Evaluation of a prototype flow cytometry test for serodiagnosis of canine visceral leishmaniasis.

Abstract

Canine visceral leishmaniasis (CVL) is considered one of the most important canine protozoan diseases of zoonotic concern (1). Various species of Phlebotomus and Lutzomyia sandflies are the potential vectors for the pathogenic agent Leishmania infantum (2). In some European, Asian, and African countries and in America, infection in dogs is associated with a risk of human disease (3–5). In Brazil, the Ministry of Health, through the Visceral Leishmaniasis Control and Surveillance Program (VLCSP), has instituted specific measures to reduce morbidity and case fatality rates, including treating human cases, instituting vector control, and, an action that is unique in the world, sacrificing all seropositive/infected dogs and prohibiting the treatment of CVL (6). During the last decade, the criteria for eliminating infected animals were based on enzyme-linked immunosorbent assays (ELISAs) for screening and indirect immunofluorescence antibody tests (IFATs) for the confirmatory diagnosis of CVL (6, 7). That these tests may lead to false-positive results due to crossreactivity with other parasitic diseases is well known (8, 9). Recently, this approach was modified, and testing is now based on a dual-path platform (DPP) for screening and an ELISA for confirmation (10). However, Grimaldi et al. (11) evaluated the DPP test for the serodiagnosis of CVL and showed that it does not perform well in detecting asymptomatic dogs from areas where canine disease is endemic. It has been shown that vaccination with Leishmune may lead to seroconversion in healthy dogs (10). The vaccination of dogs has increasingly become a common practice in areas in Brazil where CVL is endemic; recently, in addition to the Leishmune vaccine, the Leish-Tec vaccine has become available commercially, and new candidates, such as the LBSap vaccine, are being studied (12– 15). In this sense, seroconversion has become an important problem for surveillance/control programs that employ conventional methodologies in their seroepidemiological surveys, because it can lead to the unnecessary euthanasia of healthy dogs. Nevertheless, the role of vaccination in the diagnosis of CVL still has not been studied sufficiently.