Genetic Markers of Benzimidazole Resistance among Human Hookworms (Necator americanus) in Kintampo North Municipality, Ghana.

Hookworm infection causes anemia, malnutrition, and growth delay, especially in children living in sub-Saharan Africa. The World Health Organization recommends periodic mass drug administration (MDA) of anthelminthics to school-age children (SAC) as a means of reducing morbidity. Recently, questions have been raised about the effectiveness of MDA as a global control strategy for hookworms and other soil-transmitted helminths (STHs). Genomic DNA was extracted from Necator americanus hookworm eggs isolated from SAC enrolled in a cross-sectional study of STH epidemiology and deworming response in Kintampo North Municipality, Ghana. A polymerase chain reaction (PCR) assay was then used to identify single-nucleotide polymorphisms (SNPs) associated with benzimidazole resistance within the N. americanus ß-tubulin gene. Both F167Y and F200Y resistance-associated SNPs were detected in hookworm samples from infected study subjects. Furthermore, the ratios of resistant to wild-type SNP at these two loci were increased in posttreatment samples from subjects who were not cured by albendazole, suggesting that deworming drug exposure may enrich resistance-associated mutations. A previously unreported association between F200Y and a third resistance-associated SNP, E198A, was identified by sequencing of F200Y amplicons. These data confirm that markers of benzimidazole resistance are circulating among hookworms in central Ghana, with unknown potential to impact the effectiveness and sustainability of chemotherapeutic approaches to disease transmission and control.

Effectiveness of Albendazole for Hookworm Varies Widely by Community and Correlates with Nutritional Factors: A Cross-Sectional Study of School-Age Children in Ghana.

Mass drug administration (MDA) targeting school-age children is recommended by the World Health Organization for the global control of soil-transmitted helminth (STH) infections. Although considered safe and cost-effective to deliver, benzimidazole anthelminthics are variably effective against the three most common STHs, and widespread use has raised concern about the potential for emerging resistance. To identify factors mediating response to albendazole, we conducted a cross-sectional study of hookworm infection in the Kintampo North Municipality of Ghana in 2011. Among 140 school-age children residing in five contiguous communities, the hookworm prevalence was 59% (82/140). The overall cure rate following administration of single-dose albendazole (400 mg) was 35% (27/76), with a community-wide fecal egg reduction rate (ERR) of 61% (95% confidence interval: 51.8-71.1). Significant disparities were observed in albendazole effectiveness by community, with a cure rate as low as 0% (N = 24) in Jato Akuraa and ERRs ranging from 53% to 95% across the five study sites. Individual host factors associated with response to deworming treatment included time since last meal, pretreatment blood hemoglobin level, and mid-upper arm circumference. These data demonstrate significant community-level variation in the effectiveness of albendazole, even among populations living in close proximity. Identification of host factors that influence response to albendazole, most notably the timing of drug administration and nutritional factors, creates an opportunity to enhance the effectiveness of deworming through targeted interventions. These findings also demonstrate the importance of measuring anthelminthic response as part of the monitoring and evaluation of community-based deworming programs.

In vitro screening of compounds against laboratory and field isolates of human hookworm reveals quantitative differences in anthelmintic susceptibility.

A panel of 80 compounds was screened for anthelmintic activity against a laboratory strain of Ancylostoma ceylanicum and field isolates of hookworm obtained from school children in the Kintampo North District of the Brong Ahafo Region of Ghana. Although the laboratory strain of A. ceylanicum was more susceptible to the compounds tested than the field isolates of hookworm, a twofold increase in compound concentration resulted in comparable egg hatch percent inhibition for select compounds. These data provide evidence that the efficacy of anthelmintic compounds may be species-dependent and that field and laboratory strains of hookworm differ in their sensitivities to the anthelmintics tested. These data also suggest that both compound concentration and hookworm species must be considered when screening to identify novel anthelmintic compounds.

Hookworm infection among school age children in Kintampo north municipality, Ghana: nutritional risk factors and response to albendazole treatment.

Children (n = 812) 6-11 years of age attending 16 schools in the Kintampo North Municipality of Ghana were screened for participation in a study on hookworm infection, nutrition, and response to albendazole. The prevalence of Necator americanus hookworm infection (n = 286) was 39.1%, and significant predictors of infection included age, malaria parasitemia, lack of health care, school area, levels of antibodies against hookworm, and low consumption of animal foods. The cure rate after a single dose (400 mg) albendazole was 43%, and the mean fecal egg count reduction rate was 87.3%. Data for an in vitro egg hatch assay showed a trend toward reduced albendazole susceptibility in post-treatment hookworm isolates (P = 0.06). In summary, hookworm infection is prevalent among school age children in the Kintampo North Municipality and animal food intake inversely correlates with infection status. Modest cure rates and fecal egg count reduction rates reinforce the need for further investigation of potential benzimidazole resistance in Ghana.

Genetic diversity of polymorphic vaccine candidate antigens (apical membrane antigen-1, merozoite surface protein-3, and erythrocyte binding antigen-175) in Plasmodium falciparum isolates from western and central Africa.

The malaria vaccine candidate antigens erythrocyte binding antigen 175 (EBA-175), merozoite surface protein 3 (MSP-3), and apical membrane antigen (AMA-1) from Plasmodium falciparum isolates from countries in central and west Africa were assessed for allelic diversity. Samples were collected on filter paper from 600 P. falciparum-infected symptomatic patients in Cameroon, Republic of Congo, Burkina Faso, Ghana, and Senegal and screened for class-specific amplification fragments. Genetic diversity, assessed by mean heterozygosity, was comparable among countries. We detected a clinical increase in eba 175 F-allele frequency from west to east across the study region. No statistical difference in msp-3 allele distribution between countries was observed. The ama-1 3D7 alleles were present at a lower frequency in central Africa than in West Africa. We also detected little to no genetic differentiation among sampling locations. This finding indicates that, at least at the level of resolution offered by restriction fragment length polymorphism analysis, these antigens showed remarkable genetic homogeneity throughout the region sampled, perhaps caused by balancing selection to maintain a diverse array of antigen haplotyes.