The Central Veterinary Research Laboratory has identified an accurate method to test camels for brucellosis
'Breakthrough' in fight against camel-borne disease achieved in Dubai
Camels have provided milk, meat, labour and companionship to the people of the Gulf far back into history, helping the Bedouin survive in a region where nature can be harsh.
Given that camels are woven into the fabric of the region’s history and identity, it is perhaps no surprise that many Emirati families preserve pastoral traditions by keeping small herds of animals.
According to official statistics, 3.4 million camels, sheep and goats can be found in the more than 20,000 small livestock holdings in Abu Dhabi.
The prevalence of small farms, often run partly for leisure, does however bring with it health risks, such as a bacterial condition that can be caught from animals called brucellosis.
Human brucellosis infections cause symptoms similar to influenza and, while the disease is normally successfully treated with antibiotics, some cases involve complications. Anything from heart problems to arthritis to brain inflammation can occur, and in extreme cases brucellosis is fatal. Infections with brucellosis, which is found across the Middle East as well as in parts of Asia, Africa, Central and South America and other regions, can also become chronic.
Writing in the journal BMC Infection Diseases last year, four researchers at UAE University in Al Ain and another at Khasab Hospital in Oman looked at the prevalence of human brucellosis in Abu Dhabi.
Using data from an electronic reporting system introduced in 2009, the researchers found there were 480 cases in the emirate between 2010 and 2015, a rate of 3.3 per 100,000 people.
People typically contract brucellosis by drinking unpasteurised milk or consuming other untreated dairy products, or from having direct contact with infected animals. In their paper, Nawal Al Shehhi, Faisal Aziz, Farida Al Hosani, Bashir Aden and Iain Blair noted that the many small farms, where hygiene standards vary, are likely to be where many of the local cases of human brucellosis originate.
As a result, some groups were found in the study to be particularly at risk, among them Emiratis of any age (because they often keep camels and other animals that carry brucellosis), and expatriate men of working age in the emirate’s Eastern Region (because many work with animals).
In the capital, about 5 to 9 per cent of camels are thought to be infected, according to a 2009 study quoted in last year’s paper.
With animals being the source of most cases of human brucellosis – person-to-person spread is rare – eliminating the disease from the UAE’s camels and other livestock would be an important step towards reducing infection rates in people.
One tactic to eliminate brucellosis is to test herds for brucellosis and to cull and dispose of those individuals that are infected (their meat should not be eaten), as typically such animals cannot be cured.
However, commercially available tests tend to be optimised for animals other than the camel.
This is where work by the Central Veterinary Research Laboratory (CVRL) could help.
The CVRL’s scientific director, Dr Ulrich Wernery, and a doctoral student, Nina Soellner, have recently completed a project to identify which among the myriad of available brucellosis tests are the most reliable when used with camels.
It was a major undertaking involving thousands of samples from 40 camels donated by Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai.
These animals were given a brucellosis infection, either via their trachea or their noses, and were kept in a quarantined site away from other animals.
“The bacteria more or less went straight into the lungs. It’s a normal infection route – normally they inhale the bacteria. They developed the disease,” said Dr Wernery.
Every two weeks for a year, blood samples were collected from the animals and checked for brucellosis using 15 different tests. In all, 9,000 samples were tested.
“Only two were reliable tests, so 13 failed. That was very, very interesting because you cannot use these 13 test kits for the diagnosis of camel brucellosis,” said Dr Wernery
The two tests that worked were an enzyme-linked immunosorbent assay (Elisa) test, which looks for the presence of antibodies, and a Rose Bengal Test, which uses a stain called Rose Bengal and involves agglutination or clumping when the bacteria clump with their respective antibody.
“These were the most sensitive tests … Ten days after the infection the tests showed a positive reaction, [but] not all were detected. A couple of days later all 40 animals were detected with these [two] tests, whereas all the other tests failed,” said Dr Wernery.
“Some [other tests] detected the first animals only after 30 days; some only after 60 days. Some didn’t detect all of them, only 80 per cent of them.”
Dr Wernery said it was a “breakthrough” that “reliable, sensitive and specific” tests had now been identified for the diagnosis of brucellosis in camels.
“Normally the positive animals are culled; there’s no treatment. They are killed and burnt. That’s very bad and there’s not really a good vaccine,” he added.
“With these tests you can say 100 per cent …, ‘These are negative and these are positive,’ to avoid culling negative animals and to avoid not culling when they are positive.”
Dr Wernery, who caught brucellosis himself three years ago and had to take antibiotics for six months to ensure he was cured, said authorities would ultimately like to eliminate brucellosis entirely from the UAE’s population of camels and other livestock. As long as it is found in the country’s animals, people will continue to catch the disease. Dr Wernery sees elimination as achievable.
“We had brucellosis in western Europe 40 years ago. We got rid of it by culling millions of animals. Now western Europe is free of brucellosis. You get rid of the positive ones. You can only get rid of it when you have the right tests,” he said.