Endurance horse performance appears unaffected in subclinical piroplasmosis infections – study

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Forty endurance horses in Spain were evaluated in the study. Photo: File
Forty endurance horses in Spain were evaluated in the study. Photo: File

Seropositive endurance horses without clinical signs of piroplasmosis can participate in competitions of up to 80km without performance impairment, researchers in Spain have found.

Horses competing over longer distances have yet to be evaluated.

Equine piroplasmosis is a common infectious disease in southern Europe, with a high seroprevalence described by many researchers.

The disease, carried by ticks, is caused by the protozoa Theileria equi and Babesia cabali.

Infection can cause differing degrees of anemia, multi-organ failure, and associated systemic signs. There are chronic, sub-acute and acute forms.

In chronic cases, the disease can manifest with non-specific signs such as lethargy, reduce appetite, jaundice, weight loss, and poor performance.

Daniel Bravo-Barriga and his fellow researchers set out to better understand the impact of equine piroplasmosis on the performance of endurance horses.

Blood samples were collected from 40 horses in Extremadura, Spain, before and after their races, in different national elite horse endurance competitions. Fourteen of the horses competed over 40km, 11 over 60km, and 15 over 80km.

Blood and biochemical parameters were analysed and the seroprevalence of equine piroplasmosis was determined. The overall seroprevalence among the horses was 70%, with 27 testing positive for Theileria equi and three for Babesia caballi. Two horses were positive for both.

Thirty-three of the 40 horses completed their competition, with no influence on performance or position apparent in those with subclinical infection.

The study team, reporting in the journal Animals, said there were also no significant differences in key blood or biochemical values between the seropositive and seronegative horses.

“It seems that horses without clinical signs of piroplasmosis can participate without performance impairment in competitions of up to 80km,” they concluded.

Discussing their findings, the authors said, despite some variations seen in the results, all values were within the physiological range in all animals.

A further study should be conducted with a follow-up in the days after competing to see if the stress arising from their exertions causes a relapse of the acute phase of the disease, they said.

The researchers said their results cannot necessarily be extrapolated to the longer endurance distances of 120km to 160km.

They said polymerase chain reaction (PCR) testing was not performed in their study, so some positive cases may have escaped diagnosis. “It is recommended to use molecular techniques in future studies to complement immunological techniques.”

The authors said there was a need for further studies using their approach, evaluating more horses – including those competing over longer distances – to corroborate their preliminary findings.

The study team comprised Bravo-Barriga, Francisco Serrano-Aguilera and Miguel Ángel Habela, with the parasitology and parasitic diseases section of the Animal Health Department, part of the veterinary faculty at the University of Extremadura; and Rafael Barrasa-Rita, Rafael Barrera Chacón, Luis Javier Ezquerra and María Martín-Cuervo, all with the university’s Department of Animal Medicine, also part of the veterinary faculty.

Bravo-Barriga, D.; Serrano-Aguilera, F.J.; Barrasa-Rita, R.; Habela, M.Á.; Chacón, R.B.; Ezquerra, L.J.; Martín-Cuervo, M. Effects of Competitive ELISA-Positive Results of Piroplasmosis on the Performance of Endurance Horses. Animals 2022, 12, 637. https://doi.org/10.3390/ani12050637

The study, published under a Creative Commons License, can be read here.

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