Strongyloides stercoralis infection: a health issue regarding indigenous people in Taiwan

Epidemiology, clinical features, and outcomes of strongyloidiasis in Taiwan from 1988 to 2020: A case series and literature review

OBJECTIVES

We described a case of Strongyloides hyperinfection syndrome, reported a case series, and reviewed published cases of strongyloidiasis in Taiwan.

METHODS

Confirmed cases of strongyloidiasis at the National Taiwan University Hospital (NTUH) and NTUH Hsin-Chu Branch from 1988 to 2020 were identified in the medical record database. Literature search was carried out through Pubmed, Google Scholar, and Index to Taiwan Periodical Literature System to identify published cases of strongyloidiasis in Taiwan from 1979 to 2020. Data pertaining to the demographics, underlying medical conditions, clinical manifestations, laboratory findings, and outcomes were extracted.

RESULTS

A total of 117 cases of strongyloidiasis were identified, including 20 previously unpublished cases from the two hospitals and 97 published cases in the literature. Overall, 85 (73%) were male and the mean age was 64 years (range, 6-95 years). Classical symptoms such as diarrhea, cough, and skin rash were only observed in 43%, 37%, and 18% of the patients, respectively, whereas eosinophilia at presentation was only found in 48%. Strongyloides hyperinfection syndrome and disseminated strongyloidiasis were identified in 41 (35%) and 4 (3%) patients, respectively. Four (3%) patients had concurrent meningitis. In univariable analysis, being older and having pre-existing chronic obstructive pulmonary disease or asthma were associated with hyperinfection or dissemination (p = 0.024 and 0.003, respectively). The mortality rate was 43% among those with hyperinfection or disseminated infection.

CONCLUSIONS

Strongyloidiasis can cause serious complications and mortality. Efforts to diagnose strongyloidiasis early are urgently needed to improve the outcome of patients with strongyloidiasis in Taiwan.

Status of Strongyloidiasis in Japan, 2000-2017

We reported 865 cases of soil-transmitted nematodiasis occurring in Japan during 2000-2017. The predominant nematode was Strongyloides stercoralis (n = 279, 32.3% of all cases), and other species included Ascaris lumbricoides (30.7%), Trichuris trichiura (23.1%), and Ancylostomidae spp. (13.9%). Strongyloides stercoralis was detected primarily in patients in Okinawa and Kagoshima prefectures, which are in the south of Japan and are endemic areas for this parasitic infection, and also in about half of the prefectures of all Japan. At least 15.5 cases of strongyloidiasis occurred on average each year. The period incidence rate of strongyloidiasis cases relative to the total population of Japan was 0.012 cases per 10⁵ person-years. The male-to-female ratio was 2.1. The average age was 75.1 ± 16.9 years, and 96.1% of patients were older than 50 years. Several reasons may explain why this previously non-endemic outside of Okinawa region, serious nematode disease is now found in much of Japan, including the increased number of transmigration and sightseeing trips in Japan, use of immunosuppressive drugs, and lack of awareness of the risks. Thus, information of strongyloidiasis and its risks must be disseminated to travelers, residents, and physicians to prevent this life-threatening parasite infection.

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

Epidemiological study on strongyloidiasis in humans is currently lacking in Malaysia. Thus, a cross-sectional study was carried out to determine the prevalence of Strongyloides stercoralis infection among the inhabitants of longhouse indigenous communities in Sarawak. A single stool and blood sample were collected from each participant and subjected to microscopy, serological and molecular techniques. Five species of intestinal parasites were identified by stool microscopy. None of the stool samples were positive for S. stercoralis. However, 11% of 236 serum samples were seropositive for strongyloidiasis. Further confirmation using molecular technique on stool samples of the seropositive individuals successfully amplified 5 samples, suggesting current active infections. The prevalence was significantly higher in adult males and tended to increase with age. S. stercoralis should no longer be neglected in any intestinal parasitic survey. Combination of more than 1 diagnostic technique is necessary to increase the likelihood of estimating the ‘true’ prevalence of S. stercoralis.

Strongyloidiasis with emphasis on human infections and its different clinical forms

Strongyloidiasis (caused by Strongyloides stercoralis, and to a lesser extent by Strongyloides fuelleborni) is one of the most neglected tropical diseases with endemic areas and affecting more than 100 million people worldwide. Chronic infections in endemic areas can be maintained for decades through the autoinfective cycle with the L3 filariform larvae. In these endemic areas, misdiagnosis, inadequate treatment and the facilitation of the hyperinfection syndrome by immunosuppression are frequent and contribute to a high mortality rate. Despite the serious health impact of strongyloidiasis, it is a neglected disease and very little is known about this parasite and the disease when compared to other helminth infections. Control of the disease is difficult because of the many gaps in our knowledge of strongyloidiasis. We examine the recent literature on different aspects of strongyloidiasis with emphasis in those aspects that need further research.

Strongyloides stercoralis infection in an intestinal transplant recipient

Strongyloides stercoralis is a helminth in tropical and subtropical areas. It may cause latent infection and progress to Strongyloides hyperinfection syndrome, which is associated with a high mortality rate. Transplant recipients under the treatment of immunosuppressant agents are at risk of severe S. stercoralis infection. According to related literature, most cases of S. stercoralis infection after solid organ transplantation are caused by reactivation of latent infections in the recipients, whereas only a few are acquired from the donors. We report on an intestinal transplant recipient who had S. stercoralis infection diagnosed by a larva of this parasite found in the stool from the ileostomy stoma 1 month after transplantation. The donor was considered the source of the infection because the donor was from an endemic area and had marked eosinophilia, and the recipient had no contact history or clinical manifestations related to the S. stercoralis infection before transplantation. The patient was treated with ivermectin and exhibited no evidence of infection after 7 months.

Serological and molecular detection of Strongyloides stercoralis infection among an Orang Asli community in Malaysia

Detection of Strongyloides stercoralis infection particularly in asymptomatic individuals is often hampered due to the lack of standard diagnostic tools. In this study, the use of serological and molecular approaches were investigated for the detection of S. stercoralis infection among an Orang Asli (indigenous) community following a preliminary detection by microscopic examination of faecal samples. Out of 54 individuals studied, 17/54 (31.5%) were detected to be positive for S. stercoralis infection by enzyme-linked immunosorbent assay (ELISA), compared to 0/54 (0%) by faecal examination. Further confirmation performed by a nested polymerase chain reaction (PCR) using DNA extracted from faecal samples of these 17 individuals yielded 3/17 (17.6%) positives for S. stercoralis DNA amplification. No amplification was seen with the other 37 faecal samples, which were negative by microscopy and ELISA. As the high ELISA positive results were suspected to be false-positives, ELISA is not recommended for use as a detection tool but may be beneficial for evaluating the effectiveness of anti-Strongyloides drugs. The present finding indicated that PCR should be considered as an alternative diagnostic tool for the detection of S. stercoralis infection.

Strongyloidiasis: an emerging infectious disease in China

Since the first case of strongyloidiasis reported in China in 1973, there have been 330 confirmed cases as of 2011. The present study conducted a meta-analysis on 106 cases for which detailed information on clinical symptoms, diagnosis, and outcome was available. Most (63%) cases were from the past decade. Immunocompromised patients and those given cortical hormones accounted for 68% of the cases, and case-fatality rate was 38%. General clinical symptoms included abdominal pain (53%), diarrhea (46%), fever (40%), and vomiting (39%). The parasite positivity rate in feces, sputum, and urine by microscopic diagnosis was 75%, 24%, and 8%, respectively, and gastrointestinal endoscopy or other biopsy detection rates were 17%. A lack of specific clinical manifestations makes early diagnosis and correct treatment difficult. Strongyloidiasis is an emerging disease in China, and public and clinical awareness needs to be raised to improve prevention and control.