Three King Air planes are lined up on a small runway in the town of Del Rio preparing to bomb south Texas—not with explosives, but with hundreds of thousands of packets of rabies vaccine.
The packets, each about the size of fast food ketchup, contain enough vaccine to inoculate the coyotes that roam the southwest Texas brush country against rabies, which until the last two decades was threatening livestock and humans alike.
"We had two outbreaks of rabies in coyotes and in foxes," recalls Dr. Ernest Oertli, a veterinarian who works with ranchers in this area. "There were a couple of human deaths from rabies, and it was spreading northward and eastward into the populated parts of the state, and was on the outskirts of San Antonio, Austin, Waco and Ft. Worth."
Oertli said that at the time, animal and human health experts were worried about an urban rabies epidemic, and were urgently telling residents to vaccinate their pets against rabies. Rabies in humans is almost always fatal unless the patient receives immediate and lengthy treatment.
A handful of human rabies cases are reported in the United States every year. A woman in South Carolina died from the disease in December and a case was recently reported in Massachusetts, both believed to be infected from bats.
Researchers with the Texas Department of State Health Services learned of an aerial vaccination program underway in Canada, and decided to try it in the equally vast south and west regions of Texas. The results over the past 18 years have been dramatic, according to department spokesman Chris Van Deusen.
"Animal cases of the canine strain of rabies in southern Texas fell from 122 the year before the program began, to zero in 2000," Van Deusen said. "There have only been two cases since then, and both of them were within a mile of the Rio Grande."
He said the program is also concentrated against the fox strain of rabies, and those cases have been reduced from 244 animal cases in 1995, to zero cases in the past two years.
"We have effectively eliminated these two strains of rabies from Texas," Van Deusen said, adding that there have been no human cases of rabies in the region since the airdrop began.
"This is the same idea of the airborne attack against the Mediterranean Fruit Fly in California," Oertli said as he supervised the launch of the planes on one of the 12 flights they will make each day.
Flying at 500 to 1,000 feet elevation, they will drop a total of 1.8 million packets over about 7,700 square miles of rural south and west Texas before the program comes to an end later this month. The packets are dipped in fish oil and coated with fish meal to make them attractive to coyotes and foxes, which eat them and are automatically vaccinated.
"Now our goal is to put into place and maintain a barrier zone to prevent rabies from being reintroduced from Mexico," he said.
Over the 18 years of the program, a total of 36.7 million bait packets have been dropped. In the early years of the program, local media were asked to urge people in urban areas to watch out for falling bait and asked them not to touch the packets on the ground because animals could smell humans on the bait and would not eat it. Van Deusen said, as the rabies has been pushed back toward the Rio Grande and the operations now are taking place over largely rural stretches of west Texas, those warnings are less necessary.
Oertli said the idea of an aerial assault on rabies is spreading across the country. Health officials in several northeastern states are now using the same practice to fight against the spread of rabies in raccoons.
He noted that January is the best time to drop the bait in Texas for several reasons. Coyotes and foxes are short of food this time of year and are more likely to eat the bait, and spreading the baits makes them less susceptible to the roaming fire ants which crawl over everything in their path during hot weather.
"As a citizen, I am thrilled at what we have been able to accomplish with this program," Oertli said.
Now that fox and coyote rabies are nearly eradicated, crews are now planning a similar aerial assault against skunk rabies. He said a special bait packet has been developed for skunks.
Van Deusen stressed that the program is only successful because of laws requiring people who live in cities to vaccinate their pets against rabies.
"Vaccinating domestic animals is essential to stopping the spread of rabies," he said