BRADENTON — The horse was sick, and nobody knew why. It stood weakly in a stable at the Rancho Alegre.
It had lost weight. Its urine was reddish. Owner Pedro Cabrera was stumped.
So in August, he took the quarter horse to Ocala, where a "suspicious organism" turned up on a microscope slide, state authorities say.
When results came back from the laboratory, it became clear that the 7-year-old gelding suffered from equine piroplasmosis, a tick-borne disease that is often fatal.
Officials from the state's Department of Agriculture and Consumer Services raced to Cabrera's farm that same day. Observers from the United States Department of Agriculture arrived soon thereafter.
Their cause for alarm: EP was thought to have been eradicated from the United States in 1988. There is no course of treatment, nor is there a vaccine.
The state placed the ranch and two neighboring stables under quarantine. Over the next three months, authorities tested 200 quarter horses in nine counties for EP. Twenty-five farms, including one in Hillsborough County, have been quarantined.
Twenty horses have tested positive for EP, including one in Polk County in mid November. At least 17 have already been euthanized.
Even so, concerns appear to be waning. The recent positive test was the first in two months.
"We think we've got our arms around it," said spokesman Terry McElroy of the Department of Agriculture and Consumer Services. "I think we have calmed everyone down."
Authorities swept all quarantined premises for the tropical horse tick known to spread Babesia caballi and B. equi, the parasites that cause EP.
They found no such ticks, which are not common in the United States, and no traces of the parasites in 50 other tick species tested.
Instead, authorities now believe human handlers spread the parasite through needle sharing. All of the infected animals were quarter horses, a breed so named for its ability to outrun other breeds in distances of one-quarter mile or less. Most were stabled at farms with dirt oval tracks.
"Our investigation shows that many of these horses were simply brought to a local dirt track on the premises of some of these farms, and people went down and raced their quarter horses," McElroy said.
"Presumably gambling was involved," he added. "We don't know that."
In their prime, some of the infected horses had run on licensed Florida tracks such as Hialeah or Gulfstream, said Dr. Michael Short, a veterinarian who manages the equine program at the Florida Division of Animal Industry. Now they were running in makeshift races in the middle of nowhere.
"They don't deny racing," Short said. "But there was no admission of gambling or illegal practices."
Authorities say owners were tight-lipped about which drugs, if any, may have been injected. Short ventured a guess: "Anything to make them run faster."
Neither Cabrera, the owner of five infected horses, nor any of several other stables placed under quarantine returned repeated phone calls from the Times.
Word of a resurgence of EP spread quickly among local horse owners.
"I'm concerned about it," said Dave Winn of Sun City Stables in Sun City. "Right now it's something that doesn't appear to be in Hillsborough County. But it's disturbing."
Janice Scotto of the Whispering Oaks Equestrian Center in Tampa heard the buzz about an EP comeback from other owners, and read comments on Internet sites like horsetopia.com.
"It's just something to watch," Scotto said. "The problem is there isn't a vaccine."
Investigators believe that two infected quarter horses from Mexico brought EP to Polk County in 2005. From there, horses stabled together came in contact with the parasite Babesia caballi through injections.
Before the dust settled, investigators quarantined farms in Manatee, Polk, DeSoto, Lake, Dade, Orange, Pasco, Hillsborough and Hendry counties.
The number of quarantined farms has since dropped to four, in Polk, Manatee and Dade counties.
Emily Weaver, an Odessa veterinarian, said she has advised worried clients to stay away from quarantined stables. "Basically, I've told them all that they're at pretty low risk, unless they are planning to move their horses to those locations," she said.
Andrew Meacham can be reached at (813) 661-2431 or firstname.lastname@example.org.