Authors

V Colella³; C Maia²; A Pereira²; I Scandale¹; D Otranto³;  ¹ Drugs for Neglected Diseases initiative, Switzerland;  ² Universidade Nova de Lisboa, Portugal;  ³ University of Bari, Italy

Discussion

The genus Onchocerca (Spirurida, Onchocercidae) is well known mainly for Onchocerca volvulus which is estimated to infect at least 37 million people globally, as well as for including zoonotic species. Among these, Onchocerca lupi has been reported in dogs and cats from several European countries and, recently, also in the U.S. and Canada. In humans, O. lupi displays a marked neurotropism and patients require neurosurgical intervention because of nematodes localisation in the cervical spine of infant, children and adults. Though the severe outcomes of the infection in humans and the high prevalence in dogs from endemic countries have been recognised, a proper treatment regime for curing this parasitic infection is lacking, being the surgical removal of the parasitic nodules the therapy of choice in canine patients. Hence, there is an unmet medical need for treatment of this zoonotic disease in both humans and animals. In this study, we evaluated the efficacy of oxfendazole under two treatment regimes in the reduction of ocular lesions and skin-dwelling microfilariae (mfs) of O. lupi in naturally infected dogs. Eleven out of the 21 client-owned dogs (21/123; 17.1%) positive for skin-dwelling O. lupi 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 were 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, oxfendazole was ineffective in reducing ocular lesions and skin-dwelling O. lupi mfs in a six-month follow-up period. In this study, we discuss the need for more reliable diagnostic techniques and efficient treatment protocols to better plan future intervention strategies.