Clinical Signs, Symptoms, and Transmission
Visceral Leishmaniasis (VL) is a slow wasting disease, caused by a Leishmania parasite. Cutaneous Leishmaniasis, a similar disease caused by another subspecies of the parasite, is characterized by lesions of the skin. In Europe and the United States, the species found in dogs is Leishmania infantum (Duprey et al.,2006). In tropical areas of the world, this infection is due to bites from sand flies which suck blood from infected dogs or people and then bite a dog or person without infection leading to spread of the parasite. Leishmania parasites enter white blood cells underneath the skin after a bite, get into the blood stream and multiply within these cells in the spleen and liver, resulting in a chronic condition characterized by weight loss, tiredness, decreased appetite, and anemia (Petersen, 2009). The spleen, liver, and lymph nodes become enlarged and blood work abnormalities appear. Bleeding disorders resulting in bloody noses or blood in the stool are not uncommon. In later stages of disease, kidney failure and other more severe problems occur. Crusty skin disease is also not uncommon in infected, symptomatic dogs. This appears as non-itchy, raised reddish bumpy areas near the eyes or on the face, ears, axillary regions, or feet. Dogs also can develop abnormally long, brittle nails. Co-infection with other diseases such as intestinal worms, tick-borne diseases and additional stresses such as pregnancy, poor nutrition, overexertion, and being lower in the kennel pecking order can trigger appearance of clinical signs.
Spread of VL in tropical areas is primarily due to bites of sand flies transmitting the parasite between dogs and sometimes humans. In the United States, while sand flies exist in many states with demonstrated cases of canine VL, there have been no Leishmania-infected sand flies trapped in areas around kennels. The primary means of transmission is from infected dams to their offspring (Boggiatto et al, 2011 in press), as well as due to blood to blood contact through biting, wounds, and possibly sexually between infected males and females. The parasite cannot survive in the environment out of the fly or animal for more than a few seconds. There have not been any cases of hound to human spread of this disease in the US.