MALARIA: Reducing Plasmodium falciparum Malaria Transmission in Africa: A Model-Based Evaluation of Intervention Strategies

Background. Half the world’s population is at risk of malaria, and every year nearly one million people—mainly children living in sub-Saharan Africa—die from this mosquito-borne parasitic disease. Most malarial deaths are caused by Plasmodium falciparum, which is transmitted to people by mainly night-biting Anopheles mosquitoes. When infected mosquitoes feed on people, they inject sporozoites, a parasitic form that replicates inside human liver cells. After
a few days, the liver cells release ‘‘merozoites,’’ which invade red blood cells where they replicate rapidly before bursting out and infecting more red blood cells. This increase in the parasitic burden causes malaria’s characteristic fever.
Infected red blood cells also release ‘‘gametocytes,’’ which infect mosquitoes when they take a blood meal. In the mosquito, the gametocytes multiply and develop into sporozoites, thus completing the parasite’s life cycle.
Malaria can be prevented by spraying the insides of houses (where most anopheles species feed and rest) with insecticides (indoor residual spraying, IRS) and by sleeping under bed nets that have been treated with long-lasting
insecticides (long-lasting insecticide nets, LLINs). Mass screening and treatment (MSAT) with effective antimalarial drugs can also reduce malaria transmission.
Why Was This Study Done? Early attempts to eradicate malaria (reduce its global incidence to zero) in the 1950s reduced the incidence of malaria to zero in some countries (malaria elimination) and greatly reduced malarial illnesses and
deaths in others (malaria control). However, this eradication program was aborted in the 1970s in part because of emerging drug and insecticide resistance. Recently, the advent of artemisinin-based combination therapies and new insecticides and the prospect of a malaria vaccine have renewed interest in
controlling, eliminating, and ultimately eradicating malaria.
Consequently, in September 2008, the Roll Back Malaria Partnership launched the Global Malaria Action Plan, which aims to reduce malaria deaths to near zero by 2015. But are the currently available tools for reducing malaria transmission
sufficient to control and eliminate malaria in Africa, the continent where most malaria deaths occur? In this study, the researchers use a new mathematical model of P. falciparum transmission to investigate this question.
What Did the Researchers Do and Find? The researchers’ P. falciparum transmission model consists of ‘‘compartments’’ through which individuals pass as they become infected with parasites, develop immunity, become
infectious to mosquitoes, and so on. The researchers used published data about parasite prevalence (the proportion of the population infected with parasites) and about relevant aspects of mosquito, parasite, and human biology, to
estimate the chances of an individual moving between compartments. Finally, they used the model to explore the impact over 25 years of increased coverage of LLINs, IRS, and MSAT, and of a future vaccine on malaria transmission in six
representative African settings. In a low-transmission setting, 80% coverage with LLINs reduced the parasite prevalence to below 1% in all age groups. In two moderate-transmission settings, LLIN scale-up alone failed to reach this target but the addition of IRS and MSAT drove the parasite prevalence below 1%. However, this combination of interventions did not control malaria in a moderate-transmission setting in which a mosquito species that bites and rests outside houses contributes to malaria transmission. Finally, in two hightransmission
settings, parasite prevalence could be driven below 1% only by setting unrealistic coverage targets for existing interventions.
What Do These Findings Mean? This new mathematical model greatly simplifies the complex dynamics of malaria transmission and includes several assumptions about which there is considerable uncertainty. The findings of this study are not, therefore, firm predictions of the future of malaria control in specific settings. Nevertheless, they suggest that it should be possible to make large reductions in malaria transmission and the associated disease burden in Africa over the next 25 years using currently available tools. Specifically, in regions where transmission is low or moderate and mosquitoes mainly feed indoors, it should be possible to reduce parasite prevalence to less than 1% provided a sustained intervention program is achieved. Importantly, however, these findings suggest that in regions where malaria transmission is high or where mosquitoes rest and bite outside houses, new approaches will be needed to control and eliminate malaria.

http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000324

MALARIA: most malarial town on earth

To reach the most malarial town on earth, head north from Kampala, cross the Victoria Nile and, just before you come to the refugee camps that mark the southern edge of Uganda's 20-year civil war, turn east to Lake Kwania. Africa's other Great Lakes are known for freshwater beaches and cool evenings, but Kwania is more of a giant swamp: shallow, full of crocodiles and choked with lily, papyrus and hyacinth. The malaria parasite loves it here.
Kwania's creeks, looking like a million silver fish bones from the air, are perfect for a deadly subspecies of mosquito, Anopheles funestus, which feeds almost exclusively on humans, with an appetite to shame a vampire. The nearby town of Apac is packed with a living blood bank of people. The average funestus bites human flesh 190 times a night. The average resident is bitten tens of thousands of times a year, including 1,586 bites — four a day — that carry malaria.
Driving into Apac late on an August day last year, I saw a naked man lumbering toward me. Tall and thin, he was gray with dust, and his hair bristled with twigs and grass. He was talking to someone only he could see. Edging past, I was surprised by a second naked figure lurching out of a side street. He had the same cracked skin stretched over the same slender frame. Ahead, a third naked figure sat by the side of the road, his head in his hands. I felt as if I'd arrived in a town of zombies.
Apac's empty streets reinforced that impression. The town seemed to exist only for sickness and death: on one road I counted 12 medical centers, 10 drugstores and a crumbling, windowless nursing school. Soon I found a building that belonged to the Ministry of Health. I pulled in, entered and followed a dark corridor to a door marked "District Health Officer." I knocked. Behind two sets of fly screens and under a ceiling fan, Dr. Matthew Emer sat at his desk. I explained I was following a new campaign to rid the world of malaria and was in Apac to see what it was up against. Who were the naked men? I asked. "Brain damage," Dr. Matthew replied. "Severe malaria can do that to a baby. You never recover."
Dr. Matthew thought I should see some statistics. Apac is home to 515,500 people. Between July 2008 and June 2009, 124,538 of them were treated for malaria. That meant 2,000 to 3,000 patients a week for Dr. Matthew and his three fellow doctors, and the number rose to 5,000 in the rainy season. Of Apac's malaria patients, nearly half were under 5.
Signboards erected by the side of the road announced the presence of two foreign-assistance programs. One was a European-funded child-protection group, which had no malaria component to its program. The other was the National Wetlands Program (NWP), funded by Belgium. Partly because of NWP's influence, the draining of malarial swamps is banned — which amounts to preserving wetlands at the price of human life. Spraying houses with insecticide — which in 2008 cut malaria infections in half — is also forbidden. Why? Because of objections from Uganda's organic-cotton farmers, who supply Nike, H&M and Walmart's Baby George line. Chemical-free farming sounds like a great idea in the West, but the reality is that Baby Omara is dying so Baby George can wear organic.
http://www.time.com/time/specials/packages/printout/0,29239,1995199_1995197_1995176,00.html#

MALARIA: Environmental management

"As dramatically effective and universally applicable chemical methods may be, they cannot provide the long-lasting sustainability of environmental management methods. None of the chemical methods of malaria control last longer than a handful of years. Insecticide-treated bednets must be replaced or re-treated every three to four years. Drugs must be continually administered. Interior walls must be re-sprayed with insecticide every six to 12 months... The benefits of environmental management techniques -- their longer-term sustainability, ability to harness community participation, and lower overall costs -- may tip the balance in their favor in other fronts in the war on malaria" ...
http://www.treehugger.com/files/2010/05/weedwhacker-more-efficient-than-ddt-when-it-comes-to-mosquitoes.php

Zanzibar statistics

ZANZIBAR CITY, 25 April 2010 (IRIN) - Efforts to combat malaria in Zanzibar have seen the prevalence rate come down from 35 percent before 2008 to below 1 percent, but health officials are worried the gains could be reversed. "Despite the achievements in reducing malaria, a lack of funds for awareness[-raising], indoor residual spraying and surveillance, is a challenge. Also, we have a problem with people's resistance to behavioural change, particularly in keeping the environment clean and in the use of mosquito nets," said Mwinyi Msellem, head of the diagnostic unit at the Zanzibar Malaria Control Programme (ZMCP). As malaria prevalence heads towards zero, the population is also losing its natural immuniy to the disease, meaning that population screening will become increasingly important, said Msellem. Malaria prevalence was below one percent, according to the Roll Back Malaria Indicator Survey of 2007. ZMCP interventions include case management through the treatment and training of health workers, and integrated vector control through the use of insecticide-treated bednets, environmental hygiene and indoor spraying. The programme hopes to cover 95 percent of the island's estimated 280,000 households in this way as against 60 percent at present. The prevention of malaria in pregnancy has also been a key malaria control intervention although the use of prophylaxis medication by pregnant women is low at 40 percent against a target of 85. "Most pregnant women attend clinics when they are close to delivery so they just get the last dose," he said. Two doses are recommended. Along with past interventions, emphasis is on new case monitoring and research. "When you get this kind of success you have to increase surveillance," he noted. Early epidemic detection system A Malaria Early Epidemic Detection System has also been established to monitor new cases at 52 of Zanzibar's 150 health facilities. "Weekly, they [the health centres] send text messages to our server indicating the number of patients, those tested for malaria, and the number diagnosed with malaria," said Msellem. Comparisons are then drawn against previous weekly reports. "If an increase is noted, we have to investigate and check breeding grounds," he said. The health centres reported 1,671 confirmed malaria cases in 2009, of which 618 were children under five. According to the Ministry of Health and Social Welfare, health centres have been showing 2-3 percent malaria prevalence, with no change noted since the short March-May rains. Emerging challenges Challenges are, however, emerging in disease monitoring, behaviour change and funding. Among the problems is difficulty getting monitoring data from the health facilities, he said. Mobile phone technical errors sometimes also interfere with data collection. "Each district also needs its own surveillance and response team and there is a need for more trained personnel," he said. "To set up this system you also need a lot of money." Refusal to test and be treated for malaria has also been noted as cases decline, raising the risk of onward transmission or even death. This is because some people believe malaria has already been eliminated, said ZMCP. Mariam Mussa, 34, a small trader and mother of three in Tunguu village south of Unguja, one of Zanzibar's constituent islands, said: "I thank God that the last time one of my children had malaria was in May [2009]. In the past we used to have malaria frequently." "Situation remains fragile" "Although malaria is down, the situation remains fragile. Sustainable commitment by the government, including having its own funds for the anti-malaria programme and awareness of the need to keep the environment clean, is important to control mosquitoes," Juma Muchi, a doctor, told IRIN. The likelihood of donors and the government withdrawing support due to the recorded success is a major concern, according to ZMCP's Msellem. "We need to sustain control measures to avoid a resurgence. Malaria prevalence was reduced to 1-2 percent in the 1970s, and then people relaxed. If we do not have proper strategies and do not work together - yes there is a fear of sliding back." "Maintaining the gains in fighting malaria is probably the biggest challenge facing Zanzibar now," said Asha Abdallah, the Minister of Employment, Youths, Children, and Women.

Zanzibar statistics

ZANZIBAR CITY, 25 April 2010 (IRIN) - Efforts to combat malaria in Zanzibar have seen the prevalence rate come down from 35 percent before 2008 to below 1 percent, but health officials are worried the gains could be reversed. "Despite the achievements in reducing malaria, a lack of funds for awareness[-raising], indoor residual spraying and surveillance, is a challenge. Also, we have a problem with people's resistance to behavioural change, particularly in keeping the environment clean and in the use of mosquito nets," said Mwinyi Msellem, head of the diagnostic unit at the Zanzibar Malaria Control Programme (ZMCP). As malaria prevalence heads towards zero, the population is also losing its natural immuniy to the disease, meaning that population screening will become increasingly important, said Msellem. Malaria prevalence was below one percent, according to the Roll Back Malaria Indicator Survey of 2007. ZMCP interventions include case management through the treatment and training of health workers, and integrated vector control through the use of insecticide-treated bednets, environmental hygiene and indoor spraying. The programme hopes to cover 95 percent of the island's estimated 280,000 households in this way as against 60 percent at present. The prevention of malaria in pregnancy has also been a key malaria control intervention although the use of prophylaxis medication by pregnant women is low at 40 percent against a target of 85. "Most pregnant women attend clinics when they are close to delivery so they just get the last dose," he said. Two doses are recommended. Along with past interventions, emphasis is on new case monitoring and research. "When you get this kind of success you have to increase surveillance," he noted. Early epidemic detection system A Malaria Early Epidemic Detection System has also been established to monitor new cases at 52 of Zanzibar's 150 health facilities. "Weekly, they [the health centres] send text messages to our server indicating the number of patients, those tested for malaria, and the number diagnosed with malaria," said Msellem. Comparisons are then drawn against previous weekly reports. "If an increase is noted, we have to investigate and check breeding grounds," he said. The health centres reported 1,671 confirmed malaria cases in 2009, of which 618 were children under five. According to the Ministry of Health and Social Welfare, health centres have been showing 2-3 percent malaria prevalence, with no change noted since the short March-May rains. Emerging challenges Challenges are, however, emerging in disease monitoring, behaviour change and funding. Among the problems is difficulty getting monitoring data from the health facilities, he said. Mobile phone technical errors sometimes also interfere with data collection. "Each district also needs its own surveillance and response team and there is a need for more trained personnel," he said. "To set up this system you also need a lot of money." Refusal to test and be treated for malaria has also been noted as cases decline, raising the risk of onward transmission or even death. This is because some people believe malaria has already been eliminated, said ZMCP. Mariam Mussa, 34, a small trader and mother of three in Tunguu village south of Unguja, one of Zanzibar's constituent islands, said: "I thank God that the last time one of my children had malaria was in May [2009]. In the past we used to have malaria frequently." "Situation remains fragile" "Although malaria is down, the situation remains fragile. Sustainable commitment by the government, including having its own funds for the anti-malaria programme and awareness of the need to keep the environment clean, is important to control mosquitoes," Juma Muchi, a doctor, told IRIN. The likelihood of donors and the government withdrawing support due to the recorded success is a major concern, according to ZMCP's Msellem. "We need to sustain control measures to avoid a resurgence. Malaria prevalence was reduced to 1-2 percent in the 1970s, and then people relaxed. If we do not have proper strategies and do not work together - yes there is a fear of sliding back." "Maintaining the gains in fighting malaria is probably the biggest challenge facing Zanzibar now," said Asha Abdallah, the Minister of Employment, Youths, Children, and Women.