THE PREVALENCE OF PARASITE CONTAMINATION OF VEGETABLES AND THE RISK FACTORS IN THEIR TRANSMISSION IN NSUKKA ECOLOGICAL ZONE, ENUGU STATE
ABSTRACT
The prevalence of parasite contamination of vegetables and the risk factors in their transmission were investigated in Nsukka Ecological Zone, Enugu State, Nigeria. A total of four hundred and eighty-eight (488) samples of six different raw edible vegetable types, from three farms and three markets, were examined between January and October, 2013. It consisted of 241 farm vegetable samples and 247 market samples. The vegetables included fruit of Solanum marcrocarpon (garden egg), leaf of Solanum species (garden egg leaf), Amaranthus species (spinach or green), Telfairia occidentalis (pumpkin leaf), Ocimum basilicum (scent or basil leaf) and Solanum lycopersicum (tomatoes). The vegetable samples were washed with normal saline, allowed to stand overnight for sedimentation, and the sediments were examined microscopically, after centrifugation, for the presence of parasites eggs, cysts, oocysts and larvae. Eighteen samples of irrigation water, six from each farm, were also examined during the dry season, January – March. The irrigation water was allowed to stand overnight in a straight sided container for sedimentation, and the sediments were examined microscopically after centrifugation and concentration of the parasites. Modified Zieehl-Neelsen technique was used to detect oocysts of Cryptosporidium parvum in vegetable and irrigation water samples. The parasites recovered were Entamoeba histolytica cyst, Cryptosporidium parvum oocyst, Taenia species egg, Hymenolepis species egg, Ascaris species egg, hookworm egg, Trichuris trichiura egg, Strongyloides stercoralis larva, Enterobius vermicularis egg and Trichostrongylus species egg. Ascaris was the predominant parasite found, followed by E. histolytica. C. parvum had the least prevalence 11(4.6%) in farm vegetable samples while E. vermicularis and C. parvum were the least prevalent 9(3.6%) in the market samples. Trichostrongylus species and Hymenolepis species were the least prevalent 1(5.6%)r in irrigation water. Two hundred and fifty-three (51.8%) of the vegetable samples were contaminated with various parasites. One hundred and thirty-two (53.4%) of market vegetables and 121(50.2%) of farm vegetables were found to have parasitic contamination. The parasites, however, were more prevalent in vegetable samples from farms than those from the markets. The University of Nigeria, Nsukka (UNN) farm had the highest rate of contamination 47(56.6%) while Nkpologu farm had the least contamination 35(46.1%). Contamination rate among the farms however, did not differ significantly (P > 0.05). Among the markets, Ikpa had the highest rate of contamination 46(56.1%) whereas Opanda had the least 42(51.9%), but this did not differ significantly (P > 0.05). Pumpkin leaf was the most contaminated vegetable while tomatoes were the least. The difference was significant (P < 0.05). The month of August recorded the highest rate of contamination while the least were February and January for farm and market vegetable samples respectively. The difference was not significant (P > 0.05) in farm samples but was significant (P < 0.05) in market samples. The seasonal variability of parasites showed that the rate of contamination was higher in rainy than dry season. This differed significantly (P < 0.05) in the market samples but was not significant (P > 0.05) in the farm samples. Climatic factors were found to influence the prevalence of parasites in vegetables. The prevalence of some parasites increased as the climatic factors increased while that of others decreased with increase in climatic factors. The water used by farmers to irrigate vegetables did not meet WHO recommended standard of %0.1 helminth eggs per litre. The poor correlation between parasites found in irrigation water and their consequent contamination of vegetables, however, implied that the use of animal manure and environmental contamination with faeces were more important sources of contamination of vegetables in the ecological zone. Analysis of responses from the questionnaire showed that 92.1% of farmers used animal manure to fertilize vegetables, 72.3% said farmers do not treat it before use, while 94.1% of the respondents agreed to the practice of open defection in the area. It also showed that all six vegetables are consumed raw without adequate washing. These findings incriminated raw edible vegetables as important vehicle of transmission of both human and zoonotic intestinal parasites in the ecological zone. The study therefore recommended that untreated animal manure and wastewater should not be used to fertilize and irrigate raw edible vegetables respectively. It also recommended among others, adequate washing of vegetables before consumption, prevention of environmental pollution with both human and animal faeces, etc.