Three bloodsucking hard tick species, commonly found in sub-Saharan Africa, are involved in the transmission of a debilitating livestock disease called lumpy skin disease to cattle herds across Africa.
The three tick species identified as vectors for the disease are the Rhipicephalus (Boophilus) decoloratus (blue tick), R. appendiculatus (brown ear tick) and Amblyomma hebraeum (bont tick).
Researcher Dr Jimmy Clement Lubinga, who is funded by a BBSRC-supported scheme, proved the link.
Lumpy skin disease was first diagnosed in Zambia in 1929. It spread through Botswana into South Africa and now covers the entire continent.
Until now the method of lumpy skin disease virus transmission – a growing problem in herds in Africa and the Near East – has not been fully understood and mostly been associated with flying insects. Dr Lubinga's study has now confirmed that ticks are also vectors for the virus.
"The ticks also act as 'reservoirs' for the virus, as it can persist in these external parasites during periods between epidemics," explains Dr. Lubinga. "The virus has been found in their saliva and organs, and could potentially overwinter in these ticks."
Lumpy skin disease is caused by the lumpy skin disease virus, a member of the genus Capripoxvirus. It is a viral disease of cattle and is typically characterized by fever, lumps in the skin and swollen lymph nodes. Outbreaks of this disease reduce the quality of meat and milk, causing major economic losses. Cattle may become infertile due to reduced sperm quality. Abortions and reduced calving rates have been documented. It can cause permanent scarring to cattle hides, thereby reducing their quality.
Mortality rates of between 10% and 40% and higher of herds have been recorded during outbreaks.
"This disease is of economic importance due to the damage it can cause to the skin, the reduced milk and meat production and lowered fertility of cattle," says Dr Lubinga. "Restrictions on animal movement and trade can be imposed on infected areas."
Dr Lubinga recommends that tick control should form an important component of lumpy skin disease control. This is needed to ensure that these parasites do not contribute to the spread of the virus to other parts of the world.
"Ticks can be spread over long distances by moving along with their animal host, for instance while feeding on migrating birds," says Dr Lubinga. "The change of climate due to global warming is making it possible for ticks to successfully survive and quest in areas where previously they could not survive due to very cold conditions."
The research was funded by the Combatting for Infectious Diseases of Livestock for International Development (CIDLID) research programme that BBSRC contributes to.
Notes to editors
Reference: Lubinga, J. (2014). PhD thesis: The role of Rhipicephalus (Boophilus) decoloratus, Rhipicephalus appendiculatus and Amblyoma hebraeum ticks in the transmission of lumpy skin disease virus (LSDV).