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

Abstract

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 β-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 resistanceassociated 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.

Anthelmintic drug discovery: target identification, screening methods and the role of open science

“…Unfortunately, drug resistance against benzimidazoles 1 and 2 and other anthelmintics have been detected in veterinary parasites, with mutations in the beta-tubulin gene [31,32]. To date there is limited evidence of resistance to benzimidazoles in human STHs [33], although benzimidazole resistance alleles have been found with increased frequency following anthelmintic treatment [34,35]. However, as the use of these anthelmintics has increased in the past decade, thanks to the donation of millions of doses of these drugs to enable mass drug administration, the selective drug pressure on the STHs has increased.…”

Role of DNA-detection–based tools for monitoring the soil-transmitted helminth treatment response in drug-efficacy trials

“…The presence of putative benzimidazole-resistance SNPs has been studied by different molecular methods [14][15][16][17][18][19][20][21], which are presented in Table 1.…”

“…With regard to these techniques' application, qPCR was first applied to detect the changes at codons 167 and 200 of β-tubulin gene of N. americanus [14,21] and Ancylostoma duodenale, respectively [14]. More recently, restriction fragment length polymorphism (RFLP)-PCR has https://doi.org/10.1371/journal.pntd.0007931.g001 been used to study SNPs presence in N. americanus and A. lumbricoides populations in Brazil [18].…”

“…Despite being recognized as an important intestinal helminthiasis to incorporate into deworming campaigns, strongyloidiasis has been commonly neglected in STH interventions [21]. The inefficiency of microscopy to detect S. stercoralis and the latter's unique feature of internal reproduction within the human host, makes worm burden less relevant, thereby rendering CR as a sole efficacy indicator [23].…”

Complementary Approaches to Understand Anthelmintic Resistance Using Free-Living and Parasitic Nematodes

“…The economic impacts of resistance in agricultural sectors around the world are massive with global losses projected in the billions of dollars per year [1,14]. In contrast to veterinary health, resistance in human parasites is not widely reported with only a few confirmed cases [15][16][17]. However, the selective pressure placed on human parasites by mass drug administration programs will soon give rise to equivalent levels of resistance [18].…”