Using parasites to fight cattle disease

Herdsmen from Isiolo County in eastern Kenya study the carcass of a cow that died of East Coast Fever. The findings suggest that “fighting fire with fire” is a strategy that could work against a range of parasitic diseases. PHOTO | FILE |   NATION MEDIA GROUP

By CHRISTABEL LIGAMI, TEA Special Correspondent

In Summary

• African cattle infected with the lethal parasite that kills one million cows per year are less likely to die when co-infected with the parasite’s milder cousin, according to the study.
• The findings suggest that “fighting fire with fire” is a strategy that could work against a range of parasitic diseases.
• The immediate implications are for the battle in Africa against a tick-borne cattle parasite, Theileria parva, which causes East Coast fever.

Research into the cattle killer disease East Coast fever has found a protective process that may also work in human malaria infections. 

The study, published in Science Advances, suggests that seeking a simple vaccine that could protect cows from East Coast fever by inoculating them with a related but far less harmful parasite may protect them against severe disease.

A similar process may work in malaria, where infection with the less harmful Plasmodium vivax parasite may protect humans from the Plasmodium falciparum parasite. The parasites cause malaria, which kills more than 600,000 people around the world each year.

African cattle infected with the lethal parasite that kills one million cows per year are less likely to die when co-infected with the parasite’s milder cousin, according to the study.

The findings suggest that “fighting fire with fire” is a strategy that could work against a range of parasitic diseases.

The immediate implications are for the battle in Africa against a tick-borne cattle parasite, Theileria parva, which causes East Coast fever. The disease kills one cow every 30 seconds and causes $300 million in livestock losses each year, mostly for poor herders.

The worst hit countries in Africa are Kenya, Uganda, Rwanda, Tanzania and Burundi, DR Congo, Malawi, Mozambique, South Sudan, Zambia and Zimbabwe.

The study, “Co-infections determine patterns of mortality in a population exposed to parasite infections,” was conducted as part of an Infectious Diseases of East African Livestock (IDEAL) project, a multi-partner study that includes the Nairobi-based International Livestock Research Institute (ILRI).

The project followed more than 500 indigenous East African shorthorn zebu calves in Western Kenya during their first year of life.

The calves were routinely exposed to both the T parva parasite and its less aggressive relatives such as Theileria mutans. The researchers discovered that co-infection with a lesser parasite was associated with an impressive 89 per cent reduction in deaths from East Coast fever.

“This is an important finding; East Coast fever is a major burden for millions of poor people in Africa whose existence depends on healthy cattle,” said Phil Toye, a researcher at ILRI, which is leading an international effort to develop a new vaccine against the disease.

“The available control methods are very expensive for most farmers and herders, and if we could provide a cheaper approach, it could greatly reduce poverty in the region.”

The current first-generation vaccine being used by farmers is credited with saving 620,000 cows and a formulation released in 2012 has been in high demand. However, the vaccine costs $8 to $12 per animal, which is steep for many pastoralists and smallholder farmers.

Also limiting its wider adoption are its strict refrigeration requirements and its production difficulties, as it takes 18 months to make a single batch of the vaccine.

The ILRI researchers are now developing an East Coast fever jab that stimulates the production of antibodies to protect against an infection and also stimulates the cow’s immune system to use its own “natural killer T-cells” to attack white blood cells infected by the parasite.