A new tick vector with potential to spread fatal cattle diseases is rapidly spreading in the region, scientists in Kenya have warned. The invasive blue tick, which causes fevers and carries pathogens that can be transmitted to people, was until recently rare in Africa but was translocated to the continent from Asia by cattle exported via Madagascar. It has now proliferated in Kenya, Uganda, South Sudan and Burundi.

“Cattle farmers in the region need to be aware of this new tick vector, the invasive blue tick or Rhipicephalus microplus,” Kenyan parasitologist Esther Kanduma told The EastAfrican.

Dr Kanduma said the tick species carries the Babesia bovis, Babesia bigemina and Anaplasma marginale pathogens, which cause tick fevers through destruction of red blood cells. They are also transmissible to humans.

“Infections associated with B. bovis have the capacity for 70 to 80 percent death rates, high economic losses and high morbidity leading to reduced production of milk and meat, traction and decreased incomes for poor smallholder farmers,” said Dr Kanduma, who works at the Department of Biochemistry at the University of Nairobi .

Fatal bovine babesiosis, caused by B.bovis, is the most important tick-borne disease in terms of economic impact, globally.

Over the last 15 years, the blue tick has been spreading across the continent. It has been recorded in more than 20 African countries and the pathogen B. bovis has already been reported in Kenya, Uganda and Nigeria.

“The situation has changed dramatically following rapid increases of the tick in Tanzania replacing the indigenous Rhipicephalus decoloratus and two introductions into different countries in West Africa through the importation of infested cattle from Brazil,” Dr Kanduma said.

While new records of the invasive R. microplus tick are being reported all the time, the full extent of spread remains unknown and unassessed.

“The bigger problem is that most African countries have limited capacity for differentiation of R. microplus from the endemic R. decoloratus and R. annulatus,” Dr Kanduma noted.

She also noted that countries lack capacity, expertise and suitable analysis for B. bovis detection, diagnosis and surveillance.

Diagnosis of tick-borne diseases is through observation of clinical signs, sometimes combined with microscopy, methods that are not specific or sensitive, especially in immune carrier animals and those with mixed infections.

Scientists say prevalence of the invasive tick in Africa is likely to evolve rapidly given the wide range of animal hosts, pastoralism and uncontrolled trans-border animal trade.

The scientists also point to climate change as having direct effects on the biological development and adaptation of the species and the pathogens it transmits as they prefer warm and humid conditions. Africa’s wildlife is also a reservoir of ticks and tick-borne pathogens, and the unrestrained mingling of wildlife and livestock is an added factor in the spread.

A team from the International Livestock Research Institute in Nairobi, the University of Nairobi and the Washington State University is designing ways to map the tick through remote sensing and geographic information systems, the scientists propose in a scientific paper titled Role of Climate and Other Factors in Determining the Dynamics of Tick and Tick-Transmitted Pathogen Populations and Distribution in Western, Central and Eastern Africa.

“No risk assessment, surveillance systems or control strategies for the invasive ticks and fatal babesiosis have been developed for the affected African countries,” she added.

“Increased rainfall results in improved pasture and vegetation cover, which increases the number of potential vector breeding sites,” Dr Kanduma said, study co-author Peter Reich, a forest ecologist at the University of Michigan and University of Minnesota.

The rapid dispersion of the tick is driven by largely uncontrolled transboundary cattle trade in a region with mostly porous international boundaries where quarantine measures do not exist or are not enforceable. As climate change accelerates, this trade will intensify and disseminate the tick deep into new areas that are ecologically suitable. In fact, are asking African governments to provide specialist livestock extension services offering technical and informational support to farmers and pastoralists.

The team has designed strategic approaches for controlling the tick in African countries which include use of remote sensing and Geographic Information System (GIS) to map where invasive ticks and B. bovis occur linking the distribution to anthropogenic factors contributing to the spread and eco-climatic factors. They recommend use of tick distribution modelling tools and maps to guide region-specific tick management and control plans, as well as to predict disease outbreak hotspots for more proactive control of disease.