SAN FRANCISCO -- Birth control may succeed where an arsenal of toxic agents have failed: in checking the baby boom among fleas, cockroaches, mosquitoes and other insect tormentors of man and be $(TEXT OMITTED FROM SOURCE$) the market endangers these pest populations without thre $(TEXT OMITTED FROM SOURCE$) experts on the project spawned by the developer of the birth control pill for women.
Studies and field tests point to 'insect growth regulators' as the first weapon potentially powerful enough to wipe out such poison-resistant diehards as fleas and roaches, which have accompanied humans from cave to condominium.
The regulators, or IGRs -- synthesized versions of natural hormones in the brain -- interrupt the insect's life cycle, making it incapable of reproducing.
Developed at Zoecon Corp. -- 'zoe' from the Greek for 'life' and 'con' for 'control' -- in Palo Alto, Calif., IGRs do not stop adult bugs dead in their tracks.
Rather, they go after pests during the immature stages: eggs do not mature into larvae; larvae do not mature into bloodsucking adults.
Normally, as insect young develop into adults, they undergo a series of molts -- from three to as many as 20 or more -- during which the outer layer of the body wall is shed and renewed. IGRs disrupt these cycles by imitating insect growth hormones.
'While conventional pesticides poison pests, IGRs mimic their biochemistry to control their population -- presenting virtually no hazard to people, pets or environment because they are species-specific,' said Bill Donahue, senior research biologist at Zoecon's corporate headquarters in Dallas.
'IGRs are the future,' said Dallas veterinarian Jim Humphries, host of a syndicated talk show. 'They are a breakthrough that is safer and more effective than any insecticide ever developed.'
In the consumer mass market, Americans spend an estimated $600 million annually on products to control fleas, ants and cockroaches. Each year, they buy another $250 million in flea, tick and fly poisons from veterinarians and pet stores. In addition, professional pest control operators pour $80 million yearly into the pesticide market.
Hoping to cash in on the public's growing reluctance to use toxic agents, chemical companies have begun to actively pursue the development of IGRs -- which first came to researchers' attention in the 1930s.
IGR sprays, foggers and concentrates available to U.S. consumers through veterinarians, pet shops and exterminators can combat roaches, fleas, mosquitoes, horn and corn flies, pharaoh ants, beetles and some stored food insects such as weevils.
Experts at Zoecon -- founded in 1968 by birth control pioneer Carl Djerassi -- and other firms are testing the technology for such possible new uses as curbing insects that each year devour 10 percent of crops and stored grains.
'Our focus has turned toward agriculture,' said Jim Howze, Zoecon's manager of marketing communications, noting the horn fly alone causes some $70 million in damage annually by sucking blood from cattle and accounting for up to 20 pounds in lost body weight per head.
'The public's anti-chemical attit!d! and changing regulatory climate that bans pesticides has made the time right for using this technology il a'!ac /jc! #o*cidebed el'/fidabh! fendebec, such as termite control,' he said.
Zoecon's Precor -- available since 1983 -- has captured a #( 'ebcent share of all anti-flea foggers sold through veterinarians, even though it costs $11, versus $4 for the traditional standbys.
This flea season, the company introduced an on-pet spray, Ovitrol Plus, which is sold through veterinarians for $8 for a 16-ounce bottle.
Zoecon's other major product, roach controller Gencor -- launched in the United States in 1987 and in Australia this summer -- is available from chemists and hardware stores at $15 for a 300-gram can.
While mosquitoes and roaches comprise the biggest insect problem overseas, U.S. veterinary hospitals list fleas as the No. 1 complaint of pet owners.
'Fleas cause a rash of trouble -- from tapeworms to skin disease - and nothing we have works well to control them,' Humphries said.
In 45 days, 10 fleas can produce more than 250,000 offspring, he noted. Conventional insecticides kill adult fleas but leave hundreds of thousands of eggs waiting to hatch.
'IGRs may take a month or so to produce visible results, but they stop the problem at the root, and they don't harm the dog or cat. I've seen so many kidneys and livers destroyed by chemicals,' Humphries said.
In studies reported in the April-May issue of the journal Companion Animal Practice, Purdue University research!bc foel dha IEB '/b)Us 10 dai3 becidual ovicidal activity to interrupt the development of flea eggs.'
he dbaade coak o!ch -- ghich has b!an around for 350 million years, far longer than man -- presents an even greater challenge.
'When you know cockroaches can survive nuclear explosions, it is easy to understand why most surface sprays and baits seem unable to check the patter of little black feet around the kitchen,' Donahue said.
'When insecticides start killing off a population, the reproduction rate goes up to compensate, causing the numbers to rebound to the previous -- or even higher -- level once the chemical's residual effect wears off.'
One roach, which carries up to 40 eggs, can produce 240 offspring in its lifetime, said Peter MacDonald of MacDonald Pest Control in San Rafael, Calif. The eggs often hatch even if the carrier has been killed by an insecticide.
Scientists at Zoecon, a subsidiary of the Swiss pharmaceutical giant Sandoz Ltd., turned the pest's hormones against itself. As Djerassi put it: 'There is no way in theory for an insect to get resistant to its own hormones.'
By mimicking the roach hormone that controls the advance to adulthood, the IGR crumples the young bugs' wings and leaves them unable to bear young. Exposed adults will continue to breed, but their babies will be sterile.
Perhaps the IGRs' greatest triumph thus far has been against the mosquito -- a pest responsible overseas for epidemics of malaria, yellow fever, African river blindness and encephalitis.
Once, these diseases could be curbed only by spraying large areas with insecticides or protecting against mosquito bites. Neither method addressed the root of the problem: the burgeoning populations of the bloodsuckers.
Precor -- introduced in 1975 to combat mosquitoes in stagnant ditch water in Djakarta -- proved so effective in controlling the malaria-carrying pest without toxic effects on the environment, the World Health Organization has approved its use in drinking water supplies throughout the Third World.
'Through analytical techniques and sophisticated equipment, we are gaining a better understanding of how various insect pathways function,' Donahue said.
'Every time these pathways are identified, the doors fly open for us to develop a method for dropping in and disrupting the normal growth process, thereby producing a new generation of safe and effective pesticides.'
