It’s technically straightforward to eliminate malaria from an area. At least in theory. You reduce the ability of mosquitoes to bite people, treat every sick victim with curative drugs and prevent any infected person from bringing new parasites into the area. Keep working outwards from your area, and eventually there will be no more malaria.

 

But what if there’s a secret reservoir of pathogens in the bodies of wild animals, unreachable by medical interventions — as there is in yellow fever, cholera, and influenza, diseases from which humankind can never hope to be completely free?

 

In results reported in the Jan. 19 “Proceedings of National Academy of Sciences,” a team of malariologists from France and Gabon have found just that. Using new methods of tracking malaria parasites, by subjecting samples of urine and feces to PCR analysis, the scientists found genetic traces of the most malignant malaria parasite — Plasmodium falciparum, presumed since the 1930s to be an exclusively human pathogen — inside the bodies of gorillas from Cameroon and Gabon.

 

There is also evidence from Vietnam and Malaysia that malaria parasites previously considered exclusive to monkeys can often be found utilizing human blood.

 

These discoveries of a possible wild reservoir for humankind’s most malignant malaria, some 130 years after the discovery of the malaria parasite, could mean that it will be impossible to eradicate malaria. When scientists discovered in the 1930s that monkeys carried yellow fever virus, they were forced to abandon hopes for eradicating yellow fever.

 

The realization will change anti-malaria work radically. Ever since the British army surgeon Ronald Ross and the Italian zoologist Giovanni Grassi discovered early in the 20th century that mosquitoes transmitted malaria parasites, dreams of eradicating malaria have tantalized governments, public health leaders and philanthropists.

 

In 2007, Bill and Melinda Gates — whose foundation now sets the agenda in global health — announced that they intended to end malaria, an ambition that both the interagency Roll Back Malaria Partnership and the World Health Organization affirmed. Funds for the job have zoomed from $100 million a year in 1998 to nearly $2 billion by the end of 2009.

 

The Gates Foundation has given vaccine researchers $150 million since the late 1990s. There are dozens of experimental malaria vaccines in labs across the globe, with the most clinically advanced, Mosquirix, appearing to reduce the incidence of illness from malaria by 65 percent.

 

Oil companies such as ExxonMobil, plagued by malaria in West Africa, have bankrolled genomics research at Western universities in search of new drugs. Even venture capitalists such as the former Microsoft executive Nathan Myhrvold have joined in. He showed his laser mosquito-zapping system at a highly publicized lecture in February.

 

All hope to find a simple, permanent cure.

 

The new findings, however, challenge this dream. That is because eradicating a disease is, in several important respects, a goal diametrically opposed to controlling one.

 

When public health leaders want to control a disease, they devote the majority of their resources to the areas of greatest need. When their goal is eradication, they must spend their resources on areas where eradication is most likely — the areas with the least need.

 

If eradication campaigns fail, resources and political capital will have been lavished on the lowest priority areas with the lightest burdens.

 

That is precisely what happened when more than 90 nations signed up to a global malaria eradication campaign five decades ago, in schemes promoted by the U.S. State Department and the World Health Organization. After spending the modern equivalent of more than $9 billion, the campaign ended with malaria vanquished in a few island nations and in richer, more developed countries, leaving a much harder-to-control malaria still plaguing the poorest and most remote places. The W.H.O.’s Tibor Lepes called the failed eradication program “one of the greatest mistakes ever made in public health.”

 

Successfully eradicating malaria would be a tremendous gain for the health of millions. And we will not know for sure whether wild species act as reservoirs and how that may affect eradication plans until more research is done.

 

But learning to live with malaria, forever, could lead to gains. While eradication requires abrupt interventions to break the cycle of transmission, sustained just long enough for the parasite to die out, learning to live with malaria means working to permanently sever the connections between mosquitoes and humans.

 

That means providing bed nets and cheap drugs in the short term, and building level roads, better drainage, safe water systems and mosquito-proof housing in the long term. At which point, it may not matter how many wild species carry the disease, because humans will be largely malaria-free.

 

 

Sonia Shah is the author, most recently, of “The Fever: How Malaria has Ruled Humankind for 500,000 years.”

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