Filarial infection caused by Onchocerca boehmi (Supperer, 1953) in a horse from Italy

Equids may be infected by a range of skin-dwelling filarial nematodes, including four species of the genus Onchocerca. Current literature on equine onchocercosis is fragmentary, and often limited to isolated case reports. The present study describes a clinical case caused by Oncocerca boehmi (syn. Elaeophora boehmi) in an 8-years old horse from northern Italy. The animal presented a firm and painless mass on the proximal third of the right metacarpal region. Ultrasound examination showed a peritendinous enlargement around the palmar-lateral part of the tendons, characterized by an elongatedcharacterized by an elongated hypoechoic and well-defined structure, embedding a coiled hyperechoic line. The metacarpal nodule was resected and histologically examined. Fragments of a parasitic nematode were detected, isolated and examined. Total genomic DNA was extracted from individual fragments using a commercial kit and the nematode was identified as O. boehmi. Comparative sequence analysis of the nematode cytochrome oxidase subunit 1 (cox1) sequence with data available in the GenBankTM database revealed high sequence similarity (i.e., 91%) with that of Onchocerca lupi. Thus far, O.boehmi has only been described in two isolated reports in Austria and Iran, and information about its life-cycle and vectors is lacking. The systematic position of this species within the genus Onchocerca is in concordance with our morphological and molecular results. In this article, we describe the first autochthonous case of equine onchocerciasis in Italy caused by O. boehmi, and discuss novel parasitological, clinical and pathological data on these neglected pathogens of horses.