A broad range of preventive measures tailored to local needs have resulted in major progress against malaria – but declining resources underscore the need for even more efficient work.
When it comes to malaria, the value of a broad range of prevention efforts may be most visible in Kenya, where 70% of the country’s 46 million people are at risk. It is in this east African nation that a variety of preventive measures, tailored to meet the widely divergent needs of local populations, have translated into major overall progress.
“Because transmission is not the same across the whole country, each region has its own intervention package,” said Dr Rebecca Kiptui, who is in charge of surveillance, monitoring, evaluation and operational research for Kenya’s National Malaria Control Programme. “We do not do the same thing everywhere.”
The country’s malaria response, led by the Ministry of Health, has evolved as accumulated evidence has shown the value of tailored interventions for specific locations.
The coastal areas near the Indian Ocean and the Lake Victoria region, for example, are high-burden, and malaria prevalence hovers around 8% and 27% respectively. Here insecticide-treated bednets are the primary preventive tool whereas indoor spraying with insecticides is targeted towards selected areas with high transmission around Lake Victoria.
In the capital city of Nairobi, fewer than 1% of people harbour the parasite that causes malaria. The presence of the parasite is also low in the country’s arid regions, where it can peak at around 3% following heavy rains. Kenya’s malaria response in these areas focuses primarily on surveillance, effective diagnosis and treatment.
Prevention efforts focused on highest-risk areas
Beginning in 2006, the distribution of insecticide treated bednets in high-risk areas was limited to pregnant women and children under the age of 5 years, those at the highest risk of contracting the disease. In 2011, distribution was widened to include everyone living in those areas.
Another preventive measure – intermittent preventive treatment – targets pregnant women near Lake Victoria and along the coast by giving them preventive doses of an antimalarial drug.
“If the parasite is in the mother’s blood, the mother can develop malaria during pregnancy. This can cause anaemia in the mother and can also result in a miscarriage, if the disease is very severe,” said Dr Kiptui.
Many Kenyans living in areas with low malaria transmission, such as Nairobi, have little or no immunity to the disease and can easily become infected when they travel to high transmission areas, such as to visit relatives. Often, they start to develop symptoms after returning back home to low-transmission areas.
This mobility explains why health promotion messages are broadcast nationally, even to low transmission areas, so residents can learn how to limit their exposure and, if they do fall sick, recognize the symptoms and get diagnosed and treated.
Such efforts have had an impact. Countrywide, malaria prevalence dropped from 11% to 8% between 2010 and 2015. Malaria is most pervasive in the endemic region along Lake Victoria with the country’s highest rate of infection at 27% in 2015, yet this figure is down from 38% in 2010.
Still, progress has not been uniform. In 2015, the 8% prevalence in the endemic coastal region of the Indian Ocean was twice what it had been in 2010. While the reasons for this increase are unclear, it highlights the need to sustain high coverage of malaria control measures.
“A 29% drop in overall child mortality between 2008 and 2014 may be attributed, in part, to anti-malaria work,” Dr Kiptui said.
Resistance threatens to reverse gains
Maintaining these advances will not be easy. In western Kenya, around Lake Victoria , malaria mosquitoes have started to develop resistance to the pyrethroid insecticides used in the two biggest malaria prevention tools: bednets and indoor spraying. That finding has alarmed public health officials, who depend heavily on these interventions.
“The significant reductions in malaria in the past decade and a half can be largely attributed to massive scale-up of interventions using insecticides” said Dr Tessa Knox, a scientist working in the WHO Global Malaria Programme.
To determine whether mosquito resistance was undermining the impact of these tools, WHO – with the support of the Bill & Melinda Gates Foundation – commenced a large 5-country evaluation in 2008 to assess what the growing resistance could mean for vector control.
The study, which included Kenya, was completed in 2016 and provided reassuring results. “The overall conclusion was that treated bednets continue to be effective against malaria in areas where we have witnessed development of moderate levels of resistance to pyrethroids, the insecticide class used in nets,” Knox said.
Working with WHO to achieve elimination
WHO has been advising the Ministry of Health, especially on policy and strategy issues, to help Kenya progress further toward its goal of elimination.
In 2009, WHO guided the country’s malaria programme review, which helped to re-focus anti-malaria work to those geographic areas most in need. “Before, we were deploying all interventions across the whole country,” Dr Kiptui said. “WHO helped update the strategy as new information was collected.”
“WHO provides the technical and evidence-based direction,” said Dr Waqo Dulacha Ejersa, head of Kenya’s National Malaria Control Programme. He credited WHO with helping fine-tune the Ministry of Health’s strategies, “so our policies are developed, disseminated and followed-up.”
New tools on the horizon
One preventive tool that has not yet been deployed is the RTS,S/AS01 malaria vaccine.
The vaccine is being evaluated as a potential complement to the core package of WHO-recommended interventions currently in use for prevention, diagnosis and treatment of malaria. Limited roll-out of the vaccine will take place next year in selected districts in three African countries, including Kenya.
Other new tools are being investigated. For vector control, new classes of insecticides for use in bednets and sprays are being developed along with new approaches such as bait devices that attract and kill mosquitoes.
Kenyans are not pinning their hopes on any one intervention. This year, another campaign is set to deliver about 15 million nets to those areas that need them most.
Resources have been cut
But concerns are mounting.
The biggest funder of the Kenyan malaria control programme – the Global Fund to Fight AIDS, Tuberculosis and Malaria – announced in December 2016 that its 2018–2020 package would contain US$ 63 million for malaria programmes in Kenya, less than half of what it had been.
“It leaves a huge gap,” Dr Ejersa said.
“The biggest challenge is resources,” says Dr Abdisalan Noor, Team Leader for Surveillance at the WHO Global Malaria Programme. “Funding is still fragile.”
But progress continues to be made, said Dr Noor, who is Kenyan. “With declining resources, greater efforts are needed to better target their use. Kenya has made great strides in improving the quality of available data for decision making, but more work is required.”
And the economic progress that Kenya has experienced can only help. “The shift from mud huts to concrete houses with sealable windows will reduce exposure to mosquito bites,” said Dr Noor.