Molecular identification of hookworm isolates from stray dogs, humans and selected wildlife from KwaZulu-Natal and Mpumalanga provinces of South Africa.
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Date
2019
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Abstract
Hookworms are nematodes that cause infections to the host via skin penetration of the third stage larvae and they are widely distributed in the tropical and subtropical regions. They parasitize a wide range of host species including humans and companion animals such as dogs and cats. An estimated 740 million people are infected worldwide, with sub-Saharan Africa having the highest documented prevalence. With the exception of the study conducted by Lamb et al. (2012), Ancylostoma species identification in Southern Africa was solely based on egg morphology and morphological characteristics of adult worms. This study therefore aimed at using molecular techniques to identify the hookworm species and their prevalence in stray dogs, school-going children from KwaZulu-Natal province, and selected wild canids and felids from Mpumalanga province of South Africa. A total of 356 faecal samples were collected and screened for the presence of hookworm eggs using coproscopy and coproculture, which yielded prevalence of 23.04% and 21.67%, respectively. Larvae derived from coproculture of a total of 55 samples were subjected to molecular analysis. DNA was isolated and subjected to PCR amplification, PCR-RFLP and sequencing of the nuclear ribosomal internal transcribed spacer (ITS1) and 5.8S rRNA region. PCR-RFLP showed an overall prevalence of 72.7% (40/55) for A. caninum, 12.7% (7/55) for a mixture of A. caninum, A. ceylanicum, and A. braziliense, 7.27% (4/55) for A. caninum and A. ceylanicum mixed infection, and 7. 27% (4/55) for A. caninum and unidentifiable species. These results are consistent with other studies which show that A. caninum is the most dominant hookworm species worldwide even though A. braziliense is regarded as a more important zoonotic species. Phylogenetic analyses of alignments based on the DNA sequences were also used to identify isolates which were sequenced. However, results of phylogenetic analysis were not consistent with results from PCR-RFLP analysis as none of the sequences matched with A. ceylanicum. Sequencing also showed a 0.68% prevalence for both A. caninum and A. braziliense (mixed infections) in dogs. Of great importance was the revelation that A. caninum can now cause a patent infection in South African (Ingwavuma area) school-aged children as all human isolates matched with A. caninum with a prevalence of 6%. For wildlife, a prevalence of 10% was recorded. However, due to the small sample size, these results cannot be regarded as a true reflection of the prevalence in wildlife. Thus there is a need for future studies that will increase sample sizes, broaden ranges as well as look into finding better detection methods, primers and/or restriction enzymes that are specific to hookworm species isolated in South Africa.
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Masters Degree. University of KwaZulu-Natal, Durban.