Equine piroplasmosis: understanding the risks of tick infestation

Equine piroplasmosis, a parasitic disease transmitted by ticks, represents a major health concern for horses kept on pasture. A recent study conducted in the Auvergne–Rhône–Alpes region identified the main risk factors for infestation and exposure, and established practical recommendations to limit the transmission of Theileria equi and Babesia caballi, the two causative agents of the disease. Below is a clear and accessible summary of the study’s findings, presented at the 2024 Equine Science and Innovation Days (JSIE).

The disease is strongly linked to housing conditions. The horses included in the study were mostly draft horses kept on pasture for most of the year, in areas where ticks are abundant and active. This type of housing, very common in the region, represents a major exposure factor: prolonged contact with ticks, proximity to wildlife, and shared grazing with other species. The results show that horses living under these conditions are particularly exposed to the tick species identified as vectors in the study.

Reducing infestation is a central aspect of prevention. The study highlights that lowering tick burden is the first line of defense against piroplasmosis. The main recommendations include regular manual tick removal, especially at the base of the mane, axillary folds, and chest; avoiding mixed grazing with cattle, sheep, or goats; fencing high‑risk pastures to limit wildlife access; implementing pasture rotation, particularly in spring and autumn when tick activity peaks; and closer monitoring of young horses, which are more frequently infected with B. caballi than adults.

Prevention must be adapted to the epidemiological context. Strategies depend on the horse’s origin, age, activity, movement patterns, and the owner’s objectives. Horses born in highly endemic areas often develop natural immunity and become asymptomatic carriers. In the study, 50% tested positive for T. equi and 15% for B. caballi, but only 4% had a history of clinical signs. Horses from low‑exposure areas are more vulnerable and must be closely monitored when introduced into regions with high parasite circulation.

The study distinguishes between two prevention goals. The health‑oriented approach aims to limit severe clinical forms through monitoring, tick removal, and pasture management. The economic approach, relevant for exportation, aims to obtain negative PCR and serology results. In this case, prevention must be stricter, as even asymptomatic carriers are problematic.

Ticks represent a risk beyond piroplasmosis. Even if the goal is not to completely prevent the disease, tick control remains essential because ticks transmit other equine and sometimes zoonotic pathogens. Managing infestation is therefore a broader animal and public health issue.

In conclusion, this study provides valuable insights into the risk factors for equine piroplasmosis in the Auvergne–Rhône–Alpes region. It shows that tick management is central, farming practices strongly influence risk, prevention must be adapted to the epidemiological context, and young horses and newly introduced animals require increased vigilance. For horse owners, this means adopting a pragmatic, consistent, and context‑specific approach to prevention.

Source: equidee-piroplasmose-janvier-2025.pdf

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