Evaluation of oxfendazole in the treatment of zoonotic Onchocerca lupi infection in dogs

Abstract

The genus Onchocerca encompasses parasitic nematodes including Onchocerca volvulus, causative agent of river blindness in humans, and the zoonotic Onchocerca lupi infecting dogs and cats. In dogs, O. lupi adult worms cause ocular lesions of various degrees while humans may bear the brunt of zoonotic onchocercosis with patients requiring neurosurgical intervention because of central nervous system localization of nematodes. Though the zoonotic potential of O. lupi has been well recognized from human cases in Europe, the United States and the Middle East, a proper therapy for curing this parasitic infection in dogs is lacking. To evaluate the efficacy of oxfendazole, 11 out of the 21 client-owned dogs (21/123; 17.1%) positive for skin-dwelling O. lupi microfilariae (mfs), were enrolled in the efficacy study and were treated with oxfendazole (50 mg/kg) per OS once a day for 5 (G2) or 10 (G3) consecutive days or were left untreated (G1). The efficacy of oxfendazole in the reduction of O. lupi mfs was evaluated by microfilarial count and by assessing the percentage of mfs reduction and mean microfilaricidal efficacy, whereas the efficacy in the reduction of ocular lesions was evaluated by ultrasound imaging. All dogs where subjected to follow-ups at 30 (D30), 90 (D90) and 180 (D180) days post-treatment. The percentage of reduction of mfs was 78% for G2 and 12.5% for G3 at D180. The mean microfilaricidal efficacy of oxfendazole in the treatment of canine onchocercosis by O. lupi at D30, D90 and D180 was 41%, 81% and 90%, in G2 and 40%, 65% and 70%, in G3, respectively. Retrobulbar lesions did not reduce from D0 to D180 in control group (dogs in G1), whereas all treated dogs (in G2 and G3) had slightly decreased ocular lesions. Percentage of reduction of ocular lesions by ultrasound examination was 50% and 47.5% in G2 and G3 at D180, respectively. Despite the decrease in ocular lesions in all treated dogs (G2 and G3), oxfendazole was ineffective in reducing ocular lesions and skin-dwelling O. lupi mfs in treated dogs (G2 and G3) in a six-month follow-up period. Here we discuss the need for more reliable diagnostic techniques and efficient treatment protocols to better plan future intervention strategies.

A real-time PCR tool for the surveillance of zoonotic Onchocerca lupi in dogs, cats and potential vectors

“…All dogs’ and cats’ skin samples were collected in previous studies [ 17 , 29 ] and approved by the ethical committee of the Department of Veterinary Medicine of the University of Bari (Prot. Uniba 1/16) and by the ethical committee of the Faculty of Veterinary Medicine, Universidade Lusófona de Humanidades e Tecnologias.…”

“…The specificity of the assay was tested by using DNA from skin samples of naturally infected dogs, which were positive for O . lupi (n = 35) at microscopic examination [ 29 ]. Skin samples were divided in five groups (G1-G5) according to their mfs load ( Table 3 ), being 14 also co-infected with Cercopithifilaria bainae and Cercopithifilaria sp.…”

“…II. Skin samples (dogs n = 21; cats n = 152), which did not test positive to any mfs [ 17 , 29 ], were used as negative control.…”

International dog travelling and risk for zoonotic Onchocerca lupi

“…Limited scientific knowledge of helminths affecting human and animal eyes challenge their diagnosis and treatment (Otranto & Eberhard, ). Among these parasites, Onchocerca lupi is a zoonotic nematode localizing to the ocular and adnexal tissues of dogs, which act as reservoir hosts (Colella et al., ; Otranto et al., ). A recent increase in O. lupi infection has been reported from dogs, cats and humans living in European (Romania, Hungary, Greece, Switzerland and Portugal), American (U.S. and Canada), Middle Eastern Asian (Iran) and Northern African (Tunisia) countries (Grácio, Richter, Komnenou, & Grácio, ).…”

“…However, the risk for the introduction of O. lupi with travelling dogs cannot be assessed in the absence of information about the presence of the vector(s) in a given area (Hodžić et al., ; Verocai et al., ). Attempted treatments included various combination and dosages of melarsomine, ivermectin, topical and systemic antibiotics (Otranto et al., ), and oxfendazole (Colella et al, ), although studies proving the efficacy of these compounds are lacking. Likewise, surgical treatment did not prove successful in curing canine onchocercosis, which is in line with previous reports of recurrent disease in dogs relocating from endemic regions (Hodžić et al., ; Verocai et al., ).…”