04/06/2006 11:00PM

Scholar panel offers advice about foal loss


Mare reproductive loss syndrome is in the north Florida neighborhood, according to John Foltz of the University of Florida's Forest Insect Program, but the incidence of the syndrome is small and thus far limited. Only a few horse-related cases have been reported in the area.

Mare reproductive loss syndrome, known as MRLS, devastated the Kentucky breeding program in 2001 and 2002.

The University of Florida sent a life sciences crew of four to the Ocala Breeders' Sales Company on Thursday, where, before 200 or more members of the Thoroughbred community, they discussed the latest information on the syndrome and its potential consequences which, so far, have been negligible in Florida.

"There's a lot we do not know about MRLS," said Dana Zimmel, a colleague of Foltz's, "but we have learned a great deal about the source and the symptoms."

Zimmel and her colleagues went on to make a slide presentation and later took questions on the subject.

All species of caterpillars are suspect in the matter of MRLS. The main culprits are the hairy caterpillars who build gossamer tents. These are the Eastern tent caterpillar and the fall webworm, which develop into moths. There are five species of caterpillar that are easily identifiable by the hairs on their back and sides. It is these hairs, when ingested by the host, i.e. horse, that carry the bacteria that result in abortion and foal loss.

"This is not a 21st-century problem," according to Foltz, a specialist in forest entomology. Caterpillars, he said, have been roaming about pastures since time immemorial. What is new is that heretofore isolated cases of mares aborting and foals dying were not identified with the caterpillar.

"There is no cure for either mare or foal once infected," said John Roberts of the University of Florida. What there is, the panel agreed, is a preventive maintenance program that can limit the number of casualties.

The caterpillar's main hosts are trees. In Florida the larvae hatch in midwinter and develop over the next month or so. The fully developed caterpillar is a brown wormlike creature with all sorts of hairs sticking out. They forage for food and fall out of trees in the process. Horses, it seems, pay little attention to the creatures, and if the caterpillars land on vegetation suitable for grazing, they get consumed. The hairs then work their way through the horse's body, and, in a process not fully understood, set bacteria-induced MRLS in motion.

Preventive maintenance consists of selective elimination from the local environment, those trees that accommodate the caterpillars. Among the hairy caterpillars, the Eastern tent caterpillar ordinarily lives in cherry, plum, apple, and crabapple trees, seldom others. The walnut caterpillar prefers walnut, pecan, and hickory trees; the tussock caterpillar lives in oak trees; and the forest bent caterpillar lives in oak and tupelo gum trees.

The best way to handle the caterpillar problem, said Phil Kaufman, veterinary entomologist, is to take the host trees out of the paddock. He also suggested seeking a professional exterminator for caterpillar eradication.

There is no current danger of an MRLS epidemic in Florida, the university's experts said. Reported cases are few and far between.

If you suspect a foal has died as a consequence of mare reproductive loss syndrome, examine the umbilical cord. If it is yellow, show it to your veterinarian. Do not let your horses graze in a paddock where there are caterpillar tents in the branches overhead, and examine the ground beneath any trees for any type of caterpillar infestation. While the early spring is the optimum time for MRLS exposure, summer and fall can also be potentially dangerous times for exposure.