With leishmaniasis endemic in 88 countries, emergence in the United States, and the zoonotic nature of the disease, identification of infected canines remains of utmost importance so transmission can be minimized. Infected canines are the number one reservoir for human infection. Two of the diagnostic tests used in this lab determine whether an animal has been infected with Leishmania infantum through antibody production: IFAT and DPP Canine Leishmania Rapid Assay.
The CDC performs an indirect immunofluorescence assay test to determine seropositivity. IFAT employs a secondary antibody labeled with a fluorescent marker that recognizes the primary antibody mounted on a slide; fluorescence around the organisms on the slide indicated a positive result, from which two-fold dilutions were performed to obtain the final titer. The DPP test used by our lab employs capillary action to move a sample, blood or serum in most cases, across test and control areas. These areas have antigen bound to the membrane solid phase, Leishmania antigen in the test area and non-specific antigen in the control area, to which the corresponding antibodies in the sample bind. Conjugated gold particles react with the antibody-antigen complex to produce a reddish-purple line in the test and control areas; the presence of a control line only indicates a negative result, both control and test lines indicate a positive result, and a test line only indicates an invalid result.
The third diagnostic test ascertains the presence of Leishmania infantum infection through kinetoplast-specific quantitative PCR, in which a target sequence of the parasitic kDNA is tagged with a fluorescent probe and replicated repeatedly. This results in exponential amplification, allowing quantification of the original amount of the target sequence. Other tests for leishmaniasis and the L. infantum parasite exist while there is still no reliable vaccine for the disease.