While controversy still brews over the long-term effects of Lyme disease, a new government study concludes that the tick-borne illness is rarely a cause of death in the U.S.

Using death records collected from 45 U.S. states, researchers at the Centers for Disease Control and Prevention (CDC) found that between 1999 and 2003, there were 114 records listing Lyme disease as a cause of death.

But in most cases, Lyme disease was listed as one of multiple health problems contributing to a person’s death, and only 23 records showed the disease as the underlying cause.

Of those, the investigators say, just one was consistent with known “clinical manifestations” of Lyme disease. In that case, the person died of respiratory failure that the death record tied to long-term effects on the central nervous system.

The findings, the CDC researchers say, indicate that Lyme disease “is rare as a cause of death in the U.S.”

But that conclusion is unlikely to settle the broader controversy surrounding the long-term effects of Lyme disease in some people - which, some doctors and patient groups say, do include serious and sometimes fatal health problems.

Lyme disease is a bacterial infection transmitted by certain ticks. The initial symptom is most often a gradually spreading “bull’s eye” rash at the site of the tick bite.

Other early symptoms include fever, fatigue, headache and muscle and joint aches. Without early treatment, the infection can sometimes spread within days to weeks to different parts of the body - causing symptoms like neck stiffness, shooting pains from nerve damage, heartbeat irregularities and a loss of muscle tone in the face called Bell’s palsy.

The CDC and major medical groups say most cases of Lyme disease can be cured within about four weeks of oral antibiotics.

Some people do develop lasting problems after infection, sometimes even with antibiotic treatment.

According to the CDC, up to five percent of untreated people have chronic neurological complaints like shooting pain or numbness, or memory and concentration problems, months to years later. And a “small percentage” of those treated with antibiotics report symptoms that last for months to years, including arthritis pain, memory problems and fatigue.

But exactly what is causing those problems is unclear.

Then there are the people who are diagnosed with “chronic” Lyme disease based on non-specific symptoms - like chronic pain and severe fatigue - despite having no evidence of a current or past infection with the Lyme-causing bacteria.

This diagnosis is highly controversial because such people could have any of a number of other health problems, like depression or fibromyalgia, and their symptoms are common in the general population.

As for the lethality of Lyme disease, it is plausible that certain documented long-term effects of Lyme disease could contribute to some deaths, according to Dr. Kevin S. Griffith of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases.

“But the reality is that (Lyme disease) has only rarely been reported to lead to death,” Griffith said in an interview. And based on this study, he noted, even death records that do list Lyme disease as a cause often don’t stand up to scrutiny.

But Dr. Robert Bransfield, president of the non-profit International Lyme and Associated Diseases Society, took issue with the CDC study methods - including its reliance on what doctors list on death records.

“There was no attempt to identify deaths from Lyme disease that may have been identified as a death from some other illness,” said Bransfield, whose controversial group contends that chronic Lyme disease is a growing problem, and that many people with the infection need longer courses of antibiotics to help prevent it.

“You can’t generalize from this to say that deaths from Lyme disease are rare,” he said.

Exactly how many deaths might be attributable to Lyme disease is unclear, according to Bransfield. But he argued that the number could be “significant,” if the question were looked at in a broader way.

Bransfield, a psychiatrist, said that suicide may be the major way that Lyme disease can prove fatal. He acknowledged, though, that this belief is based on anecdotal evidence, and there is a lack of hard statistics on Lyme disease and suicide risk.

Bransfield also noted that some researchers have speculated that the infection can ultimately contribute to cases of dementia, multiple sclerosis and amyotrophic lateral sclerosis

(ALS).

There is, however, no proof of that in the scientific literature, Griffith said.

The CDC report, Griffith stressed, is not intended to be “dismissive.”

“We encourage clinicians to report on any patient that they suspect has died due to Lyme disease,” he said.

He added that it’s important to get that information out to the medical community so that the evidence can be evaluated.

“While anecdotes are compelling, scientific progress must be based on evidence,” he said.

SOURCE: Clinical Infectious Diseases, online December 28, 2010.