Canine Visceral Leishmaniasis in an Area of Sporadic Transmission in Brazil

Canine visceral leishmaniasis is a zoonotic disease caused by the protozoan Leishmania infantum in Latin America. Visceral leishmaniasis (VL) diagnosis in Brazil includes two serological tests according to the Ministry of Health (MH) protocol. Sensitivity and specificity of diagnostic tests, as well as clinical signs of VL, are usually reported in disease-endemic areas; however, it is known that local epidemiological factors can influence these results. This study aimed to evaluate the clinical features, sensitivity, and specificity of TR-DPP^® and EIE-LVC in naturally infected dogs in a region of sporadic VL transmission to humans in Brazil. A total of 288 dogs were clinically evaluated and serological and parasitological (lymph node aspirates) samples were collected for VL diagnosis. TR-DPP and EIE-LVC showed poor sensitivity (0.62 and 0.44, respectively) to detect infected animals, compared with the direct parasitological examination, which is considered a gold standard method. Thus, the protocol of MH presented low sensitivity (0.42) to estimate prevalence and control measures in this region. TR-DPP presented a high negative predictive value (0.89), resulting in its indication as a confirmatory test in sporadic transmission areas. Classical clinical signs of VL were not frequently observed; therefore, clinical scoring systems might not be useful in this region. Veterinarians of nonendemic areas should be alert for asymptomatic dogs, especially those presenting lymph adenomegaly.

Improving the serodiagnosis of canine Leishmania infantum infection in geographical areas of Brazil with different disease prevalence

Serodiagnosis of Leishmania infantum infection in dogs relies on the detection of antibodies against leishmanial crude extracts or parasitic defined antigens. The expansion of canine leishmaniasis from geographical areas of Brazil in which the infection is endemic to regions in which the disease is emerging is occurring. This fact makes necessary the analysis of the serodiagnostic capabilities of different leishmanial preparations in distinct geographical locations. In this article sera from dogs infected with Leishmania and showing the clinical form of the disease, were collected in three distinct Brazilian States and were tested against soluble leishmanial antigens or seven parasite individual antigens produced as recombinant proteins. We show that the recognition of soluble leishmanial antigens by sera from these animals was influenced by the geographical location of the infected dogs. Efficacy of the diagnosis based on this crude parasite preparation was higher in newly endemic regions when compared with areas of high disease endemicity. We also show that the use of three of the recombinant proteins, namely parasite surface kinetoplastid membrane protein of 11 kDa (KMP-11), and two members of the P protein family (P2a and P0), can improve the degree of sensitivity without adversely affecting the specificity of the diagnostic assays for canine leishmaniasis, independently of the geographical area of residence. In addition, sera from dogs clinically healthy but infected were also assayed with some of the antigen preparations. We demonstrate that the use of these proteins can help to the serodiagnosis of Leishmania infected animals with subclinical infections. Finally, we propose a diagnostic protocol using a combination of KMP-11, P2a y P0, together with total leishmanial extracts.