Solving the problem of tick damage for Africa's livestock

Overview

Results

The team

Related information

So what's the problem?

Ticks are small bloodsucking arthropods that mainly feed on domestic and wild animals and sometimes humans. They’ve caused great economic losses to the livestock market globally by transferring disease from animal to animal. There are many diseases spread by ticks, including: east-coast fever, tick-bite fever and Nairobi sheep disease. Global losses are estimated to be between US$13.9 and US$18.7 billion annually with over 800 million cattle constantly exposed to the threat of ticks.

In Africa ticks are considered to be the most important animal-health problem. In Tanzania for example, it is estimated that the annual cost of damage from ticks is US$364 million – killing around 1.3 million cattle. Livestock is an important source of income for both small and large scale farmers who benefit from the sale of meat, milk, skins and hides while animals are also a valuable resource for transporting goods or cultivating the land.

Currently chemical pesticides are the main form of control against ticks, but these often prove to be expensive and there have been many cases where the ticks have become resistant. There are also concerns over the side-effects of these chemicals on human health, the health of the cattle and the surrounding environment. A strategy to control ticks which combines chemical, immunological and biological techniques is generally seen as the best way forward.

What is this project doing?

CABI is looking for an organism that is harmful to ticks and could be used to control them, hopefully becoming a core component of a new integrated tick-control strategy. To do this, CABI has teamed up with the International Centre of Insect Physiology and Ecology to help in the search. An ideal natural enemy would be a highly infectious fungus which would debilitate the tick population. A fungus which inhibits the tick’s ability to feed or breed (but not initially kill the tick) could also be a successful control agent, and will be built into the testing regime. There are various species of tick that impact upon the livestock industry in Africa. For this project, two species that are highly damaging in central and east Africa have been selected: Amblyomma variegatum and Rhipicephalus appendiculatus.

Surveys are being carried out on grass pastures and on the actual livestock where ticks are collected and then taken back to the lab where they can be kept in a stable environment. Regular checks are made for dead ticks. For each dead tick all pathogens are collected and separated – these could be fungi, bacteria, protozoa or nematodes. Each pathogen is then identified and one sample kept and put into long-term storage whilst another will be used in further testing.

For each of the tick-infecting fungi, reproductive spores will be grown, harvested and tested for fertility as well as its harmful effects on ticks. The infection and mortality rates can be determined by infecting ticks and the effects of infection on feeding, breeding and egg fertility can also be measured. The results from each species of pathogen can then be pulled together and comparisons should then indicate which are best suited for controlling ticks.

Results so far

A survey for ticks was carried out in Juja in central Kenya – an area commonly used for grazing livestock. Ticks were collected from both cattle and grass pastures and soil samples were also taken at random. 295 ticks were collected, most were from the Rhipicephalus genus. These ticks were kept in room conditions and any fungi that may have caused the death of the tick were collected. Samples of fungi were also extracted from the soil samples.

Full identification of fungi is still in progress but so far, various harmful fungi have been found either in the soil or on the dead ticks. Pure cultures of each of the fungi species have been taken and will be preserved and tested. Testing the suitability for use as a tick-control agent is in its early stages, but scientists are hopeful of finding a species with the potential of helping Africa’s livestock industry.

Project Executive