By Laura Lockard, College of Veterinary Medicine

PULLMAN, Wash. — Foot and mouth disease (FMD) is a highly infectious disease of cattle that is responsible for causing considerable nutritional and economic insecurity in many developing countries with an estimated US$2.3 billion impact. FMD is endemic in much of Africa, including East Africa where Washington State University Paul G. Allen School for Global Animal Health (WSU) researchers are working to find solutions to the frequent outbreaks of the disease that affect rural household cattle.

In Nature Ecology and Evolution, WSU researchers, Dr. Thomas Marsh, Professor, Umesh Bastola, PhD student of WSU’s School of Economic Sciences and Paul G. Allen School for Global Animal Health, and Dr. Felix Lankester, Clinical Assistant Professor at WSU Global Health Tanzania, working with Drs. Tiziana Lembo, Sarah Cleveland, Professor, Miriam Casey-Bryars, Richard Reeve and Dan Haydon, Professor, an interdisciplinary group from University of Glasgow, and Tanzanian collaborators, present findings indicating that FMD outbreaks in East Africa are not caused by frequent transmission from wildlife, but rather are limited to specific virus types that are spread through the domestic cattle population. These findings suggest that, in contrast to the erecting of ecologically damaging fences to separate wildlife and livestock as practiced in southern Africa, FMD control programs involving targeted vaccination of cattle could be effective in eastern Africa.

FMD occurs frequently across the region, and these findings establish this a disease of considerable concern, with lactating cattle being particularly affected. This is important as children in the area are vulnerable to undernutrition and are particularly reliant on milk as a protein source. In addition, where cattle also serve to provide field labor, FMD caused a loss in traction. This loss will negatively impact crop production, further impacting household nutritional security.

“We know FMD is one of the most economically devastating livestock diseases worldwide,” stated Dr. Felix Lankester, Clinical Assistant Professor at WSU Global Health Tanzania. “In addition to affecting the food and economic security of cattle-keeping families, the presence of this disease impedes domestic and international trade with FMD-free countries. Our research takes aim at this global health challenge at the wildlife-livestock interface.”

Existing approaches to control FMD include the Progressive Control Pathway for FMD control (PCP-FMD) devised by the Food and Agriculture Organization and the World Organization for Animal Health. In southern Africa for example, one method of control implemented is to have wildlife and livestock physically separated by extensive fence lines.  This approach can be effective but it is also controversial as it impedes natural movement of wildlife. However, this new body of research found that in eastern Africa there was no evidence of frequent infection originating from wildlife.

This finding that wildlife do not play a major role is good news as it suggests that the separation of wildlife and livestock, through the ecologically damaging (and expensive) fence system employed in South Africa, will not be required to control FMD in East Africa. This is important given how vital unfenced, viable wilderness areas and wildlife migration routes are to the national economies and ecotourism of East Africa.

In addition, although there are five of the seven FMD serotypes circulating in Africa, because of a lack of resources single dose vaccines effective against multiple serotypes have not been developed. Consequently, the vaccines that are available to cattle keepers are not always effective because they may not be targeting the serotype responsible for infection and as a result there is little faith in vaccination.  Indeed, only 5 percent of households reported vaccinating livestock for FMD. This study found that rather than different serotypes all swirling around the region at the same time requiring a one size fits all vaccine, there appears to be a pattern to FMD epidemics, with successive outbreaks, each caused by a dominant serotype, sweeping slowly across the region, akin to the human flu.

This finding that FMD outbreaks are caused by waves of successive serotypes is also potentially good news as it suggests that the timely identification of the specific serotype that is causing an epidemic could allow proactive vaccination ahead of each wave of infection. In addition to mitigating the household level impacts of FMD, such proactive vaccination could also offer market opportunities in regional and international trade.

Dr. Marsh stated, “The findings indicate that FMD is a disease of major concern causing considerable nutritional and economic insecurity. However our findings also suggest that an FMD control program involving targeted vaccination, rather than the separation of wildlife and livestock, is a feasible intervention.”

DOI: 10.1038/s41559-018-0636-x

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