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.
Soil-transmitted helminth infections remain a major public health burden in low- and middle-income countries. The traditional diagnosis by microscopic examination of fecal samples is insensitive and time-consuming. In this study, a pentaplex real-time polymerase chain reaction (PCR) was evaluated for the simultaneous detection of Ancylostoma, Necator americanus, Ascaris lumbricoides, and Strongyloides stercoralis. The results were compared with those obtained by conventional parasitological diagnostic methods. Real-time PCR was positive in 48 of 77 samples (62.3%) and microscopic examination was positive in six samples (7.8%) only (P < 0.05). In conclusion, the real-time PCR assay described in this study provides a specific and sensitive diagnostic tool for the detection of these four helminth species in epidemiological studies and monitoring of treatment programs.
The Orang Aslis are indigenous minority peoples of Peninsular Malaysia, numbering 147,412 in 2003.Currently, the Orang Asli are divided into four language groupings namely the Northern Aslian, the Central Aslian, and the Southern Aslian groups, all of whom speak Austroasiatic languages; a fourth group in the South of Peninsular Malaysia speak a Malay dialect belonging to the Austronesian group of languages.This research was carried out on only one of the Northern Aslian group, the Jehai, who are also named Negritos based on their physical features. The Jehai live in the Belum and the Temenggor Forest that straddles Upper Perak and West Kelantan and until recently, were nomadic and lived by hunting-gathering.The World Health Organization (WHO) estimates that approximately two billion people worldwide are infected with the soil-transmitted nematode helminths,Ascaris lumbricoides, Trichuris trichiura and the hookworms Necator americanus and Ancylostoma duodenale, with 400 million of these infected being children of school age.Global numbers of A. lumbricoides infection have been estimated at about 1.5 billion cases. (Crompton, 2001). T. trichiura infection affects approximately 1,049 million people worldwide and an estimated 1.2 billion people are infected by hookworms. In Malaysia, the most common soil-transmitted helminth infections are A. lumbricoides, T. trichiura and hookworms.
However, as there have been no extensive surveys on these infections, it is difficult to estimate with certainty the current overall incidence of infection with soil-transmitted helminths (STHs) among the Malaysian population.
A total of 819 Indian inhabitants (from 6 months to over 60 years of age) in an oil-palm plantation in West Malaysia was examined for soil-transmitted helminthiases using the brine flotation and Kato thick smear techniques. Half (51.0%) of the inhabitants were found to be infected (33.9% had Ascaris lumbricoides; 36.4% had Trichuris trichiura and 15.6% had Necator americanus). Soil-transmitted helminthiases (both single and mixed infections) were significantly more common among children and young adults from 6 months to 20 years of age where 67.1% (range: 64.7-70.3%) of this age group were infected. The infection rate declined to about 25% or less among elderly people over 50 years of age. Trichuris trichiura was the commonest helminth observed--both as single and mixed infections--and Trichuris mixed with Ascaris was the commonest type of double infection reported. However, there were no significant differences in the distribution of the types of single and double infections among inhabitants of different age groups, nor were there any significant differences in the distribution of soil-transmitted helminthiases among male and female inhabitants. The socioeconomic, environmental and cultural factors contributing to persistently high rates of infection with soil-transmitted helminths among plantation inhabitants are discussed.