Potenciais candidatos a construção de sistemas rápidos, sensíveis e específicos para o diagnóstico da leishmaniose visceral canina

Abstract

Visceral leishmaniasis (VL) is a serious disease, of a systemic character, that can affect the man and mammalian animals, such as domestic dogs, which are considered as the main parasitic reservoirs in Brazil. The diagnosis of canine visceral leishmaniasis (CVL) consists of the use of serological, parasitological and molecular methods, however, none of the currently available options is adequate to monitor the treatment or cure of the disease, requiring an efficient diagnostic method for dogs with VL, as well as to make the correct distinction between symptomatic and asymptomatic dogs. In this way, the objective is to evaluate the potential serological diagnosis of recombinant antigens for CVL in order to improve the detection of the disease in Brazil. Diagnostic actions of the calazar were carried out in neighborhoods of the Tirirical District, in São Luís-MA, for clinical evaluation and collection of blood from dogs. The collected blood was used to perform hemogram and smears on microscopy slides for the diagnosis of canine ehrlichiosis. Serum samples obtained from blood were initially screened with ELISA/S7 kit, to verify the presence of reactive and non-reactive dogs for VL, and the positive cases were confirmed by direct parasitological examination. From the results of clinical and laboratory evaluation, the dogs were classified as symptomatic to VL, asymptomatic to LV, healthy or with another infection. Subsequently, serum groups were used to test the antigen SLA and seven recombinant antigens of Leishmania infantum chagasi, as well as the function of immunological markers for the serodiagnosis of CVL, by the ELISA techniques. A total of 180 dogs were clinically evaluated and obtained biological samples. The predominant clinical signs in the animals were lymphadenomegaly (45,55%), presence of ectoparasites (41,66%), onychogrifose (30%), opaque coat (27,22%), skin lesion (22,77%), muzzle/ear injury (18,33%), alopecia (17,77%) and alteration in nutritional status (17,77%). The clinical score presented by each animal allowed the determination of a cut-off point > 7 to separate VL dogs from dogs with another infectious disease. With the screening performed using the ELISA/S7 kit, antiLeishmania antibodies were detected in 48,33% of the dogs in the Tirirical District area. Among dogs with VL, 26,11% (n=47) were identified as asymptomatic and 22,22% (n=40) as symptomatic and among the no-reactive for VL, 32,77% (n=59) were healthy and 18,88% (n=34) had another infection (canine ehrlichiosis). Three recombinant antigens presented better sensitivity, specificity and high or moderate accuracy scores for ROC curves, obtaining a better diagnostic accuracy than SLA. The other recombinant antigens evaluated, despite recognizing sera from symptomatic and asymptomatic dogs for VL, did not obtain superior results to the SLA. Therefore, ELISAs performed with the antigens indicated three proteins as important candidates for the improvement of LVC diagnosis, due to their satisfactory performances in all parameters evaluated.