The man who beat a dangerous horse disease
When veterinary scientist Don Knowles got give-and-take 3 years agone that a rare but deadly infection was discovered amidst a grouping of horses inwards southward Texas, he felt a jar of adrenaline.
Not alone were the horses infected amongst Equine piroplasmosis, a parasitic affliction similar to malaria inwards humans, but the epicenter of the outbreak was at no ordinary ranch.
It was the King Ranch, legendary for its world-class quarter horses, in addition to before for its thoroughbreds including Triple Crown winner Assault in addition to Kentucky Derby winner Middleground.
The 825,0000-acre family-owned estate that stretches across 4 counties is i of the largest in addition to most famous ranches inwards the world.
“Anyone who knows anything virtually quarter horses knows virtually this ranch,” said Knowles, a professor at Washington State University.
“Universally, it’s on the map for the best horses in addition to cattle.“
One King Ranch horse, virtually 45 miles southwest of Corpus Christi, had tested positive for the affliction when the federal authorities kickoff alerted Knowles. Influenza A virus subtype H5N1 few days later, it was a dozen horses, in addition to thence 4 dozen.
“The number but kept going up,” recalls Knowles inwards his academy office, where a large photograph of appaloosa horses inwards a champaign punctuates i wall in addition to a route bike leans against another.
Knowles, inwards his silver-rimmed spectacles, hiking shorts in addition to athletic shoes, resembles somebody to a greater extent than at dwelling solid on a bike trail than a scientist at the beck in addition to telephone phone of deadly, infectious animate beingness diseases that line him to regions close in addition to far.
“This sort of outbreak had never been seen inwards this province before,” he said. “People were asking ‘What’s going on downwardly there?’ “
And so, at the asking of federal agriculture officials, Knowles boarded a bird in addition to headed southward to investigate. As leader of the the States Department of Agriculture’s Animal Disease Research Unit at Washington State University, he had a Texas-sized riddle to solve.
Parasitic storm
Equine piroplasmosis is thence feared inwards the the States that the authorities bans horses that examination positive from entering the country. Until the outbreak inwards Texas, alone a few sporadic cases had e'er been reported.
Dudley Hoskins, an attorney amongst the American Horse Council inwards Washington DC, said at that time: “We had regarded piroplasmosis every bit a unusual animate beingness affliction in addition to all of a precipitous hither it was on the States soil, amongst non i or 2 cases but nearly 300 – all concentrated at a ranch recognized for exemplary administration practices.
“To say nosotros were concerned would hold upward an understatement.”
Piroplasmosis, too called equine tick fever, is transmitted to horses through the seize amongst teeth of a tick that carries either the Babesia caballi or Theileria equi parasites inwards its saliva.
Similar to malarial parasites that infect humans, these pear-shaped creatures move through the horse’s circulatory system, multiplying, drilling through blood-red blood cells in addition to multiplying some more.
Knowles, too a professor of microbiology in addition to pathology at WSU’s veterinary college, teaches his students virtually it.
“I enjoin them that i of their responsibilities every bit a veterinary volition hold upward to foreclose piroplasmosis in addition to how an outbreak could termination inwards a slap-up loss of horses in addition to bargain a severe blow to the Equus caballus industry,” he said.
“Once the parasite becomes established inwards the tick in addition to equine population, it could spread rapidly every bit horses are transported to equestrian shows in addition to races around the country.”
No treatment, painful options
Many infected horses exhibit footling to a greater extent than than cold-like symptoms, but inwards regions where piroplasmosis is uncommon, such every bit the US, horses take keep no natural resistance to the disease. Unimpeded, the parasites proliferate in addition to destroy blood cells, triggering fever, anorexia in addition to anemia.
“If a Equus caballus dies of piroplasmosis, anemia is oftentimes the cause,” said Knowles. “It’s a progressive procedure in addition to a misfortunate way for an animate beingness to die.”
Before the outbreak inwards 2009, no criterion handling existed. If a Equus caballus tested positive for piroplasmosis, the possessor had 3 government-mandated options to proceed the affliction from spreading: euthanize, quarantine, or ship the Equus caballus out of country.
“Our horses are vitally of import to us,” said King Ranch director Dave Delaney. “The sentiment of euthanizing them was out of the question.
“Many of us had heard of piroplasmosis but had never dealt amongst it,” he said. “So when Don got here, whenever he spoke, believe me, people paid attention.”
On the trail
Long before Knowles boarded that Texas-bound bird inwards tumble 2009, he knew a lot virtually piroplasmosis. The periodic clusters that surfaced inwards temperate-climate states such every bit Florida proved the parasites sometimes slipped across the the States edge inwards horses that had tested negative for the affliction when, inwards fact, they were positive.
Because the examination sometimes gave faux negatives, Knowles was charged amongst developing a to a greater extent than reliable diagnostic test. He too was instructed to do a standardized handling to kill the parasites.
“Until Texas, much of the operate had been done inwards the lab,” he said.
This meant that, after Knowles in addition to his squad arrived at King Ranch, “you mightiness say nosotros provided him amongst a real-world representative to examination the effectiveness of his preliminary work,” said Delaney.
Hungry vectors, vulnerable hosts
Armed amongst 2 decades of piroplasmosis inquiry in addition to a squad of scientists from his the States Department of Agriculture unit of measurement in addition to Washington State University, Knowles non alone contained the outbreak but he in addition to colleague Glen Scoles too identified a novel blood-sucking culprit that had spread it.
“Prior to that outbreak, nosotros knew of 2 tick species capable of transmitting the disease. There, nosotros discovered a third,” said Knowles.
He in addition to his squad identified the cayenne tick every bit the predominant carrier, a finding thence of import that the grouping later on published a newspaper virtually it inwards the journal, Emerging Infectious Diseases.
It’s probable a cayenne tick snagged a ride on an infected Equus caballus years before the outbreak, drawing parasites inwards through its blood repast in addition to thence moving on, injecting in addition to infecting other horses, said entomologist Scoles who, after the outbreak, proved that the cayenne species was involved.
The outbreak at King Ranch “could take keep coincided amongst climate factors which, inwards turn, caused an growth inwards tick numbers”, Scoles said.
“They saved our horses”
All said in addition to done, Knowles in addition to his squad did to a greater extent than than position a novel eight-legged transmitter of piroplasmosis in addition to railroad train an internationally accepted examination to diagnosis it.
“How about, ‘They saved our horses?’ ” said Delaney of King Ranch.
The scientists used high doses of imidocarb dipropionate, a drug used to process sure enough diseases inwards cattle.
“The parasites look to hold upward eradicated. All of our horses are healthy,” he said.
The outcome of administering the drug was thence successful that, after subsequent trials, it is straightaway beingness evaluated every bit a criterion handling protocol inwards the US.
“If approved for use, the handling would offering a way to clear horses of infection,” said Hoskins, who has followed Knowles’ research. “This would hold upward huge.”
Which agency that, largely because of Knowles’ work, the possessor of a piroplasmosis-infected Equus caballus may take keep the selection of curing the animate beingness – in addition to and thence i twenty-four threescore minutes menstruation watching it flash across a meadow or fifty-fifty a complete line.
» More on Equine Piroplasmosis
Reporting: Linda Weiford
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