To the best of our knowledge, this is the first cross-sectional study with a longitudinal follow-up that attempts to investigate the impact of STH infections on the nutritional status of Orang Asli children in Malaysia as well as the possible benefit of deworming on the affected individuals. STH infections, anaemia and malnutrition remain among the major public health problems afflicting underprivileged people, particularly in developing countries . Children from rural communities tend to be more vulnerable due to their low socioeconomic status and social isolation . It is estimated that Asia had the highest number of malnourished children in the world .
The findings of our study indicated that 41.0% of all the subjects examined were anaemic. This is in agreement with the results obtained in previous studies among aboriginal children in Malaysia [14, 15]. A similar prevalence was reported elsewhere [26, 27]. However, lower prevalence rate was reported among the Malaysian adults . The high prevalence reported in this study could be related to the fact that the study population live in remote rural communities with high rate of poverty which contribute to poor access to good diet and proper healthcare.
The results of this study also showed that malnutrition is common among the study subjects. The prevalence of significant stunting, underweight and wasting were; 28.0%, 29.2% and 12.5%, respectively. Our findings were consistent with the results of some previous reports among some Malaysian populations [19, 28, 29]. Higher prevalence of malnutrition was also reported in India , Nigeria , and Brazil . The high prevalence of malnutrition by our study likely reflects the low socioeconomic status of most of the households in Orang Asli communities. Low socioeconomic status relates to poverty which affects the purchasing power of an individual or group, hence affecting the dietary intake. The long established synergism with helminthiasis may also contribute to the high prevalence of malnutrition among these subjects.
Our study showed that age < 10 years was a significant risk factor of anaemia among these children. This is consistent with the findings by Calis et al., who reported that the Malawian pre-school and early school-age children had the highest risk of anaemia. It is also in agreement with the findings of a previous study among Orang Asli children by Al-Mekhlafi et al., which demonstrated that the prevalence of anaemia decreased significantly with age. It is well known that females tend to be more anaemic than males especially in the reproductive age as a result of physiological differences. However in the present study no significant difference in the prevalence of anaemia was found between males and females. Previous studies from Kenya  and Tanzania  demonstrated high prevalence of anaemia among the male compared to the female schoolchildren.
Moderate-to-heavy ascariasis was also found to be significantly associated with anaemia among these subjects. The association between anaemia and intestinal helminthiasis has been reported previously [15, 31]. However, in a previous study among Malaysian adults , no association was found between anaemia and helminth infections, probably due to the very low prevalence of helminth infections. It was suggested that blood loss due to hookworm and T. trichiura infections strongly correlated with worm load . Moreover, it was reported that even light hookworm infections could be associated with lower haemoglobin concentration and higher prevalence of anaemia . Although ascariasis is known to influence the nutritional status, its impact on anaemia is less clear . The strong association between anaemia and moderate-to-heavy ascariasis observed among these children could be attributed to the heavy intensity of infections and the long synergism with other contributory factors such as poverty and poor dietary intake. As a limitation, the present study did not measure the daily iron intake. However, a previous study had shown that the daily iron intake by Orang Asli children in rural Malaysia was only about 29% to 49% of the recommended daily intake .
Our investigation revealed that children below the ages of 10 years old were significantly less stunted compared to those ≥10 years. This is in agreement with previous similar studies [38–40]. It has been established that stunted children continue to deviate from normal growth with increasing age. Hence, the risk of becoming stunted continues as children get older. In this study, male children tend to be significantly more stunted than the females. Male sex, have been reported as a risk factor of stunting in a previous study in Indonesia . Conversely, in a study among under-five children in Nepal, girls were reported to be at higher odds for stunting . We assume that the higher odds of stunting among the boys in our study could be attributed to limited food supply in many households and coupled with the fact that the boys are more likely to suffer from hard tasks at home such as farming, fishing and other domestic upkeep activities.
Our study also demonstrated that moderate-to-heavy intensities of infection with T. trichiura or A. lumbricoides are significant predictors of stunting among the children. This is consistent with the findings from previous studies in Peru , China  and Tanzania . Trichuriasis and ascariasis tend to be very prevalent among children of school age in many endemic areas. More so, STH infections are associated with decreased appetite and low food intake , which result to decreased growth rate, poor fitness, decreased activity and poor cognitive function. Micronutrient losses and nutrient malabsorption due to ascariasis and blood-loss due to trichuriasis can lead to iron deficiency, iron deficiency anaemia and poor growth rate [3, 44].
Post-treatment assessments following anthelminthic treatment showed that the moderate-to-heavy infected children benefitted more from the deworming and gained more weight than the negative-to-light infected children but the difference was not statistically significant. This agrees with previous studies conducted in India , Jamaica  and Guatemala . However, Stephenson et al., reported significant improvements in height and weight among the treated Kenyan school boys harbouring multiple helminth infections at 4 months after treatment.
In the present study, the moderate-to-heavy infected children showed a significant increment in the mean haemoglobin concentration after 3 months compared to the negative-to-light infected children. This is in agreement with a clinical trial conducted among Zanzibari preschool children which reported that anthelminthic treatment using mebendazole, significantly reduces anaemia status among the children . The improvement in haemoglobin levels among the subjects following anthelminthic treatment lead to the assumption that the burden of helminthiases is a significant contributor to anaemia in the population.