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Sunday, April 27, 2014

Why isn’t there a Lyme vaccine for people, like there is for dogs?

With spring comes ticks and with ticks comes Lyme disease, and with Lyme disease comes a common question: Why do our dogs have a vaccine against it, but humans don’t?

The answer, according to public health officials, is that exaggerated concern about the vaccine’s side effects, the byproduct of a debate about “chronic Lyme disease” that continues to this day, produced poor sales that led the manufacturer to abandon the business in 2002. ...

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With spring comes ticks and with ticks comes Lyme disease, and with Lyme disease comes a common question: Why do our dogs have a vaccine against it, but humans don’t?

The answer, according to public health officials, is that exaggerated concern about the vaccine’s side effects, the byproduct of a debate about “chronic Lyme disease” that continues to this day, produced poor sales that led the manufacturer to abandon the business in 2002.

Some argue the fault lies more with the pharmaceutical industry and medicine, but either way, the vaccine was withdrawn.

“Because of that, it’s unlikely – but not unthinkable –
that we’ll have another Lyme disease vaccine in the United States,” said Abigail Mathewson, the state’s surveillance epidemiology program manager and public health veterinarian.

There is some hope. Trials are taking place in Austria and Germany for a human vaccine developed by researchers at Stony Brook University in New York, Brookhaven National Laboratory and Baxter International, a U.S.-based pharmaceutical company, which went to Europe because of legal concerns.

“If the vaccine takes off in Europe and is proven successful, and there is outcry here for it, then it might change,” Mathewson said.

But even a useful vaccine might be less valuable than people think because the black-legged or deer tick, which transmits the bacteria that causes Lyme disease to humans, increasingly transmits bacteria that cause other diseases that wouldn’t be blocked. They include babesiosis, anaplasmosis and Powassan encephalitis, recently found in New Hampshire for the first time.

Like Lyme disease, these diseases generally produce mild flu-like symptoms in people, if any symptoms at all, that usually can be cured with antibiotics. But they can be dangerous to people, even fatal in rare cases. None can be ignored.

Precautions against ticks

As a result, enjoying the outdoors requires taking care against ticks, since a study found that a whopping 60 percent of all black-legged ticks in New Hampshire carry the bacteria that causes Lyme disease.

“A few precautions and the management of infected ticks in the residential or recreational landscape can substantially reduce the risk of Lyme disease and other tick-associated illnesses. Prompt recognition of infection and treatment can prevent more serious manifestations of disease,” is how the Connecticut Agricultural Experiment Station puts it in a 75-page bulletin titled “Tick Management Handbook.”

It can be downloaded from the station’s website, www.ct.gov/caes.

Among the steps the handbook recommends are deer-proofing your property, because white-tailed deer carry ticks, and clearing litter off lawns so sunshine can dry out ticks.

“The sun drying out, desiccating ticks, is the main way they are controlled,” Mathewson said. “They don’t mind the cold, snow – it’s dry conditions.”

Insecticides (technically called “acaricides” because ticks, which have eight legs, aren’t insects) can be effective when applied to lawns, although they also kill beneficial bugs.

More important for personal protection is to dress properly – wear light-colored clothes so you can see ticks that grab on when you brush against vegetation where they cling. In tick habitat, such as fields with tall grass, it’s best to wear long pants and tuck them into socks to make it harder for them to get inside your clothes.

Finally, check yourself for ticks after coming back inside.

Even if a tick has already attached to a person, it takes 48 to 72 hours before the bacteria passes from it into the bloodstream. The tick should be pulled off with tweezers or tools such as a “tick spoon.” Don’t try to burn it off, cover it with Vaseline or perform any other trick – just pull it off.

Ticks can be killed by dropping them into a little alcohol or wrapping them in tissue and flushing them.

As with mosquitoes and black flies, dealing with ticks is just part of New Hampshire life.

“It’s not something to keep you from going outside and exploring and enjoying yourself,” Mathewson said. “It’s just to keep you aware.”

Hard to develop

It’s difficult to develop a vaccine against bacteria – which are bigger and more complex than a virus – that is transmitted to humans by insects.

Vaccines are much more likely to exist for diseases such as smallpox, which is transmitted directly by a virus, than diseases such as malaria, which is caused by a parasite transmitted by mosquitoes.

The bacteria that causes Lyme disease, a spirochete called Borrelia burgdorferi, has a complicated life cycle passing back and forth between mammal hosts that carry ticks – hereabouts, mostly deer and white-footed mice.

The most successful human vaccine, called
Lymerix, was developed by SmithKline Beecham. Interestingly, it didn’t tackle the bacteria inside people after they were infected. Instead, it created antibodies in humans’ blood that the ticks ingested when feeding, and those antibodies attacked the bacteria inside the tick, altering the proteins on its surface.

“It was an interesting way of trying to create a vaccine,” Mathewson said.

Robert Aronowitz, of the University of Pennsylvania, analyzed the history of the vaccine in a 2012 article titled “The Rise and Fall of the Lyme Disease Vaccines: A Cautionary Tale for Risk Interventions in American Medicine and Public Health,” published in Milbank Quarterly, a journal of public health.

Lymerix was approved by the Federal Drug Administration in 1998, but even during its development, there was controversy.

Advocacy groups have long maintained that mainstream medicine under-
diagnosed Lyme disease and refused to accept patient reports of long-term, serious neurological, rheumatological and other symptoms, even dismissing the disease as “yuppie flu.”

Most notably, advocacy groups believe Lyme disease can persist for years, requiring continued antibiotic use. Mainstream medicine says these case involve misdiagnosis, and that long-term antibiotic use does more harm than good, hiding other ailments and leading to drug-resistant bacteria.

Most medical societies frown on, or even forbid, long-term antibiotic regimes for people claiming to have chronic Lyme, but advocates have been able to convince many state legislatures to overrule that constraint.

New Hampshire lawmakers did that in 2011.

After Lymerix came on the market, advocates complained it caused joint inflammation and other side effects – a claim largely disputed by mainstream medicine – and some lawsuits resulted. SmithKline Beecham, citing poor sales, withdrew the drug in 2002.

Dog vaccine

No similar controversy has arisen over canine vaccines, which operate in much the same way as Lymerix. A couple types of vaccine are now prescribed by veterinarians.

That’s necessary because many dogs in New Hampshire that go outside – perhaps most of them – have been infected by the bacteria that causes Lyme disease, even though relatively few show any symptoms.

This is known because dogs regularly get a “snap test” that looks for Lyme disease along with a number of other diseases, such as heartworm.

No such test is given regularly to people in doctors’ offices, however, so it’s unknown whether Lyme bacteria infection is also prevalent within the state’s human population. Generally, people are tested for Lyme only after they show symptoms.

It’s possible that in people, as in dogs, many individuals have been infected via tick bites but don’t get sick, for some reason.

David Brooks can be reached at 594-6531 or dbrooks@nashua
telegraph.com. Also, follow Brooks on Twitter (@GraniteGeek).