Dubai tests to stop the spread of Mers in its tracks
Vaccine trials expected next year to counter coronavirus carried by camels, writes Daniel Bardsley
Six years after Middle East Respiratory Syndrome was first reported, infections are still being recorded and people are still dying from it.
Mers, a viral illness, has affected more than 1,750 people, figures from the International Society for Infectious Diseases show. And more than 700 of them have lost their lives – a death rate of about 40 per cent.
In a typical week several new cases are announced and, while most are in Saudi Arabia, the UAE is among the handful of other nations that are most severely affected.
But a scientific institute in the Emirates, Dubai’s Central Veterinary Research Laboratory, is still playing an important role against the threat.
Some of the people who have been ill with Mers contracted the coronavirus from camels they worked with. Dromedaries – the one-humped camels familiar in the Gulf – are carriers of Mers, so they do not fall ill.
Very young camels are protected from the virus by antibodies in the milk from their mothers but by the time a calf is four to six months old, it will have lost this immunity.
After that, there is a “window” of between three and five months when the animal may become infected and pass the virus to people.
“Maybe 95 per cent of all camel calves [that contract the virus] are infected during this time. At this time we can isolate the virus from the calf’s nose, not from the lung,” says Dr Ulrich Wernery, scientific director of the Dubai laboratory.
“After that they become immune again because they produce antibodies against the virus. The dangerous time for camel keepers is during this window.”
Fortunately, young camels tend to be lively and so direct contact with people, even those who work with camels, is rare. But it happens and there have been cases in Saudi Arabia of people infected this way.
“There’s no need to vaccinate adult camels but if you vaccinate camels when they’re four, five and six months old then they cannot transmit to humans,” Dr Wernery says.
Researchers in Germany, the Netherlands and Spain have genetically engineered a vaccine called the modified vaccinia virus Ankara, which is used to stimulate immunity against pox, a type of disease caused by members of the poxviridae virus family.
But it can also be used against Mers. In a study published in 2016 in Science journal, the researchers said that this recombinant vaccine appeared to confer immunity to Mers in camels on which it had been tested.
Vaccinated animals produced antibodies against the coronavirus and had much lower levels of it in their system.
However, only a small number of animals were involved in that study and the laboratory is to begin a much larger field trial.
“We are interested to include more animals,” says Prof Christian Drosten of Charite, a large university hospital in Berlin. “We would like to do the first studies in the beginning of next year after preparatory work in the second half of this year.”
Prof Gerd Sutter of the Ludwig Maximilian University of Munich is the lead researcher of the initiative, which is funded by the German government.
Prof Sutter says trials in Dubai will indicate whether the laboratory results can be replicated.
“It’s not an easy experiment to do in the dromedary population in the field,” he says.
The scientists hope that the field trials will indicate the optimum dose to use, and help them to determine the most effective way of vaccinating camels to prevent the spread of Mers to people.
“Are we able to identify the dromedary camels that you would want to vaccinate in order to have an impact on human public health?” Prof Sutter asks.
“There’s a huge camel population – camels needed for meat, for milk, hobbies and sports animals. It’s highly unlikely you would vaccinate all of them. The camel population is highly infected with Mers and we certainly need to learn more about what’s their normal infection cycle, what are the drivers of the infection in the camel population.
“Probably when we understand that a bit better, that might help to answer the question.”
One consequence of using, as a starting point, a vaccine against pox disease is that it means that the camels vaccinated against Mers will also develop immunity to camelpox, a condition that can kill up to one in four young camels that contract it.
“That’s a very nice bystander effect. Because this is a pox virus and is derived from smallpox, it will elicit preventive immunity against poxes including camelpox,” said Prof Sutter.
Dr Wernery says this could encourage camel owners to have their animals vaccinated. Owners might hesitate to pay for a vaccine against a disease that doesn’t directly affect their beasts.
But camelpox can stop camels from racing.
Phase one of clinical trials of a human form of the vaccine are also taking place.
And separate research in Canada is using a camelpox vaccine called Ducapox – developed by the Dubai laboratory – instead of the Ankara vaccine as the starting point for another attempt to develop a vaccine against Mers.
This project is less advanced but could yield positive results.