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S. stercoralis infection ‘widely prevalent’ in Bolivia

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January 23, 2019

Researchers discovered a wide prevalence of strongyloidiasis — a chronic intestinal infection caused by a soil-transmitted intestinal nematode — among immunocompromised patients in Bolivia.

Writing in PLOS Neglected Tropical Diseases, Laurent Getaz, MD, MPH, from the department of medicine and penitentiary psychiatry and service of tropical and humanitarian medicine at Geneva University Hospitals, and colleagues explained that infection caused by Strongyloides stercoralis is one of the most overlooked neglected tropical diseases and can lead to severe complications and high mortality rates in immunocompromised individuals.

The researchers conducted a cross-sectional study in two Bolivian cities — Cochabamba and Santa Cruz — from July 2012 to April 2013. They sought to estimate the burden of the parasite in 1,151 patients aged 18 years or older who were at high risk for complications, including those with cancer (32%), HIV (30%) and rheumatic (29%) or hematologic diseases (9%). Stool and blood samples were collected and tested for parasitology and serology using four coproparasitological techniques and one serological test, according to the study.

Getaz and colleagues said the serological prevalence of S. stercoralis was 23% (95% CI, 20.7-25.5), and the coproparasitological prevalence was 7.6% (95% CI, 6.2-9.3). The researchers estimated an actual prevalence of 20.2% (95% CI, 17.9-22.5). According to the study, younger age and lower levels of education were significantly associated with positive findings on serology and coproparasitology. Getaz and colleagues did not observe significant differences between Cochabamba and Santa Cruz. Specifically, the prevalence of coproparasitology was 6.4% in Cochabamba compared with 8.9% in Santa Cruz. Moreover, serology prevalence was 24% in Cochabamba compared with 22% in Santa Cruz.

S. stercoralis 
A wide prevalence of strongyloidiasis was discovered among immunocompromised patients in Bolivia.
Source: CDC/ Dr. George R. Healy

Getaz and colleagues concluded that strongyloidiasis is “widely prevalent” in Bolivia. Transmission of the parasite that causes the infection occurs in tropical lowlands and temperate elevation, they said. Approximately 5.2% of the global population is infected with the enteric parasite, but the researchers believe this number may be underestimated due to the low sensitivity of conventional diagnostics.

Currently, albendazole is administered in primary schools as part of Bolivia’s national deworming campaign, but the drug demonstrates suboptimal efficacy for S. stercoralis, and the researchers suggested adding ivermectin to the program in areas with a high prevalence of infection.

“Because S. stercoralis is the most dangerous enteric parasite, laboratory methods sensitive for S. stercoralis must be accessible to monitor prevalence and treatment,” Getaz and colleagues wrote. “Given the high prevalence in this population, the mortality associated with [hyperinfection syndrome]/[ disseminated strongyloidiasis] and the efficacy and safety of early treatment, we recommend the presumptive use of ivermectin for patients that undergo immunosuppression, or before initiating immunosuppressive therapy.” – by Marley Ghizzone

Disclosures: The authors report no relevant financial disclosures.

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Photo of Peter Hotez
Perspective

When we talk about the world's intestinal worm infections (also known as soil-transmitted helminth [STH] infections), there are three major ones — ascariasis, trichuriasis and hookworm — that come to mind. However, studies like this point to the fact that there is also a fourth STH infection — strongyloidiasis — that is more common than is often appreciated. Among the problems for the clinician is that strongyloidiasis is often more difficult to diagnose compared with ascariasis, trichuriasis and hookworm infection because of the fact that it is often difficult to recover or identify Strongyloides larvae in human feces, and other more complicated methods are required.

The current paper is a reminder of the importance of making the effort to try and detect strongyloidiasis in patients or populations living in resource-poor areas of Latin America, Asia and Africa and then treat appropriately with ivermectin. Diagnosis and treatment are especially important for individuals scheduled to receive corticosteroids because of findings that these drugs can activate Strongyloides worms to cause hyperinfection or disseminated infection, leading to serious morbidities or even death. The paper also highlights the potential importance of integrating mass drug administration approaches by adding ivermectin to albendazole for the mass treatment of STH infections, to also target strongyloidiasis.

Peter J. Hotez, MD, PhD

Professor of pediatrics
Dean, National School of Tropical Medicine
Baylor College of Medicine

Disclosure: Hotez reports no relevant financial disclosures.