As the board of trustees of the International Livestock Research Institute (ILRI) meets in Addis Ababa, Ethiopia, this week, reviewing ILRI’s animal health research among other work, an ILRI vaccine project is highlighted in a new publication, DFID Research 2009–2010: Providing research evidence that enables poverty reduction. The UK Department for International Development (DFID) and the Bill & Melinda Gates Foundation both support the Global Alliance in Livestock Veterinary Medicines (GALVmed), which works to convert existing or near-market technologies into livestock medicines and vaccines for use in developing countries. The notable success of this strategy in 2009, says DFID, is an East Coast fever vaccine produced by ILRI. East Coast fever is a tick-transmitted disease that kills one cow every 30 seconds in eastern, central and southern Africa, where it threatens some 25 million cattle in 11 countries and is now putting at risk a further 10 million animals in new regions, such as southern Sudan, where the disease has been spreading at a rate of more than 30 kilometres a year. The disease is a major cattle killer. In herds kept by the pastoralist Maasai, it kills 20–50% of all unvaccinated calves, which makes it difficult and often impossible for the herders to plan for the future or to improve their livestock enterprises. A vaccine for East Coast fever could save over a million cattle and up to £170 million a year in the 11 countries where the disease is now endemic. An experimental vaccine against East Coast fever, which makes use of live but weakened parasites, has existed for more than three decades, with batches mass produced in ILRI’s Nairobi laboratories. Although constrained by the need for a ‘cold chain’ to keep the ‘live’ vaccine viable, field use of this vaccine in Tanzania and elsewhere has proved it to be highly effective and in demand by poor livestock keepers, who are paying for the vaccine to keep their animals alive. GALVmed has worked with ILRI and private companies, such as VetAgro Tanzania Ltd., to make East Coast fever vaccine available to the livestock keepers who need it most and to scale up production in future. With £16.5 million provided by DFID and the BMGF, GALVmed began working on the registration and commercial distribution and delivery of a new batch of the vaccine produced by ILRI. The vaccine was successfully registered in 2009 in Malawi and Kenya, with Tanzania and Uganda expected to follow soon. If it is approved in Uganda, it will be the first veterinary vaccine formally registered in that country. GALVmed is now working to establish viable commercial production and delivery systems, aiming that by the end of 2011, all aspects of the production and delivery of East Coast fever vaccine are in private hands.
More than 1 in 5 people in sub-Saharan Africa live below the poverty line. Many of these people live in rural communities heavily dependent on livestock for their livelihoods. One of the most important diseases of cattle in this region is East Coast fever, a lethal infection of cattle caused by the tick-borne parasite Theileria parva. This disease afflicts cattle populations in 16 countries across eastern, central and southern Africa and is the most economically important cattle disease in 11 of these countries. Losses due to East Coast fever exceed US$300 million annually. Imported high-yielding breeds of cattle, which are increasingly being used to satisfy increasing demands for milk in this region, are particularly susceptible to this disease.
Although East Coast fever can be controlled by treating infected animals with anti-parasitic drugs and by regularly spraying or dipping animals with anti-tick chemicals, these methods are difficult to apply and costly for poor livestock keepers. Vaccination offers a more sustainable means of controlling the disease.
Cattle can be immunized against the disease by infecting them with live parasites while simultaneously treating the animals with long-acting antibiotics. Because several strains of the parasite exist in the field, this vaccination comprises a mixture of strains. A vaccine cocktail mixing three parasite strains is being used successfully in some endemic countries, but applying this so-called ‘live vaccine’ remains hindered by difficulties in maintaining the quality of the vaccine material and in finding ways to distribute the vaccine, which needs to be kept cold, cost-effectively to widely dispersed cattle herders. In addition, it remains uncertain whether the current mix of parasite strains in the vaccine is optimal for obtaining robust immunity.
Recent studies of East Coast fever have shown that the so-called ‘protective’ proteins of the causative parasite—that is, the antigenic molecules that are recognized by the T lymphocytes of the bovine immune system and thus help animals fight development of disease—vary among the different strains of the parasite that exist in the field. This project will build on these advances to investigate the nature and extent of variability in these antigens between parasite strains. This knowledge will help scientists understand the factors that determine which parasite strains induce protective immune responses in animals that have been vaccinated.
Results of the project should provide methods for maintaining high quality of the current live vaccine and identifying parasite strains that could be incorporated into an improved second-generation live vaccine. The information should also help researchers design new, genetically engineered, vaccines, which comprise not whole parasites but rather antigenic molecules of the parasite—and thus are safer, cheaper and easier to distribute than the current live vaccine.
‘This is an important project for us,’ said Philip Toye, a vaccine developer from International livestock Research Institute (ILRI). ‘The information we expect to generate will greatly increase our understanding of the current live vaccine that is being used to protect animals against East Coast fever. We can use this information to get this vaccine into wider use in the region.’
This project is being conducted jointly by scientific groups at the universities of Edinburgh and Glasgow, in Scotland, and at ILRI, in Nairobi. The project is part of a new initiative called Combating Infectious Diseases of Livestock in Developing Countries funded by the UK’s Biotechnology and Biological Services Research Council, the UK Department for International Development and the Scottish Government. ILRI’s research in this area is also supported by members of the Consultative Group on International Agricultural Research.