Identificação morfológica e molecular de Acanthocheilonema reconditum em um canino: relato de caso

Abstract

Acanthocheilonema reconditum (A. reconditum), also known as Dipetalonema reconditum, is a nematode helminth that causes filariasis in dogs, which presents global distribution and produces microfilariae that circulate in the blood of its natural hosts. The filarial worms are preferably housed in the subcutaneous tissue and the perirenal tissue of dogs. Fleas and lice are marked as the intermediate hosts and vectors. Due to the fact that it is a parasite of low pathogenicity and because there are other filarial nematodes that also release microfilariae in the bloodstream, it becomes important to distinguish between them by means of morphological observation of the circulating microfilariae, detection of circulating antigens, histochemical or immunohistochemical staining of microfilariae or by molecular diagnostics. Among the nematodes that must be differentiated from A. reconditum are the Dirofilaria immitis and the Dirofilaria repens, which are recognized as the causative agents of cardiopulmonary and subcutaneous dirofilariosis in dogs, respectively. This paper describes a case of A. reconditum infection in a dog, diagnosed by fine needle aspiration cytological examination of two cutaneous nodules and through the thick blood smear technique, being confirmed by PCR. This canine presented volume increase in the perineal region, nodule in the right pelvic limb, dorsal region and inner face of the ear. The CAAF of the perineal volume increase was suggestive of adenoma / adenocarcinoma of the perineal gland, whereas the same procedure performed on the pelvic limb was compatible with mastocytoma. The material of the costal node and the inner face of the ear, when evaluated at a magnification of 100x, demonstrated the presence of microfilaria morphologically suggestive of A. reconditum. However, the clinical manifestations of the patient probably worsened not by A. reconditum infection itself, but due to a possible paraneoplastic syndrome related to second degree mastocytoma, which was diagnosed by cytology and confirmed by histopathological examination. With this report, it can be concluded that this parasite is present in the Santa Maria region and that the differentiation of its most similar filarid, Dirofilaria immitis, is of the utmost importance, since A. reconditum infection does not imply in such expensive and potentially aggressive therapy as for Dirofilaria immitis.