Worm Infestation and Child Health in Zimbabwe

Schistosomiasis is one of the major communicable diseases of public health and socio-economic importance in the developing world. More than 600 million people are at risk of infection with schistosomiasis, 207 million are infected and 120 million are suffering from severe morbidity due to schistosomiasis. Soil transmitted helminths (hookworms, Trichuris trichura and Ascaris lumbricoides) infect more than 2 billion people with children being the most at risk age group. Common clinical outcomes of soil transmitted helminths (STHs) include anaemia, impaired physical development, cognition and malnutrition area especially in primary school children. Global estimates indicate 243 million cases of malaria worldwide of which (85%) were reported in African region only. It accounted for an estimated 863 000 deaths in 2008, of which 89% occurred in the Africa alone.

The high prevalence of schistosomiasis, STHs and malaria and the striking similarity of the conditions that favour their survival, reproduction and transmission that include poverty, lack of preventive measures, health care, safe water and sanitary facilities, and the similarity in temperatures conditions, make polyparasitism from these parasites a "norm that an exception" in tropical and sub-tropical areas. Separate studies have shown endemicity of schistosomiasis, STHs and malaria in Zimbabwe and all these studies have demonstrated high prevalence of schistosomiasis, STHs and malaria among primary schoolchildren. Though only single parasite were investigated in separate studies, results from previous studies indicate geographic overlap of helminths and Plasmodium and thus polyparasitism especially in primary schoolchildren. However data is scarce on extend of polyparasitism with schistosomiasis, STHs and Plasmodium malaria in Zimbabwe and else where. Delineation of areas co-endemic for helminthiasis and malaria and the knowledge of the proportion of the population with co-infections is a first step in allocating limited public health resources for integrated control programmes. Using parasitological methods this study sought to determine the distribution of polyparasitism in primary schoolchildren living in rural and commercial farming areas in Zimbabwe.

Prevalence of anaemia among children under 5 years of age in Zimbabwe is 58% (range 55.4%-63.1%) and it is 38% (range 30.7%-47.5%) for women. However the prevalence of anaemia in primary school age children (5-15 years) is not reported. Neither is there a report on the etiology of anaemia in this age group. Data is also lacking on the contribution of STHs, schistosomiasis and Plasmodium falciparum on the reported anaemia prevalence in Zimbabwe although they are major contributors to this disease. There is also a paucity of evidence on the impact of polyparasitism with helminths and Plasmodium on anaemia especially among the most susceptible primary schoolchildren in the developing world including Zimbabwe. These gaps derail policy decisions on appropriate integrated control strategies that should be based on scientific evidence from field studies. The impact of polyparasitism on anaemia among primary schoolchildren living in the commercial farming area was determined in this study.

The growing interest for the global control of polyparasitism by combining different interventions is economically considered cost effective and the global attention is focused on this strategy. However a number of operational research questions including the choice of different integrated control strategies, timing of treatment cycles, feasibility of implementation and impact on prevalence of polyparasitism, and anaemia requires evaluation before rolling out large scale control programmes. A longitudinal study was conducted to investigate the impact of combined regular school based treatment and delayed treatment of parasitic diseases on polyparasitism and anaemia.

Zimbabwe is among WHO member states that have placed control of schistosomiasis, malaria and STHs high on the agenda. Wide spread use of Praziquantel will be inevitable. However whilst global use of Praziquantel is scaling up, there is also a growing concern in the use of this single drug for treatment of a disease affecting more than 200 million people especially in the wake of low cure rates reported in Senegal and Egypt. Consequently recommendations for continued monitoring for Praziquantel resistance under the pressure of wide spread use of the drug have been made. Current data is lacking on the efficacy of Praziquantel in treatment of schistosomiasis in Zimbabwean population. Praziquantel drug efficacy was determined in this study in order to advice health managers on the implications of mass drug administration that is pending as Zimbabwe prepares from mass treatment using the school based approach.

The World Health Organization recommends that any large scale control programme should be preceded by a baseline survey in order to monitor and evaluate control strategies during and after implementation. For the control of helminthiasis, conducting the baseline survey in grade three children (8-10years) is recommended since they harbour the highest prevalence and intensity of infection in the community and can be followed up to at least two years to monitor and evaluate effectiveness of any control strategy implemented. Thus the prevalence of helminths in this age group can be used as an index for assessing community prevalence. However data on Knowledge attitudes and practice (KAP) of grade three children in relation to schistosomiasis, STHs and malaria is lacking. The impact of school health education on behaviour modification of the school children towards prevention of helminthiasis and malaria in Zimbabwe is also scarce. A follow up KAP study was conducted in grade three children before and after school based health education integrated with treatment.