Chickenpox sweeties and the social ecology of infectious disease

This post contributed by Liza Lester, ESA communications officer

No one speaks for the endangered poliomyelitis. No one raises money to protect the last survivors, as health workers stalk the virus through its last redoubts in India, Pakistan, Nigeria and Afghanistan. On the contrary, the WHO spends billions on hunting it to extinction. But the virus has held out longer than expected.

Joshua Michaud, policy analyst at the Kaiser Foundation, thinks the polio fighters are falling behind. Guinea worm will be the next scourge to fall, he said on an AAAS panel engaged to discuss Infectious Disease: Challenges to Eradication on Monday. Why have efforts with guinea worm been so successful? a precocious Georgetown student wanted to know. Biology was on our side.

There is no vaccine for guinea worm, and no medicine to cure infection. To extract the worm, you must wind it slowly around a stick as it emerges through a sore in your leg (an oft-repeated story holds that the treatment has not changed since the Egyptians of the XVIII dynasty described it in 1550 BCE, though the source appears to have been exaggerated). The process is excruciating, and it takes weeks.

But we know key details of the worm’s biology that the ancient Egyptians did not.

Basic technology and careful hygiene can defeat the worm. Larvae harbor in the bodies of invisible copepods, “water flies” tiny enough to swallow. Once swallowed, female larvae nestle against the long limb bones of their hosts, growing up to a meter in length over the course of a year. They surface inside a burning ulceration that sends their victims running for a dip in a cool pond—and the next generation of larvae escape to start the cycle of life anew.

The good news, said Michaud, is that guinea worm does not have another host. It has no environmental bolt hole to hide in while under siege, only to emerge when health forces are not looking. It needs humans. And affected people are visibly affected.

Break the cycle for one year, and you can free a communal water source, and its community, from the worm. Copapods may be microscopic, but a simple nylon strainer on the end of a drinking tube saves you from swallowing them (although not bacterial and viral parasites that might also lurk there, interjected Dennis Carroll, in charge of avian flu and other emerging threats at USAID). Help the infected, persuade them to stay out of drinking water sources when their worm breaches, and you break the cycle. Success requires the help and good will of village elders. The Carter Foundation has been courting good will and promoting local efforts tirelessly since 1986. President Carter even negotiated a Guinea Worm Cease-Fire in Sudan in 1995, to help locals cope with a slate of infectious diseases.

“The last case of smallpox was in Somalia. Imagine trying to carry out a vaccination campaign in Somalia today,” said Michaud.

Eradication campaigns require public goodwill. Which is not always forthcoming. Warzones and disaster areas are holdfasts for disease, their populations dangerous and hungry, and lacking in organization and basic services. Foreign visitors with needles and vials aren’t necessarily trusted. Reports of CIA shenanigans in the guise of vaccination programs do not help with trust.

In 2003, polio flared in Nigeria following rumors that that the West was using the WHO immunization program to sterilize Muslim girls and spread HIV. Nigerian travelers sparked spot fires in other countries that took years and millions of dollars to put out. The program didn’t get back on track, said Josh Rosenthal, until Saudi Arabia got on board, and told Muslims, “If you want to do the Hajj, if you want to come to Mecca, you have to be vaccinated.” Rosenthal is director of the NIH’s Fogarty International Center.

Polio earned its place in the eradication crosshairs as much for its weaknesses as its dangers. Like guinea worm, it needs humans. But aspects of its biology also hinder the vaccination effort. Polio is a harder sell because it doesn’t kill enough.

“Eradication of smallpox gave rise to a glow of optimism,” said Rosenthal. But Polio is not the spotted fever. It isn’t as virulent, and doesn’t present with a dramatic, hideous rash. For every child paralyzed by polio, 200 have no symptoms at all—but are infectious. The bar to achieving herd immunity is higher. And smallpox killed 30% of its victims.

“Polio is not that,” said Carroll, shaking his mane of hair. “Diseases of morbidity never gain the same gravitas with the public as diseases of mortality.” Or hideousness. How do you get people to trust, to cooperate, when they don’t think their kids are sick?

Carroll thinks it’s the wrong question. “Polio is a disease of poor sanitation. Vaccines allow you to get around the systemic problems.” Sometimes. But eradication campaigns divert limited local resources from basic health. Locals are already trying to cope with malnutrition, enteric disease, and sanitation all of which feed back negatively on polio risk, and vaccination success. Why not invest eradication dollars into systemic improvements? “I don’t believe in eradication. I think it’s fool’s gold.”

NPR science reporter Richard Harris, on hand to moderate and generally keep the conversation interesting (with notable success), said, “I think this is the first time a panel has all agreed that the challenges we’re here to talk about don’t have to be met!” The audience liked that. The rest of the panel looked uncommitted.

What about misinformation, the audience wanted to know. How do you combat social media? How do you explain the statistics of herd immunity? We inform, said the panel. What about lack of trust at home? Harris prompted. Does it undermine global efforts? Are people not afraid of infectious disease anymore? “We hear people saying, ‘I don’t know anyone who’s had whooping cough, it’s a thing of the past.’”

None of the panelists looked eager to bite on domestic affairs. They ventured that human papillomavirus vaccination is an awkward topic to discuss with parents. No one wants to think about their kids having carnal knowledge, in the future, or ever, said Michaud.

“Is it a non-starter in the current wave of vaccine suspicion?” asked Harris.

The men on stage looked blankly at the audience. When regularly working with people struggling to secure access to medicine and clean water, it may be hard to wrap your mind around news of parents sending chickenpox lollipops through the mail to secure access to infection (pox parties being, apparently, in short supply). In their realm, public health is more of a community movement than an evocation of consumer choice. The dynamics, social and biological, of a mild disease isn’t their challenge.

Photo: A sign warns those with Guinea worm disease not to enter the water in Taha, Ghana, March 2006. Credit: The Carter Center/E. Staub