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Leishmaniasis

1. Type of disease: protozoal zoonosis
2. Forms of the disease: cutaneous (New World and Old World) and visceral
3. Agent: Leishmania – L. mexicana, L. braziliensis, L. tropica, L. major, L. aethiopica (all cutaneous) and L. donovani (both cutaneous and visceral)
4. Affected species: humans - both forms; dogs - both forms; rodents, horses and cats -cutaneous
5. Severity: chronic and fatal if not treated (Even the cutaneous form can be fatal through secondary bacterial infections in lesions)
6. Transmission: Sandflies carry the infective protozoa from the host specie and transmit it through biting. Interestingly, sandflies have a short lifespan - usually 3-4 weeks.
7. Hosts: Human, dogs and other canids- visceral; rodents- cutaneous
8. Incubation period: Cutaneous - usually 2-6 weeks, but as long as 10 years; Visceral - usually 2-4 months, but as long as several years
9. Symptoms of visceral form: victim becomes progressively weaker and experiences fever that may come and go, disinterest in food, hair loss, weight loss, bleeding from gums and mucous membranes, kidney failure, swollen lymph glands and joints. Cutaneous form causes papules that develop into slow-healing ulcers.
10. Treatment: Pentavalent antimony compounds, such as sodium stibogluconate and meglumine antimoniate, are used for treating humans, but not officially approved for use on dogs. The dosage is usually 30-50 milligrams per kilogram of weight per day for several weeks, running the risk of toxic effects.

Current Importance: Visceral leishmaniasis is not usually seen in the United States, and has until this year (2000) appeared mostly in the southern tier of states ( Oklahoma in 1980; Kansas in 1982; Ohio in 1988; Michigan in 1989; and Texas and Alabama in 1991. An outbreak in foxhounds in New York State began in April, and is believed to be continuing as cases are recognized in Virginia, Michigan and Maryland. Other outbreaks of the disease this year have been reported in Kenya, Nepal and Spain. 1998-99 saw outbreaks in Nicaragua, Brazil, Panama and Sudan. How the disease came to New York State and how it is spreading in the absence of sandflies is being investigated. The supposition is, however, that it is being transmitted between dogs by their own bites. The aggressive nature of foxhounds make this highly possible. As to the origin of this particular outbreak, some have suggested that dogs brought into the U.S. from the Middle East may be responsible. On the other hand, given that the incubation can be as long as several years, the 1980 cases may have spawned all those that followed. There is no evidence that dogs can transmit the disease to humans. The caveat is, however, that there is no evidence either that dogs can transmit the disease by biting other dogs.
Sources: Merck Veterinary Manual, 7th Edition; Zoonoses, Iowa State University Press 1995; print and broadcast media; ProMED-AHEAD-mail reports and project archives.