By Sarah Carey

Dr. Sarah Reuss and Dr. Jim Wellehan inspect the ear of a healthy horse. (Photo by Maria Farias)

A rare, potentially fatal species of parasite never before found in North America has been identified in a Florida horse.

University of Florida veterinarians identified the parasite, called Leishmania siamensis, in the summer of 2011. This particular species of parasite previously had been found only in Thailand and parts of Europe while other species of Leishmania have been found all over the world. No Leishmania infections of any species had been previously reported in a horse native to the United States.

The UF discovery raises awareness of how widespread the parasite is and suggests a need for watchfulness regarding potential transmission to humans, the researchers said.

“We now know the parasites that cause this disease also exist here in the U.S. and that we have some insect, presumably the sandfly, that is capable of transmitting the disease,” said Sarah Reuss, V.M.D., a clinical assistant professor of large animal medicine at the UF College of Veterinary Medicine, who along with UF colleagues and a private practice clinical pathologist described the findings in the September issue of Emerging Infectious Diseases, a journal of the Centers for Disease Control and Prevention. “Our findings raise several potential avenues of further investigation, including the prevalence of this disease in horses in the U.S., a better understanding of the sandfly life cycle and the potential of this leishmaniasis species to be transmitted from animals to humans.”

Leishmaniasis is a parasitic infection spread through the bites of infected sandflies. The disease shows up most commonly in two forms: cutaneous, which causes sores on the skin, is self-healing; and visceral, the most severe form, which affects the entire body and is almost always fatal if left untreated. After malaria, leishmaniasis is the leading parasitic cause of death in humans. The disease has been found in four continents and is considered to be endemic in 88 countries, including 16 developed nations, according to the World Health Organization. The WHO estimates the worldwide prevalence at 12 million cases, with about 350 million people at risk of infection and about 60,000 people dying from the disease each year. Leishmaniasis is rare in people in the U.S.

“It really hasn’t been a disease that has affected Americans, but there are really good data with climate change models that predict sandfly ranges will expand, making this disease much more of a threat because of global warming,” said co-author James Wellehan Jr., D.V.M., Ph.D., a veterinarian from the UF research team, who confirmed the presence of the disease in the Florida horse by analyzing the genes of the parasite.

The visceral form of leishmaniasis is endemic in foxhounds in the U.S, associated with a different species of Leishmania. But aside from some regional transmission in the Southwest, most of the cases of skin infection due to leishmaniasis in the U.S. are believed to have occurred in animals brought in from countries where the disease is common, or in people who had recently spent time in those countries.

“Thousands of people serving in the U.S. military have returned from Iraq and Afghanistan with cutaneous or visceral leishmaniasis,” said Christine Petersen, D.V.M., Ph.D., an associate professor of veterinary pathology at Iowa State University’s College of Veterinary Medicine and an expert on Leishmania transmission, immune responses and veterinary disease, who was not involved in the study. “In a few cases, these individuals have brought dogs back with them that also have leishmaniasis.”

The horse diagnosed at UF had no history of travel outside of the eastern U.S. The pregnant 10-year-old Morgan mare was treated as an outpatient at the University of Florida Large Animal Hospital for sores inside her left ear. A biopsy done in the field had suggested that the rare parasite was present when organisms that looked like the protozoa were seen within the inflammatory cells in that tissue. Further tissue samples and genetic analysis were used to identify the species of the disease-causing organism at UF.

Often, leishmaniasis of the skin will resolve without medical treatment. But the mare’s sores worsened over time — a development the veterinarians attributed to the pregnancy.

“Many of the horses in other countries that have been diagnosed with leishmaniasis were pregnant, so we think perhaps these horses have pregnancy-altered immune systems and are therefore more vulnerable to the disease,” Reuss said.

The drug used to treat horses with the disease in other parts of the world isn’t readily available in the U.S., and surgery wasn’t an option because the sores were inside the horse’s ear. After treatment with anti-fungal drugs, the sores eventually regressed. Horses housed at home with the affected horse did not show any signs of illness. Though the disease needs the sandfly as a carrier and does not pass directly among horses or between horses and humans, veterinary experts say the discovery of the new parasitic species in the U.S. is cause for increased vigilance.

“As a disease of animals capable of being transmitted to humans, leishmaniasis requires more attention to ensure we do not have vector-borne transmission within larger areas of the country,” Petersen said.

Director, Hofmann Equine Neonatal ICU
Large Animal Clinical Sciences
Large Animal Internal Medicine
sanchezl@ufl.edu
PO Box 100136
2015 SW 16th AV
Gainesville, FL 32608-0136
352-392-2229
FAX: 352-392-8289

Education

• PhD, University of Florida, Gainesville, Fla., 2003
• Diplomate, American College of Veterinary Internal Medicine, Large Animal, 1999
• Resident, Large Animal Internal Medicine, University of Florida, Gainesville, Fla., 1996-1999
• DVM, University of Florida, Gainesville, Fla., 1995

Honors and Awards

• Large Animal Clinician of the Year, University of Florida, Gainesville, Fla., 2005, 2010 and 2011
• Florida Veterinary Medical Association Clinical Investigator Award, University of Florida, Gainesville, Fla., 2007
• Excellence in Doctoral Studies, University of Florida College of Veterinary Medicine, Gainesville, Fla., 2003
• Large Animal Resident of the Year, University of Florida, Gainesville, Fla., 1999

Research Interests

My research has primarily been focused in three main areas: the equine gastric ulcer syndrome, pain management in the horse, and critical care of equine neonates. My laboratory has evaluated the effectiveness of various drugs for the treatment of gastric ulcers in foals and adult horses and for pain management in adult horses. We have also evaluated how different factors (age, housing, illness) can affect the physiologic environment of the stomach in foals and adult horses. The overall goal of this work is to gain a better understanding of the equine gastric ulcer syndrome and to improve our ability to manage various types of pain in horses.

Recent Publications

Publications listed here.

Large Animal Clinical Sciences
Large Animal Internal Medicine
mackayr@ufl.edu
PO Box 100136
2015 SW 16th Ave
Gainesville, FL 32608-0136
352-392-2229
FAX: 352-392-8289

Education

• Diplomate, American College of Veterinary Internal Medicine, 1981
• PhD, Department of Pathology, University of Florida, Gainesville, Fla., 1987
• BVSc (Dist), Massey University, Palmerston, New Zealand, 1975

Honors and Awards

• Large Animal Medicine Clinician of the Year, University of Florida, Gainesville, Fla., 1991
• Daniels Young Clinical Investigator, University of Florida, Gainesville, Fla., 1991
• Large Animal Clinician of the Year, University of Florida, Gainesville, Fla., 1989
• Resident of the Year Award, University of Florida, Gainesville, Fla., 1980
• Outstanding Large Animal Intern Award, University of California, Davis, 1977
• Massey University Scholarship, Palmerston, New Zealand, 1974
• BVSc with Distinction, Massey University, Palmerston, New Zealand, 1975
• Veterinary Parasitology Prize, Massey University, Palmerston, New Zealand, 1972

Research Interests

Expertise includes general internal medicine and a special interest in clinincal neurology. Research interests are also in the area of inflammation/endotoxemia and in the diagnosis and biology of equine protozoal myeloencephalitis (EPM). Through this work, the pathogenesis of endoxemia in horses has been clarified and at least one new treatment developed and extensively used. In the field if EPM, Dr. MacKay has contributed to an understanding of the life cycle of the parasite and is actively involved in developing new and more satisfactory diagnostic tests.

Recent Publications

Publications listed here.

Equine Extension Specialist
Director, Equine Research Programs
Course Director, Practice Based Equine Clerkship
Large Animal Clinical Sciences
Large Animal Internal Medicine
housea@ufl.edu
PO Box 100136
2015 SW 16th Ave
Gainesville, FL 32608-0136
352-392-2229
FAX: 352-392-8289

Education

• Diplomate, American College of Veterinary Internal Medicine, Large Animal, 2005
• DVM, Tufts University, North Grafton, Mass., 2001
• BS, Animal Science, Cornell University, Ithaca, NY, 1997

Honors and Awards

• University of Georgia Outstanding Graduate Teaching Award, Athens, Ga., 2005
• Tufts School of Veterinary Medicine Academic Excellence Award, North Grafton, Mass., 2001
• AVMA Auxiliary Award, 2001
• Tufts Veterinary Medicine Award for Excellence in Equine Medicine, North Grafton, Mass., 2001
• Society of Phi Zeta, 2000

Research Interests

Dr. House’s clinical interests include neonatology, infectious disease, and camelid medicine. She is also working on a multi-center clinical research grant in neonatology funded by the Grayson Jockey Club Research Foundation.

Recent Publications

Publications listed here.

Department of Infectious Diseases and Pathology
PO Box 110880
2015 SW 16th Ave
Gainesville, FL 32608-0880
longm@ufl.edu
352-294-4162
Fax: 352-392-9704

Education

• PhD (1998) Washington State University – Veterinary Science
• MS (1993) University of Illinois – Veterinary Science
• DVM (1986) Iowa State University – Veterinary Medicine

Honors and Awards

• 1996, Diplomate, American College of Veterinary Internal Medicine
• 1996, Dr. Lynn A. George Scholarship for Basic Science Research
• 1993, LE Boley Award in Research Excellence, University of Illinois
• 1982, Honors Graduate, Iowa State University
• 1979, Top 2% Ag College, Iowa State University
• 1977-1982, Dean’s List 1977-1982

Research Interests

Research interest include several equine and large animal infectious diseases which inclue Ehrlichia risticii, Neospora caninum, Toxoplasma gondii, Equine Infectious Anemia Virus and West Nile Virus. Clinical interests are infectious diseases, immunology, and endocrine diseases.

Recent Publications

• Multiplexed microsatellite loci in American crow (Corvus brachyrhynchos), a severely affected natural host of West Nile virus.

Additional publications here

Large Animal Internal Medicine
Large Animal Clinical Sciences
zimmeld@ufl.edu
PO Box 100136
2015 SW 16th Ave
Gainesville, FL 32608-0136
352-294-4379
FAX: 352-392-8289

Education

• Diplomate, American Board of Veterinary Practitioners, 1999
• Diplomate, American College of Veterinary Internal Medicine, 1999
• DVM, University of Florida College of Veterinary Medicine, Gainesville, Fla., 1995
• BS, Animal Science, University of Florida College of Veterinary Medicine, Gainesville, Fla., 1990

Honors and Awards

• UF CVM Alumni Achievement Award, 2013
• UF Superior Accomplishment Award, Gainesville, Fla., 2010
• Outstanding Contribution Award, Florida Association of Equine Practitioners, 2006
• UF Superior Accomplishment Award, Gainesville, Fla., 2006
• Raleigh Burroughs Media Award, 2005
• Upjohn Clinical Proficiency Award in Large Animal, 1995
• Lloyd’s of London Bursary Award, 1995

Research Interests

Dr. Zimmel’s clinical interests include neonatology, exercise physiology, and endocrine disease.

Recent Publications

Additional publications here.