Oklahoma-Farm-and-Ranch_543839

AUGUST 2026 | 7 O By Barry Whitworth, DVM Theileria orientalis in Oklahoma Over the past few years, Thei- leria orientalis has been detect- ed in cattle in Oklahoma. Early cases were primarily diagnosed in adult cattle. However, more recent cases in Oklahoma have been identi ed in stocker cattle. All cattle producers should be familiar with the clinical signs of this disease and observe their cattle daily for any signs of trouble. In the United States, the rst case of theileriosis was identi ed in Virginia in August 2017. These cattle exhibited clinical signs of weakness and anemia. An initial diagnosis of anaplasmosis was made. Blood samples from the animals were tested for Ana- plasma, Babesia, and Leptospira. Test results were negative for all three; however, a blood proto- zoan was detected. This organ- ism was identi ed as T. orientalis genotype Ikeda. Since this initial herd outbreak, the organism has been detected in several states. Cattle infected with and showing illness from T. orientalis genotype Ikeda may exhibit clini- cal signs such as fever, weakness, anorexia, and exercise intoler- ance. If forced to move, a ected cattle may stagger and gasp for air. If stressed excessively, they may collapse and die. Upon examination, the gums, eyes, or vaginal mucosa may appear pale (white) or yellow in color. Reproductive losses, including stillbirths and late-term abor- tions, may occur, along with a reduction in milk production. Clinical signs reported in adult cattle in Oklahoma include anemia, sudden death, weight loss, abortion, failure to thrive, and failure to calve. In stocker cattle, weight loss, anemia, poor performance, and sudden death have been reported. Because Anaplasma margi- nale and T. orientalis genotype Ikeda produce similar clinical signs, distinguishing between the two can be challenging. One notable di erence is that clinical signs are more com- monly observed in young cat- tle infected with T. orientalis, whereas this is less common in cattle infected with A. marginale. Additionally, cattle with anaplas- Summer pneumonia is the name given to bovine respiratory disease in young cattle still with their mothers on pastures. (Courtesy photo) Continue on page 8