The prevalence and differentiation of human taenia spp. infections in two districts of the Southern province of Zambia
Mwapa, Kabemba Evans
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Taeniosis and cysticercosis are public health problems in many developing countries, with the former being due to the adult worm of both Taenia solium (T. solium) and Taenia saginata (T. saginatd) while the latter is due to the larval stages of T. solium. Extensive studies in pigs and cattle, which are the intermediate hosts of these important zoonotic parasites, have been carried out in Zambia. However little or no information about the infections in humans is available. Hence, the objective of this study was to determine the prevalence and the potential risk factors associated with taeniasis/cysticercosis in humans in the districts of Gwembe and Monze of the Southern province of Zambia. We also undertook to differentiate the human Taenia spp. found in the study area. The prevalence of human taeniosis was assessed using coproscopic examination and diagnostic PCR. Presence of circulating parasite antigens in urine and serum to detect cysticercosis was assessed by enzyme-linked-immunosorbent assay (Ag-ELISA). Restriction fragment length polymorphism (PCR-RFLP) was used to differentiate the two human Taenia spp. A questionnaire was administered to individuals above 12 years of age in order to obtain information on the awareness of the infection by the participants and to study other associated risk factors to taeniosis/cysticercosis infections in man. A total of 678 faecal samples were examined. Of these, 294 and 384 samples were from Gwembe and Monze districts, respectively. Of the total faecal samples examined 21 (3.1%) were positive for taeniosis after coproscopic examination. PCR XX was conducted on a sub sample of 200 from the 678 faecal samples and 21 (10.5%) were found positive for taeniosis. There was no significant difference in prevalence between the two districts on both tests and perfect agreement (kappa = 0.851) was found between the two tests. Urine Ag-ELISA analysis gave a total cysticercosis prevalence of 13.4% (n = 627). No significant differences in cysticercosis prevalence were detected between individuals from Gwembe 37 (13.8%) and Monze 47 (13.1%) districts. There was no statistical association between gender or age group and positivity on either coproscopic examination or urines Ag-ELISA. Of the 101 serum samples collected from both urine Ag-ELISA positive and negative individuals, 8.9% had cysticercal antigens while 47.5% had antibodies. Comparing the three tests, only slight agreement was found between urine Ag-ELISA and serum Ab-ELISA. Even though the agreement was very slight, it was statistically significant (p < 0.05). Upon RFLP, all extracted Taenia DNA was confirmed to be that of T. solium and no pattern corresponded to that of T. saginata. The following risk factors were noted to be present despite not being statistically significant; lack of pork inspection at slaughter, consumption of pork with cysts, selling of pork infected with T. solium cysticerci, free-range pig husbandry system and poor sanitation, thereby allowing pigs access to infected faeces because of absence of toilets. This study showed a high prevalence of T. solium taeniosis/cysticercosis in humans in the surveyed areas, and that all the necessary factors required for the transmission of the parasite are present. The life cycle of T. solium is bound to be sustained by pigs being allowed access to infected human faeces because villagers with no toilets defaecated in open bushes. Consumption of uninspected cysticercosis-infected pork by villagers further enhances this maintenance of the parasite. It is evident from this study that T. solium infection poses a high public health risk not only in the study areas but also in urban areas due to migration of tapeworm carriers. The vast baseline data gathered thus far on the status of the diseases in humans should give the impetus to conduct further taeniosis and cysticercosis prevalence study in humans not only in these areas but also in other areas where pigs are raised.
- Veterinary Medicine