Onchocerciasis in the Arabian Camel (Camelus dromedarius L.) in the Central Region (Riyadh and Qasim Provinces) of Saudi Arabia PDF

Keywords

camels, Saudi Arabia, Onchocerciasis

Abstract

Skin snipping of the head and neck regions of live Arabian camels (Camelus dromedarius) in the Central Region (Riyadh and Qasim Provinces) of Saudi Arabia and the release of Onchocerca species microfilariae (mff) into 80% Tyrode's solution with 20% camel serum and antibiotics have been used to estimate the prevalence of camel onchocerciasis in this region. The study has also been complemented by skin snipping of camels to be slaughtered for human consumption at Riyadh Central abattoir and at Buraydah abattoir during ante-mortem examination and by post-mortem examination of carcasses of the same camels for adult Onchocerca worms. Onchocerca fasciata is the only species detected with an overall prevalence rate of 59.1% which is corrected to 77.2% by the elimination from the sample of young and old camels that do not have mff in their snips. The prevalence of infection is higher in camels in Qasim Province (65% for all camels samples and 84.3% when corrected by removing young and old camels with no skin mff) than in those in Riyadh Province (56% and 73.4%, respectively). However, camels in the agricultural parts of both provinces show the highest rate of onchocerciasis and those in the drier western parts of Riyadh Province (Al-Dawadmi and Afif) are the least infected. Sedentary camels in farms have the highest prevalence of infection and the highest density of skin mff than free-ranging nomadic camels. This has been discussed in accordance with the suitability of breeding habitats of supposed vectors (possibly midges of the genus Culicoides) in and around farms than anywhere else. Both sexes are equally infected and the infection is chronic, non-seasonal and results in no overt clinical disease, but increases with the age of the animal (older camels are more infected than young ones). Onchocerca fasciata has a predilection to the ligamentum nuchae where infections seem to start and thereafter, spread to other locations, especially subcutaneously in the regions of the flanks before becoming generalized in old camels. No pathological conditions have been observed in association with mff in the skin of infected camesl, but the general host reaction to adult worms consists of non-suppurative worm granuloma formation, but with far less degree of fibrosis and cellular reaction than in any other Onchocerca infection.