Epidemiological Characteristics of Strongyloidiasis in Inhabitants of Indigenous Communities in Borneo Island, Malaysia

Ineffectiveness of TF-Test® and Coproplus® Methods in Strongyloides stercoralis Infection Diagnosis

PURPOSE

S. stercoralis diagnosis is currently performed by parasitological methods, mainly by Baermann-Moraes (BM), although Agar Plate Culture (APC) presents a higher sensitivity. New techniques, such as TF-Test® and Coproplus® have been suggested as more practical alternatives. The aim of this study was to evaluate the sensitivity of TF-Test® and Coproplus®, compared with APC, BM and Spontaneous Sedimentation (SS) methods.

METHODS

One-hundred and forty male alcoholic patients, who provided three stools samples collected on alternate days, were included in this study. The most frequently found parasite was S. stercoralis, 20% (28/140), and the most sensitive method was APC, 96.4% (27/28), followed by BM, 89.3% (25/28) and SS, 57.1% (16/28). TF-Test® and Coproplus® presented a sensitivity of 46.4 (13/28) and 39.3% (11/28), respectively. In samples with a parasitic load of 1-10 larvae/g of feces, which occurred in 39.3% (11/28) of the infected patients, both the TF-Test® and Coproplus® methods demonstrated sensitivities of 18.2% (2/11), while APC and BM methods reached a sensitivity of 100% (11/11) (p < 0.05). For other intestinal helminth infections, TF-Test® and Coproplus® sensitivities were 22.2 (4/18) and 11.1% (2/18), respectively, this being lower than the SS, 66.7% (12/18) (p < 0.05). On the other hand, for protozoa infection diagnosis, TF-Test® and Coproplus® presented the highest sensitivities, 62.2 (46/74) and 43.2% (32/74), respectively.

CONCLUSION

TF-Test® and Coproplus® methods presented the lowest sensitivities for S. stercoralis and other helminth infection diagnosis; therefore, they can be indicated for use in parasitological diagnosis, only when associated with other more effective methods of helminth identification.

Prevalence and risk factors of strongyloidiasis among schoolchildren in Sabach Sanjal and Upper Badibou districts in the North Bank East Region of The Gambia

Background

Strongyloidiasis is a parasitic disease that mainly affects humans and is caused by a roundworm called Strongyloides stercoralis. It is endemic in humid tropical regions that include Africa, Latin America and Southern Asia. Among the public health important soil-transmitted helminths (STHs) classified as neglected tropical diseases, S. stercoralis is the most neglected. A study of schistosomiasis and STHs mapping was conducted and S. stercoralis larvae were detected using the utilized diagnostic method; thus, this current study described the prevalence and risk factors of S. stercoralis infection in districts of Sabach Sanjal and Upper Badibou in The Gambia.

Methods

The cross-sectional study enrolled 851 schoolchildren, ages 7 to 14 years old. The participants were enrolled from 17 schools in Sabach Sanjal and Upper Badibou Districts. The WHO random sampling technique n/50 (25 boys and 25 girls) was used. Stool samples were collected from each participant and Kato-Katz smear method was used to screen for S. stercoralis infection.

Results

Out of the total 851 pupils, 76 pupils (8.9%) were positive for S. stercoralis infection. The mean age of infected persons was 10.1 years (±2.2). The prevalence of infection was higher among females (9.2%) than males (8.7%). Rates of infection for age categories 7–10 years and 11–14 years were 12.4% and 4.2%, respectively. Rates of infection by districts were 12.3% for Sabach Sanjal and 7.1% for Upper Badibou. Schoolchildren from Sabach Sanjal were 1.6 times more likely to have strongyloidiasis compared to those from Upper Badibou (aOR = 1.64, p-value = 0.058). Schoolchildren aged 7–10 years were 3.2 times more likely to have strongyloidiasis infection compared to the 11–14-year-olds (aOR = 3.20, p-value <0.001). Schoolchildren who ‘sometimes’ have water or tissue after defaecation have more infection rate compared to those who ‘always’ have water or tissue after defaecation. However, this difference was not statistically significant (aOR = 1.36, p-value = 0.308).

Conclusion

The study revealed the prevalence of strongyloidiasis in Sabach Sanjal and Upper Badibou districts of The Gambia. Kato-Katz technique might be inadequate for detecting S. stercoralis; thus, more studies are needed to determine the true prevalence of the disease in these two districts through the combined use of highly sensitive techniques such as Baermann, Koga Agar Culture and polymerase chain reaction.

Assessing seroprevalence and associated risk factors for multiple infectious diseases in Sabah, Malaysia using serological multiplex bead assays

Background

Infectious diseases continue to burden populations in Malaysia, especially among rural communities where resources are limited and access to health care is difficult. Current epidemiological trends of several neglected tropical diseases in these populations are at present absent due to the lack of habitual and efficient surveillance. To date, various studies have explored the utility of serological multiplex beads to monitor numerous diseases simultaneously. We therefore applied this platform to assess population level exposure to six infectious diseases in Sabah, Malaysia. Furthermore, we concurrently investigated demographic and spatial risk factors that may be associated with exposure for each disease.

Methods

This study was conducted in four districts of Northern Sabah in Malaysian Borneo, using an environmentally stratified, population-based cross-sectional serological survey targeted to determine risk factors for malaria. Samples were collected between September to December 2015, from 919 villages totaling 10,100 persons. IgG responses to twelve antigens of six diseases (lymphatic filariasis- Bm33, Bm14, BmR1, Wb123; strongyloides- NIE; toxoplasmosis-SAG2A; yaws- Rp17 and TmpA; trachoma- Pgp3, Ct694; and giardiasis- VSP3, VSP5) were measured using serological multiplex bead assays. Eight demographic risk factors and twelve environmental covariates were included in this study to better understand transmission in this community.

Results

Seroprevalence of LF antigens included Bm33 (10.9%), Bm14+ BmR1 (3.5%), and Wb123 (1.7%). Seroprevalence of Strongyloides antigen NIE was 16.8%, for Toxoplasma antigen SAG2A was 29.9%, and Giardia antigens GVSP3 + GVSP5 was 23.2%. Seroprevalence estimates for yaws Rp17 was 4.91%, for TmpA was 4.81%, and for combined seropositivity to both antigens was 1.2%. Seroprevalence estimates for trachoma Pgp3 + Ct694 were 4.5%. Age was a significant risk factors consistent among all antigens assessed, while other risk factors varied among the different antigens. Spatial heterogeneity of seroprevalence was observed more prominently in lymphatic filariasis and toxoplasmosis.

Conclusions

Multiplex bead assays can be used to assess serological responses to numerous pathogens simultaneously to support infectious disease surveillance in rural communities, especially where prevalences estimates are lacking for neglected tropical diseases. Demographic and spatial data collected alongside serosurveys can prove useful in identifying risk factors associated with exposure and geographic distribution of transmission.

Serological assays for the diagnosis of Strongyloides stercoralis infection: a systematic review and meta-analysis of diagnostic test accuracy

The standard method for the diagnosis of Strongyloides stercoralis, stool examinations, is inconvenient and, therefore, serological methods have been proposed. This study aimed to evaluate the accuracy of serological assays for the diagnosis of strongyloidiasis using a systematic review and meta-analysis model. Four electronic databases were reviewed. We used a random effects model and 95% CIs to determine the overall sensitivity, specificity and diagnostic odds ratio (DOR). Heterogeneity was intended with Cochran Q χ2 test and I2 statistic. The accuracy of serological assays resulted in a sensitivity of 71.7% (95% CI: 56.07 to 83.4%), a specificity of 89.9% (95% CI: 80.8 to 94.9%) and a DOR of 22.5 (95% CI: 10.8 to 46.9). The forest plot showed high heterogeneity regarding sensitivity (I2=90.4%, 95% CI: 87.4 to 93.3%; Q=228.1, p=0.000) and specificity (I2=98.9%, 95% CI: 98.8 to 99.1%; Q=2066.4, p=0.000). Fagan's nomogram showed that the probability of someone having the infection and with a positive test result was 49%. Deeks' funnel plots showed no evidence of potential publication bias for the studies (p=0.26). The current review suggests that serological techniques have acceptable sensitivity and specificity and therefore can be recommended for the screening of S. stercoralis infection.

Seropositivity and geographical distribution of Strongyloides stercoralis in Australia: A study of pathology laboratory data from 2012-2016

Background

There are no national prevalence studies of Strongyloides stercoralis infection in Australia, although it is known to be endemic in northern Australia and is reported in high risk groups such as immigrants and returned travellers. We aimed to determine the seropositivity (number positive per 100,000 of population and percent positive of those tested) and geographical distribution of S. stercoralis by using data from pathology laboratories.

Methodology

We contacted all seven Australian laboratories that undertake Strongyloides serological (ELISA antibody) testing to request de-identified data from 2012–2016 inclusive. Six responded. One provided positive data only. The number of people positive, number negative and number tested per 100,000 of population (Australian Bureau of Statistics data) were calculated including for each state/territory, each Australian Bureau of Statistics Statistical Area Level 3 (region), and each suburb/town/community/locality. The data was summarized and expressed as maps of Australia and Greater Capital Cities.

Principal findings

We obtained data for 81,777 people who underwent serological testing for Strongyloides infection, 631 of whom were from a laboratory that provided positive data only. Overall, 32 (95% CI: 31, 33) people per 100,000 of population were seropositive, ranging between 23/100,000 (95% CI: 19, 29) (Tasmania) and 489/100,000 population (95%CI: 462, 517) (Northern Territory). Positive cases were detected across all states and territories, with the highest (260-996/100,000 and 17–40% of those tested) in regions across northern Australia, north-east New South Wales and north-west South Australia. Some regions in Greater Capital Cities also had a high seropositivity (112-188/100,000 and 17–20% of those tested). Relatively more males than females tested positive. Relatively more adults than children tested positive. Children were under-represented in the data.

Conclusions/Significance

The study confirms that substantial numbers of S. stercoralis infections occur in Australia and provides data to inform public health planning.

Strongyloides stercoralis, a parasitic roundworm, is endemic in many countries world-wide. In Australia, groups at risk for strongyloidiasis include Aboriginal and/or Torres Strait Islander people, who acquired this parasite locally, and immigrants and returned travellers who acquired the infection outside Australia. We obtained deidentified results of ELISA IgG antibody tests for Strongyloides from diagnostic pathology laboratories during 2012 to 2016 and calculated the number of people who were positive at least once and the number who never had a positive result. We drew maps showing the number positive per 100,000 of population, the percent positive of those tested, and the number tested/100,000 for each region and the number positive in each suburb of residence according to the Australian Bureau of Statistics. The highest seropositivity (260-996/100,000 of population) was in Northern Australia, north-west South Australia and north-east New South Wales where many Aboriginal and Torres Strait Islander people live in remote communities. There were also some regions in Greater Capital Cities with a high number of people positive per 100,000 of population (112-188/100,000), likely reflecting higher populations of immigrants and returned travellers who were infected outside Australia.

Prevalence and risk factors of Strongyloides stercoralis infection among Orang Asli schoolchildren: new insights into the epidemiology, transmission and diagnosis of strongyloidiasis in Malaysia

This cross-sectional study aimed to determine the prevalence and risk factors of S. stercoralis infection among 1142 Orang Asli primary schoolchildren in six different states of Peninsular Malaysia. Fecal samples were examined using direct smear, formalin-ether sedimentation (FES), agar plate culture (APC) and PCR techniques. Overall, 15.8% of the children were found to be infected with S. stercoralis. The prevalence was 0.2, 1.3, 15.2 and 13.7% by direct smear, FES, APC and PCR, respectively. Multivariate analysis showed that an age of >10 years, being male, belonging to a Proto-Malay tribe, belonging to the Senoi tribe, indiscriminate defecation, using an unimproved water source for drinking water and not wearing shoes when outside were the significant risk factors of infection among these children. In conclusion, we provide new evidence on the occurrence of S. stercoralis in Malaysia to show that there is a relatively high prevalence of infection among Orang Asli schoolchildren. Therefore, the use of specific methods for detecting S. stercoralis should be considered when screening these children for intestinal parasites. Moreover, prevention and control measures specific to S. stercoralis should be integrated into the intestinal parasitic infections control programme in Malaysia.

Soil-Transmitted Helminths in Tropical Australia and Asia

Soil-transmitted helminths (STH) infect 2 billion people worldwide including significant numbers in South-East Asia (SEA). In Australia, STH are of less concern; however, indigenous communities are endemic for STH, including Strongyloides stercoralis, as well as for serious clinical infections due to other helminths such as Toxocara spp. The zoonotic hookworm Ancylostoma ceylanicum is also present in Australia and SEA, and may contribute to human infections particularly among pet owners. High human immigration rates to Australia from SEA, which is highly endemic for STH Strongyloides and Toxocara, has resulted in a high prevalence of these helminthic infections in immigrant communities, particularly since such individuals are not screened for worm infections upon entry. In this review, we consider the current state of STH infections in Australia and SEA.