Peer-reviewed veterinary case report
How often Theileria equi passes from healthy mares to foals in horses
By Hermans, Lisa-Marie et al.·Published in Ticks and tick-borne diseases·2025·Clinical Department of Companion, France·View original on PubMed →
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Original publication title: Evaluation of Theileria equi vertical transmission rate and routes in a cohort of asymptomatic mares and their foals.
- Species:
- horse
Plain-English summary
A group of 179 healthy mares and their foals were tested for a tick-borne disease called equine piroplasmosis, caused by the parasites Theileria equi and Babesia caballi. Researchers found that while most mares and foals had antibodies against these parasites, only a small number of foals (7.4%) were born with T. equi. These foals showed no signs of illness, although one experienced acute kidney failure. The study suggests that T. equi can be passed from mare to foal, possibly through colostrum (the first milk), but more research is needed to understand how this happens.
People also search for: horse foal T. equi transmission · equine piroplasmosis symptoms · mare foal health issues
Abstract
Equine piroplasmosis is a tick-borne disease mainly caused by Theileria equi and Babesia caballi. The objectives of this study were to analyse the frequency and routes of vertical transmission of these blood parasites from 179 asymptomatic mares to their foals. Foals were sampled within 72 h post-partum. The seroprevalences determined by Indirect Immunofluorescent Antibody Test (IFAT) and based on a subset sample of 107 couples, were 59.8% and 42.1% for T. equi and B. caballi, respectively in the mare population, and 54.2% and 40.2% in the foal population. A species-specific nested PCR was performed on all blood samples (358) and on available samples of placenta (24), umbilicus (6) and colostrum (18). For mares, 30.2% (54/179) and 2.2% (4/179) were PCR-positive for T. equi and B. caballi, respectively. Vertical transmission was not observed in the case of B. caballi, and four foals were born T. equi PCR-positive, giving a transmission rate of 7.4% (4/54). The blood smear evaluation showed viable T. equi parasites for the four foals without clinical signs of neonatal equine piroplasmosis, but one foal had acute renal failure. Theileria equi DNA was detected in umbilical cords, placenta and/or colostrum from PCR-positive mares, without correlation with the carrier status of the foal. One foal was born carrier but T. equi DNA had not been detected in the placenta. The 18S rRNA genotype E of T. equi was characterized in the four foals, foetal parts of the placenta and colostrum. The routes of transmission and particularly the possibility of colostral passage warrant further investigation.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/39724815/