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United States Department of Agriculture

Agricultural Research Service

Healthy Animals 48

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Issue 48, January 2012
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International Partnerships Focus on Preventing Animal Diseases

A healthy pig rests its snout on the back of another pig.

Research Briefs

Boosting Soil Moisture. Studies examine soil improvement through use of "biochar"—charred biomass created from wood, other plant material and manure.

Breeding Grass. Researchers team up to create a widely popular variety of forage grass.

Rice for the Right Market. New aromatic, soft-cooking, long-grain rice varieties suited for markets predominantly filled by imports.

Sheep Tolerate Parasites. Scientists are first to discover genetic locations for parasite resistance in African sheep.

In developing regions like Sub-Saharan Africa, livestock producers are often faced with the challenge of managing diseases that infect animals, making it difficult to sustain herds and farm productivity. Rift Valley fever, East Coast fever and foot-and-mouth disease are three devastating diseases that harm livestock and threaten the livelihood of poor farmers.

To help keep animals alive, healthy and productive, scientists at the Agricultural Research Service (ARS) and the International Livestock Research Institute (ILRI) have formed partnerships to find solutions to these serious diseases.

Taking Steps to Develop East Coast Fever Vaccines

For more than five years, researchers at the ARS Animal Disease Research Unit (ADRU) in Pullman, Wash., and at ILRI in Nairobi, Kenya, have been working to develop a vaccine that protects cattle against East Coast fever, a destructive disease in eastern and central Africa.

Developing a vaccine to help control East Coast fever in Kenya could lead to a vaccine for Texas cattle fever, which is a problem for cattle producers in the United States, says ADRU entomologist Glen Scoles.

"That's because these parasites and the ticks that transmit them are so similar," Scoles explains. "Proteins we identify in one organism can also be studied in the other."

Although diseases like East Coast fever are controlled in the United States, results from collaborations such as the one with ILRI will help prevent parasitic diseases here as well as in other countries, says Don Knowles, ADRU research leader.

"It's important that the global community works together to control diseases that limit food and fiber production, and East Coast fever is one of those diseases," Knowles says.

Ticks are injected in a test designed to reveal more about the tick's genes.
At ILRI, Rhipicephalus appendiculatus ticks are injected in a test designed to reveal more about the tick's genes involved in infection and transmission of East Coast fever.

Scientists at ADRU and ILRI are studying the tick—Rhipicephalus appendiculatus—that transmits the parasite—Theileria parva—that causes East Coast fever. They have developed a polymerase chain reaction (PCR) test that detects parasite DNA in ticks to quantify the level of infection.

In one study, researchers worked with two populations of nymphal ticks called Mugaga and Kiambu, which were developed at ILRI to have different Theileria parva susceptibilities. The two ticks were fed simultaneously on infected calves and then compared. The Muguga strain of tick had a low level of parasitic infection, and the Kiambu strain of tick was highly susceptible.

The next step is to look at genetic differences between the tick populations and to identify proteins produced in response to infection, Scoles says. These proteins might be good targets for a vaccine that would help control both the parasite and the tick that transmits it.

Preparing for Rift Valley Fever Vaccine Trials

Scientists at the ARS Center for Grain and Animal Health Research (CGAHR) in Manhattan, Kan., and in Kenya are developing and evaluating control strategies for viruses like Rift Valley fever, which is transmitted by mosquitoes.

Cattle in an enloseure at the International Livestock Research Institute (ILRI) in Nairobi, Kenya.
Cattle at the International Livestock Research Institute (ILRI) in Nairobi, Kenya.

The disease affects humans as well as animals, and can be deadly. In livestock, it causes abortions and high mortality in young animals.

William Wilson, a microbiologist in CGAHR's Arthropod-Borne Animal Disease Research Unit, is collaborating with researchers at the Kenya Medical Research Institute, the Kenya Agricultural Research Institute and ILRI. The group is studying mosquito populations at the Kenya Medical Research Institute for potential Rift Valley fever activity between outbreaks.

"We're laying the groundwork to conduct vaccine studies that will use ILRI researchers' expertise in immunology," Wilson says.

Part of that groundwork includes building an infrastructure and developing tools to conduct large Rift Valley fever vaccine trials and diagnostic evaluations at the Kenya Agricultural Research Institute, he adds.

Applying New Technology to Track FMDV

A highly contagious infection, foot-and-mouth disease threatens the health and economic value of livestock in many countries. The disease hasn't occurred in the United States since 1929, but recent outbreaks have been reported in Japan, Bulgaria and South Korea.

At the ARS Foreign Animal Disease Research Unit, located at the Plum Island Animal Disease Center in Orient Point, N.Y., scientists are using a new tool that tracks the adaptive immune response of cattle to foot-and-mouth disease virus (FMDV) vaccines.

The new technique, based on what are called major histocompatibility complex (MHC) tetramers (molecules), has only recently been applied to livestock, says ARS microbiologist William Golde. The method was first developed in mice and humans.

"The technology allows scientists to follow more complicated T cell immune responses, in addition to B cells," Golde says. "It is based on typing cattle, just like you type a human for an organ transplant and know exactly which molecules you're working with."

T cells have different jobs. Some send instructions to the rest of the immune system so the body can produce the most effective weapons against invaders—bacteria, viruses or parasites. Other types of T cells recognize and kill virus-infected cells directly. T cells also help B cells to make special Y-shaped proteins called antibodies that stop invaders in their tracks and alert the body, which then makes toxic substances to fight and destroy intruders.

The objective is to show that MHC tetramers can be applied to vaccine development in cattle and create tools for working with livestock diseases, says Golde, who has used the technique in pigs.

In the study, pigs were vaccinated either with a vaccine targeting T cells or another vaccine targeting B cells and then compared. The research showed that a different kind of immune response to FMDV could be induced by redesigning vaccines to target T cells.

Golde is partnering with ILRI researchers to apply these tools to other cattle diseases such as East Coast fever.

Rift Valley fever, East Coast fever, and foot-and-mouth disease studies are just a few of the many research projects under way between ARS and international scientists. Such collaborative research continues to help nations deal with global threats to livestock. It also promotes food security worldwide.

For more information about animal disease research, contact Cyril Gay, leader of the ARS National Program #103, Animal Health.

About This Newsletter

ARS Animal Health Research Laboratories

Healthy Animals Archive

Last Modified: 1/26/2012
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