This study focused on the investigation of T. gondii
infection among indigenous communities in Malaysia using standard commercial kits to detect their seropositive titer specific for anti-Toxoplasma
IgG and IgM antibodies and determine the current seroprevalence of T. gondii
infection and risk predictors. About one-third of the Orang Asli had latent toxoplasmosis, which indicated that they had previous exposure to this infection. To our surprise, this prevalent rate (37.0%) was comparatively much higher than the previous studies carried out in Malaysia, which varied from 10.6% to 17.5%.8,11,12,13
Certain factors such as sample size, locations, and differences in serodiagnostic tests may have contributed to a sharp rise in the prevalence of toxoplasmosis in these indigenous populations.
The seroprevalence rate of toxoplasmosis in Malaysian indigenous people is comparable with that of indigenous people in Taiwan (40.6%),1
and Thailand (37.9%).15
However, other studies among Taiwan indigenous people have reported a lower seroprevalence of 19.4% to 21.8% in Atayal,16
26.7% in Paiwan,17
and 9.1% in Akka17
subgroups. In contrast, seroprevalence rates among indigenous people in Brazil18
have been relatively high: 73.5% and up to 88.0%, respectively. This global status on T. gondii
infection indicates that, although these minority people stay in different geographical locations, they still experience similar poor sanitary living conditions. Epidemiological surveillances are, therefore, essential to investigate the trend of T. gondii
infection in these marginalized communities.
Apart from the prevalence of latent/chronic T. gondii
infection, the present study also found that, by using IgG avidity, 21 (4.2%) samples positive for both IgG and IgM antibodies were also confirmed as recently acquired infection. IgG avidity has recently been tested in a single serum sample and was found to be effective for diagnosis of acute toxoplasmosis in pregnant women and other adults.24,25
In this present study, there were no pregnant women involved. Additional study is, therefore, recommended to be carried out on a larger scale, particularly in screening women of reproductive age, to prevent the risk of congenital transmission.
The present study also showed that there are certain factors contributing to T. gondii
infection in this community. It is interesting to note that a high seroprevalence rate was found among females of this community. There were 33 IgG seropositive and 7 IgG/IgM seropositive in 55 women aged above 12 years. However, there was no significance with gender, suggesting that the rate of infection for T. gondii
is not sex related or that the differences observed are not crucial. Moreover, it has to be highlighted that activities performed by men and women among these communities are different and that most of them had varying degrees of frequent contact with risk factors. Although there was no pregnant woman who participated in this study, toxoplasmosis is an important parasitic disease, which can be congenitally transmitted to the fetus from a primary infected pregnant mother. Therefore, we recommend additional study to include the investigation of seroprevalence and associated risk factors of toxoplasmosis among pregnant women in these communities. Studies have shown that women are susceptible to acute T. gondii
infection during the childbearing years and therefore, increasing risk of congenital toxoplasmosis.26
Results also showed that the seroprevalence rate was comparatively higher in those participants above 12 years old compared with those participants below 12 years. In addition, the seroprevalence rate also showed significant heterogeneity among age groups in which infection rate increases with age. A recent study among Brazilian indigenous groups has also indicated that the frequency of infection with T. gondii
increases with age.27
This finding is most probably because of the fact that, with an increase of age, the probability that an individual may be associated with at least one of the mechanisms of transmission also increases.28,29
Nonetheless, the high frequency of toxoplasmosis among young age groups suggests that these children have already been exposed to the risk for acquiring the infection. They may acquire infection from unhygienic habits, such as putting contaminated hands into their mouths. During the visit to each village, children were noted playing with soil and sand outside their houses. Because of their young age, many children are still not fully aware of personal hygiene and good cleanliness practices or realize the significance of exposing themselves to pathogenic organisms. This condition is also aggravated by some degree of negligence and lack of parental supervision in personal hygiene and cleanliness, such as in cases where both parents were working and not at home to supervise the children. They were frequently exposed to infection and reinfection because of lack of proper parental guidance. Therefore, educational efforts targeting mothers are needed so that they can, in turn, teach children about cleanliness and personal hygiene.
In the present study, the villagers' most common livelihood is small-scale animal husbandry (e.g., pigs, chickens, and ducks). The villagers also keep dogs, cats, monkeys, rabbits, and birds, and the majority of these domestic animals are left to roam freely. Occasionally, dogs would be observed following their owners into the jungle to hunt. The villagers have very close contact with dogs and cats. These animals were observed sharing food from the same plate with their owners and sleeping on the clothing racks. They defecate outdoors promiscuously, and some cats also defecate indoors, especially near the fire wood in the kitchen area.
This situation is exacerbated by the type of kitchen flooring, which is usually made of mixed soil and sand, providing an ideal condition for the development, survival, and transmission of the Toxoplasma
oocyst. Some of the domestic and stray cats that live in close proximity to these people may acquire infection while hunting and foraging (especially those cats eating wild prey that act as intermediate hosts, such as mice, rats, an birds). They may also defecate in the kitchen, and they are capable of shedding millions of oocysts in their feces during primary infection, thus spreading oocysts inside the house. These oocysts remain infectious for months in the tropic soil environment.30,31
In addition, roaches and flies can also serve as transport hosts, because they have access to cat feces in the soil or kitchen area, which was shown experimentally.32
Nevertheless, these potential transport hosts were not examined in the present study and should be considered in the future study.
Thus, it was not surprising that our results showed that close contact with pets, especially cats, played a significant role in facilitating the transmission of T. gondii
. It has also been reported in a previous local study that high prevalence of toxoplasmosis is significantly associated with close contact with cats among the Peninsular Malaysia indigenous community.12
This finding was also consistent with other studies reported from Taiwan1
Based on the overall results obtained, these indigenous communities were possibly exposed to the infection through T. gondii
oocysts excreted from infected cats that contaminate soil. Therefore, it is imperative to promote awareness of this parasitic infection through educating this community on the importance of collecting cats' feces in litter boxes, discarding them properly, spaying cats to reduce overpopulation, and most importantly, washing hands before eating, after gardening, and after contact with soil.
Water-borne toxoplasmosis associated with drinking water contaminated with T. gondii
oocysts has since been reported in some large-scale outbreaks.33–40
In the present study, using untreated river and mountain water for domestic needs (i.e., drinking, cooking, bathing, and washing clothes) was also identified as a risk factor for acquiring the infection. The majority of the indigenous communities, especially those people living in rural and remote areas, totally rely on rivers located adjacent to the village as their main source of water. A possible source of infection could be the consumption of water contaminated with T. gondii
oocysts from feces of infected wild or domestic felines, because they may come to the river bank to drink and at the same time, defecate in or near the river. In support of the present study, similar findings were found among indigenous women in Taiwan1
and in a multiethnic Indian community in Brazil.18
In addition, from our personal communication with the villagers, drinking of unboiled (especially mountain water) or improperly boiled water is a common practice in this community.
Significant correlation between consumption of unboiled water and the seropositivity of toxoplasmosis has been noted in many studies, particularly among disadvantaged and indigenous communities living in rural and remote areas.38,40–42
Therefore, these communities, especially women of childbearing age and particularly pregnant women, should be given health education on the danger of drinking unboiled or improperly boiled water. Given the significant role of water in the transmission of toxoplasmosis as shown in this study, other ways of transmission by contaminated water, such as washing of vegetables with untreated water before eating, should be further investigated in the future, because it has been shown to be a significant risk factor of infection in one recent study.42
The lack of a significant association with eating with hands is rather surprising. However, this finding could be because of the fact that eating with hands is a general practice among these communities: almost all of the participants (98.4%) eat using their hands. In fact, eating with hands without proper washing could be the source of T. gondii infection through accidental ingestion of oocysts, especially after contact with contaminated soil or cleaning up cat's feces.
In general, this indigenous population lives near or within the forest, and game hunting is a common practice for the adults in most of these subgroups. Although data on meat consumption were not collected in this study because of the traditional cultural taboo, beliefs, and sensitivity in some subgroups, it is believed that eating raw or undercooked meats, especially hunted wild animals (i.e., wild feline and canine, which also can be definitive and intermediate hosts, respectively for T. gondii
), is a common practice among these indigenous populations. This practice could be an explanation for the continued exposure to infection because of the higher consumption of infected game meat, particularly among the adults. A previous study among these indigenous communities also reported that adults who were involved in hunting activities were more likely to acquire toxoplasmosis compared with other family members.8
Thus, these communities should also be advised on the importance of eating well-cooked meat, especially hunted wild prey, to avoid acquiring toxoplasmosis from tissue cysts in raw or improperly cooked meat.
In conclusion, this study showed a high seroprevalence rate of T. gondii infection among Peninsular Malaysia indigenous people. Increased age, use of untreated river and mountain water for daily chores, and close contact with pets (i.e., cats) were significant risk factors for acquiring Toxoplasma infection in these communities. This epidemiological study has provided baseline data for future studies to be carried out among other minority groups living in different parts of Peninsular Malaysia. A health surveillance program on toxoplasmosis and effective preventive measures should be initiated, especially among pregnant women during their antenatal visit, to facilitate early diagnosis and treatment. Educating these communities on the various ways of acquiring toxoplasmosis is also crucial, and they should be provided with the proper knowledge to effectively prevent the transmission of this disease in their communities.