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Fall 1998

Research Magazine > ARCHIVE > Spring 98 > Article

Contraceptive Safari
by Judy Bolyard Purdy

Efforts to save African elephants have been so successful that scientists now must find ways to limit elephant populations.

Armed but not dangerous, Richard Fayrer-Hosken stalks the wild elephants that roam South Africa’s Kruger National Park. His mission: to reduce the size of the burgeoning herd, not by killing, but by contraception.

"Kruger is really suffering ecologically because of elephant overpopulation," said the UGA associate professor of large animal medicine. "Elephant nutrition needs are so enormous and their method of eating is not conservation-minded. They’ll bulldoze over trees to get a few roots, and with that they start to destroy a habitat."

If their numbers are not curbed, elephants could end up destroying the national park for plants and other wildlife. So Fayrer-Hosken stalks the herds with an elephant gun that fires darts laced with a special contraceptive he first developed for horses.

Park officials culled several hundred elephants a year from the mid-1960s until 1995. Their goal was to maintain a balance between the herds and park habitats. Sometimes elephants were relocated. More often they were killed and the meat was sold to local villages.

Looking for a better solution and a more humane management approach, park managers in 1995 contacted the UGA veterinarian about his contraceptive vaccine.

"This vaccine is one of the most revolutionary technologies on population control. It’s nonhormonal, which makes it safe and effective, and there don’t appear to be any side effects," said Fayrer-Hosken, who has tested the vaccine on wild horses and white-tailed deer.

Hormone-based contraceptives, such as those given to lions, leopards and other big cats in zoos, can cause cancer or infections, he said. Based on Fayrer-Hosken’s research the protein-based contraceptive appears to have no such side effects.

The active ingredient in Fayrer-Hosken’s vaccine is a protein from pig ovaries, specifically from a protein coating, called the zona pellucida, that surrounds each egg.

The vaccine works by injecting the porcine (pig) zona pellucida, or pZP, into a female mammal, prompting her body to make antibodies that interfere with egg fertilization. All mammalian eggs have a zona pellucida, and so far, studies indicate that the zona pellucida’s protein structure is very similar in many mammals. This close similarity is what scientists call a "conserved" protein because it exhibits little variation across a wide spectrum of species.

Through a series of laboratory investigations, Fayrer-Hosken’s team discovered that the contraceptive mechanism is elegantly simple at the molecular level.

"The art of my job as a veterinarian is to bring in the molecular science and show how the vaccine works at the electron microscope level," Fayrer-Hosken said. "We know that the egg and sperm [of mammals] bind at two structures on the egg’s surface. One is a carbohydrate and one is a protein. I believe that the antibodies in the contraceptive bind to the egg’s carbohydrate receptor, which blocks the sperm from binding to the egg."

Wildlife contraception, however, is a relatively new field, and only a handful of researchers worldwide are experimenting with pZP contraceptive technology. In addition to UGA scientists, they include theriogenology Professor Irwin Liu at the University of California, Davis; Professor John Turner at the Medical College of Ohio; and Zoo Montana’s Director of Conservation Jay Kirkpatrick.

Through combined efforts, the scientists have tested the vaccine on more than 40 species of wild or captive mammals, including white-tailed deer, wild horses, monkeys and mice.

In each case, the pZP vaccine was safe, effective and reversible.

"As a quartet, we probably have access to the knowledge on most all the field applications of this vaccine in the world," Fayrer-Hosken said. But in 1995 when Kruger park officials contacted the UGA research team, no one had ever tested the vaccine on wild elephants.

Kruger’s elephant population has soared because elephants have few natural enemies and the park’s effective elephant protection and management program has virtually eliminated poaching. The 1990 worldwide ban on ivory trading also has helped safeguard elephants. In addition, herd behavior ensures a high rate of survival to adulthood.

Overpopulation and Birth Control

"Very occasionally, a baby runs away and can get grabbed by one of the big predators," Fayrer-Hosken said. "But female elephants are so maternal and so protective of the babies that survival is incredibly high. If a baby falls into a hole or gets sick, the herd will stay with it. They really have a concept of family."

The high survival rate spells bad news for healthy park habitats, however. When park managers compared aerial photographs of the park from the 1950s with more recent ones, they noticed that many natural areas were being destroyed because of elephant overpopulation.

Wild elephants have made a strong comeback since the dawn of the 20th century, when only four wild elephants were known to exist in all of what is now the Republic of South Africa. Nearly a century later, the population has soared to approximately 8,500, and more than 80 percent of them live in Kruger. Park managers set the desirable population for Kruger between 7,000 and 7,500 elephants.

In the past, elephants had a huge range, easily roaming 50 to 100 miles, and by the time they returned to an area, the plant life had recovered. Now they are confined to the park boundaries with nowhere else to go.

The Humane Society of the United States is funding Fayrer-Hosken’s elephant research because it is interested in conservation. "It wants to prevent elephants from being culled as a population control," he said. "Before 1995, when we began this program at Kruger, 700 elephants were being killed each year to keep the elephant population in balance with the park’s carrying capacity."

Additional support for developing the pZP vaccine has come from the U.S. National Park Service and the UGA College of Veterinary Medicine.

Theoretically at least, Fayrer-Hosken figured his pZP vaccine would work on elephants. But before he injected any wild elephants, he wanted to know more about the female elephant reproductive system, which had never before been studied at the molecular level. He and his graduate students began an investigation of elephant ovaries and eggs. The team then compared the elephant reproductive system, specifically the ovary, to the contraceptive source, the female pig, and found the two mammals had enough similarities that the vaccine should work. "That meant the probability of the animal being contracepted would be very high," Fayrer-Hosken said.

The UGA team included research technician Paula M. Brooks, graduate students Matt Barber, Chris Brandon, Robert Fulton and Jay Faircloth, and Electron Microscopy Laboratory coordinator Mary B. Ard. They needed to know how much contraceptive to give an elephant and how long it would last. "We knew how much vaccine to give a rabbit or a lemur or a horse, but we’re talking an order of magnitude to an elephant," he said.

With the help of the elephants and the staffs of zoos in South Carolina and Canada, the research team found its answers. At the Riverbanks Zoo in South Carolina, staff veterinarian Nadine Lamberski and elephant caretakers Richard Elgin and Deborah Thompson agreed to let the UGA researchers use a 4 1/2-ton elephant cow as the first guinea pig.

"Richard and Deborah have look-ed after the elephants for many years, so for them, these elephants are not just animals — they are very smart and very endearing," Fayrer-Hosken said. "One of the bravest steps was the zoo people allowing us to vaccinate their kid. Because of their belief in conservation, we were able to vaccinate her and measure blood levels."

The Riverbanks Zoo elephant responded well to the vaccine, but the researchers wanted to run additional tests before vaccinating wild elephants. Janie Raxter, the elephant trainer at the Greenville Zoo in South Carolina, and the staff at the Calgary Zoo in Canada also agreed to let their elephants be tested.

"We predicted from other [mammal] species that we were in the safe zone, and we were," Fayrer-Hosken said. "We only had to change the dose just a little bit."

A Successful Safari

Just as Fayrer-Hosken was departing for South Africa, he received a good omen; he learned that the Riverbanks Zoo elephant, the very first ever to receive the pZP vaccine, was born and raised in Kruger National Park.

"By now she has actually helped save 2,000 of her kin because no elephant has been killed in Kruger since 1995, when we started this experiment," he said.

Accompanying Fayrer-Hosken on his research safari were Zoo Montana’s Kirkpatrick, University of Pretoria Professor H. J. Bertschinger and Kruger National Park veterinarians Cobus Raath and Douw Grobler.

The band of researchers tracked their prey of elephant cows and calves across the savanna, tranquilizing the adults and collecting a variety of data: height, girth, half girth, body length, tusk length, foot-pad circumference, etc.

They also gathered samples of blood, milk and feces, which contain steroids that provide information on estrus cycles.

So far, the group has logged data on 200 elephants. Of those, approximately 40 non-pregnant elephant cows were selected for the first round of research in 1996 and given radio-transmitter collars so they could be tracked over time.

"The elephants aren’t really bothered by the collars," Fayrer-Hosken said. "When they stand up, they give it a tug because they can feel it and then off they go."

Pregnancy status was determined by an ultrasound examination in the field, with the help of Dr. Robert Hermes of the Berlin Zoo and Reproductive Center.

"The way you ultrasound an elephant — and also a horse or a cow — is to insert a probe into the rectum to see the uterus, which lies directly under the rectum," Fayrer-Hosken said. The results show up on the screen of a portable computer.

"If the animal is not pregnant you can get a good picture of the uterus and ovaries," he said. "On a pregnant animal the uterus and ovaries are pulled forward and downward where you can’t see them on the ultrasound."

The procedure is not only messy but also potentially dangerous because elephants eat thorns, which can cause puncture wounds to the researchers.

Half the nonpregnant elephants were vaccinated with the contraceptive and the other half — the control group — got a vaccine of harmless saltwater. From start to finish, the whole procedure, including data collection, ultrasound exams, collaring and vaccinating, took about half an hour per elephant.

Previous pZP contraceptive research on the zoo elephants, as well as wild horses and white-tailed deer, indicated maximum effectiveness through a series of vaccines within a short time frame. With the aid of helicopters and high-speed rifles, the wild elephants also received follow-up injections. The researchers injected the contraceptive via an aluminum dart fueled by carbon dioxide gas.

"When it hits the elephant, the brass divider tumbles forward and the vinegar and bicarbonate mix, giving you carbon dioxide gas, which then sends the plunger thundering forward and the vaccine is injected instantaneously," Fayrer-Hosken said.

In 1997, the researchers returned to Africa, tracked down their collared elephants and again conducted field ultrasound exams. They found the vaccine had been effective.

"Pregnancy rates among the elephants that were vaccinated are very low compared with the control group," Fayrer-Hosken said. "Our results are statistically significant."

Birth Control Benefits

The vaccine lasts for about a year, and that’s just one of its many advantages. It also will be easy to deliver. Park personnel can just jump into a helicopter, head out across the savanna and vaccinate as few or as many elephants as necessary.

Kruger’s game management team already has shown its savvy at reliably predicting which elephants are pregnant.

"The helicopter pilots are extremely accurate in judging the size of the calf, and size relates to age," Fayrer-Hosken said. Since cows with young calves usually are not pregnant, managers "will never have to lay a hand on the elephants. They can all be vaccinated from a helicopter. It’s a practical tool.

"We can ship the vaccine to them, and they can keep it in the refrigerator until they are ready to use it," he said.

Even if a pregnant elephant were to be vaccinated accidentally, the researchers don’t expect any adverse side effects. Wild horses on Assateague Island occasionally get vaccinated and "they have had foals and their foals have had foals," Fayrer-Hosken said.

Based on the tissue toxicity trials, the protein-based pZP vaccine is totally safe, he said. "If you do hit one twice, it may be contracepted longer. With some hormone-based contraceptives, however, if we hit them two or three times we could cause significant side effects."

Another benefit is that park managers will be able to determine from one year to the next how many elephants should be vaccinated to maintain peak population numbers.

"The people at Kruger think about 3,000 elephants would need to be vaccinated each year to have a stable population," Fayrer-Hosken said.

But supplying that kind of demand will require a synthetic form of vaccine. And that means a lot more time in the lab for the UGA team, which already is filing a patent on the vaccine.

"Right now we are extracting all our protein from the pig ovary," he said. "And we are working on making a synthetic form because we won’t be able to get enough from the natural source for millions of vaccinations."

Birth control may mean improved health among the elephant herds. It also may lead to longer life expectancies.

"The wild horses that Jay Kirkpatrick vaccinated at Assateague Island in North Carolina became healthier and lived longer, which was not expected," said Fayrer-Hosken. "The normal life expectancy could not be applied to their population model because the vaccinated horses seemed to be doing far better than the unvaccinated ones. They didn’t have babies and so they didn’t need to lactate."

Fayrer-Hosken said he predicts that private African photo safari game reserves also may be interested in the contraceptive.

Failure Breeds Success

Fayrer-Hosken came upon the notion of developing wildlife contraceptives in 1989 while studying ways to improve horse fertility with UGA large animal science Professor

Al Caudle. The scientists were trying to gain a better understanding of the molecular basis for fertilization, infertility and disease mechanisms that cause mares and stallions to become infertile. Their research included unsuccessful attempts at developing test-tube foals.

"The problem turns out that of all the species, the horse is one that we cannot get to grow as test-tube babies," Fayrer-Hosken said. "I figured that if I couldn’t do in vitro fertilization, I could examine the horse’s zona pellucida and backtrack to find out how fertilization occurs in the horse."

That path led straight to contraception based on zona pellucida antibodies.

"My colleagues were skeptical at first," he said, but it wasn’t long before Fayrer-Hosken had refined a horse contraceptive.

Interest in his birth control methods came not only from horse breeders but also from the U.S. Park Service and private groups interested in controlling wild horse populations at places such as the Georgia coastal barrier islands.

This past fall Fayrer-Hosken and his students vaccinated wild horses on Little Cumberland Island, Ga. This spring Fayrer-Hosken will assist Kirkpatrick vaccinate wild horses in Nevada.

With his patent application to file, papers to publish and ongoing research projects, Fayrer-Hosken said his plate is full. Eventually, though, he plans to continue his collaborative work on a vaccine for white-tailed deer. He and Kirkpatrick have figured out the right dosage and protocol for deer, but the delivery system needs to be refined. The deer vaccination program would be a formidable job because deer have such speed and are so elusive, he said.

But for now, the elephants get top billing.

Pictures by Richard Fayrer-Hosken and Paula Brooks.

For more information, e-mail Richard Fayrer-Hosken at rfh@calc.vet.uga.edu


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Hosken and elephant