Scientist’s Mosquito Hunt Amid Old Tires Pays Off : Health: Researchers turn attention back to infectious diseases. Bug from Asia found to carry brain affliction.

He must have made a comical sight, this youthful-looking doctoral student from Notre Dame, prowling about tire dumps in the heat of July and August, searching for an exotic silver-striped mosquito that until 1985 had never been seen in the United States.

Mark Niebylski spent three summers, from 1989 through 1991, on the trail of the Asian tiger mosquito, which often breeds in stagnant pools of water that accumulate in discarded tires. He traipsed through back country burgs in Florida, Louisiana, Missouri and Illinois--a bug-trapping vacuum on his back and an eager look on his face.

“I’d show up hoping my smile would open some doors for me,” recalled the 29-year-old whose bug-collecting mission was directed by government researchers at a laboratory here in the foothills of the Rocky Mountains. “I would stop at the local public health office or the local university and say, ‘I’m here to get some mosquitoes. Is there anybody who could show me where the local tire piles are?’ ”

This unusual quest was far from an esoteric academic pursuit. During those three summers, Niebylski performed work that is an essential, if often unheralded, component of the nation’s public health system.

For that brief time, it might be said, Niebylski was a disease detective.

Last year his footwork paid off. Using specimens that Niebylski brought back, scientists at the National Center for Infectious Disease in Ft. Collins made a finding that confirmed their long-held fears: The Asian tiger--which has rooted itself in 23 states since coming to this country amid a boatload of used tires, probably from Japan--can transmit Eastern equine encephalitis, a rare but deadly brain affliction.

In the annals of infectious diseases, the threat of Eastern equine encephalitis hardly ranks alongside AIDS or tuberculosis or even the flu. So far, no cases of the disease have been traced to the Asian tiger, although making such a direct connection would be extremely difficult.

But the Ft. Collins discovery comes at a time when scientists, after more than two decades of focusing intense attention on illnesses such as heart disease, cancer and stroke, are growing increasingly concerned about the specter of infectious disease. The common wisdom that illnesses spread by infection have been conquered through vaccines, antibiotics and pesticides no longer holds.

And in that context, experts agree, the arrival of the Asian tiger--formally known as Aedes albopictus --illustrates two important lessons:

First, in a shrinking world where commodities and people move about more rapidly and easily than ever before, infections and the agents, or vectors, that carry them no longer stop at a country’s borders. In this new world order of disease, the old notion of illnesses as “domestic” and “international” is now as dated as the Hula Hoop.

Secondly, the world needs disease detectives now more than ever.

“It’s a very small world,” said John LaMontagne, who directs infectious disease research for the National Institute of Allergy and Infectious Diseases, an arm of the National Institutes of Health. “Infections can be transported across long distances very rapidly. You can be sitting in Madras, India, one day and be in New York City 20 hours later. That’s not very much time.”

Last year, for instance, 31 passengers aboard a plane from Argentina to Los Angeles were found to have cholera--a disease that has reached epidemic levels in South America and has been creeping northward toward the United States, where cases have been reported in New York, New Jersey and San Francisco. The airplane outbreak, which killed one person, sent public health officials in four countries--the United States, Japan, Canada and Argentina--scurrying to find all 336 passengers to prevent the disease from spreading.

Malaria is also turning up more frequently in the United States, where about 1,200 cases are now diagnosed each year. Most cases occur among travelers or immigrants who bring the disease with them. But in 1988, infected migrant farm workers brought the disease to San Diego County, where local mosquitoes spread it to uninfected people.

In Chicago, a man who visited Nigeria in 1989 for his mother’s funeral returned home with Lassa fever--a deadly virus so rare in this country that most American doctors would not recognize it. After several doctors misdiagnosed the man’s condition, a specialist made the correct call. By that time, 102 people had come into contact with the man, who died soon afterward. The others were given an experimental drug; surprisingly, none got sick.

Much like the arrival and spread of the Asian tiger mosquito, each of these incidents was a product of the shrinking world. Each was a potential menace to public health. And, scientists say, the arrival of these diseases on U.S. soil could have been predicted--if only there were enough disease detectives out there, watching trends, picking up clues and looking for potential threats.

“Look at cholera,” said Michael Osterholm, president of the Council of State and Territorial Epidemiologists. “Five years ago, people would have said, ‘Cholera in the Americas like that? Never!’ And look at it now.

“I think there are more choleras out there. There are other diseases that are just waiting to happen. Should we have anticipated cholera? Well, you could have.”

Some go so far as to say that if the world had a better network of infectious disease laboratories, the human immunodeficiency virus, which causes AIDS, might have been detected before it spread around the globe.

“Most people would agree that HIV disease was present certainly in Africa, perhaps in other parts of the world, in a form which could have been recognized if somebody had been looking for it,” said Robert Shope, a Yale University virologist who co-edited a report on infectious disease by the prestigious Institute of Medicine. “Whether we could have done something about it, I’m not sure. But we need to have listening posts.”

Yet the institute’s report concluded that the world’s network of such listening posts is woefully inadequate and suggested that the United States take the lead in developing one. To that end, the U.S. Centers for Disease Control and Prevention is drafting a plan to combat future epidemics; a key part of the proposal is to create a global confederation of 15 infectious disease laboratories.

Although the CDC has not estimated the cost, officials acknowledge that persuading Congress to finance the plan might be difficult. The battle over funding for prevention is one that public health officials across the nation know well.

Legislators are wont to “focus their attention on diagnosis and treatment of sick people,” said Dr. Shirley Fannin, director of disease control for the Los Angeles County Department of Health Services. “That’s the big drama. When you come to budget crunch times, nobody understands the necessity of putting up barriers to prevent things from happening.”

Joshua Lederberg, a Nobel Laureate in bacteriology who co-edited the Institute of Medicine report, cites the Asian tiger as a perfect example, noting that little effort has been made to eradicate the bug.

“Although we knew that this was a perfectly capable vector for a range of diseases, (an outbreak) hasn’t happened yet,” Lederberg said. “And it is very hard to get an investment of public money for things that have not happened.”

Nowhere has that reality been clearer than in Ft. Collins, where a team of scientists has devoted years of painstaking research to following the path of the Asian tiger, examining its breeding habits, isolating the viruses it carries and studying ways to control it--all the while watching in frustration as the mosquito spread unchecked from state to state.

The Asian tiger, they have found, is worthy of its name. It is an especially aggressive biter, it multiplies quickly, and it favors cities and suburbs--a dangerous combination for a bug that transmits disease.

The mosquito made its United States debut in May, 1985, in Harris County, Tex., on the outskirts of Houston. Daniel Sprenger, a laboratory supervisor in a local mosquito control district there, recalls that when a colleague spotted the strange-looking insect, with its bright silver scales and distinctive silver bands on its legs, the two of them rushed to the airport and the local shipping channels on the hunch that if the mosquito had come here from another country, it would be there.

They were right. “We concluded that . . . this mosquito had somehow gotten in and was already widespread and established within the county,” Sprenger said.

Sprenger sent samples to the Smithsonian Institution, which identified the bug as Aedes albopictus . And Sprenger notified the National Center for Infectious Disease at Ft. Collins, the arm of the CDC that serves as a world reference center for the study of a class of diseases called arboviruses--scientific shorthand for arthropod-borne viruses.

More than 600 viruses fall into this class. Although other arthropods--such as spiders, scorpions and ticks--can carry and spread disease, mosquitoes are the most common vector. The cycle of transmission starts when the mosquito feeds by taking a blood meal from a “reservoir”--an infected animal, typically a wild bird. The virus is then passed from the bird to the mosquito, where it multiplies inside the insect. The mosquito then passes the virus along to the “host”--another animal or a human.

The discovery of the Asian tiger on U.S. soil quickly set the Ft. Collins group in motion. Their main concern was that the insect would spread dengue fever or yellow fever, both common to Africa and both known to be transmitted by the mosquito.

“Here we have a species that comes along, is a little more aggressive in its biting pattern and has the capability of carrying a lot of the viruses that we are worried about,” said Ft. Collins epidemiologist Tony Marfin, who recently returned from studying a yellow fever outbreak in Kenya. “Because of its behavior and its ecology, it is in a better position to infect humans, and that’s the big concern.”

In 1986, the Ft. Collins team convened a conference in Harris County to determine what could or should be done about the mosquito. But the insect was outrunning the scientists and popping up all across the South: in Louisiana, Florida, Missouri. Later research conducted at Ft. Collins would show that Aedes albopictus seems to be crowding out the more common, and less aggressive, Aedes agypti mosquito.

Chester Moore is the medical entomologist at Ft. Collins charged with charting the path of the Asian tiger and studying its habits.

A cherubic-looking man with an easy smile and a shock of white hair, Moore can often be found in one of two places: his cluttered cubicle of an office, tapping at the keyboard of a computer database that lists every spot in the nation where the Asian tiger has turned up, or down the road in the laboratory’s insectary--a prefabricated steel building that contains humid growth chambers where he is breeding the Asian tiger and other insects.

In 1987, hoping to at least slow the spread of the Asian tiger, Moore launched a fledgling effort aimed at wiping out the insect in a handful of cities where it had not yet become firmly established.

After conducting research in Texas, Indiana, Missouri, Louisiana, Florida and Tennessee, Moore and his colleagues concluded that it would be possible to eradicate the insect in certain spots by spraying insecticides, removing the tire piles that serve as breeding grounds and conducting a public information campaign. But, he said, the CDC eventually decided it did not want to pay for the plan.

Some, including Sprenger, say the effort would simply have been a waste of money.

“I though it was wrongheaded,” he said. “This mosquito is so well-adapted to the environment and has such a high rate of reproduction, it’s silly to think that one can go out and eradicate it. It would take tons and tons of money and if you just miss one place, you would have an infestation all over again.”

With the insect firmly rooted in the U.S. landscape, the Ft. Collins scientists turned their attention to identifying the different viruses it could carry. This is where Niebylski, the Notre Dame graduate student, came in.

Little research had been conducted on the Asian tiger, making it a ripe topic for Niebylski’s doctoral thesis in disease ecology. Through a cooperative arrangement with Notre Dame, he went to work for Carl Mitchell, chief of the medical entomolygy branch at Ft. Collins.

During three summers of mosquito trapping, Niebylski captured nearly 40,000 insects. It was difficult, time-consuming work. He wore a motor-powered vacuum fan of sorts, covered by netting, on his back. When the fan sucked the bugs into the netting, Niebylski would seal the insects in a plastic bag. The bags were transferred to dry ice, which kept the insects in a nether world between life and death.

Back in his motel room at night, he would spill the insects onto his portable, plug-in “chill table” and spend hours poring over them, picking out the ones with the Asian tiger’s distinct silver markings, sorting them by sex (only the females bite) and dropping them into vials, 50 at a time.

Eventually, Niebylski became so familiar with the creatures that he could tell them apart without the aid of a microscope. He paid special attention to those with swollen abdomens; this was a sign that they had just taken a blood meal.

Those insects, he knew, would provide crucial clues in the laboratory at Ft. Collins, helping the scientists to learn more about the feeding patterns of the Asian Tiger. Others would be ground up in a mortar and pestle and inoculated into cell cultures to be tested for the presence of virus.

Thus far, Mitchell and his staff have isolated four viruses carried by the Asian tiger in the United States. Three do not pose any apparent threats to people. The fourth, a surprising find, was Eastern equine encephalitis, which usually strikes no more than a handful of U.S. citizens each year but kills a third of those who become ill with it.

No one was more startled--and concerned--about this discovery than Niebylski. He was immediately tested for the disease but showed no signs of exposure. “I’m lucky,” he said in retrospect. “When I was collecting, I had no idea they were infected.”

In the meantime, Mitchell and his colleagues say there are still unanswered questions about the Asian tiger. If a traveler from, say, Ecuador brought yellow fever to Florida, would the mosquito become involved in spreading that disease? What about dengue fever? Or St. Louis encephalitis, a less deadly but more common form of encephalitis already prevalent in the United States? And what about the spread of the mosquito itself? Will it travel to Latin or Central America, putting residents there at risk?

The answers, the experts say, will come only with time--and additional detective work.