Molecular detection of intestinal helminths and protozoa among young children in Dosso Region, Niger

Introduction

Eukaryotic parasites are significant contributors to childhood illness in Niger. In 2012, the World Health Organization estimated that 10–49% of Nigeriens lived with intestinal or urogenital schistosomiasis, while more than two-thirds of children required preventative chemotherapy for soil-transmitted helminths (STH)¹. In 2015, over 75% of pre-school aged children across Niger were targeted for preventative anthelmintic treatment². While mass deworming programs have drawn attention to the public health significance of helminthiases, the epidemiology of intestinal protozoa in Niger is not well described³. However, limited data suggest that protozoa may cause an appreciable fraction of clinically evaluated enteric infections^4,5.

Real-time polymerase chain reaction (qPCR) assays targeting high-copy-number genetic elements have been validated for many globally burdensome parasites and have been shown to provide greater sensitivity and specificity than traditional copromicroscopy^6–8. This study makes use of these significant strides in diagnostic accuracy to evaluate the age-dependent prevalence of seven eukaryotic pathogens in nine rural communities of the Niger River Valley.

Methods

Study background

We conducted a cross-sectional study to evaluate the prevalence of helminthiasis, schistosomiasis and intestinal protozoa infection in Boboye Department, Dosso Region, Niger. The study was nested within the Macrolides Oraux pour Réduire les Décès avec un Oeil sur la Résistance (MORDOR) trial, a cluster-randomized trial investigating the effects of community mass administration of azithromycin on child health and mortality (Clinicaltrials.gov ID NCT02048007). Details of the MORDOR study design are available elsewhere⁹.

This nested sub-study occurred in 9 of the 30 MORDOR study communities (see Figure 1) in Niger during a regularly scheduled study visit between May and June of 2017. These 9 communities were included because at the time this nested sub-study commenced there were only 9 study communities remaining for the annual site visit. All children residing in the study communities who were sampled for participation in the parent trial were eligible to participate. In the 9 communities, 447 children age 0–4 years were eligible to participate and 354 participated in the MORDOR study visit and 86 were able to provide a same-day bulk stool sample.

Figure 1. Giardia duodenalis prevalence by study site in Dosso Region, Niger.

Study communities are indicated by red dots on the map. The prevalence is listed as the number of samples that tested positive for Giardia duodenalis over the total number of samples tested followed by the percentage.

Results

Stool samples were collected from 86 children residing in 9 communities. The median age was 2 years old (IQR 1-4). Overall, 59.3% (51/86) of participants were female. The mean child growth z-scores were less than zero for all indicators (HAZ = -1.53 [SD 1.39], WAZ = -1.55 [SD 1.22], WHZ = -0.97 [SD 1.1]).

G. duodenalis infection was detected in 65% (56/86) children living in 7 of the 9 surveyed communities. The 2 communities for which no infections were observed, Goberi Peulh and Tombo, only contained 1 and 3 total participants, respectively. For the 7 communities in which G. duodenalis was detected, prevalence ranged from 30% (3/10) to 89% (16/18) (Figure 1). The prevalence of G. duodenalis increased with age, with 88.2% (15/17) of two-year-old children testing positive. The median Cq value for G. duodenalis positive stool was 29 (IQR 25.2, 31.7). Only 1 helminth infection was detected (S. haematobium) (Table 1).

Children who tested positive for G. duodenalis had a -0.18 (95% CI: -0.77–0.40) lower height-for-age Z-score, a 0.22 (95% CI: -0.3–0.75) higher weight-for-age z-score and a 0.52 (-0.07–1.1) higher weight-for-height Z-score. However, none of these differences were statistically significant at the 0.05 level. Individual-level de-identified anthropometric, demographic and infection data are available (see Underlying data)¹⁶.

Discussion

We found that young children residing in the MORDOR study area in rural Niger had a high prevalence of G. duodenalis and a low prevalence of helminthic infections as measured by PCR in stool specimens. The population was generally undernourished, with all three anthropometric indices below average. Lower HAZ scores were observed among children positive for G. duodenalis, similar to prior observations in rural Amhara Region, Ethiopia¹⁷. However, there was no significant difference in growth indices between children with and without G. duodenalis infection, though this could be related to sample size.

The administrative Region of Dosso is situated in the Niger River Valley, a more densely populated region with higher rates of infectious disease than the majority of the nation¹⁸. In 2016, children 4 years of age and younger represented 81.1% of diarrhea cases, 43.7% of dysentery cases, and 37.7% of intestinal parasitisms recorded in Dosso Region, yet the etiological agents of these complaints remain unreported⁴. In other rural regions of sub-Saharan Africa the prevalence of giardia in young children has been reported to be as high as 56% when using a molecular assay on stool³. In a 2016 cross-sectional sero-survey in the Amhara region of Ethiopia over 80% of two year old children were seropositive for G. intestinalis¹⁹. Risk factors for giardia infection include close contact with animals and animal feces and manure, residing in a rural area, drinking contaminated water and eating raw fruit³. Given the high prevalence of G. duodenalis observed in the present study – albeit within a limited sample –the contributions of G. duodenalis infection to public health in the Niger River Valley warrant further investigation.

The low prevalence of STH and S. mansoni and S. haematobium in this cohort may relate to the success of national mass drug administration programs. In 2015, over 800,000 citizens of Dosso Region received praziquantel through mass drug administration, including over 200,000 living in Boboye Department; over half a million received albendazole, with over 100,000 residing in Boboye Department⁴. However, without data on baseline prevalence and community-level anthelmintic distribution in this population, conclusions cannot be drawn. Another possible explanation for the low prevalence of S. haematobium may be that we tested stool rather than urine, the standard specimen type for this species. Though S. haematobium predominantly evacuates via urine, this species was detected in the feces of a single child. Ectopic elimination in the brain and intestine has been observed in S. haematobium, sometimes attributed to high parasite loads²⁰. Whether a greater number of children would have tested positive for S. haematobium by urine analysis cannot be known but could be an area of further research.

These findings indicate that G. duodenalis infections may be a significant contributor to child morbidity in the Dosso Region of Niger.

Data availability