Every year, thousands of wildebeest cross East Africa in search of green pastures. This great seasonal migration is accompanied by a virus called “alcelaphine herpesvirus 1”. Although harmless to wildebeest, it is fatal when it affects the cattle of the Maasai people that frequent the same grasslands.  Benjamin Dewals and a team from the Immunology/Vaccinology laboratory of the University of Liege have succeeded in unlocking its secrets and perfecting a potential vaccine, the result of more than ten years of research.

Every year, hundreds of thousands of wildebeest (around 1.5 million according to current estimates) cross East Africa in search of green pastures, leaving barren and arid lands behind them. Those who have witnessed this great procession proclaim it to be one of the most beautiful natural spectacles. This journey, which is more than 1,000 kilometers, takes place between the Serengeti National Park in Tanzania and the vast plains of the Maasai Mara National Reserve in Kenya. It is also the biggest seasonal migration in the world and includes great numbers of zebra, gazelles and predators. This type of event inevitably attracts hyenas, lions and leopards in search of vulnerable prey. When the procession has to cross the river Mara (usually in the month of July), crocodiles lie in wait to ambush slower or weaker animals without pity.

In reality, however, this imposing procession also involves the migration of a virus, more precisely, AlHV-1, which is the abbreviation scientists use to refer to alcelaphine herpesvirus 1. This virus is present in practically all wildebeest. It is transmitted during calving when the females re-excrete it. The young then become lifelong carriers but are not affected by the disease in any way. “This is a fascinating example of optimal adaptation in evolutionary terms, because over time the virus has become totally non-pathogenic for its host. Being able to go unnoticed is the ultimate characteristic in terms of parasitism!” Exclaims Professor Alain Vanderplasschen, head of the Immunology-Vaccinology Unit of the Faculty of Veterinary Medicine of the University of Liege

But although this organism remains passive in its reservoir host, the situation becomes more complicated when it is transferred to other species. The Maasai cattle breeders who graze their herds in the reserves of the Serengeti and Maasai Mara, have learned this to their cost: they now know that they must avoid allowing their cattle to come into contact with migrating wildebeest or their animals will suffer acutely from malignant catarrhal fever caused by AlHV-1 before dying. The infected animals generally end up prostrate with their heads facing downwards and develop inflammation of the eyes and nasal and oral mucous membranes. Their secretions become purulent and they become very feverish. The longer they survive the worse their symptoms become. In zoos, this disease can also affect animals such as some species of deer or buffalo that have seemingly never come into contact with wildebeest. Thirty-three species have been referenced as being particularly prone to this infection.