Testing of blood serum from 555 Purebred Spanish horses showed that nearly one in five had been exposed to equine arteritis virus.
The blood testing revealed a seroprevalence in 16.8 percent, based on testing for antibodies against the virus.
Equine viral arteritis is present in many European countries. In Spain, the last confirmed outbreak was reported in 1992.
The European researchers, writing in the Equine Veterinary Journal, said there were few seroprevalence studies in Spain relating to the disease. They said it had a major impact on the country’s equine breeding industry, mainly represented by the Spanish Purebred (Pura Raza Española – PRE) horse.
They set out to estimate the seroprevalence of the virus in the Purebred Spanish horse breeding population in central Spain, and to identify through a questionnaire potential horse-related and stud farm-level factors associated with positive tests.
Individual blood serum samples were collected from 555 horses between September 2011 and November 2013 across 35 stud farms.
They estimated the seroprevalence of the virus in the Spanish Purebred breeding population in central Spain, standardised for the sex distribution of the reference horse population, at 16.8 percent.
Increasing numbers of breeding mares in the stud farm and an increasing percentage of mares with reproductive problems during the last 12 months were identified as being positively associated with seropositivity to the virus.
Mares vaccinated against Equine Herpesvirus-1 and/or -4 were also positively associated with seropositivity, they reported.
“These findings are of importance for informing appropriate biosecurity measures for stud farms and could help facilitate the development of an equine viral arteritis surveillance programme in the Spanish Purebred breeding horse population.”
The virus was first isolated internationally in 1953, during an outbreak of respiratory disease and abortion on a standardbred breeding farm near Bucyrus, Ohio, in the United States, although the disease probably existed for many years before that.
In 1984 an outbreak in Kentucky gave the disease global prominence.
Infected horses have been recorded in many countries.
Clinical signs of infection are extremely variable. The typical picture is a fever, upper respiratory tract inflammation and discharges, weakness, depression, anorexia, limb swelling, sheath and scrotal swelling in stallions, and abortion in pregnant mares, usually from two months of gestation onwards. Many cases are subclinical, with little more than a loss of appetite.
It can also cause severe respiratory disease and inflammation of the small intestine in young foals.
Severity tends to be greater in old, young or debilitated animals. Mortality from the disease in older horses is uncommon.
Transmission can occur by the respiratory route via aerosols and in semen.
It is classed by the World Organisation for Animal Health (OIE) as a list B disease.
The virus is relatively fragile and is readily destroyed by sunlight and most disinfectants. However, it does survive chilling and freezing so all semen from shedding stallions must be considered infective.
During outbreaks transmission occurs by the respiratory route via aerosols. Mares are thought to spread the virus for about 14 days after infection and to then establish a lifelong immunity.
In experimentally infected animals the virus can be recovered from various sites for up to 19 days. Carrier stallions play the major role in dissemination and perpetuation of the virus by shedding it in their semen. Shedding stallions may remain shedders for many years.
Seroprevalence and factors associated with seropositivity to equine arteritis virus in Spanish Purebred horses in Spain
F. Cruz, P. Fores, L. Mughini-Gras, J. Ireland, M.A. Moreno and R. Newton.
The abstract can be read here.