High infection rates for onchocerciasis and soil-transmitted helminthiasis in children under five not receiving preventive chemotherapy: a bottleneck to elimination

Background

The current mainstay for control/elimination of onchocerciasis and soil-transmitted helminthiasis (STH) relies on ivermectin- and mebendazole/albendazole-based preventive chemotherapies. However, children under five years of age have been excluded in both research activities and control programs, because they were believed to have insignificant infection rates. There is therefore a need for up-to-date knowledge on the prevalence and intensity of STH and onchocerciasis infections in this age group. This study aimed at assessing the rates and intensities of onchocerciasis and STH infections in children under five years of age who are excluded from ivermectin- or mebendazole/albendazole-based preventive chemotherapies.

Methods

A series of cross-sectional surveys was conducted in four Health Districts in the Centre and Littoral Regions of Cameroon between 2018 and 2019. All subjects aged 2 to 4 years, were screened for prevalence (or infection rate) and intensity [number of eggs per gram of stool (epg) or number of microfilariae per skin snip (mf/ss)] of STH and onchocerciasis infections respectively using the Kato-Katz and skin snip methodologies. Chi-square and the non-parametric tests (Mann Whitney and Kruskal Wallis) were used to compare infection rates and intensities of infections between Health Districts and genders, respectively.

Results

A total of 421 children were enrolled in this study. The overall prevalence of onchocerciasis was 6.6% [95% confidence interval (CI): 4.3‒9.9], ranging from 3.6% (in the Ntui Health District) to 12.2% (in the Bafia Health District). The intensity of infection ranged from 0.5 to 46 microfilariae per skin snip [median: 5; interquartile range (IQR): 2.25‒8.5]. The overall prevalence of STH was 9.6% (95% CI: 6.5‒13.9), with a high infection rate (29.6%) in the Akonolinga Health District. Two STH species (Ascaris lumbricoides and Trichuris trichiura) were found among infected individuals. The median intensities of STH infections were 1,992 epg (IQR: 210‒28,704) and 96 epg (IQR: 48‒168) for A. lumbricoides and T. trichiura, respectively.

Conclusions

This study reveals that children < 5 years of age are highly infected with STH and onchocerciasis, and could contribute to the spread of these diseases, perpetuating a vicious circle of transmission and hampering elimination efforts. These findings reveal the urgent need to provide (or scale) treatments (likely pediatric formulations) to these preschool-aged children, especially in areas of high transmission, to accelerate efforts to reach WHO 2030 target.

Graphical Abstract

PO 8527 GLUCOSE-6-PHOSPHATE DEHYDROGENASE DEFICIENCY AND ASSOCIATION WITH UNCOMPLICATED MALARIA IN CONGOLESE CHILDREN CONSULTING IN A PAEDIATRIC HOSPITAL IN BRAZZAVILLE

Background

Malaria remains a public health problem in Republic of the Congo. The sub-microscopic infection including gametocytaemia constitutes a parasite reservoir that is recognised to contribute to malaria transmission. It is known that primaquine, an 8-aminoquinoline, is effective to eliminate Plasmodium falciparum (Pf) gametocytes. However, it induces haemolytic anaemia in individuals with glucose-6-phosphate dehydrogenase deficiency (G6PDd). It has been reported G6PDd also confers protection against severe malaria. To know the prevalence of G6PDd in the Congolese population is important in the case of future utilisation of this drug in the country. Therefore, in this study, we investigated 1) the prevalence of G6PDd in children infected with Pf and 2) the possible association between the presence of malaria, the presence of G6PD mutation and haemoglobin concentration.

Methods

229 children aged 1 to 10 years old presenting with fever (axillary T°≥37.5°C) were enrolled at the paediatric hospital Marien Ngouabi in Brazzaville. Thick and thin blood smears were done to detect and identify malaria parasites and determine parasite density. To detect the different glucose-6-phosphate dehydrogenase genotypes, a 968 bp fragment of the G6PD gene containing the polymorphisms 202G&gt1;A and 376&gt1;G was amplified by PCR followed by sequencing.

Results

Malaria prevalence was 22 (10%). With regard to G6PD analysis, it was found that 206 patients had G6PD genotype available including 74.8% (154/206) with G6PD normal, 12.1% (25/206) with heterozygous genotypes and 13.1% (27/206) with G6PD deficiency [11.6% (24/206) were male hemizygous and 1.4% (3/206) were female homozygous]. Data are further analysed to investigate the association between G6PD genotype, uncomplicated malaria, haemoglobin concentration as well as parasite densities.

Conclusion

A high prevalence of G6PD deficiency is reported for these Congolese children. Further investigation with larger sample size in different areas of the country is needed to design future and adapted interventions.