An inactivated African horse disease vaccine shows promise — the horse

An inactivated vaccine targeting all nine African Equine Disease (AHS) virus serotypes is showing encouraging results in trials in the United Arab Emirates, where levels of protective antibodies remained high in vaccinated horses for about a year.
Marina Rodriguez-Cavini, DVM, of the Central Veterinary Research Laboratory (CVRL), said that with annual boosters, the vaccine can keep horses safe from any of the AHS serotypes without the risks associated with a live virus vaccine, which can sometimes to illness. ) in Dubai.

CVRL researchers said the inactivated vaccine effectively protects horses from disease — or at least from death. It appears to be working whether they live in endemic areas of Africa or areas hit by temporary outbreaks, like the one that struck Thailand last year, leaving scores of dead horses in its wake.

Testing retired horses in the UAE

Caveney and her fellow researchers tested two types of inactivated AHS vaccine developed at their facility, focusing on a group of 25 mares and four mares, ages 20 to 30, living in the United Arab Emirates.

Eighteen horses were divided into nine pairs of horses, and each pair was vaccinated against one of the nine serotypes. The other 11 horses received a vaccine targeting all nine serotypes (in two injections simultaneously).

All 29 horses received a booster dose 28 days and 12 months after the first injection.

Caveney said the researchers took blood samples from each horse every two weeks in the first year of the study to investigate antibody production. They also drew blood at multiple intervals during the two weeks following each vaccine or booster for a polymerase chain reaction (PCR) test.

They said the team did not find any apparent virus in any of the horses’ systems. However, all horses developed antibodies protecting against hypersensitivity syndrome.

Caveney explained that those receiving a single serotype vaccine took longer to get a protective effect. Most had effective levels of protection several weeks after the second booster dose – approximately 100 days after the initial vaccine.

By contrast, horses receiving all nine serotypes of inactivated virus at the same time only needed one booster one month after the first shot, she said. All but one of these horses – 90% – are fully protected against all serotypes within five to 14 days of that booster.

The researchers report that the results indicate that vaccination with inactivated viruses of all nine serotypes, with a one-month boost followed by annual boosters, can effectively protect most horses from AHS.

This is not new, but not well known

CVRL developed its inactivated vaccine in 2014, and a six-year study of 27 horses in Kenya also showed optimistic results. Its use has not yet been widely adopted either in Africa or in AHS-free countries, said Kavini, who cited “political” reasons for “poor sucking.” Although her foundation has tried for years to collaborate with various foundations in Africa, only That “all the answers were negative,” she said, with the exception of Kenya, where many horses have been vaccinated since 2014, and Sudan, where authorities recently ordered 1,000 doses of the inactivated AHS vaccine for CVRL.

Kavini said Thai officials did not accept offers for the CVRL vaccine during the 2020 pandemic. “An inactivated vaccine could have been the solution to this outbreak,” she said. the horse. “Instead, Thailand and Malaysia had to fight not only the field virus but the risk of… reverting to virulence from the attenuated vaccine.”

the horseOfficial sources in Thailand did not respond to requests for comment.

The researchers reported that none of the 50 Kenyan horses recently vaccinated with the inactivated vaccine died of hypersensitivity syndrome, although six developed a mild form of the disease six months after the initial vaccine, possibly from the virus circulating in their endemic area. They all fully recovered within 72 hours.

She said future studies on the team’s inactivated vaccine will include challenge tests – assessing how well vaccinated Emirati horses can resist exposure to the virus in real-world conditions.

The report is published in BMC Veterinary Res in September 2020.

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