Tiny Ticks Causing Lyme Disease Should Not be Underestimated

Tiny Ticks Causing Lyme Disease Should Not be Underestimated

Washington area health departments are stepping up Lyme disease education and prevention efforts in response to a steep rise in the number of reported cases of the tick-borne illness in Maryland, Virginia and the District.


Deer and rodents, such as the white-footed mouse, are the most common reservoirs of Lyme disease. Adult deer ticks are red-brown in color and about 3mm in size. Larvae and nymphs are considerably smaller and tend to be paler in color. They are found in the eastern coast of the United States, from Florida to central Texas in the south and from Maine to Minnesota and Iowa in the north.

Some of the rise is attributable to better disease reporting due to increased awareness about the disease, according to Kevin Griffith, a medical epidemiologist with the Centers for Disease Control and Prevention, but more people are also being infected. Local health departments want residents to know that even if they are bitten by a tick carrying Lyme disease, they can greatly reduce the risk of infection by removing the insect promptly, Griffin said.

The number of reported Lyme disease cases in Virginia almost tripled last year to 945, from 357 in 2006. In Maryland, the count reached 2,576, more than double the 1,248 reported in 2006. And in the District, the number jumped to 116, up from 64 in 2006. As of early June, District health officials had confirmed 36 new cases. Maryland and Virginia don't have numbers yet for 2008.

One thing that's probably not responsible, say experts: the region's unusually rainy spring. Tick numbers are more dependent, they say, on other, complex factors, such as the local deer population and ticks' two-year life cycle.

The jump in reported cases comes as debate continues over the best strategy for diagnosing and treating the sometimes painful bacterial disease. The conflict, which has spilled over onto blogs and into state legislatures and spawned charges of conspiracy and cover-up, pits the medical establishment against patient activists, some of whom claim to suffer from a chronic form of the ailment. Activists say this form should be treated with long-term antibiotic therapy; mainstream experts generally oppose such treatment as ineffective and possibly dangerous.

Lyme disease, estimated to affect about 20,000 Americans each year, is the most common tick-borne infection in the Northern Hemisphere. In 2006, President Bush was treated for a rash that may have been caused by Lyme disease.

Lyme disease can affect people of any age. People who spend time in grassy and wooded environments are at an increased risk of exposure. The chances of being bitten by a deer tick are greater during times of the year when ticks are most active. Young deer ticks, called nymphs, are active from mid-May to mid-August and are about the size of poppy seeds. Adult ticks, which are approximately the size of sesame seeds, are most active from March to mid-May and from mid-August to November. Both nymphs and adults can transmit Lyme disease. Ticks can be active any time the temperature is above freezing. Not all deer ticks are infected with the bacteria that cause Lyme disease. Ticks can become infected if they feed on small animals that are infected.

Transmitted through the bite of the tiny deer tick, Lyme often causes a bull's-eye rash in the area of the bite. Those infected may suffer from flulike symptoms, such as muscle aches, fever and fatigue. If not treated promptly, the infection can potentially lead to heart, joint and nervous system damage, according to the CDC, which has been collecting data on Lyme infections since 1991.

People who receive prompt antibiotic treatment often recover in a few weeks, although symptoms such as fatigue can last for several months, said Gary Wormser, chief of infectious diseases at New York Medical College and the lead author of Lyme treatment guidelines published by the Infectious Diseases Society of America in 2006.

The guidelines use the term "post Lyme syndrome" for cases in which the lingering symptoms are severe. However, the guidelines do not recognize "chronic" Lyme because there is no evidence the disease's bacteria remain alive in humans after a standard course of antibiotic therapy and because there is no good evidence that repeated or prolonged courses of antibiotics help patients.

Antibiotic therapy is usually given for two weeks but may be given for up to four weeks for certain manifestations. The guidelines allow for re-treatment for relapses that occur infrequently. Because insurers often won't pay for treatment outside the guidelines, activist groups are fighting to have the rules changed.

Gregg Skall, general counsel for the National Capital Lyme and Tick-Borne Disease Association, a McLean-based nonprofit advocacy group for Lyme patients, said groups like his want the medical community to recognize that there are cases in which long-term treatment offers relief.

Some individuals believe they suffer long-term symptoms related to Lyme disease even though they have never been diagnosed with Lyme. Some believe they may have been given faulty tests or have symptoms similar to those of people who were given a Lyme diagnosis. Absent a diagnosis followed by the recommended treatment, the IDSA guidelines do not recognize their problem as any form of Lyme, chronic or otherwise.

Lyme advocates also maintain that sometimes the tests are faulty and do not pick up all Lyme infections.

Last year, Connecticut Attorney General Richard Blumenthal launched an investigation of the process by which the IDSA compiled the guidelines, charging conflicts of interest by several review panel members. Donald Poretz, president of the IDSA, denied the charge. In May, activists were cheered when the IDSA agreed to review the guidelines rather than continue to fight the investigation.

"We viewed the settlement as a victory for patients, in the sense that patients [who considered the guidelines inadequate] felt vindicated,'' said Pat Smith, president of the Lyme Disease Association.

Poretz, a physician based in Annandale, said a new IDSA panel will review the guidelines this summer and determine whether research supports a rethinking of current treatment strategies.

"We're always willing to change if science shows there is new research,'' Poretz said.

Former panel members, he said, opposed long-term treatment with antibiotics because patients "can develop drug resistance, infections in their [intravenous lines] and allergic reactions. And there are extraordinary costs.''

Connecticut has long been a battlefield in the debate over the treatment of Lyme disease. It was in the Connecticut town of Old Lyme that the infection was discovered in 1975. Last year Connecticut led the nation in the rate of Lyme infections: 51 cases per 100,000 people; other northeastern states also report relatively high rates.

Local officials are focusing on public education to reduce the risk of infection.

Fairfax County has one of the most ambitious outreach efforts. In April, county health officials sent a 19-page color booklet to every household in the county with advice on protection against Lyme disease, West Nile virus and other insect-borne diseases. People who are bitten by a tick are invited to bring it to health officials for inspection. The booklet is also downloadable at http://www.fairfaxcounty.gov/hd/westnile/wnvpamp.htm.

Jorge Arias, an environmental health supervisor for the Fairfax County Health Department, said that although several varieties of ticks bite humans, only one carries the bacterium that causes Lyme disease. While infections have been reported countywide, most have occurred in Fairfax's less developed western part, Arias said.

District resident Linda Baranovics knows it pays to be vigilant.

In May Baranovics went on a camping trip with her son's class in Prince William County. She figured her risk of being bitten was low because she'd worked in the kitchen for most of the trip.

But about four days after she returned, she discovered a tick about the size of a sesame seed on the back of her thigh. She didn't think much of it until about two weeks later, when she developed a low-grade fever, chills and the worst body aches she said she'd ever had. Because she didn't get a bull's-eye rash, she thought perhaps she had the flu. But when a visit to the doctor confirmed she had Lyme, her doctor prescribed antibiotics. Now Baranovics said she feels much better.

"I know what to look for now,'' she said. "How that thing got on me, I don't know.''

Other Tick-borne Diseases

Spring and summer bring warm temperatures, just right for walking in the woods and other outdoor activities. Warm weather also means that ticks become active, and this can lead to the transmission of tick-borne disease. The tick-borne diseases most often found in Virginia are Lyme disease, Rocky Mountain spotted fever and ehrlichiosis.

In the Northeast, the "deer" tick (Ixodes dammini) may transmit Lyme disease. The deer tick is quite a bit smaller than the American Dog tick, and usually has a two-toned body with no patterning on the back. In comparison, the deer tick also has larger mouth parts than the dog tick.

Transmission and Development

The black-legged tick, Ixodes scapularis, is the most common carrier of Lyme disease in the mid-west and eastern states. I. pacificus is known to be the vector in the west. Other species of ticks such as the dog tick or wood tick, the lone-star tick and the rabbit tick, and biting insects such as mosquitoes, deer flies and horse flies have been shown to carry the Lyme disease bacterium. However, their ability to transmit the disease is not known at this time. Recent investigations have uncovered populations in Southwest Michigan and studies are continuing to determine the extent of the Lyme tick population.

The black-legged tick has a complex life cycle involving development through three active stages: larva, nymph, and adult. This process usually takes two years or more. Larvae and nymphs require blood to proceed to the next development stage, and adult females need blood to lay their eggs.

Seasonal Life Cycle in Michigan

Studies of the life cycles of disease vectors are important in many ways:

The life cycle of the black-legged tick has been studied in detail in many regions. The most recognized life cycle pattern is based on studies conducted in the Northeast United States. Life cycles, however, differ in many areas based on local and regional habitat and climactic variation. Recent longitudinal (long term, repeatable) surveys in Southwest Michigan have provided detailed seasonal information about the black-legged tick in our region. Below is a graphic example of the black-legged tick life cycle in Michigan.

Adult Ticks

The peak of adult activity in Michigan is during the early spring and autumn months. Female and male ticks search out their preferred host, the white-tailed deer, for feeding and reproduction. Female ticks require a large blood meal to develop large egg batches. The male ticks, which rarely feed, locate the female ticks at their feeding sites on the host by pheromones (reproductive chemical cues). After mating and engorging on blood, the female tick drops off the host and begins to lay eggs, usually in a protective bed of leaves, and the male dies. The mother tick, if infected, rarely passes Lyme disease infection to her offspring. Upon completing egg laying, the female tick dies.

Larval Ticks

Larval ticks begin to hatch from their eggs in the early spring, although in Michigan, there may be two larval hatching periods. Larvae will hatch in early spring from eggs that were laid by females in the autumn months. Eggs that were laid in the early spring will hatch in the early summer months.

Larval ticks are very small (approximately 1 millimeter in size) and may bite people. Their preferred hosts, however, are small mammals that live in forested environments (mice, chipmunks, squirrels, etc.). It is at this stage where the tick can acquire the Lyme bacteria. Small mammals may be carriers of the bacteria, previously infected by nymphal ticks, which have fed during the spring. The Lyme disease cycle is dependent on the nymphal ticks emerging and feeding before the larvae to successfully pass infection from one generation to the next. The small mammals remain carriers for a defined period (usually several weeks to months) and show no serious illness. Note: The chance of becoming infected by the bite of a larva is low.

Once the larva has successfully fed, it drops to the forest floor and finds a sheltered environment to ‘hibernate’ and to molt (transform) to the nymphal stage. The nymph will remain inactive until the next spring.

Nymphs

Nymphs emerge in the early spring and prefer to feed on small and medium sized mammals. These nymphs may have been infected the previous year while in the larval stage. When they feed, if infected, they will pass on the Lyme bacteria to the mammal host. This continues the cycle, creating infected hosts for newly emerged larvae to feed on. The nymphs are the most dangerous stage for human contact. They will readily attach themselves to people, and because of their small size (appx. 1.5 millimeter), are difficult to see or notice. Once the nymph has completed its blood meal, it drops from the host and finds a sheltered area (preferably forest) to undergo transformation to the adult stage.

Transmission Dynamics

The ability of the tick to transmit Lyme bacteria is dependent on the amount of time it is attached to the host. Studies have shown that removal of infected, feeding ticks prior to 48 hours significantly reduces the potential for infection.

The Lyme disease bacteria are ingested from the host in a blood meal and the bacteria then reside on the midgut (stomach) lining of the tick.

Lyme disease is not an easy diagnosis to make. This is especially so if the patient has no rash and does not recall an episode of tick bite. If a patient remembers a tick bite and then becomes unwell, Lyme disease is a possibility. There is no diagnostic test that is absolutely reliable in confirming a case of Lyme disease. Negative test results therefore, do not necessarily mean it is absent. After all exclusionary tests have been done; the diagnosis can be made on clinical grounds alone.

Source:

http://www.washingtonpost.com
http://www.michigan.gov
http://www.nyhealth.gov
http://www.loudoun.gov
http://www.health.ri.gov
http://www.lymediseaseaction.org.uk/

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