Mar 11, 2015
The first sign is that the animals develop a fever. They grow weak and lose the desire to eat. Then, after two to three weeks of suffering, most of the cattle die – dead of a disease caused by tiny single-celled organisms. Theileria is the name of the genus of parasites that claim the lives of thousands of cattle in northern and eastern Africa every year.
“Theileria protozoans are tricky pathogens, and they are absolutely unique,” says Professor Jabbar Ahmed of Freie Universität Berlin. Together with his colleagues Professor Peter-Henning Clausen and Ard Nijhof, Ahmed, a veterinary researcher, is coordinating a German-African research project with a single goal: to study the pathogens – which Robert Koch himself studied in his day – in greater detail and develop new treatment methods to get the epidemic under control. “After all, this bovine disease leads to heavy financial losses and threatens the livelihoods of large segments of the local population,” Ahmed says.
The epizootic disease has been raging in the north and east of Africa for years, which has also brought it the names “Mediterranean theileriosis”and “East Coast fever.” The tropical and subtropical climates in these areas offer optimum conditions for the blood suckers that the parasite needs in order to spread. Unlike the single-celled organisms that cause malaria, which are related to Theileria, these organisms are not transmitted by mosquitoes, but instead by the bite of a kind of tick known as a “hard” tick.
Once they enter the animal’s body, the single-celled organisms attack its immune cells, stimulating uncontrolled cell division and flooding the body’s entire lymph system with infected cells before infiltrating the lung tissue and the cells of the digestive tract. The animals suffer high fever, pulmonary edema, and shortness of breath before finally succumbing. The epidemic is a major problem for the local dairy and meat industry, since preventive measures and treatment options are limited in availability – and expensive, to boot.
So far, African farmers and government agencies have been engaged in efforts to gain control of the disease not only with medications and spraying pesticides to combat ticks, but also by vaccinating the animals. Although the current costs of immunization are astronomical by Tanzanian standards, “the farmers can’t even be certain that vaccination will provide their cattle with full protection,” says Professor Paul Gwakisa, who has been working on the disease in Tanzania for years. The live vaccine that is currently in use does not protect against all strains of Theileria, he points out.
Gwakisa calculates that the disease represents a massive strain not only for local farmers, but also on the entire economy. He says, “Each year, more than 40 percent of livestock die of some form of theileriosis in Tanzania alone. That adds up to losses of about 43 million dollars. And then that means the money is missing from somewhere else, such as education.”
The fact that it has so far not been possible to halt the epidemic is due in part to the parasite’s tricky nature, but also to the fact that some of the affected countries lack the funding and infrastructure to do the research. “When I was doing research for my thesis on Theileria, I discovered that there is hardly any Egyptian research literature on the topic. And yet, the parasite is a major problem in my home country,” says immunologist Amira Alhosarivon of Assiut University in Egypt.
But the young researcher refuses to be discouraged. The fight against this deadly infection is simply too important. As part of the cooperative project supported by the German Research Foundation (DFG), which involves scholars and scientists from Kenya, Uganda, Tanzania, Sudan, South Sudan, Tunisia, and Egypt, she and her colleagues now hope to bridge previous gaps in their knowledge on the subject and to be able to develop new treatment methods and vaccines that are both more effective and safer.
The first meeting was held late last year. It took place in Berlin – a location where research on theileriosis has a history: Researcher and Nobel laureate Robert Koch, who later also headed the Institute of Infectious Disease, in Berlin, discovered and described the blood-borne parasites, then dubbed “Koch spheres” during his travels in Africa for research back in the 19th century. And 40 years ago, scientists from the Institute of Parasitology and Tropical Veterinary Medicine at Freie Universität Berlin clarified the development cycle of Theileria in ticks. Perhaps there will be reports of another success from Berlin a few years from now.
Prof. Dr. med. vet. Peter-Henning Clausen, Freie Universität Berlin, Institute of Parasitology and Tropical Veterinary Medicine, Email: Peter-Henning.Clausen@fu-berlin.de