Detection of Leishmania infantum in Peripheral Blood Smear and Lymph Node of a Domestic Feline

Abstract

 Background: Cats can become infected and develop feline visceral leishmaniasis (LVF) and manifest variable clinical signs. The diagnosis of the disease in this species has been made more frequently by means of serological and molecular techniques. Different from what happens with dogs, the use of parasitological analysis of lymph node, in clinical practice, for agent detection in felines are infrequent. Therefore, the aim of this study was to disclose the diagnosis of visceral leishmaniasis in a domestic cat from the blood smear analysis and aspiration cytology of lymph node.Case: An adult mixed breed queen, from the city of Campo Grande, Mato Grosso do Sul state, Brazil was referred for clinical care due to the presence of a nodule, with approximately 4 cm, near the inguinal breast. Other parameters, on physical examination, are within the normal range for the specie. For the investigation, additional tests were requested. Eosinophilia was found in a complete blood count (CBC). The association between macroscopic characteristics and cyto­logical findings allowed the diagnosis of inguinal lymph node hyperplastic. Furthermore, amastigotes of Leishmania sp. were visualized both in the peripheral blood sample and in the analyzed material mass. The diagnosis of visceral leishmani­asis and identification of specie of Leishmania was performed by PCR technique (Polymerase Chain Reaction), from the detection of genetic material from Leishmania infantum. After diagnosis of the disease, the owner opted for the conduct of animal euthanasia in the Zoonosis Control Center (CCZ), making impossible the realization of post-mortem examination.Discussion: Hematologic changes described for cats with feline visceral leishmaniasis may be absent or multiple and vari­able, such as for example, anemia, agglutination of erythrocytes, leukocytosis, leukopenia and thrombocytopenia, however, isolated eosinophilia, identified in this report, has not been observed by other authors. The viewing of the amastigote forms in blood smears is considered unusual. A study in which there were examined 1438 samples of dogs, the agent detection did not exceed 0.28%. In cats, there is only one report, of a pancytopenic feline, describing this finding and corroborates for the rarity of the observation of amastigote forms in peripheral blood feline of this report. The use of serologic and mo­lecular methods for the diagnosis of disease in felids has been most frequently used, however, high titers of anti-Leishmania antibodies associated with protective humoral immune response and degenerated genetic material of the amastigotes can be detected by PCR techniques, not identifying active infection. The parasitological diagnosis by means of cytological evaluation of lymph nodes is fast, low cost, presents high specificity and is frequently used in research of canine visceral leishmaniasis, however, the use of this technique for the diagnosis of the disease in cats is still restricted to academic environment. The identification of amastigotes in peripheral blood and lymph nodes, detected in this study, indicates the possibility of using the blood test and, especially, the cytological examination of lymph node for parasitological research of feline visceral leishmaniasis and highlights the need of studies to determine the sensitivity of these tests in this species.Keywords: cat, diagnosis, leishmaniasis, complete blood count, cytology.