Early in the morning, not long after the sun rises above the Zambian plains, they map out their plan of attack. A detailed strategy is needed; after all, they are on the trail of a killer.
Dressed in orange t-shirts, riding on bicycles, motorcycles, in cars, trucks and occasionally in ox carts, they fan out across their target or "catchment" areas. They travel along paved roads, dirt tracks, through fields and villages, and eventually go door-to-door on the hunt for Plasmodium falciparum - the mosquito-borne parasite that kills hundreds of thousands of people every year in sub-Saharan Africa, most of them children under five. A child dies from malaria every 30 seconds, according to the United Nations children's agency, Unicef.
Zambia's malaria trackers are the latest component of a comprehensive malaria control program aimed at eliminating the disease from the country. The Malaria Control and Evaluation Partnership in Africa (Macepa) in 2005 began partnering with African governments, the Roll Back Malaria Partnership and others to help achieve eradication.
"What's the alternative" to elimination, asks Duncan Earle, director of Macepa, which is a program at PATH. "There are those who think we can tread water, but it's an unending investment, because if you don't eliminate it then you have to continue preventing, controlling and treating. So we have to go for it. We have done it in 111 countries around the world, why not another 90?"
The World Health Organisation (WHO) in December said in its World Malaria Report 2012 that a "concerted effort by endemic countries, donors and global malaria partners" had led to strengthened malaria control around the world.
"The scale-up of malaria prevention and control interventions had the greatest impact in countries with high malaria transmission; 58 percent of the 1.1 million lives saved during this period were in the 10 highest burden countries," the report said.
But it said funding problems were a growing threat to anti-malaria gains.
Scaling Up for Impact
One way to bring down malaria infection rates has been through an approach, championed by Macepa, known as Scaling Up for Impact (SUFI).
While it now includes testing and treatment in certain areas as transmission drops, the primary tools have been distribution of insecticide-treated bed nets and indoor residual spraying of insecticide. As a result of all these efforts, malaria transmission rates have dropped to near zero in some parts of Zambia. Large-scale distribution of free bed nets has had a particularly significant impact.
"The campaign for the past five to eight years has been trying to get bed nets out and get a high level of usage of those bed nets - to understand what that single intervention could do in terms of a key health outcome, which is childhood deaths," said Macepa's veteran malariologist Dr. Carlos (Kent) Campbell. "To our tremendous amazement, the impact has been even greater than we could have imagined."
He said there was a 29-percent reduction in all childhood deaths within the first two years. "To put that in perspective: there's nothing matching that, which is reflective of how much death malaria caused in Zambia and how powerful bed nets are to decrease transmission," said Campbell.
Since 2000, childhood deaths from malaria have dropped by 20 percent in other African nations using the SUFI approach, according to Macepa. An estimated 300,000 children were saved from dying from malaria in 2010 alone, it said.
Macepa has a presence in Senegal, Ethiopia, Zambia, Mozambique and Tanzania, and it is about to start working in Kenya.
Trackers Face Challenges
The latest step in Zambia's program includes the Test and Treat campaign that began in December 2011 in certain districts of the country. Malaria trackers visit communities in those districts three times a year to conduct malaria tests, collect information, administer medication and deliver bed nets.
They're up against major challenges, including transportation. "Some of these areas are pretty rural, and even if you try to look for vehicles locally it is very difficult," said Kafula Silumbe, monitoring and evaluation officer with Macepa/PATH in Zambia. "You find they have ox carts and things like that, and even when you get a vehicle sometimes it is not a vehicle that can go to some of these terrains ... and you either have to walk or use a bicycle."
And once the malaria trackers do reach a community, finding the people they need to test for P. falciparum infection or treat can be daunting as well.
"This is an area that has polygamous marriages, and household size can be anything from three people to 35 people," Silumbe said. "So you get to the household, you have to test each and every one of them. You may find that a quarter of them are positive for malaria. So you have to make sure that you just treat everyone."
But, he said, sometimes many of the people aren't home. The children could be at school and the parents might be out in the fields. In that case, he said, the malaria trackers will have to return at a different time when more people are likely to be home.
Eliminating infection is central to the goal of malaria eradication.
Even asymptomatic people who are infected can pass the parasite on to a mosquito, which then bites someone who can become ill.
No Time for Rest
An effective vaccine is not expected to be sufficiently effective against malaria in the near future, possibly not for another decade. And despite progress otherwise in the malaria fight, it is a race against time. There are three threats working against recent gains: lack of sufficient funding, resistance to insecticide that kills mosquitoes, and resistance to artemisinin-based medication - the most effective treatment in the highest-risk areas.
In its World Malaria Report 2012, WHO said that after a rapid expansion of international support between 2004 and 2009, global funding for malaria prevention and control leveled off between 2010 and 2012.
Progress in the delivery of some life-saving commodities has slowed. The report said the lack of sustained commitment to maintaining and extending the efforts "could threaten to reverse the remarkable recent gains in the fight against one of the world's leading infectious killers".
In terms of the other threats - drug and insecticide resistance - Campbell said the world's malaria fighters have to believe new tools will be developed before there is a crisis.
"There is resistance to pyrethroids, which is the insecticide that is impregnated into bed nets in some parts of Africa," he said. "Still, that resistance has not translated into making bed nets ineffective, but conceivably, and I think realistically, that's going to evolve."
In addition, Campbell said, "Resistance to the artemisinins is a fact in pockets in Southeast Asia. Although not documented to date in Africa, drug resistance will spread the more the drug is used. That doesn't argue that we can't eliminate malaria or that we shouldn't try. It says that we should be doing this rapidly so that this doesn't become a long, drawn-out operation."
Macepa is a program of Path, a Seattle, Washington-based non-profit organization focusing on global health. The malaria program was launched with a major grant from the Bill & Melinda Gates Foundation, which also supports AllAfrica's reporting on development issues.