D323 - Canine Leishmaniosis

Description:

Various species of the genus Leishmania are the causative agents of visceral, cutaneous, and mucocutaneous leishmaniosis in humans and of leishmaniosis in dogs. With increasing international travel, cases of imported leishmaniosis are regularly diagnosed in dogs in areas where the disease is not endemic. In dogs, Leishmania infantum is main causative agent of canine leishmaniosis and usually causes chronic systematic disease. Not every dog experimentally or naturally infected with Leishmania develops disease. Studies indicate that protective immunity to leishmaniosis in dogs is mediated by T cells and the cytokines they produce. The incubation period varies from 3 months to as long as 7 years. Signs are highly variable and often begin with slight but progressive dullness and insidious exercise intolerance. Weight loss and muscle atrophy are the most common signs canine leishmaniosis. Some dogs lose weight despite having a ravenous appetite, but serious loss of conditions is usually associated with anorexia and other signs of renal failure including mental depression, polyuria, polydipsia, and vomiting. Transient diarrhea may occur. Combined infection with Erlichia, Babesia, and Dirofilaria are quite common if Leishmania infection occurs in regions where these organisms are also endemic.

Diagnosis:

For diagnosis of leishmaniosis in dogs, serological methods, such as the indirect fluorescent-antibody test, ELISA, and Western blotting, or in vitro cultivation is of great value. However, diagnostic in vitro cultivation is cumbersome (because it includes preparation of complex media and time-consuming preparation of blood-containing samples) and expensive. Cultivation for diagnostic purposes takes in general 3 to 4 days and in few cases up to 10 days until positive results are obtained. In areas where the disease is endemic the usefulness of serological methods is limited to epidemiological studies because there are infected dogs that do not show a specific antibody reaction.
An alternative approach to parasitological methods is identification by using molecular biological techniques such as specific PCR. Several Leishmania DNA targets have been identified, and their values for use in a PCR-based diagnosis were evaluated. The results of PCR and in vitro cultivation showed an excellent congruence. The sensitivities of both PCR and cultivation were 100% with bone marrow biopsies and with lymph node aspirates from dogs. Detection of the parasites in whole blood samples was possible but had a lower sensitivity of 84%. This noninvasive blood PCR assay may be used as an initial test, reducing the need for bone marrow biopsies and especially to follow the parasitemia during treatment.

Sample:

1. Lymph node aspirate in sterile container.
2. Whole blood (3 ml) in a lavender top (EDTA) tube.
3. Tissue samples.

Special Handling:

Store blood sample at 4°C until pick up or shipment.

Test Code:

D323

1. Roura et al. (1999) Diagnosis of canine leishmaniasis by a polymerase chain reaction technique. Vet. Rec. 144:262-264.
2. Ciaramella et al. (1997) A retrospective clinical study of canine leishmaniasis in 150 dogs naturally infected by Leishmania infantum. Vet. Rec. 141: 539-543.