Unusual cytological finding of sheathed microfilariae in a fine needle aspirate: a case report

Abstract

Filariasis is a neglected mosquito-borne tropical parasitic disease with public health importance in tropical and subtropical countries. Canine filarial infections are caused by many nematode species such as Dirofilaria immitis, D. repens, Brugia pahangi, B. malayi and Acanthocheilonema reconditum (Satjawongvanit et al., 2019). Microfilariae of Brugia spp. are sheathed while those of others are non-sheathed (Ravindran et al., 2014). Canine filarial infections are highly endemic to the state of Kerala with the reports of prevalence of microfilaraemia ranging from 8.1 per cent in Thrissur district to very high prevalence of 42.68 per cent in Alappuzha district (Chirayath et al., 2017; Ravindran et al., 2014). The major clinical signs in dogs associated with circulating microfilariae are fever, anorexia, conjunctivitis, dermatitis, oedema of limb and scrotum (Tarello, 2011). The traditional methods for identification of the microfilariae are based on morphological microscopic observation of Giemsa stained peripheral blood smears. Despite the high prevalence of filarial infections in dogs, it is infrequent to find the microfilariae in fine needle aspiration cytology (FNAC) in suspected cases of limb oedema. The demonstration of microfilariae in the aspirate or body fluids plays a pivotal role in diagnosis of the condition and institution of specific treatment modalities, especially in case of lymphatic filariasis (Panicker et al., 2012). In the present communication, a case of canine filarial infection with right forelimb oedema, chronic nonhealing ulcers and localized alopecia diagnosed based on fine needle aspiration cytology ( FNAC) is discussed