Presence of Leishmania sp. and Dirofilaria immitis in Cutaneous Canine Transmissible Venereal Tumor

Background: Canine Transmissible Venereal Tumor (CTVT) is a neoplasm transmitted by implantation of its cells into genital and extragenital organs, while Heartworm and Visceral Leishmaniasis are zoonosis transmitted by hematophagous insects that are often underdiagnosed in asymptomatic animals. Coinfection by the agents of these parasitosis is well documented, however, the association of both diseases with the CTVT is still unusual. Thus, it was aimed to report a case of incidental identification of microfilariae of D. immitis and amastigotes forms of Leishmania sp. in cutaneous CTVT by cytology in an asymptomatic dog for the parasitosis.Case: A 6-year-old, male, mongrel, sexually intact dog from the city of Patos, Paraiba, Brazil, was presented with a cutaneous circumscribed tumoral lesion in a region adjacent to the right olecranon, with an ulcerated surface of reddish color, having areas of necrosis inside and larvae (myiasis), draining bloody secretion. The material was collected for cytological analysis, which proved to be Canine Transmissible Venereal Tumor (CTVT) with the presence of amastigote forms of Leishmania sp. and microfilariae of D. immitis among neoplastic cells. Blood count, serum urea, creatinine and albumin, ALT, AST, FA, CK, Na+, K+, Ca++, CK-MB, Troponin I (cTnI), Snap 4Dx Plus (Idexx®), Snap Leishmania (Idexx®), and Knott's test were performed, plus chest radiography, blood pressure measurements and electrocardiogram (ECG). The alterations found corresponded to normochromic normocytic anemia, thrombocytopenia, hypoalbuminemia, microfilariae in the Knott test, increase of CK, CK-MB and cTnI, positivity for Erlichia sp., Anaplasma sp., Leishmania sp. and Dirofilaria immitis. Furthermore cardiomegaly on radiographs and sinus arrhythmia associated with atrioventricular block (AVB) of the first degree on the ECG. Euthanasia was performed after necropsy, in which adult worms were observed in the right heart chambers.Discussion: The coexistence of neoplastic diseases and infectious microorganisms is often detected only incidentally in asymptomatic animals and complementary tests are important tools to support clinical suspicions, as was observed in the present case. The fact that the animal is not neutered, be in full sexual activity and have unrestricted life habit, favored his involvement by CTVT due to greater contact with other whole canines. Coinfection by Dirofilaria sp. and Leishmania sp., identified in this case, has already been confirmed in several countries, suggesting the presence of distinct vectors in the same geographical area and the imminent exposure of humans to these agents. Despite the studies evidencing the systemic infection by the two parasites, there are no reports of mutual parasitism by the pathogens mentioned in canine neoplasms, especially in the cutaneous extragenital form of the CTVT, making the present case uncommon. The cytological examination was fundamental not only to show that the cutaneous lesion was a CTVT, but also to have evidenced the parasites Leishmania sp. and Dirofilaria immitis, whose infections remained hidden. The changes present in hematology are commonly present in the diseases diagnosed in this case, and elevation of CK, CK-MB and cTnI denote damage to cardiomyocytes due to the action of both parasites. Cardiomegaly on radiographs and 1st degree AVB on the ECG also correspond to secondary changes in the presence of worms in the animal's cardiovascular system. Thus, the presence of a dog autochthonously infected by parasites with a zoonotic potential reveals the susceptibility of other animals and humans in the region to infections.