What makes tick-borne diseases so tough?

Nature tries to figure out why we’re not making the headway we should against Lyme, Rocky Mountain spotted fever, and the rest of the tick-borne nasties:

[Scott] Williams is testing whether vaccinating mice against Borrelia burgdorferi, the bacterium that causes Lyme disease in the United States, can reduce the proportion of ticks that are infected. Health officials are looking on with interest. Connecticut has one of the highest rates of human Lyme disease in the country, and June is peak time for transmission. Borrelia burgdorferi infects an estimated 329,000 people in the United States each year, according to the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. And although most people who get prompt treatment recover quickly — Williams has had Lyme three times — up to one in five develops long-term and potentially life-threatening symptoms, including heart, vision or memory problems, or debilitating joint pain.

Even the time-honoured protective strategies that most people use are not evidence-based. “We tell people to wear repellents, to do tick checks and to shower if they’ve been in the field, but there’s very little data to show that these things reduce human illness,” explains Ben Beard, chief of the CDC’s bacterial-diseases branch in the division of vector-borne diseases.

Diseases spread by ticks are on the rise around the world, spurred by a combination of factors, including shifting climates and population sprawl into rural areas. Reported cases of Lyme, the most common US tick-borne illness, have nearly tripled in the country since 1992, although some of the increase could be due to heightened awareness.

In the United States, ticks spread at least 16 illnesses, including anaplasmosis, babesiosis, ehrlichiosis and Rocky Mountain spotted fever, all “serious, life-threatening infections”, Beard says.

In light of the problems faced by LYMErix, however, the question remains whether health officials and consumers will embrace a human vaccine. “I think, maybe optimistically, that the emotional situation has changed over the last 10 or 15 years — that is, that more people are convinced of the importance of Lyme disease,” [University of Pennsylvania researcher Stanley] Plotkin says. But it is hard to know whether fears about Lyme will trump fears about the vaccine.

Mouse vaccines would not raise such concerns, but some researchers, including Plotkin, are sceptical about whether they could dose enough mice to reduce Lyme rates.

The stereotype of Lyme and other US tick-borne diseases as primarily ‘yuppie’ illnesses does not help; [Cary Institute of Ecosystem Studies disease ecologist Richard] Ostfeld says he has seen comments to this effect on reviews of his grant proposals. “They say something like, ‘Is it really worth spending taxpayer dollars on a disease of the affluent in the northeastern United States, when there are so many diseases of people who live in poverty overseas?’,” he says. “In one sense, I think that’s a legitimate point, but in another, I think it underestimates the impact of this disease on a vast number of citizens, not all of whom are affluent, not even close.”

Repeating one line for emphasis: “But it is hard to know whether fears about Lyme will trump fears about the vaccine.”

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