Theileria orientalis Ikeda in New York
Theileria orientalis genotype Ikeda, an emerging protozoan parasite that causes bovine infectious anemia, has been found on a dairy farm in Genesee County, New York. It has also been found on cattle farms in Virginia, West Virginia, and Tennessee. There are three genotypes of Theileria orientalis: Buffeli, Chitose and Ikeda. T. orientalis genotype Ikeda infects red and white blood cells. Clinical signs of theileriosis are similar to anaplasmosis in cattle and include anemia, fever, jaundice, weakness, and abortion.
Theileria orientalis genotype Ikeda is transmitted in the saliva of Ixodid ticks, primarily by Haemaphysalis longicornis, the Asian Longhorned Tick (ALT). The first report of ALT in the United States was in New Jersey in 2017, but it likely arrived in this country long before that. To date, ALT has been found in numerous states on the east coast, including Virginia, West Virginia, North Carolina, Pennsylvania, New Jersey, New York, Tennessee, Maryland, Kentucky, Connecticut, Delaware, Georgia, Ohio, South Carolina, Arkansas, Missouri, and Rhode Island. In addition to tickborne transmission, T. orientalis can also be spread by iatrogenic means. Use of shared needles should be discouraged, and equipment used between animals (i.e., for tattoo and dehorning) should be properly cleaned and disinfected after each use.
T. orientalis genotype Ikeda infections may cause varying rates of mortality in herds depending on prevalence of vectors and other routes of transmission. Most reports have occurred in beef cattle out on pasture, where ticks are prevalent. Cattle that recover from theileriosis often become carriers, serving as a source of infection for others in the herd. Infections can lead to major economic loss due to death, illness, and reduced milk production.
Farmers should regularly inspect their cattle for ticks, especially those animals that are not gaining weight, look unthrifty, or have patchy hair loss. Newly purchased animals should also be inspected for ticks prior to adding them in with the rest of the herd. Keeping pastures mowed and keeping cattle away from wooded areas may also help to reduce tick exposures. Control of ALT using acaricides alone may not be sufficient since this tick spends most of its time in the environment and not on its biological host.
More information on ALT control methods can be found in a publication produced by Virginia Cooperative Extension, Managing the Asian Longhorned Tick: Checklist for Best Management Practices for Cattle Producers.
Currently, there are no approved treatments or vaccines for Theileria orientalis infection. Theileriosis is a reportable disease in New York. If you suspect Theileria orientalis infection in a herd, contact the New York State Department of Agriculture and Markets at 518-457-3502 or report it to your area field veterinarian.