Setaria labiatopapillosa (Filarioidea, Nematoda) in Moroccan cattle: atypical localization and morphological characterization of females and microfilariae by light and scanning electron microscopy

Filarioid nematodes are parasites of the tissues and tissue spaces of all vertebrates except fish. Females produce microfilariae that enter the host's blood circulation or skin and may cause ocular and neurological pathology, leading to important implications in veterinary and public health. The present work is the first investigation on Setaria labiatopapillosa conducted in Morocco to characterize the morphological features of both adult and microfilaria forms. Two adult female nematodes were found free in the thoracic cavity of a slaughtered 3.5-year-old (6 teeth) Moroccan enhanced cross-breed bull which was born and raised in Morocco. The worms were identified as S. labiatopapillosa by light microscope (LM) and scanning electron microscopy (SEM) on the basis of their characteristic features of the anterior and posterior parts of the worms. The two S. labiatopapillosa worms measured 90 mm and 105 mm in length and 0.55 and 0.64 mm in width, respectively. Microfilariae were detected in the fully developed eggs contained in the uterus of both nematodes. A detailed morphology of both the adult females and larvae of S. labiatopapillosa is described using LM and SEM. Although the origin of S. labiatopapillosa analyzed in the present study is unknown and there is currently no evidence that Setaria spp. have invaded Morocco, further surveillance is warranted to determine the incidence of setariasis, identify its vectors, and take appropriate measures to protect the livestock and cattle industry of the country.