TOPICS > Science

Progress Towards a Malaria-Free Tanzania

BY Talea Miller  September 17, 2009 at 12:00 AM EST

Vaccine trials in Tanzania

For Westerners, the emphasis on the Atlantic slave trade often obscures the long and sad history of the Indian Ocean slave trade. Bagamoyo is Tanzania’s oldest city, and was the major shipment point for slaves from the East African interior to the trade networks of the Arabian Peninsula, the Persian Gulf, and west Asia.

The legacies of that trade are many: the Swahili language that dominates a big, arcing slice of East Africa from Kenya and Tanzania to the eastern Congo; the Islamic faith illustrated in the call to prayer throughout the day and the mosques that run from homemade sheds to grand, soaring minarets in the cities; and the gene pool that marks the faces of coastal peoples, lighter of skin and eye, with aquiline noses and long, sharp chins.

Today Bagamoyo is a backwater. A few buildings dating from the multiple colonial eras, from the Omani Arabs to the Germans to the British, are slowly disintegrating near an Indian Ocean beach. Amidst the decrepit stone buildings stand huts and shelters fashioned from wooden poles and palm fronds. One by one through the day, small fishing boats with beautiful triangular sails glide in, pull up on the sand, and start selling the day’s catch to passersby.

A few streets head out from what once had been this city’s commercial hub. The road that hugs the shoreline passes a mosque and then jogs right toward an unlikely spot to make medical history. A collection of low-slung buildings with corrugated metal roofs, Bagamoyo hospital is the only place prepared for serious medical treatment for miles around. It serves hundreds of thousands of chronically medically underserved Tanzanians.

This hospital also carries the distinction of being the home of the world’s most advanced clinical trial for a malaria vaccine. If Bagamoyo’s phase three trials are a success, just a few more rounds of testing stand between this new drug and the waiting bloodstreams of hundreds of millions of people vulnerable to the malaria parasite.

This area has already made remarkable progress in combating malaria, which had been widespread and deadly here. In villages surrounding Bagamoyo there were malaria infection rates as high as 80 percent. Some of the worst-effected villages now have rates approaching 10 percent prevalence. Addressing the density of infected humans, it turns out, is an easier way to fight malaria than trying to wipe out mosquitoes.

Mosquitoes don’t “cause” malaria as much as the parasite just hitches a ride using the female Anopheles mosquito. When the mosquito bites an infected human, a bit of parasite is sucked into the digestive tract and biting mechanism. When that same mosquito pokes its proboscis into its next human victim, a bit of the last meal, and the malaria-causing parasite, is injected, and is now free to reproduce, run riot in the newly bitten.

Reduce the number of infected humans in a local population, and you reduce the chances that the next blood meal taken by a local mosquito will contain the parasite. So it won’t hitch a ride to its next victim, and the next victim won’t be infected. It’s so simple you might want to believe it’s more complicated than that. But it’s not.

Rather than head out into the countryside looking for every pond and puddle to spray a mosquito-killing chemical, the control strategy seeks to reduce the human targets of opportunity. Beds are more and more commonly draped with insecticide-treated mosquito netting. Homes are sprayed around the windows, beneath the doors, and on the walls where a blood-sated mosquito might alight to rest for a few minutes before heading on to the next sleeping target.

When a case of malaria is identified, a network of village-based medical extension workers send word up the information chain, and all the members of a family are treated with anti-malarial drugs.

A country with as little money to spend on anti-malarial drugs as Tanzania could never try to treat the whole country, and doing so would only risk developing immunity to the drug over time, as happened with the quinine-based compounds which can no longer be used in Southern Africa. By treating just the infected, and their intimate circle, you attack the parasite only where it’s living, and make the next mosquito that lands on your neck much less likely to carry the malaria Plasmodium parasites.

Back at the hospital, a group of two dozen or so children are examined, weighed, charted. Their mothers are interviewed to supplement what can be ascertained through blood tests. The children are all malaria free. In a tiny office a computer assigns each child a number that identifies them, and the injection they’re about to receive.

Two by two, the mothers are called from underneath a canopy shielding them from a warm drizzle, and bring their babies for their shot. Like babies getting a shot anywhere, they’re welcomed by a small delegation of smiling doctors and nurses, who tickle and caress the wide-eyed child, who then feels the pain and lets out their piercing wail.

Half the children have just gotten the new malaria vaccine. Half have not. I asked the doctor running the double-blind test about the ethics of withholding potentially life-saving medicine from a baby at high risk for malaria infection in their lifetime. He said double-blind tests were vital for building a scientifically sound and statistically relevant record before moving forward to eventual approval of the drug.

These injections (and to be clear, not even the doctors know which child is getting which injection) will answer the questions that matter: Does the drug suppress the growth of the malaria parasite in a human host? Does it carry side-effects. Will some children show signs of infection anyway after three months, six months, two years?

The children who don’t get the anti-malaria injection are not getting saline solution or some other benign liquid. They are getting inoculations against childhood diseases. By participating in the clinical trial, these mothers are still able to access far more pediatric medical care than the average Tanzanian child receives. Reflecting the area’s population, some of the mothers are Muslim, some Christian. Most are from settled agricultural communities, while a few still live pastoral lives, walking their herds along with their families through a big swath of northeastern Tanzania.

The mothers nurse and play tickle games, relax and gossip on this hot and humid day. A few are still teenagers. One of the older mothers is a 37 year old with a baby boy named Isa. Her first three children died of raging fevers and convulsions she assumes were malaria, though the children never got the screening that would have determined infection for sure. Now there are four other children at home, and she is participating in the clinical trial in hope that she won’t have to bury another child.

If her children to survive to young adulthood, it’s a rough world waiting out there for them. The poverty of this part of the country is desperate,. Though people do have enough to eat, they don’t have much more than that. The housing is commonly hand-made and simple… dirt floors, brick walls made from clay dug right in the neighborhood, sheet metal roofing. A classroom can be little more than four wooden posts, a blackboard on a stand, and a palm roof to keep out the sun.