UAE-developed vaccine could end killer horse disease

African horse sickness has been responsible for hundreds of thousands of deaths in South Asia

Men on horseback carry the UAE flag on the 2019 opening meeting at Jebel Ali racecourse. Researchers in Dubai have developed a vaccine against African Horse Sickness that is fatal in 80 per cent of anShow more

Efforts to combat a deadly horse disease that has killed hundreds of thousands of animals are taking a step forward thanks to researchers in Dubai.

Scientists at the Central Veterinary Research Laboratory (CVRL) have developed what is thought to be the most effective vaccine yet against African horse sickness (AHS), a viral disease which can prove fatal to more than eight in 10 infected animals.

The disease has been known for nearly 800 years, but there is no effective treatment, making the creation of a reliable and safe vaccine all the more important.

Dr Ulrich Wernery, the CVRL’s scientific director, has seen animals infected with the condition and described it as “one of the worst equine diseases you can think of”.

“I had a dream when I saw these poor animals dying that I must do something,” he said.

Although vaccines against the disease have been used from as far back as the early 1900s, the vaccine most widely applied currently contains an attenuated or weakened virus that, on occasion, has mutated and turned virulent, killing vaccinated animals.

“It’s a good vaccine but in specific circumstances it can produce the disease,” said Dr Wernery.

The CVRL vaccine, however, uses inactivated viruses that are unable to become virulent again.

Clinical signs of AHS vary because there are several forms of the disease, but often infected animals develop a fever and breathing problems, with lung congestion eventually causing death.

Between 60 and 85 percent of horses that become infected go on to die from AHS, which was first identified in the year 1237.

The disease has never been found in the UAE, but the midges that transmit it are present in the Emirates. In previous decades there have been outbreaks in Saudi Arabia and Yemen.

AHS has also infected horses in Asian countries. Between 1959 and 1961, it caused an estimated 300,000 horse deaths in India and Pakistan. It remains endemic in sub-Saharan Africa.

The vaccine CVRL has developed is now being used in Kenya and Sudan, and appears to be effective at reducing infection rates.

“We have very good news just recently that Kenya has not one case of African horse sickness this year, most probably because of our vaccine,” said Dr Wernery.

“This is the first year that they didn’t have an outbreak, but they have previously reduced outbreaks because now everybody uses our vaccine. I believe we can eradicate the disease from parts of Kenya.

“It’s really a fantastic project and a great breakthrough in fighting this disease.”

The virus that causes AHS exists in nine serotypes – forms that cause a particular immune response in infected animals in terms of the antibodies produced – and the CVRL began identifying and isolating them in its laboratories in 2002.

It was not until 2014, however, that CVRL’s head of virology and senior scientist, Dr Sunitha Joseph, and her team completed the task of isolating all nine.

CVRL had to produce separate vaccines against each of the nine serotypes. Once this had been done, vaccine testing took place between 2018 and early 2019 on 29 retired race horses.

A PhD student at CVRL, Marina Rodriguez injected the horses - kept at a desert location in Dubai - with the vaccines and analysed their immune response.

A pair of horses was vaccinated against each of the nine serotypes and the remaining 11 animals were vaccinated against all nine, receiving the vaccine in two shots.

Each week blood samples were taken and tested for the presence of antibodies against the serotypes.
"We immunised the horses with the vaccine to study the serological response, the response of the immune system," said Ms Rodriguez.

Horses vaccinated against just one serotype produced antibodies against only that serotype, while those vaccinated against all nine produced antibodies against them all, indicating the vaccine’s effectiveness.

The CVRL keeps stocks of the vaccine so that, in the unlikely event of an AHS outbreak in the UAE, horses can be vaccinated once the serotype causing the outbreak is identified.

“We have a vaccine bank with single serotype vaccines, and all nine mixed together,” said Dr Wernery.

“For example, if we have an outbreak here of serotype four, we’ll vaccinate against this serotype four.”

CVRL’s vaccine is currently produced only at the organisation’s laboratories in Dubai, but they are keen to find a partner in Africa who can carry out production there.

In January, Dr Wernery and his wife, Renate, a virologist, will travel to South Africa to meet officials and discuss the introduction of the vaccine in the country.

If the vaccine does become more widely used in Africa, it would benefit not just horses, but horse owners too.

“They are [often] small farmers; they are very poor. When one of the horses dies it’s a big, big loss for the family,” said Dr Wernery.