The nucleotide sequences of the second internal transcribed spacer of rDNA were determined for adult worms of Necator americanus originating from Togo (Africa) and Sarawak (Malaysia). The length of the sequences of specimens from Togo (325 bp) were shorter than those from Sarawak (327 bp). There were six fixed genetic differences in the aligned sequences of N. americanus from Sarawak and Togo, excluding one or two polymorphic sites within the sequence of N. americanus from each geographical region. These findings suggest that there is either population variation in the sequence of N. americanus, or that N. americanus from the two countries may represent genetically distinct but morphologically similar (i.e. cryptic) species, however, comparison of the sequence differences among other hookworm species supports the latter conclusion.
Species identification of human hookworm infections among eight communities in rural areas of Peninsular Malaysia was determined during 2009-2011. Fecal samples were examined by microscopy and subsequently, the internal transcribed spacer 2 and 28S ribosomal RNA region of Necator americanus and Ancylostoma spp. were sequenced. Overall, 9.1% (58 of 634) were identified positive by microscopy for hookworm infection, and 47 (81.0%) of 58 were successfully amplified and sequenced. Sequence comparison found that N. americanus (87.2%) was the most predominant hookworm identified, followed by Ancylostoma ceylanicum (23.4%). No A. duodenale infection was detected in this study. Detection of A. ceylanicum in humans highlighted the zoonotic transmission among humans living near dogs. Thus, implementation of effective control measures for hookworm infections in future should seriously consider this zoonotic implication.