Two Malarias

Stimson Spotlight

Two Malarias

By Karen Masterson - The November 2011 newsletter of Roll Back Malaria - a partnership sponsored by the World Health Organization, the United Nations and the World Bank - contains the following headline: "Nearly a third of all malaria affected countries on course for elimination over the next decade."

In this short sentence, RBM conjures images of great progress against the world's millennia-old malaria pandemic. So it may sound like nit-picking to point out that RBM's list includes mostly economically developing countries that should have eliminated malaria long ago (former Soviet Republics; Turkey; Sri Lanka; North Korea; sub-regions of Indonesia, Thailand, India, China, and Bhutan; several Pacific Islands; countries of the Middle East and North Africa; and from the Western Hemisphere, Mexico, Argentina, and Paraguay). Add that not making the list are the world's most malaria-burdened countries, all in sub-Saharan Africa - where 85 percent of the world's infections and 90 percent of all malaria-related deaths take place - and it becomes clear that RBM's headline misses the mark.

The RBM report that inspired this headline should highlight that global health programs are fighting two malarias and making great progress against only one of them. Technically, there are four types of human malaria and at least one monkey malaria that routinely jumps species to infect us.  Only two -- vivax and falciparum -- cause a vast majority of illnesses. The latter thrives in the climates and ecosystems of sub-Saharan Africa; the former thrives everywhere else. It is vivax that we're making progress against, and have been for a hundred years.

Vivax plagued much of the world prior to World War II, including the United States, northern Europe, and northern Asia - places that are today virtually malaria-free. These regions eliminated it by getting people out of shacks, off mosquito-infested flood plains, and into properly built homes and decent-paying jobs. The last of it in the United States dried up in the 1930s and 1940s, when states like Georgia, with the health and development standards of rural Africa, were transformed by social safety nets and market-driven job creation.

Such economic development disrupts the so-called cycle of infection because the cycle is inherently fragile. Malarial parasites - all types of them - are wholly dependent on mosquitoes biting not once, but twice. The first bite drinks in a small handful of microbes that have infected a person long enough for them to reach a type of adult status. Once in the mosquito's belly, the parasites sexually merge into egg sacs. A week or two later - depending on air temperature - the sacs burst with infant parasites that swim into the mosquito's saliva. With bite No. 2, they slip back into our blood to launch a new infection, during which they mature and migrate to our surface cells waiting to be sucked in again by biting mosquitoes.

To keep the cycle going for all types of malaria, a lot of mosquitoes are needed to ensure that a few live long enough for that second bite. This means the disease is transmittable only where people live unprotected from abundant populations of malaria's night-feeding mosquitoes - of which there are about 40 species living all over the world. If anything disrupts the process - cold weather, land reform, screened dwellings, broad bed-net use, massive insecticide spraying - the microbes die off. If the cycle is disrupted long enough, a region is considered to have eliminated malaria.

Vivax is distinct in that it rarely kills people, and survives temperate and semi-tropical climates in places like Eastern Europe, Asia, and South America by hibernating in the human liver during cooler months, coming out into the blood stream when larvae molt into mosquitoes. Infection cycles in these places are easier to break because they tend to be seasonal, not year round.

Today, vivax is disappearing in many of the RBM listed countries in large part because economic development and urbanization (away from mosquito-filled habitats) are reducing human-mosquito interaction, making malaria harder to sustain. Most of the RBM-identified countries also have programs that deliver drug treatments, bed nets and/or insecticides to affected people. These low-tech malaria control strategies - developed during World War II - are quickening the natural tendency for malaria to steadily disappear as economies modernize. The RBM report helpfully tracks this dynamic.

The other malaria, African falciparum, presents a different story. Unlike vivax, it is quite deadly. It can clump up and stick like Velcro to the brain, triggering coma and death just hours after the onset of symptoms. It is best suited for tropical zones because it tends not to hibernate in the liver; mosquitoes must be ever present to keep the disease cycling. This makes sub-Saharan Africa ideal for this microbe. Mosquitoes bite year round and are the most efficient, durable, long-living and abundant vectors on Earth - in countries with among the most intense poverty known to man.

An Irish entomologist working in rural Tanzania said that in one village he measured an average of 2,000 falciparum-infected mosquitoes per person, per year - or 5.5 potential infectious bites per day. In these places, nearly everyone either acquires limited immunity to their local strains, becoming carriers of the microbes for mosquitoes to pick up and pass on to others, or they die. In such places, about 30 percent of child/infant mortality is caused by malaria alone, and much of the remaining mortality is at least in part from malaria. These populations are "seeded" with falciparum and have little hope of escaping the cycle. They live in mud huts, subsistence farm on rich mosquito habitat, are miles from decent health services, and suffer from a hundred other poverty-induced afflictions - cholera, dysentery, malnutrition - making malaria infections even more deadly.

Global health programs can reduce infection rates in these places by pouring money into intensive treatment and bed-net distribution programs. But the money spent in Africa is rarely accompanied by the kind of economic progress seen in sister programs targeting vivax in Eastern Europe, North Africa, Southeast Asia, and South America. As soon as the programs pack up and leave African countries, malaria returns in full force. The political will needed to push for economic change is hard to find.

Falciparum malaria in Africa, the phoenix that rises from every attempt to eradicate it, is different from the malaria headlined by RBM. The spin RBM chose for its "elimination" report uses a narrow slice of the problem to imply a broad optimism. To more honestly address both of the world's malaria woes, it should have read: "Of the world's two malarias, one is on track for elimination in X countries; for the other, much, much, more is needed."

That way we can remain optimistic about global progress against this disease, while also pressuring the world to recognize African malaria as part of a bigger system that needs new, broader-based strategies that involve bringing much-needed prosperity and health services to nearly a half billion smart and spirited, but horrendously impoverished African people.

 

This article first appeared online in The Last Word on Nothing, at http://www.lastwordonnothing.com/2011/12/07/guest-post-two-malarias/.

Karen Masterson is a writing instructor at Johns Hopkins University and is finishing a book about malaria and World War II.


Photo Credit: Karen Masterson