A live-attenuated strangles vaccine already in use in Europe has proven safe and effective in pregnant mares, according to a recent study.
The researchers studied the strangles vaccine EQUILIS StrepE (manufactured by Intervet/Schering-Plough Animal Health), a live attenuated strangles vaccine available in Europe for submucosal administration in the upper lip, on pregnant Warmblood mares on a large stud farm in Germany. The main outcome of the the study was that the vaccine did not have any deleterious effect on the pregnancy outcome of vaccinated mares.
A group of 224 pregnant mares were vaccinated every three months until parturition with EQUILIS StrepE. A group of 206 mares were used as controls and only received water as a placebo vaccine. None of the 430 mares developed strangles or suffered adverse vaccine reactions at the site of injection or systemically.
Ten mares aborted during the study (six in the vaccine group and four in the control group). In addition, two foals were stillborn in the vaccinated mare group and two foals in the control group died within two days after birth. However, none of the abortions or foal deaths was due to infection with Streptococcus equi, the organism that causes strangles.
"A large farm in Germany was chosen because it was well-managed from a veterinary stand point, but still had a high incidence of strangles, with an annual prevalence of up to 60% in yearlings (in the years before and after the study)," said Dr. Roberto Ragni-Alunni, Global Technical Lead at Intervet-Schering Plough International, which sponsored the study. "At the end of the study there was no statistically significant difference between the vaccinated and the control groups. The researchers concluded that EQUILIS StrepE did neither have any deleterious effect on development of gestation nor induction of side effects on the pregnant mares."
"In addition, the incidence of strangles was reduced on the farm in the year of the study, although annual fluctuations of the disease cannot be ruled out as an explanation," he said. "However, previous field experiences have demostrated that the vaccine is able to protect farms that have a high incidence of the disease."
"Strangles is perhaps the most frequent infectious disease of horses in Europe," Ragni-Alunni added. "In Sweden, where strangles is a reportable disease, there are between two and 20 cases of strangles for each case of equine influenza.
"I believe that no other strangles vaccine has been so thoroughly tested by the manufacturer than EQUILIS StrepE, both due to the stringent EU regulations for vaccine authorization as well as the commitment of Intervet/Schering-Plough Animal Health on providing scientific data support for its products," Ragni-Alunni said.
He could not comment on whether the company would seek approval for the vaccine to be distributed in the United States.
The study by Reinhold and Venner titled "Safety of multiple submucosal inoculations of a live attenuated strangles vaccine in pregnant mares" was published in the January 2010 issue of Equine Veterinary Education.
Reference: Reinhold, B.; Venner, M. safety of multiple, submucosal inoculations of a live attenuated strangles vaccine in pregnant mares. Equine Vet Educ 2010;22:40-42.
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