Clinical case presentation and a review of the literature of canine onchocercosis by Onchocerca lupi in the United States

Abstract

Background: Onchocerca lupi, a filarioid of zoonotic concern, infects dogs and cats causing ocular lesions of different degrees, from minor to severe. However, infected animals do not always display overt clinical signs, rendering the diagnosis of the infection obscure to the majority of veterinarians. Canine onchocercosis has been reported in the Old World and the information on its occurrence in the United States, as well as its pathogenesis and clinical management is still meagre. This study reports on the largest case series of O. lupi infection from the United States and reviews previous cases of canine onchocercosis in this country. Methods: Information on the clinical history of a series of eight cases of O. lupi infection in dogs diagnosed in Minnesota, New Mexico, Colorado and Florida, from 2011 to 2014, was obtained from clinical records provided the veterinary practitioners. Nematodes were morphologically identified at species level and genetically analyzed.

Aberrant laryngeal location of Onchocerca lupi in a dog

“…Nevertheless, O. lupi DNA has recently been detected in the black fly Simulium tribulatum in the USA [14]. Clinical manifestations of canine ocular onchocercosis range from no apparent clinical signs to blindness [1,10]. In an initial phase, it is generally associated with the onset of nonspecific ocular discomfort (i.e., epiphora, photophobia, serous or mucopurulent discharge, conjunctivitis, blepharitis, exophthalmos, periorbital swelling, uveitis, chemosis, protrusion of the nictitating membrane or even corneal oedema or ulcers) [2].…”

“…After its first description in the sclera of a wolf (Canis lupus) in the Republic of Georgia [2], several cases have been increasingly reported in domestic dogs worldwide, including Hungary [3], Greece [4], Germany [5], Switzerland [6], Portugal [7,8] and the USA [9,10]. Onchocerca lupi infects ocular tissues causing acute or chronic ocular lesions of different degrees, with clinical features ranging from no apparent clinical signs to blindness [1,10]. From where the infection is reported in dogs, zoonotic ocular infection may also occur in humans, mostly in the ocular region [11].…”

Human case of Onchocerca lupi infection, Germany, August 2014

“…It clusters in particular with Onchocerca lupi sequences from Portugal (canine infection, GU365879 (100% nt identity, 393 of 393 nt)) and Iran (human infection, JN863696 (99% nt identity, 393 of 395 nt)), followed by those from Turkey (human infection, HQ207645 (99% nt identity, 373 of 375 nt)) and California (canine infections, KC763783 (100% nt identity, 326 of 326 nt) and KC763784 (97% nt identity, 383 of 396 nt)). [9,10]. The clinical picture in humans is characterised by the development of a bulbar subconjunctival nodule [5][6][7]10].…”

“…[9,10]. The clinical picture in humans is characterised by the development of a bulbar subconjunctival nodule [5][6][7]10]. In one case also multiple eye nodules were observed [8].…”

“…In all eight clearly diagnosed human cases we found in the literature, surgical excision led to a complete cure. Only in two cases [9,10] additional anthelminthic drugs (ivermectin and/or albendazole) were administered. In one case dexamethasone was applied after surgery and cryotherapy because of generalised urticaria [8].…”