Lexington, KY - Springtime for most people brings flowers, green pastures and warmer weather, but for those in horse country, it brings the sight of playful foals running beside their mothers.
For Kentuckians and visitors alike, there is no sight more indicative of the state and none more welcome by horse farm owners and managers.
Aside from its beauty, the horse industry is a strong economic engine as well, generating more than $900 million annually in state revenue.
With that in mind, it is hard to imagine that something as small and simple as a caterpillar could create havoc in such a powerful entity, but that is exactly what happened in 2001 and 2002, or at least the small pests were the prime suspects.
Mare Reproductive Loss Syndrome (MRLS), as it became known, cost the equine industry an estimated $336 million, affecting all breeds and approximately 30 percent of the 2001-2002 Thoroughbred foal crop - all thought to be caused by accidental ingestion of eastern tent caterpillars by pregnant mares.
According to research from the University of Kentucky (UK), the losses of foals occurred because of embedded caterpillar hairs in the lining of the alimentary tract of the horse. Once that protective barrier is breached, normal alimentary tract bacteria may gain access to and reproduce in sites with reduced immunity, such as the fetus and placenta, resulting in fetal death, the hallmark of MRLS.
The insects hatch in the spring and are most noticeable because of the tent-like structures that appear in host trees, generally the cherry tree, that serve as incubators.
Lee Townsend, UK College of Agriculture entomologist, said that while the numbers of caterpillars now don't match that of seven years ago, there has been a steady increase over the last three years.
"Populations of the eastern tent caterpillar have increased noticeably over the past three years," he said. "While infestations of the magnitude seen during the 2001-2002 MRLS outbreak are not anticipated, it is clear that eastern tent caterpillar populations are on the upswing and could be heavier than normal in some areas. Assessments and management decisions can be made in a few weeks as the silvery, baseball-sized tents start to show up on branches."
The outbreak was a true mystery for months as research experts worked feverishly to discover the origin.
Bruce Webb, a professor at UK and director of the agricultural biotechnology program, was just one of many who conducted research in an effort to discover the origin of MRLS.
"When this started, no one had a clue. The caterpillars have been around forever, so why didn't we see this before," he said.
The answer, as it turned out, may have had something to do with the concentration levels of the caterpillars, which were very high at the time.
The insects go through natural biological cycles of population increases and decreases. Research since the outbreak has determined that the rises and declines are most likely linked to a virus that kills them. When the virus is prevalent, the caterpillar numbers go down and vice versa. Webb emphasized that their primary focus initially was to find the cause of the problem so preventative measures could be put in place, but it has been the scientific aspect of the research since that outbreak that has taught them much.
"There was no way to understand the process until we started doing experiments. There were a lot of people working on this. It was very much a team effort," he said.
Webb added that in 2001 the concentration of caterpillars was high within a 200-mile radius around Lexington, something they don't expect this year; however there could be isolated areas with heavy enough populations to cause concern.
Mike Owens is the manager at Cobra Farm, a 340-acre farm in the middle of famed horse country. It was his concern for the trees back in 2001 that quite possibly kept their mares safe.
"I'll do what I've always done and make an honest effort to eradicate them while they are still in the trees at a small stage," he said. "I did that seven years ago, honestly, trying to keep the trees from defoliating, not because we thought something else was going to happen. I didn't know at the time they could do something to horses. We had the caterpillars, but we didn't have any losses. We were very fortunate."
Owens added that he has recently been out on the farm working with trees because of ice storm damage, seeing only one caterpillar egg shell so far, but he expects more.
"There is still a lot of research to do but I believe the caterpillars had something to do with it," he said of the MRLS outbreak. "We are cautious and feel comfortable that we can control it. No one is panicking."
Owens also said that since that outbreak, farms have stepped up their management to guard against another, and technology that could help determine a cause has advanced. But still anytime there is a loss, farm managers can't help but worry a little.
"I can remember when this was going on. I was afraid of what could have happened," he said. "We're all in the mode that when something occurs we think of it happening again, but by the same token, we wouldn't be here if we didn't cherish each and every one of these animals."
Owens reiterated what a team effort was made to find the solution to a terrible problem, noting the work of the Kentucky Thoroughbred Farm Managers Club, the UK College of Agriculture including the Livestock Disease Diagnostic Center and the Gluck Equine Research Center, the veterinary community, and a host of others from around the world that were pulled into this, he said. "That team effort continues today, as it should."
UK entomologists recommend that farm managers keep pregnant mares out of fields bordered by cherry or other host trees for the next several weeks unless they have been aggressive in managing the caterpillars.
For more information visit http://www.ca.uky.edu/equine.