Abstract
The genus Onchocerca includes several species associated with ungulates as hosts, although some have been identified in canids, felids, and humans. Onchocerca species have a wide geographical distribution, and the disease they produce, onchocerciasis, is generally seen in adult individuals because of its large prepatency period. In recent years, Onchocerca species infecting animals have been found as subcutaneous nodules or invading the ocular tissues of humans; the species involved are O. lupi, O. dewittei japonica, O. jakutensis, O. gutturosa, and O. cervicalis. These findings generally involve immature adult female worms, with no evidence of being fertile. However, a few cases with fertile O. lupi, O. dewittei japonica, and O. jakutensis worms have been identified recently in humans. These are relevant because they indicate that the parasite’s life cycle was completed in the new host—humans. In this work, we discuss the establishment of zoonotic Onchocerca infections in humans, and the possibility of these infections to produce symptoms similar to human onchocerciasis, such as dermatitis, ocular damage, and epilepsy. Zoonotic onchocerciasis is thought to be an emerging human parasitic disease, with the need to take measures such as One Health Strategies, in order to identify and control new cases in humans.
Highlights
The genus Onchocerca comprises several parasitic nematode species [1], which are transmitted by arthropod vectors, namely, blackflies belonging to the genera Simulium and Culicoides [2], and it has been suggested that the biting habits of these blackflies influence the presence and distribution of microfilariae in the subcutaneous tissues of the hosts [3]
The appearance of skin nodules is often asymptomatic, and it is not usually noticed by Onchocerca lupi was described for the first time in the ocular tissues of wolves [73], and since owners, but it could manifest with dermatitis, impaired function of the ligaments, and even it has mainly been reported in dogs [74,111]
Adult Onchocerca parasites are usually located coiled in the ligamentum nuchae of the ocular nodules, which could result in eye damage, such as conjunctivitis, swelling, exophthalmia, horses [30] and within nodules infecting the connective tissue of the flexor tendons or the suspensory ligament of the fetlock [110]
Summary
The genus Onchocerca comprises several parasitic nematode species [1], which are transmitted by arthropod vectors, namely, blackflies belonging to the genera Simulium and Culicoides [2], and it has been suggested that the biting habits of these blackflies influence the presence and distribution of microfilariae in the subcutaneous tissues of the hosts [3]. Adult Onchocerca parasites are usually located coiled in the ligamentum nuchae of without being included within a nodule [47,94] Regarding the microfilariae, they were located inside horses [30] and within nodules infecting the connective tissue of the flexor tendons or the suspensory the hind limbs [8], the ventral zone [58], ears and muzzles [109] of the hosts. The appearance of skin nodules is often asymptomatic, and it is not usually noticed by Onchocerca lupi was described for the first time in the ocular tissues of wolves [73], and since owners, but it could manifest with dermatitis, impaired function of the ligaments, and even it has mainly been reported in dogs [74,111] In the latter, O. lupi adult worms are generally found in blindness [19]. The wide geographical distribution of Onchocerca vectors indicates favorable environmental conditions for spreading infection [5]
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