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Nemotode vs. Tick: Fear of the Immortal

When my daughter Sylvia was 11 months old, we visited a family in rural Nyack. After lunch, we trekked through the low shrubs and bending trees behind their house. Three days later, my wife, Violet Snow, swept back my daughter’s gold hair to find an Ixodes scapularis, fat and engorged, on her neck. It looked like a tiny football.

An Ixodes scapularis is a “deer tick”—correctly known as a black-legged tick. It had swelled by siphoning Sylvia’s blood!

Afterward followed two weeks of semi-comic attempts to inject a fluorescent pink liquid, laden with Amoxicillin, into Sylvia’s mouth. Thankfully, she never developed any of the symptoms—Malar rash, Syncope (fainting), Myocarditis (inflammation of the heart muscle), Bell’s palsy, Hemiparesis (partial paralysis), Arthralgias (joint pain), Panopthalmitis (eye infection), mood swings, vomiting, etc.—associated with Lyme disease.

“Lyme disease is probably ancient,” avers Dr. Rick Ostfeld, an ecologist at the Center for Ecosystems Studies in Millbrook. “It is probably thousands, or even millions of years old.”

The modern history of this illness begins, however, when Polly Murray and her family moved to Lyme, Connecticut in 1959. “Within a few years, I began having periodic flu-like illnesses, headaches and odd rashes,” she recalls, in Protect Yourself from Lyme Disease by Diana Benzaia. “In 1971 and 1972, I was constantly running a low-grade fever, and my other symptoms became so severe that I was hospitalized several times for testing.” In 1975, her son Todd was diagnosed with juvenile rheumatoid arthritis (JRA). In three weeks of research, Polly discovered 35 cases of JRA in her locality—at least 100 times the rate among the general population. She brought these figures to Dr. Alan Steere, a postdoctoral fellow in rheumatology at Yale, and research began.

In 1982 the bacterium Borrelia burgdorferi was identified as the agent of this disease. By now, every state has Lyme disease, and it has appeared as far distant as Australia.

Gary Myers, Senior Public Health Sanitarian for Ulster County, says that typically there are 150 cases a year in the county. Nearby areas, however, are more profuse: “Down by Newburgh, I’ve seen dogs with two or three hundred ticks on them, after an afternoon of hunting.” Dutchess County has shown, at various times, the highest rate of Lyme disease in the country. And Columbia County is experiencing a dramatic increase in infection. “The number of cases is still small, but the rate of increase is unbelievable,” Myers remarked.

Ticks are not insects; they are arachnids—along with spiders, scorpions and mites. Ticks go through three phases. They are born without sin (unlike humans, according to some theologians), as minuscule larvae. These attach to a host for two to four days, using a hypostome, a barbed organ which secretes a serum containing cement, anticoagulants, and anesthetics (so the host does not feel the bite). Larvae which choose white-footed mice, the greatest known reservoir of Lyme disease, may then become infected.

The larvae molt, grow into nymphs, and attach to another host for four more blood-savoring days. (At this point, the tick is the size of a poppy seed.) A second molt produces the adult. This time, the creatures connect to a host for up to seven days. The male and female ticks mate, and the female lays eggs—somewhere between 2,500 and 3,000 eggs.

Not every tick, of course, contains Lyme disease. The infection rate varies, from 40-60 percent, according to periodic samples.

But how can the Lyme menace be battled? Dramatic new evidence suggests that fungi and nematodes may be our allies. One such nematode, Steinernema, enters the body cavities of engorged female ticks. Another, Heterohabditis, uses one pointed tooth to break through the tick’s cuticle, or thick skin. These nematodes murder ticks by unfurling bacteria that turn the tick’s tissues to liquid. This is an ironic death for a parasite—death by a smaller parasite.

The Agricultural Research Service at the USDA has discovered a new fungus, Gliocladium, which eradicated 60 percent of nymphs in two weeks. The fungus Metarrhizium anisopliae killed 100 percent of nymphs in one week.

Now, for the first time, these researchers will meet to compare strategies. The Conference on Biological Control of Ticks will convene on March 5th and 6th in Poughkeepsie. This is the first such forum bringing together researchers from across the nation. About 15 scientists will attend, including Dr. Dolores Hill of the USDA Parasite Biology and Epidemiology Laboratory, who will discuss nematodes, and Dr. Sandra Allan of the University of Florida, who will address pheromones.

This conference is being coordinated by Rick Ostfeld of the Center for Ecosystems Studies. Dr. Ostfeld began working with the Metarrhizium anisopliae this fall. The meeting is being funded by the Dutchess County Legislature.

“Is there hope that we will eradicate black-legged ticks?” I asked Dr. Ostfeld.
“I think that the notion of eradicating or annihilating the ticks, these military terms, is foolhardy. The approach we should take is to reduce numbers of ticks. If we set up a goal of eradication that we can’t possibly achieve, then we’re setting ourselves up for failure.”

“Will this fungus spread naturally through the tick community, or must we administer it to each tick?” I inquired.

“This fungus is also ubiquitous. It’s local; it’s in the forest floor foliage and soil. What we need to know is how can we enhance its ability to kill ticks, since it’s obviously not killing them all.
“Another thing we have to figure out is how to prevent this fungus from killing things we don’t want it to kill—spiders, and other creatures with important ecological roles.”

Dr. Ostfeld explained that fungi directed at the gypsy moth in the 1920s proved ineffective, then returned in the 1990s to destroy other moths and charming butterflies.

Send your prayers to these valiant eco-savants!

Though the conference is not open to the public, Dr. Ostfeld will present a paper to the Legislature by the end of April, summarizing the results. At that point, his report will become public knowledge. For more information, contact Patty Hohmann, clerk of the Dutchess County Legislature, at (845) 486-2100, or consult the Dutchess County Legislature Web site: www.dclegislature.org.
—Sparrow