Malnutrition is an underlying cause of over half of child deaths in many developing countries and affects the physical, mental, social wellbeing and child development. Malnutrition is associated with lower enrollment and poor cognitive functioning among children attending school [1,2,3].

In Uganda, an assessment of school children aged 9–15 years in 2006–2007 revealed that 8.7%, 13% and 10.1% were stunted, underweight and thin respectively [4]. In comparison, several studies in Ghana, Tanzania, Indonesia, Vietnam and India found stunting and underweight to be high, ranging between 48% to 56% for stunting and 34% to 62% for underweight [5,6].

Globally an estimated 100 million people have been reported to have experienced stunting or wasting as a result of worm infections [7]. The nutritional status of people infected with helminths is altered through a decline in food intake and/or an increase in nutrient wastage through blood loss, vomiting or diarrhea [8]. These effects can lead to or aggravate protein energy malnutrition, anemia and other nutrient deficiencies.

In Africa, 90 million school-age children are estimated to be infected with soil transmitted helminths [9]. School-age children are more predisposed and vulnerable to helminth infections compared to other age groups [9,10,11,12]. A total of 40–50 million school-age children in sub-Saharan Africa were reported to be infected with hookworm in the year 2009 [11]. A study among 20,185 school children in Uganda revealed that 6.3%, 5.0%, 43.5% were infected with Ascaris lumbricoides, Trichuris trichiura and hookworms respectively [13].

Elimination of helminth infections can improve the nutritional status of children. The provision of periodic anti-helminth treatment in Uganda and Zanzibar has been reported to be associated with an increase in weight gain of 10% above expected [14,15]. The WHO resolved to have a 75% to 100% de-worming coverage among school-age children in countries where the prevalence of helminth infections is more than 50% [16]. In Uganda, despite the ongoing 7 year de-worming program, helminth infections remain a major health problem. The Wakiso District monthly reports of 2009 show that 23% of the 171,472 children aged below 5 years that attended the health units were infected with intestinal worms.

It is not known whether after carrying out routine de-worming for over 7 years, intestinal helminth infections still remain an important factor in the causation of malnutrition among children attending primary schools in Uganda. This study therefore, aimed at establishing whether helminth infections should be given priority as a risk factor for malnutrition among children attending primary schools in this District and Uganda in general.

The study revealed that 22.5% of the children were stunted, 5.3% underweight and 18.5% had moderate acute malnutrition. The prevalence of helminth was 16% with a low intensity of infection. The prevalence of stunting revealed by our study is lower than that reported among school children in Ethiopia of 26.5%; China; 25.6% and India 37% [22,23,24]. One explanation for the lower prevalence of stunting in this community could be the lower helminth infection prevalence and intensity of infection compared to settings where both helminth and stunting levels are high. Moderate-to-heavy intensity helminth infections have been reported to be a risk factor for the high stunting prevalence among school children [23]. A study in Nepal also revealed that out of the 818 primary school children assessed, 65.8% were infected with helminths and 61% were malnourished [25].

The prevalence of stunting was found to be significantly higher among children attending urban slum schools (14.1%) than among those in rural schools. A study by Amuta et al. also revealed a higher prevalence of malnutrition among children attending schools in urban slum settings of Nigeria [26]. It is possible that food insecurity may be one of the contributing factors. The socio-economic conditions of the parents/families in urban slum may be poorer than for the population in rural areas who may have agricultural fields and therefore have better access to and food security.

The study showed that the prevalence of underweight was low compared to that reported in other countries. Several studies by Medhi et al., Osei et al., and Nitish et al. done in Indian school children showed an underweight prevalence of 51.7%, 60.9% and 44%, respectively [5,24,27]. Fitsum et al. also reported a high prevalence of underweight of 58.3% among school-age girls in Ethiopia [22]. The low prevalence of underweight reported in our study may be attributed to the routine de-worming programme that has been running in the country since 2003. A number of studies reveal that de-worming can lead to increase in weight among those de-wormed. Provision of periodic anti-helminth treatment as part of child health services in Uganda resulted in an increase in weight gain of 10% above expected when treatments were given twice a year and an increase of 5% when treatment was given annually [14]. A randomized double blind study on Ascaris infested children aged 2–12 years in Dhaka (Bangladesh) also revealed a statistically significant weight gain among children given anti-helminths than those given placebos [28].

The prevalence of Underweight and MAM was significantly higher among children aged 10–14 years compared to those aged 6–9 years. These findings agree with Del Rosso’s conclusion that nutritional status does not improve with age [1]. The extra demands that come as children grow (like increased play or walking long distances to school) create a need for energy that is much greater than that of pre-school and early-school goers. Indeed, the majority (78.5%) of the children recruited in this study were teenagers aged between 10–14 years.

The prevalence of acute malnutrition (wasting) of 18.5% established by this study is somewhat similar to that reported by Medhi et al. and Nitish et al., of 21.2% and 21.5%, respectively, among Indian school children [5,27]. The presence of moderate acute malnutrition among school goers is an indication that severe form acute malnutrition might exist in the community among school-age children however; this study may not have been able to capture them because a severely acutely malnourished child cannot attend school.

The study revealed a significantly higher prevalence of underweight and moderate acute malnutrition (MAM) among boys than girls. Our results are consistent with those of Ingunn Marie et al. and Mupfasoni et al., which showed that boys are more vulnerable to malnutrition compared to girls [29,30]. The biological, psychosocial and cognitive changes associated with rapid growth and development in teenagers directly affect their nutritional status and nutrient needs. These needs are however, different for boys and girls [31].

The study showed that 16% of the children were infected with intestinal helminth. The prevalence of these infections in this study is lower than that reported by Kabatereine et al. [13,32]. The fact that the studies by Kabatereine et al. were undertaken only 2–3 years after starting a country wide de-worming policy as compared to this done after 7 years might explain the lower prevalence of helminth infections revealed by this study. Thus the policy of child days plus during which de-worming of children take pace may be having some effects.

The study revealed that children who were last de-wormed more than 6 months to the time of research were twice more likely to be infected with helminths than those last de-wormed less than six months. This may suggest that helminth re-infections may be occurring frequently during the year. This may be associated with poor sanitation environment in which the children live in the urban slums and rural communities.

Children attending rural schools had a higher risk of being infected with helminth infections compared to those in the urban slums. These findings are not different from those of Stoltzus et al., where hookworms were more prevalent among the rural Pemba island school children than those in the urban areas [33]. It is important to note that none of the children investigated had a moderate to heavy form of infection. All (16%) the infected children had a very light intensity of infection. It is possible that the de-worming campaign that has been running in this country since 2003 could have reduced the prevalence and intensity of the helminth infections.

The study showed that acute and chronic malnutrition is high among children attending primary schools. Urban slumming is a risk factor for chronic malnutrition while early adolescence and being a male child are a risk to acute malnutrition. Therefore programs directed towards improving the nutritional status of school children should be formulated, monitored and periodically evaluated. Such programs should treat males and teenage school goers as children more vulnerable to malnutrition and thus make special arrangements for improvement of their nutritional status.

The study revealed that 26.6%, 46% and 10.3% of the incidences of stunting, underweight and moderate acute malnutrition (MAM) cases respectively are attributable to the potential effects of intestinal helminthes infections. The study also showed that, 5.8%, 79% and 19.1% of the incidences of stunting, underweight and MAM in the total population of primary school goers in this district are attributable to intestinal helminthes infections. These findings do not differ much from those of Shang who mentioned moderate-to-heavy intensity helminthes infections a risk factor for the 25.6% stunting prevalence among school children in China [23].

Basing on the findings of this study, the following conclusions can be made: