Foxhounds, with a long tradition as hunting dogs, have recently become the hounded ones. They have become the prey of leishmaniasis, a disease that can be deadly to dogs.
The Division of Parasitic Diseases, National Center for Infectious Diseases, national Centers for Disease Control and Prevention, has been assisting state and local health and agricultural officials in the investigation of an outbreak in New York and Virginia. The protozoan has infected at least three Foxhound packs in the past 10 years. Scientists from the Walter Reed Army Institute of Research have assisted in field and laboratory investigations.
A small animal medicine resident, a clinical pathologist, and two fourth-year veterinary students from North Carolina State University made the initial diagnosis in February, from a Foxhound in a hunt club in Dutchess County, New York. As the JAVMA went to press, 39 (41.9 percent) of 93 dogs at the hunt club had a positive serologic test result for leishmaniasis, and aspiration or biopsy of lymph nodes and other tissue has resulted in the isolation of Leishmania (belonging to the species complex donovani) from each of the 15 dogs tested. No human infections have been identified in relationship to these canine infections.
The CDC has issued an alert to all states about the outbreak. On April 14, leaders of the Masters of Foxhounds Association of America, in conjunction with the Foxhound Club of North America, decided to cancel all Foxhound shows for the spring season.
Dutchess County, with its reputation for cross-country equestrian events such as fox hunting, is home to Basset Hounds, Beagles, and Foxhounds, but it is only Foxhounds that have tested positive for the disease.
Foxhounds in neighboring hunt clubs in Dutchess County and pet dogs, horses, and wild rodents in the vicinity of the outbreak in New York have recently tested negative for leishmaniasis. Sera from dogs in other states were also tested at the CDC for evidence of infection. Of those, five Foxhounds in Virginia have had positive serologic test results that have been confirmed by isolation of Leishmania.
Leishmaniasis has been transmitted to North America via pets from military personnel formerly stationed in foreign locations. But it has also developed in Foxhounds that have never been out of the United States.
Why Foxhounds? No one knows for sure, but leishmaniasis seems drawn to this breed, which may possess a unique susceptibility to the disease. The route of transmission in these dogs is unclear. Leishmaniasis is a parasitic infection usually transmitted by the bite of an infected female sand fly. Sand flies capable of transmitting certain species of Leishmania are found in the southern United States, but species of sand flies known to transmit L donovani have not, as yet, been reported in the United States. In the absence of infection from sand flies, dog-to-dog transmission is another possibility. The dogs involved in the recent outbreak had traveled to other states for competitions and rest, yet they did not enter any of the states where leishmaniasis had been identified.
Although leishmaniasis is, obviously, not a stranger to this country, approximately 90 percent of the visceral cases (the most severe form) in the world have occurred in Bangladesh, Brazil, India, and Sudan. According to the World Health Organization, however, it is believed many cases are unreported or misdiagnosed. Leishmania infantum is widely disseminated in the Mediterranean countries where it is enzootic in wild and domesticated dogs.
Manifestations of canine visceral leishmaniasis can include skin lesions, epistaxis, wasting, seizures, hair loss, lymphadenopathy, kidney failure, and swollen limbs and joints. Treatment of visceral leishmaniasis in dogs is often not as effective as it is in humans. Leishmaniasis can be a zoonosis, and dogs are reservoirs of vector-borne transmission in other countries, but there have been no cases of autochthonous (ie, indigenous or endemic to a region) human visceral leishmaniasis reported in the United States.
To coordinate future efforts to determine the scope of this problem, the CDC has requested that each state designate a contact person to receive updates from the agency about this investigation. Contact persons' names should be directed to Dr. Jane Rooney, EIS Officer, Virginia State Health Department, phone, (804) 786-6261. Dr. Rooney can also advise veterinarians who are contacted by dog owners who want their dogs tested for leishmaniasis.
An immunofluorescent antibody test using the NY Foxhound isolate and polymerase chain reaction is available for canid diagnostics through the Tickborne Disease Testing Service at North Carolina State University, College of Veterinary Medicine. For details regarding sample submission and fees, contact Matthew Poore at (919) 513-6293.
For further information about canine visceral leishmaniasis, contact Dr. Peter Schantz, e-mail, pms1cdc [dot] gov or Tom Navin, MD, e-mail, trn1cdc [dot] gov, at the Parasitic Diseases Epidemiology Branch, DPD, NCID, CDC, phone, (770) 488-7760.