An experimental study to assess the role of the goat in the decrease of virulence and transmission of Theileria lestoquardi

Malignant Ovine Theileriosis (MOT) is a haemoprotozoan disease affecting sheep and goats, transmitted by the tick Hyalomma anatolicum anatolicum . The acute form is more commonly observed in sheep than in goats. This experimental study aimed to evaluate the effect of the goat on the virulence and transmission of T.lestoquardi . The experimental work was conducted between April 2020 and September 2021. In the first phase, sheep and goats were infected with T. lestoquardi via adult H. a. anatolicum ticks. Daily clinical and paraclinical examinations were performed, and infected animals were treated with buparvaquone (2.5 mg/kg) to prevent mortality. In the second phase, Theileria -free H.a. anatolicum nymphs were allowed to feed on the infected sheep and goats. The salivary glands of the emerged adult ticks were examined for T. lestoquardi using PCR. Four healthy, six-month-old sheep were divided into two groups. Each group was infected with 30 adult ticks (10 male, 20 female) originating from either ovine or caprine T. lestoquardi infections. Clinical signs were monitored daily, and blood and lymph node biopsy smears, as well as whole blood samples (in EDTA), were collected on days 0, 4, 8, 12, 14, 18, 22, 26, and 30 post-infection (PI) for paraclinical and molecular analysis. Initial clinical signs, such as fever and enlargement of the prescapular lymph nodes, appeared in both groups within 4–5 days PI. However, the clinical signs in Group 2 (infected with the ovine isolate) were significantly more severe. These sheep exhibited higher body temperatures, greater lymph node enlargement, and higher parasitemia levels compared to Group 1(infected with the caprine isolate) (P < 0.05). Piroplasms and schizonts of Theileria spp. were typically observed from days 8 and 13 PI, respectively. Transmission of T. lestoquardi to sheep was confirmed via PCR. Significant differences were observed between the two groups in packed cell volume (PCV), red blood cell (RBC) count, and white blood cell (WBC) count (P < 0.05). These findings indicate that the T. lestoquardi derived from a goat exhibited lower virulence than that derived from a sheep. The results suggest that goats may serve as potential carriers of T. lestoquardi .