Canine leishmaniasis
Sandfly-borne parasitic disease affecting dogs, expanding beyond Mediterranean regions.
Canine leishmaniasis is a zoonotic disease caused by Leishmania parasites transmitted by the bite of an infected phlebotomine sandfly. No documented cases of transmission from dogs to humans exist. First identified in Europe in 1903, by 1940 40% of all dogs in Rome tested positive, and the disease is now expanding into continental climate areas of northwestern Italy.
Quick Facts
- First identified in europe
- 1903
- Canadian provinces with leishmania-posit
- 2
- Effectiveness of deltamethrin collars
- 86%
Facts from the source article.
Cause
Numerous strains and subgenus strains of Leishmania exist, with new ones still being discovered. In the Old World, Leishmania transmitted by Phlebotomus sandflies includes L. donovani in Sri Lanka and L. infantum, which began appearing in U.S. dogs in 2000. New World strains are spread by Lutzomyia, though whether North American sandflies can transmit the disease remains unconfirmed. Dogs are known reservoirs of L. infantum, and dog-to-dog spread has been confirmed in the United States. Suspected causes of canine visceral leishmaniasis are geographic variants of the Leishmania donovani complex, including L. infantum, L. chagasi, and L. donovani. The Mexicana and Viannia strains are not commonly found in dogs; Viannia strains occur only in Central and South America and cause human leishmaniasis. Traditionally, transmission is from sandfly to dog, but U.S. cases have proven L. infantum Mon1 strain transmission via direct contamination with blood and secretions, as well as transplacentally from an infected bitch to her pups. This mode appears unique to the Mon1 strain, which remains viable for sandfly transmission. A Brazilian study of 63 puppies from L. donovani-infected parents found no evidence of congenital or transplacental infection.
Diagnosis
In the United States, certain breed clubs strongly recommend screening for Leishmania, especially in imported breeding stock from endemic locations. The Foxhound and Neapolitan Mastiff appear predisposed to the disease for unidentified reasons. The Italian Spinone Club of America requests all breeders and owners to submit samples; 150 Spinone Italiano dogs have tested positive in the U.S. Veterinary colleges and government bodies assisting with testing include the Centers for Disease Control and Prevention, Iowa State University Department of Pathology, and North Carolina State University College of Veterinary Medicine. Diagnostic testing uses molecular biology and genetic techniques with high accuracy and sensitivity. Common methods include Enzyme-Linked Immunosorbent Assays (ELISA) and DNA amplification via Polymerase Chain Reaction (PCR). PCR is highly sensitive and specific, producing accurate results quickly. In one study, PCR showed approximately 20% of Foxhounds positive, while serological assays showed only 5%. Diagnosis can be complicated by false positives from the leptospirosis vaccine and false negatives from insufficiently sensitive methods.
Prevention
In areas where the known vector is a sandfly, deltamethrin collars worn by dogs have proven 86% effective. The sandfly is most active at dusk and dawn; keeping dogs indoors during those times helps minimize exposure. No single prevention method or vaccine covers multiple Leishmania species, as different virulence factors and immune mechanisms exist. In 2003, Fort Dodge Wyeth released the Leshmune vaccine in Brazil for L. donovani, with studies indicating up to 87% protection. Common side effects include anorexia and local swelling. The president of the Brazil Regional Council of Veterinary Medicine warned that vaccinated dogs develop antibodies, making them difficult to distinguish from asymptomatic infected dogs. Studies suggest the Leshmune vaccine may be reliable against L. chagasi and a possible treatment for dogs already infected with L. donovani. Vaccination and immunotherapy may also treat ongoing L. infantum infection.
Research directions
In the United States, research examining the Foxhound and Neapolitan Mastiff is scheduled to continue into 2011 at the University of Iowa. The project aims to screen for Leishmania parasite DNA and serve as a stepping stone for future T-cell function research, with the goal of understanding canine leishmaniasis as a model for human leishmaniasis. The CDC is monitoring Italian Spinones, with no end date indicated on sample submissions.
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