 85% of the Neglected Tropical Diseases (NTD) disease burden results from helminth infections. Targeted control on school children is often advocated and is usually the main operation in sub-saharan Africa due to limited resources. However, exclusion of other groups, oftentimes comprising the adult population, makes re-infection almost inevitable in low resource rural endemic regions of the developing countries. These neglected groups (pregnant women Journal of Biosciences and Medicines are inclusive) which are believed not to be sufficiently exposed to infection and often left untreated could serve as reservoirs of infection, bringing the distribution of the disease to pre-control level over time [1]. Hookworm infection occurs in almost half of Sub-saharan Africa's poorest people, including 40 -50 million school-aged children and 7 million pregnant women in whom it is a leading cause of anaemia. Schistosomiasis is the second most prevalent NTD after hookworm [2]. An estimated 40 million women of child bearing age suffer from schistosomiasis [3] while recent estimates suggest that 819 million people worldwide are infected with A. lumbricoides, 465 million with T. trichiura, and 439 million with hookworm [4]. The risk of the individuals suffering from Soil Transmitted Helminth (STH) infection related morbidity appears to be a joint function of the number of species harboured and/or the infection intensity of any species [5]. Therefore the significance of co-infection of Schistosoma mansoni and soil transmitted helminthes in developing countries cannot but be emphasized taking into cognizance the significant morbidities attributed to these infections which include malnutrition, growth retardation, anaemia, vitamin A deficiency, and impaired intellectual performance [6]. This is even more among the vulnerable population such as pregnant women with suppressed immunity due to their pregnancy status. A number of studies have highlighted the significance of co-infection among different strata of the population but there are limited available epidemiological data on pregnant women. This study assessed the prevalence of these infections among pregnant women in Lagos.

Materials and Methods
A cross-sectional survey was carried from June to October 2016 at two Primary Health Care facilities located in Lagos Mainland Local Government Area, Lagos, Nigeria. Consented pregnant women were recruited and semi-structured questionnaires were administered to the pregnant women to obtain demographic and risk factors information. Rapid diagnostic test (RDT) for malaria (SD BIOLINE Malaria Ag P.f/Pan) was carried out for each pregnant woman. Thick and thin blood smear were done on same slide for those that were positive by RDT. Blood was also collected into heparinized capillary tubes for the estimation of packed cell volume (PCV). Stool examination for the presence or absence of Schistosoma mansoni and soil transmitted helminthes was carried out using Kato-Katz technique. The intensity of infection of the species of worms was expressed as the number of eggs per gram (epg) of faeces. The required sample size for this study was calculated based on 95% confidence level and 5% marginal error. Sample size (n) was determined using the formular as described by Araoye [7], ( )

Ethics Statement
The study protocol was reviewed and approved by the Institutional Review

Discussion
Ascaris lumbricoides was the most common soil transmitted helminth infection moderate to high malaria transmission in Africa [8] [9]. Though, A. lumbricoides infections are commonly asymptomatic, clinical complications of extra-intestinal or high numbers of ascarids have been well described [10]. The presence of hookworm and Ascaris lumbricoides infections could be responsible for blood loss as observed by van Ejik et al. [11] in Kenya and therefore soil transmitted helminthes could be regarded as a major cause of anaemia in these pregnant women having ruled out malaria infection using RDT. Also the anaemia observed in the only pregnant woman with moderate Schistosoma mansoni infection according to WHO [12] could be buttressed by other studies that evaluated the association of S. mansoni with pregnancy outcomes which have demonstrated an increased risk for anaemia, preterm deliveries, and low birth weight infants [3]. The significant statistical relationship between light A. lumbricoides infection and mild anaemia was consistent with the findings of Larocque et al., [13] in Peru.

Conclusion
This finding confirms the public health impact of soil transmitted helminthes and schistosomiasis infections in pregnancy. This may necessitate initiation of preventive treatment of helminth infections during pregnancy.