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Member Research & Reports

Member Research & Reports

Iowa Study Indicates Possibility of Vectorborne Transmission of Parasite within the U.S.

A recent study conducted by University of Iowa researchers indicates that Leishmaniasis – a tropical disease caused by infection with Leishmania parasites — can be transmitted from infected U.S. dogs to humans via the bite of infected sand flies.

[Photo: Dr. Christine Petersen]

There are several different forms of leishmaniasis in people. The most common forms are cutaneous leishmaniasis, which causes skin sores, and visceral leishmaniasis, which affects several internal organs (usually spleen, liver, and bone marrow) and is fatal.

In the United States, a species of the parasite that causes visceral leishmaniasis circulates among hounds used for hunting. Previous evidence has indicated that spread of these parasites among hounds is from mother to pups (vertical transmission) rather than by sand fly bites (vectorborne transmission).

However, experimental work reported in the December issue of Emerging Infectious Disease showed that sand flies that had fed on infected hounds were capable of supporting the parasite and spreading it to hamsters.

Dr. Christine Petersen is an associate professor of epidemiology and director of the Center for Emerging and Infectious Diseases at the University of Iowa College of Public Health, and served as corresponding author of the study. According to Dr. Petersen, the study shows that the U.S. strain of Leishmania does not behave differently that the tropical version and it can spread from infected U.S. dogs by an insect vector.

“Sand flies found already in this country are capable of spreading the disease that can be fatal to both people and dogs,” she says.

Peterson says the disease is fairly rare in humans, but the study indicates that given the right subject – one that is immunocompromised and working closely with infected dogs, for example – and the right conditions, the parasite can be transmitted to humans.

This vectorborne transmission from hounds (and possibly coyotes, foxes, and opossums) to another mammalian species indicates a possible risk for spread to companion dogs and people in the United States. Because no vaccines or drugs to prevent infection are available, the best way to prevent infection is to avoid insect bites.

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