Strongyloides stercoralis is associated with significant morbidity in rural Cambodia, including stunting in children

Abstract

Background: Strongyloides stercoralis is a soil-transmitted nematode that can replicate within its host, leading to long-lasting and potentially fatal infections. It is ubiquitous and highly prevalent in Cambodia. The extent of morbidity associated with S. stercoralis infection is difficult to assess due to the broad spectrum of symptoms and, thus, remains uncertain.

Methodology/principal findings: Clinical signs were compared among S. stercoralis infected vs. non-infected participants in a cross-sectional survey conducted in 2012 in eight villages of Northern Cambodia, and before and after treatment with a single oral dose of ivermectin (200μg/kg BW) among participants harboring S. stercoralis. Growth retardation among schoolchildren and adolescents was assessed using height-for-age and thinness using body mass index-for-age. S. stercoralis prevalence was 31.1% among 2,744 participants. Urticaria (55% vs. 47%, OR: 1.4, 95% CI: 1.1-1.6) and itching (52% vs. 48%, OR: 1.2, 95% CI: 1.0-1.4) were more frequently reported by infected participants. Gastrointestinal, dermatological, and respiratory symptoms were less prevalent in 103 mono-infected participants after treatment. Urticaria (66% vs. 11%, OR: 0.03, 95% CI: 0.01-0.1) and abdominal pain (81 vs. 27%, OR: 0.07, 95% CI: 0.02-0.2) mostly resolved by treatment. S. stercoralis infection was associated with stunting, with 2.5-fold higher odds in case of heavy infection.

Conclusions/significance: The morbidity associated with S. stercoralis confirmed the importance of gastrointestinal and dermatological symptoms unrelated to parasite load, and long-term chronic effects when associated with malnutrition. The combination of high prevalence and morbidity calls for the integration of S. stercoralis into ongoing STH control measures in Cambodia.

Fig 1. Study flow chart.

Flowchart detailing the number of participants included in the three sub-studies. Insufficient parasitological data corresponds to one (out of four) or more missing diagnostic examinations for S. stercoralis, to one (out of two) or more missing diagnostic examinations for other helminths, and to any missing diagnostic examination for protozoa.

Fig 2. Proportion of participants harboring S. stercoralis mono-infections and reporting abdominal pain, nausea, vomiting, diarrhea, urticaria, and cough before and 21 days after ivermectin (200 μg/kg BW) treatment.

The decreases in the proportion of participants reporting any of the symptoms in the figure was significant at 5% level, as assessed by the McNemar’s test. S. stercoralis low parasite load: positive count and ≤ 1 larvae per gram (LPG). S. stercoralis moderate or high parasite load: > 1 LPG. Data were collected in 2012 in Preah Vihear Province, North Cambodia, from 103 participants in the post-treatment survey who harbored S. stercoralis mono-infection at both surveys and met the case definitions used in this work for all parasites.