Role of larvae in transstadial transmission and endemicity of in chronically infected sheep.

, transmitted by ticks, is the causative agent of ovine babesiosis, a disease characterized by fever, anemia, hemoglobinuria, and high mortality in sheep. This study investigates whether sheep that survived babesiosis without treatment can serve as a source of infection for -free host-seeking larvae in a later season. Three donor sheep were experimentally infected with , and after six months, persistence of was assessed through blood and tick transmission experiments. Blood from donor sheep was intravenously injected into three recipient sheep, while donor sheep were also infested with -free larvae. Engorged nymphs molted to adults, and new recipient sheep were infested with these ticks. All recipient sheep were monitored for for 100 days using microscopic, serological, and molecular approaches. The presence of was confirmed in the recipient sheep that received blood, leading to clinical infection in two. However, no was detected in recipient sheep infested with ticks. These results suggest that sheep recovering from infection do not serve as a source of infection for larvae in subsequent seasons.