From the Research
Theileria orientalis is a tick-borne hemoparasite that can be transmitted by Asian longhorned ticks (Haemaphysalis longicornis), causing anemia, ill thrift, and death in cattle, with the Ikeda strain being more virulent than other strains. The disease can lead to significant economic impacts on the cattle industry, particularly in regions where the parasite is endemic. According to a study published in 2021 1, the U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis.
Key Points
- Theileria orientalis is a tick-borne hemoparasite that causes anemia, ill thrift, and death in cattle globally.
- The Ikeda strain of T. orientalis is more virulent than other strains, leading to severe clinical signs and death of up to 5% of affected animals.
- Asian longhorned ticks are invasive to North America and were first detected in the United States in 2017, raising concerns about the spread of Theileria.
- Prevention focuses on tick control through regular inspection of livestock, application of acaricides (tick-killing chemicals) such as permethrin or fipronil, and pasture management to reduce tick habitats.
- Treatment for infected animals typically involves supportive care and sometimes antiprotozoal medications like buparvaquone or imidocarb dipropionate, though these may not be available in all regions.
Diagnosis and Transmission
The diagnosis of oriental theileriosis is usually based on clinical signs, the detection of piroplasms of T. orientalis in blood smears, and/or the use of serological or molecular techniques 2. The transmission of T. orientalis by Haemaphysalis longicornis ticks has been confirmed in several studies, including a study published in 2021 1, which demonstrated that U.S. H. longicornis ticks are competent vectors of the VA-U.S.-T. orientalis Ikeda strain.
Epidemiology and Control
The spread of these ticks is concerning because they reproduce asexually through parthenogenesis, allowing a single female to establish a new population, and they can survive in various environments. While primarily affecting livestock, there is growing concern about potential impacts on wildlife and, theoretically, humans, though human infection with tick-borne Theileria remains rare 3. Control measures should focus on reducing the tick population and preventing the spread of the parasite, including regular inspection of livestock, application of acaricides, and pasture management to reduce tick habitats.