INTRODUCTION

Ascaris lumbricoides is one of the soil-transmitted helminthes (STH) and is known to be the largest intestinal round­worm of humans. It is a cosmopolitan intestinal parasite with a high prevalence in poor and socio-economically deprived communities in the tropical and sub-tropi­cal areas and is more common in child­ren. About 25% of the world's popula­tions are infected by A. lumbricoides and this causes up to a million cases of the disease annually. Poverty, overcrowded living conditions, poor environmental sa­nitation and lack of health education are the factors related to the intestinal hel­minthic infection (Norhayati et al. 2003). Several studies have demonstrated a high prevalence of A. lumbricoides infec­tion among Orang Asli (Aborigines) child­ren in Malaysia (Norhayati et al. 1997; Mohamed Kamel et al. 2001; Hesham Al-Mekhlafi et al. 2007) where the preva­lence of ascariasis ranged between 33.3% - 69%.

The objectives of this study were to determine the prevalence of A. lumbricoides infection among 1-12 years old Orang Asli children in Pos Lenjang, Pahang and to evaluate the outcome of the concentration technique compared to direct faecal smear in detecting Ascaris infection.

MATERIALS AND METHODS

Subjects and study area

Pos Lenjang is an aboriginal settlement in Pahang, situated about 320 km from Kuala Lumpur. The aborigines are from the Semai tribe and the village comprises a very small population. After an in­formed consent was obtained, stool containers were distributed to the popu­lation. A total of 71 faecal samples were collected from children aged between 1-12 years old of which 31 were boys and 40 girls.

Faecal parasitological examination

Each faecal sample was subdivided into two parts: one part was unfixed (fresh sample) and the second part was fixed with 10% formalin.  Both types of sam­ples were examined for the presence of A. lumbricoides ova. The fresh samples were screened immediately in the field using the direct faecal smear technique and two smears were made from each sample. Meanwhile, the formalin-fixed samples were examined later using the formalin-ether concentration technique at the Parasitology Laboratory, Department of Biomedical Science, Universiti Ke­bangsaan Malaysia

RESULTS

Seventy one faecal samples were ex­amined using direct faecal smear and formalin-ether concentration techniques. Out of 71 children, 30 (42.3%) were found to be positive for A. lumbricoides. The prevalence of Ascaris infection was higher (45.2%) in males compared to females (40%) (p>0.05). A higher preva­lence was also found among the school-aged children (48.6%) as compared to the preschool children (35.3%) (p<0.05) (Table 1).

Of the 30 positive samples, the formalin-ether concentration recorded a detection rate of 100%  (30 of 30) while the direct faecal smear technique detected only  46.7% (14 of 30) of the total positive samples (p<0.05)(Table 2).

DISCUSSION

The overall prevalence of ascariasis in this study was 42.3% which revealed that A. lumbricoides infection was common among the Orang Asli children in Pos Lenjang, Pahang. This finding is in agreement with previous studies done in Malaysia where the overall prevalence of Ascaris in 1-12 year-old Orang Asli child­ren reported were 62.9% (Norhayati et al. 1997) and 59.5% (Rahmah et al. 1997). It should be noted that these studies were done at different study areas. Two more recent studies conducted among 2-15 year-old Orang Asli children from different study areas have reported similar findings with 61.9% prevalence of ascariasis (Hesham Al-Mekhlafi et al. 2006; Nor Aini et al. 2007).­ In other local studies involving the Orang Asli commu­nity where all age groups were included, the results showed a 33.3% (Mohamed Kamel et al. 2001) and 25.7% (Lokman Hakim et al. 2007) prevalence rate of the infection.

According to Zulkifli et al. (2000), the prevalence of the STH infection is closely related and dependent on socio-eco­nomic and hygiene conditions.During the study, the Orang Asli’s ac­tivities, basic facilities and environmental conditions were observed.Like other disadvantaged communities in Malaysia, the Orang Asli at Pos Lenjang also belongs to a lower socioeconomic group.  Be­cause of the poor educational level of the villagers, they work as farmers, animal hunters and traders of forest products. Due to low family income, the children live in poor-conditioned houses. Most of the houses in this village were inhabited by large families. This overcrowded living condition may enhance the faecal–oral transmission among the children in this community.

Poor personal hygiene was observed among the Orang Asli children due to the lack of knowledge about health and hy­giene practices. Hand washing before eating and after defecation was not reg­ularly practiced by the children. They also ate raw food especially fruits without washing them first. The disease trans­mission may be enhanced among this population group who fail to practice good personal hygiene. Based on the review prepared by Fung & Cairncross (2009), there was some evidence impli­cating that the practice of hand washing is effective in reducing the prevalence of Ascaris infection.

Lack of basic facilities such as safe drinking water, proper housing and proper sanitary and garbage disposal render the Pos Lenjang community es­pecially the children vulnerable to Ascaris infection. There was very limited number of stand pipes provided in this Orang Asli village. Several families had to share one pipe for their needs and therefore, the existing stand pipes could not supply enough water to all families in the village. Therefore they had to resort to alterna­tive sources and the river played an im­portant role as a source of water for them. They used water from the river for daily activities such as washing clothes, bathing, cooking and drinking. Toilets were not available and generally the vil­lagers, especially children, were inclined to defecate indiscriminately among the bushes close to their homes. Besides bushes, some of the villagers used the river as a defecation site and using river water to clean themselves. The improper disposal of excreta practiced by this community will increase the risk of Ascaris infection among the children. A number of studies have reported that in­adequacy of safe water supply (Norhayati et al. 1998) and poor sanitary disposal (Norhayati et al. 1998; Hesham Al-Mekhlafi et al. 2007) were the signifi­cant risk factors for ascariasis in Orang Asli communities. According to Luong (2002), the optimum development of Ascaris occurs in moist warm soils where the eggs develop into an infective stage. The conditions in the Pos Lenjang area may be favourable for the development of Ascaris. The soil is suitable for hel­minth´s egg survival and transmission since there are many shady areas from the presence of many trees contributing to the high prevalence of Ascaris infec­tion among the children in this commu­nity.

This post has no accessible road for the provision of adequate garbage disposal. Hence, piles of garbage were left ex­posed and unattended which attracted flies, cockroaches and other pests. A re­cent study showed that the housefly is a potential mechanical vector for STH in­fection, which could spread the infection by transmitting the infective eggs of hel­minthes to the community with poor sa­nitary conditions (Maipanich et al. 2008).

Based on the review carried out by Kan (1988), there was little difference in the distribution of helminthes infection be­tween genders, especially boys and girls as they share similar socio-behavioral activity. In this study, males showed a slightly higher prevalence of infection at 45.2% as compared to females 40%, which were not significant statistically. 

The result of this study showed that the highest prevalence of Ascaris infection was among the schoolchildren (48.6%) as compared to preschool children (35.3%). Bundy et al. (1988) and Norhayati et al. (1997) have reported that the prevalence of Ascaris was signifi­cantly increased with age. Results from another study performed on children in Gombak by Rajeswari et al. (1994) showed that the prevalence of Ascaris increased reaching a peak in the 9-year age group (15.2%). Sagin et al. (2002) also reported that Ascaris infection was more common among children aged 6-14 years than in children below 6 years old who lived in the Bakun Valley, Sarawak. The possible reasons for the obvious difference in the preva­lence between age groups are probably due to the children´s habits and exposure. Children aged 7-12 years spend more time out of the house. Therefore, they have higher chances of exposure to the infective agent especially when playing on contaminated soil. On the other hand, the younger preschool children are usually under constant su­pervision by their parents and spend more time indoors thus reducing expo­sure. 

In this study, the faecal specimens were examined for the presence of Ascaris ova by two techniques namely the direct smear and the formalin-ether concentration.  Based on the results, the formalin-ether concentration was found to be the more sensitive in detecting Ascaris ova in faeces with a detection rate of 100% as compared to 46.7% with the di­rect smear (p<0.05). In this study, two faecal smears were made from the single stool specimen collected, the result could be different if more stool samples were examined for direct faecal smear. A pre­vious study (Oguoma & Ekwunife 2007) reported that 9.47% of A. lumbricoideswas detected by the concentration technique while 5.26% was detected by the direct smear. They suggested that the concen­tration technique is a very useful tech­nique in diagnosing intestinal helminthes since it depicted a higher percentage of helminthes infection missed by the direct smear technique. Thus, it is recom­mended that both techniques (the direct smear and concentration techniques) be performed in routine parasito­logical examination for a more accurate diagnosis before any control efforts be implemented in the affected areas.

Ascariasis is still very prevalent among the Orang Asli children at Pos Lenjang, Pahang and it is one of the major causes of public health problems among Orang Asli communities in Malaysia that needs to be addressed.

ACKNOWLEDGEMENT

We would like to thank Ms. Shafariatul Akmar, Mr. Rahman from Parasitology Laboratory, Universiti Kebangsaan Ma­laysia for their field and technical assis­tance. We would also like to express our gratitute to the Kuala Lipis Health and Orang Asli Department for their invalua­ble assistance and support throughout this study.