Role of seasonal variation on the prevalence and risk factors of trichuriasis among the aboriginal community in Malaysia

Trichuris trichiura, also known as whipworm, is one of the most common soil-transmitted helminths affecting rural and poor communities especially in tropical countries. The infection has been associated with anemia and undernutrition (Freeman et al., 2016). The infection is also attributed to lack of sanitation, sources of poor drinking water and poor hygiene (Adu-Gyasi et al., 2018). Similar to other soil-transmitted helminth infections, trichuriasis is associated with poor socioeconomic conditions including low education level, low household income and poor access to sanitation facilities and clean drinking water (Campbell et al., 2016).

Although the clinical consequences associated with the infection may not pose a major problem, the prevalence of the infection is still high, therefore it is still of public health concern in Malaysia. In addition, it is common in low-income communities including the aborigines, rural and poor Malay community, children in estates and squatter areas (Anuar et. al., 2014).

Development of T. trichiura ova requires optimum temperature and moisture. Transmission of T. trichiura ova is via accidental consumption of egg-contaminated food or drinks (Anuar et. al., 2014). Malaysia is a country with tropical weather and due to the proximity to water, the climate of Malaysia is often humid. As a result of this, Malaysia has the optimum climate for the embryonation of T. trichiura ova. In Malaysia, the infection is still endemic among rural communities, particularly the aborigines (Muslim et al., 2019). Although there are many epidemiological studies associated with T. trichiura infection among the poor communities in Malaysia, there is an absence of studies that determine the seasonal variation in the prevalence and risk factors of T. trichiura infections. To the best of our knowledge, this is the first study to identify the prevalence and risk factors of T. trichiura infections in the aboriginal community during two seasons in Malaysia.

The study protocol was approved by Research and Ethical Committee, Faculty of Medicine, Universiti Kebangsaan Malaysia (FF-2014-219) prior to stool samples collection. Permission for fieldwork was granted from the Department of Orang Asli Development (JAKOA) (JAKOA/PP.30.032Jld29(04)). Prior to the study, informed consent was obtained from all participants and from the parent or guardian (for participants aged 16 years old and below)

Soil-transmitted helminth (STH) infections are important neglected tropical diseases which cause diarrhea, growth retardation, iron deficiency anemia and cognitive impairment. In Malaysia, among all the STH, infection with T. trichuria is the most common, especially among the aboriginal community (Anuar et al., 2014). The present study indicated the overall prevalence of 59.2 % trichuriasis during both seasons which is within the range of previous prevalence studies (Anuar et. al., 2014; Muslim et al., 2019; Mohd-Shaharuddin et al., 2018). Trichuriasis has been reported to be more prevalent than other STH infections regardless of the tribal difference: Mah Meri, a sub-tribe of Senoi, and Temuan, a sub-tribe of Proto-Malay, both have similar trend of precedence of trichuriasis over the other STH infection (Chin et al., 2016). In general, the aborigines in Malaysia have experienced transition state between hunter-gatherer lifestyle towards modernity. The government of Malaysia has demarginalized many of the aborigines by improving existing aboriginal villages and part of the aboriginal villages has been equipped with treated tap water supply. On the other hand, some aboriginal communities are still living and remaining in or near the forested areas (Muslim et al., 2019). The aborigines in the current study are of Senoi tribe and Jahut sub-tribe. They are mainly rubber tappers and farmers while the remaining are government and private sector’s employees. Among the three villages of the study area, only one village, known as Kampung Penderas, is equipped with facilities such as treated tap water supply, electricity, toilets with pit latrine system, primary school, road access to a small town namely the Kuala Krau and several other facilities. The other two villages, known as Kampung Terbol and Kampung Lubok Wong are lack of these facilities, except for road access to other villages and a rainwater storage tank in each village. In terms of customary cultures, only a few of the aborigines who lived in Kampung Penderas are involved in professions in the government and private sectors. Meanwhile, the others spent their days on fishing, hunting, collecting and selling rattans and farming. Despite the effort of the government and public health authorities to improve the lifestyle of some of the aborigines, particularly those with settlements at the downstream of the river, most of them are still living with their common customary cultures and belief. In terms of sanitation and hygiene, most of them still live with a lack of hygiene practices and the utilization of latrines is low. This might explain the reason why trichuriasis is still endemic in the community although many facilities are provided to some of them.

A higher prevalence of trichuriasis during the dry season might be due to heavy rainfall during wet season, which may wash away most of the Trichuris ova on the soil and spread the ova into the wider environment. Daily activities were restricted during the wet season due to heavy rainfall and flood. Since most of the aborigines performed their usual domestic activities which may expose them to the wider environment such as fishing, farming, hunting and others more frequently during the dry season, therefore the risk to contract trichuriasis through contaminated hands was higher.

STH infection is endemic in many parts of the world, particularly in low-income communities (Ediriweera et al., 2019). Low income has been reported to be a strong predictor of various diseases, including intestinal parasitic infections; people with low income significantly had a higher risk to be infected with intestinal parasites (Dai et al., 2019). In this study, a monthly household income of less than RM500 was found to be the significant risk factor for the aborigines to acquire trichuriasis during the wet season with the odds of 1.545. A strong association between low income and health was reported where there is a higher risk of health problems for the low-income groups in comparison with middle to higher income groups (Stronks et al., 1997). Our study found the same association; low income is associated with a higher risk to contract trichuriasis during the wet season. Most of the aborigines could not get their usual earnings during the wet season due to restrictions in movement particularly heavy rainfall and flood. Low income leads to poor medical care, poor nutrition thus increasing the exposure to harmful agents (Syme & Berkman, 1976).

Low education level has been previously suggested by various studies to be associated with soil-transmitted helminth infections (Pham-Duc et al., 2013). Rural communities in Ghana with low education levels had a higher prevalence of soil-transmitted helminths infection in comparison to those with a high level of education (Adu-Gyasi et al., 2018). In agreement with that, our study indicated that aborigines with low education levels had a higher risk to contract T. trichiura infections in comparison to the aborigines with medium to a high level of education during the wet season. The aborigines with low education level are still involved in outdoor activities even during rainy days. Meanwhile, aborigines with medium or high education level restricted their outdoor activities due to worry of the danger and accidents that they may experience while performing various activities such as hunting, fishing, farming, playing and others during the wet season.

Open defecation is a common practice among the aborigines. In our study, we found that this practice is very common since many of the aborigines still hold on their cultural belief to perform such practice. Among the aboriginal community in this study, those who perform open defecation had a higher risk to acquire trichuriasis during the wet season with the odds of 2.740 as compared to the aborigines who defecate in a latrine. Such practice increases their chances to be exposed to many sources of infection in the environment. Besides, aborigines who perform open defecation may not practice proper handwashing after defecation. Open defecation practices among rural community in Ghana as a result of lack of toilet facilities leads to high prevalence of soil-transmitted helminths infection (Adu-Gyasi et al., 2013). A study in India found that although sanitation has been improved, however low usage of latrine among the community leads to no reduction in soil-transmitted helminths infection (Clasen et al., 2014; Patil et al., 2014). Soil moisture and relative humidity are among the factors which influence the survival of viable ova of soil-transmitted helminths (Gyawali, 2018). In our study, open defecation practice during the wet season may have spread the ova to a wider area. With optimum soil moisture and humidity, this may have contributed to infection among the aborigines during the wet season.

Utilisation of untreated water was the major risk factor that increased the transmission of intestinal parasitic infection among the aboriginal community (Chin et. al., 2016). In line with that, Moktar et al., (1998) reported usage of untreated water sources from well water was the risk factor for trichuriasis among aboriginal children. The present study identified usage of untreated tap water supply which originated from rivers and wells for domestic activities as a significant risk factor to acquire T. trichiura infection during the dry season with the odds of 2.253. Open defecation at the open field may introduce Trichuris ova into the water bodies such as rivers, well water and other water sources by various means, such as rainfall. Besides that, open defecation is performed at the river bench; hence the non-infective ova can become infective via exposure to the soil.

Activities such as washing, bathing and others at the river bench may introduce the infective ova into the river water. Natural water bodies especially river water are one of the most important sources of water used for daily activities within the community. As described previously, untreated tap water from the river was used daily and the river water was collected and stored in the houses by the most of the aborigines although several houses located at the downstream of the river are equipped with treated water supply (Noradilah et al., 2017). Water contaminated with helminth ova pose significant public health risks where people may be infected by exposure to the contaminated water such as wastewater and sludge (Gyawali, 2018). In our study, river water contaminated with fecal materials serves as an important source of infection to the aboriginal community. Using tap water originating from the contaminated river through various activities such as cooking preparations, washing, bathing and others and consuming untreated tap water via food or drinking water put the aborigines at higher risk to contract trichuriasis during the dry season.

This study also identified an association between T. trichiura infection and the other STH, namely Ascaris lumbricoides and hookworm infection, respectively during both seasons. Since soil is required for the development of the infective egg, therefore this might explain the association between T. trichiura infection and the other STH in the aboriginal community. Giardia lamblia was also found to be associated with T. trichiura infection during the dry season. Giardia cyst is known to survive in the soil and the mode of transmission is similar for both T. trichiura and Giardia via the faeco-oral route.

This study highlighted that low socioeconomic status contributes to high prevalence of trichuriasis in the aborigines living in Kuala Krau, Temerloh, Pahang especially during the wet season. In addition, unhygienic lifestyle and behavior play important roles in the acquisition of trichuriasis. Unsafe water supply used for daily activities during the dry season puts the aborigines at high risk to contract trichuriasis. Provision of treated water supplies, health education, access to sanitation facilities and promotion of good health behavior such as high usage of a proper latrine for defecation are hoped to reduce the prevalence of trichuriasis among the aboriginal community.