Limping sheep? Check for foot rot
After a dry winter season, the sight of rain is welcome on many Missouri farms. However, for sheep and goat producers it can bring about the resurgence of a debilitating disease.
Foot rot is a disease that continues to plague the sheep industry. It affects all ages and breeds of sheep in all areas of the United States, especially in regions from northeast to northwest. And wet weather seems to be the trigger.
Warm, wet conditions soften the hooves and tissue between the toes, making the foot more susceptible to infection. Any cut or abrasion during this time allows an opening for the foot rot bacteria to enter the hoof.
• Foot rot bacteria is present in the soil and manure.
• More than 50 strains of bacteria have been discovered to date.
• Researchers are looking for the prominent strain in Missouri.
Two bacteria genera cause the disease in sheep and goats, Dichelobacter nodosus and Fusobacterium necrophorum. Both work to destroy the tissue in the hoof, which can cause lameness.
Unfortunately, both are present in the soil and manure and spread animal to animal. Dichelobacter nodosus can live for up to two weeks in the environment, and require an animal host to survive longer periods. However, the Fusobacterium necrophorum can live in the environment for months or even years.
While the disease typically does not result in death, infected flocks have reported weight loss, poor reproductive performance and reduced wool quality.
With increasing sheep and goat numbers across the state, researchers at Lincoln University are studying the disease to find the cause and offer possible solutions for producers.
Cultures growing in the labs at Lincoln University may hold the key to identifying the exact strain of bacteria causing foot rot on Missouri farms.
“The problem is that the Dichelobacter nodosus has up to 20 strains and the Fusobacterium necrophorum also has many substrains,” says Tumen Wuliji, a Lincoln University research animal scientist.
Wuliji is leading a team of researchers working on projects surrounding foot rot in sheep and goats.
The first is identifying the strain or strains present on farms across the state. For that, Wuliji and his team enlists the help of producers.
Researchers field calls from sheep producers affected with foot rot. Then they travel to the farm to analyze the situation and collect samples.
“We will take a swab of the infected foot and hooves,” Wuliji says. “Then we bring it back to the lab to culture it.”
He uses an anaerobic chamber to grow the bacteria. Then the researchers identify the bacteria types under a high-powered microscope.
“This is what you are looking for,” he says, pointing to a chart hanging on the wall. “You are looking for something that looks like the Fusobacterium necrophorum.” Then he will isolate the bacterium colonies for DNA sequence identification.
However, he admits there can be variations. “Some animals may be infected by one type of bacteria with several strains — others, more than one type, with a dozen different strains,” he says. “We look for all [strains] in that animal.”
Wuliji says that identifying strains affecting animals in the state can aid in the development of programs for prevention and treatment.
Breeding out bacteria
Lincoln University is also conducting work in breeding for resistance.
Research over the last 20 years has linked a group of genes with the ability of sheep to tolerate foot rot. “These genes regulate immune response,” Wuliji says. “It has been found for parasite resistance, we assume the similar block of genes for foot rot.”
Using the university flocks, Wuliji collects blood samples from animals: some infected, others not infected. Then he screens for a particular genotype that is causing the resistance.
Similar research is going on at Lincoln University in New Zealand. In that country, researchers identified the major histocompatibility complex, or MHC, as the gene associated with a greater or lesser likelihood of getting foot rot. Sheep are typed and then coded on a scale of 1 to 5, 1 being the least likely to contract foot rot and 5 being the most likely to contract the disease.
Wuliji says his research, which started two years ago, is in the beginning stage of securing samples and analyzing data. What will be interesting is if the same gene is found to be the culprit in different breeds and different countries.
Ultimately, by identifying the resistant gene, producers will be able to breed sheep that are less likely to get foot rot.
GROWING CONCERN: Bacteria collected from Missouri sheep farms may provide information to breed foot rot out of flocks.
This article published in the April, 2012 edition of MISSOURI RURALIST.