Tropical Health Matters

News focuses on getting a handle on urban malaria in Uganda and Tanzania. Listen to a program on the disease burden of malaria in Africa.  Chad reports a high test positivity rate. Algeria is re-experiencing malaria after it was officially eliminated. Links for more details are found in each section.

Modelling and mapping the intra-urban spatial distribution of Plasmodium falciparum parasite rate using very-high-resolution satellite derived indicators

Stefanos Georganos, Oscar Brousse, Moritz Lennert, and others in International Journal of Health Geographics report on the rapid and often uncontrolled rural–urban migration in Sub-Saharan Africa is transforming urban landscapes expected to provide shelter for more than 50% of Africa’s population by 2030. Case studies include two Sub-Saharan African cities, Kampala and Dar es Salaam.

Openly accessible land-cover, land-use, population and OpenStreetMap data were employed to spatially model Plasmodium falciparum parasite rate standardized to the age group 2–10 years (PfPR2–10) in the two cities through the use of a Random Forest (RF) regressor. The RF models integrated physical and socio-economic information to predict PfPR2–10 across the urban landscape. Intra-urban population distribution maps were used to adjust the estimates according to the underlying population.

The results suggest that the spatial distribution of PfPR2–10 in both cities is diverse and highly variable across the urban fabric. Dense informal settlements exhibit a positive relationship with PfPR2–10 and hotspots of malaria prevalence were found near suitable vector breeding sites such as wetlands, marshes and riparian vegetation. In both cities, there is a clear separation of higher risk in informal settlements and lower risk in the more affluent neighborhoods. Additionally, areas associated with urban agriculture exhibit higher malaria prevalence values. This study demonstrates the importance of remote sensing as an epidemiological tool for mapping urban malaria variations at large spatial extents, and for promoting evidence-based policy making and control efforts.

Malaria: Africa’s nagging health burden

Listen to Episode Nine of Africa Science Focus is on malaria, which is one of the biggest killers on the continent. “Malaria is so common you can get it anywhere, anyhow, any time,” Jessica, a malaria sufferer in Liberia, tells the programme. This is because Africa’s mosquitoes are “supremely efficient vectors of malaria disease”, says the World Health Organization’s David Schellenberg.

Malaria: More than 500K cases reported in Chad, Deadliest disease in country

According to data from the National Committee for Epidemic Control (CTNLE), out of the 943,040 malaria tests conducted between 1 January and 13 September 2020, a total of 571,258 cases were confirmed (60.5 percent), with 1,280 deaths across the country. In addition close to 1,140,000 suspected cases based on clinical symptoms but who have not been tested. Among these suspected cases, 1,368 people have died. The most affected provinces are, among others, Logone oriental (with a total of 80,930 cases), Mandoul (82 258 cases), Moyen-Chari (60 207 cases), Tandjle (55 777 cases) and N’Djamena (53 976 cases).

Officials say the situation is slightly better than last year around the same period when 689,563 cases were confirmed and 1,323 died – a difference of 118,305 cases and 43 deaths. However, the situation has worsened compared to 2017 and 2018 when the number of confirmed cases were 524,148 and 534,781 (with 957 and 922 deaths) respectively.

Algeria faces new malaria cases one year after victory over deadly disease

Algeria Tuesday registered over 1,000 cases of malaria, one year after the World Health Organization (WHO) declared the country malaria-free. The cases, according to the health ministry, are imported cases and have been spotted in five governorates namely Tamanrasset (918), Adrar (96), Illizi (89), Ouargla (5) and Ghardaïa (2).

The ministry noted that every year, in September after first rains, the country often registers imported malaria cases, hailing from Sahel neighboring countries or Algerians who sojourned in those countries. The WHO in May 2019, declared Algeria malaria-free. The certification is awarded to countries after three straight years of zero home-born cases of malaria.

First we look at how disease can influence urban planning. We have four news stories focus on field activities for vector control from Hyderabad, India, Borno State, Nigeria, Papua New Guinea and CHAD. Finally there is an ancestry article of sorts examining plasmodia in chimpanzees and humans. Click on the links to read full details.

Can Covid-19 inspire a new way of planning African cities?

Health crises are not new in Africa. The continent has grappled with infectious diseases on all levels, from local (such as malaria) to regional (Ebola) to global (Covid-19). The region has often carried a disproportionately high burden of global infectious outbreaks.
How cities are planned is critical for managing infectious diseases. Historically, many urban planning innovations emerged in response to health crises. The global cholera epidemic in the 1800s led to improved urban sanitation systems. Respiratory infections in overcrowded slums in Europe inspired modern housing regulations during the industrial era.

Urban planning in Africa during colonisation followed a similar pattern. In Anglophone Africa, cholera and bubonic plague outbreaks in Nairobi (Kenya) and Lagos (Nigeria) led to new urban planning strategies. These included slum clearance and urban infrastructure upgrades. Urban planning in French colonial Africa similarly focused on health and hygiene issues, but also safety and security.

Unfortunately regional experiences with cholera, malaria and even Ebola in African cities provide little evidence that they have triggered a new urban planning ethic that prioritises infectious outbreaks. Our recent research paper discusses three areas that can transform urban planning in the continent to prepare for future infectious outbreaks, using lessons from Covid-19.

The Coronavirus and other viruses like Ebola have always been ‘out there’ in nature.

But it’s only when we disrupt the natural habitats of the wild animals. Deadly viruses stay beneath the surface and need just one moment of triggering to emerge in the atmosphere and take the world by storm – historian Dr Mark Honigsbaum. The point is we cannot prevent all spillover events or predict precisely when or where the next one will happen. What we can do — and should do often — is invest in local laboratories and diagnostic services so that we can spot unusual outbreaks early and close them down quickly

We should note that Plasmidium Knowlesi is an example of a form of malaria from monkeys that arose because of urban expansion on forest habitats.

Hyderabad: People sensitised on mosquito breeding

As part of a novel initiative, every Sunday 10 am, 10 minute programme, the entomology wing of Greater Hyderabad Municipal Corporation conducted awareness drive on mosquito breeding grounds at various places on Sunday. They explained the importance of cleanliness and the ways the mosquito breeding takes place in stagnated water. Speaking on the occasion, Banjara Hills Corporator Gadwal Vijayalaxmi called upon everyone not to allow accumulation of water in containers, utensils and surroundings.

Borno, WHO Administer Malaria Prevention Drug on 2.1m Children

WHO National Coordinator Malaria Emergencies in Nigeria, Dr. Iniabasi Nglas gave the figure during a four round Malaria Chemoprevention Campaigns (MPCs aka SMC) in 25 of the 27 local government areas of Borno State. During the advocacy, Nglas said the IDP camps “are given special attention for there is high threat of malaria infection due to the environment. Record has shown that the treatment has reduced malaria morbidity in the state.” She revealed that during the first cycle, 1.9 million children were targeted but due to high reception 2.1 million children were administered with the drug.

Rotary Against Malaria Distributes Nets in PNG

ROTARY Against Malaria has finally completed its distribution of bed net mosquito nets throughout the Eastern Highlands Province (EHP) after three months. Team leader of Rotary Against Malaria in the province, Helmut Magino, during a ceremony in Goroka, acknowledged his working staff, the Eastern Highlands Provincial Health Authority, district health officers, logistic company Mapai Transport, Summer Institute of Linguistics (SIL)
and the communities in Papua New Guinea.

“Without these partners, our work in distributing mosquito nets wouldn’t have been successful,” Mr Magino said. “Mapai Transport assisted with vehicles to travel to the remote parts in Okapa, Henganofi and Lufa. “SIL assisted with distribution via airplane to remote parts which are not connected by road like in Obura-Wonenara district.” The volunteer-run organisation funded by Global Fund, a US-based organisation, distributed 145,900 mosquito nets in the province. “We distributed around 45,000 nets to Okapa and Lufa, 35,000 to Obura-Wonenara and 66,900 to rural areas in Goroka district. “We will visit EHP again next year to distribute nets …”

Donating Emergency IRS Supplies to CHAD

Last week, despite the COVID-19 pandemic, a Hercules military transport aircraft took off from an Israeli military base in the south, filled to capacity with items donated by Israeli Flying Aid IFA and the American Jewish Committee (AJC) — 2,000 six-person tents, personal protection equipment (PPE) for medical teams, backpack sprayers to eradicate malaria-carrying mosquitos, and more.

Why humans can run marathons and apes cannot (implication for plasmodium species)

Chimpanzees share more than 99 percent of their genes with modern humans, but the CMAH gene is one of the areas of difference. Two to three million years ago, gorillas, chimpanzees, and other primates were dying from a type of malaria called Plasmodium reichenowi (Science, 2011;331:540-542). At that time, all primates had a surface protein called Neu5Gc on their cells that was made from Neu5Ac. Then along came a primate with a gene that had lost its ability to make Neu5Gc from Neu5Ac, so it had only Neu5Ac (Proc Natl Acad Sci USA, Sept 6, 2005;102(36):12819-12824).

That pre-human did not die from malaria like other primates, his and her children lived and proliferated, and today their descendants (all humans) have a gene that makes Neu5Ac instead of Neu5Gc. As often happens in nature, the malaria parasite then modified its genetic makeup into a variant called Plasmodium falciparum which can infect humans, but not chimpanzees, so today humans can be infected only with Plasmodium falciparum and chimpanzees can be infected only with Plasmodium reichenowi. This same genetic mutation gave homo sapiens greater endurance so they were able to run long distances while the apes could not, which gave humans an advantage in hunting for food (J Hum Evol, 2014;66:64-82).

Today we learn about malaria-carrying A. stephensi invading African cities, how malaria outpaces COVID-19 in Central African Republic, and the need to examine malaria service delivery in the context of strong health services. Malaria Journal looks at ITN use in Uganda and malaria genetic variability even at the household level. Click on links to read full articles.

Spread of city-loving malaria mosquitoes could pose grave threat to Africa

An Asian malaria-carrying mosquito that has adapted to urban life has the potential to spread to dozens of cities across the African continent, a new modeling study suggests.
The mosquito species, Anopheles stephensi, poses a serious new threat for African cities, says Francesca Frentiu, a geneticist at the Queensland University of Technology who was not involved in the research. She praises the work as “an important effort, underpinned by robust methods.” A. stephensi hopped from Asia to the Arabian Peninsula between 2000 and 2010 and then made another jump to the Horn of Africa; scientists first discovered it in Djibouti in 2012, then later in Ethiopia and Sudan.

In times of COVID-19, malaria remains the number one killer of children in CAR

Since the beginning of the year, MSF teams have treated 39,631 malaria cases in Batangafo, compared to 23,642 in the same period last year. The hospital in Batangafo – a town of 31,000 people, including 22,000 displaced from elsewhere in the Central African Republic – is bustling with activity. While a particular focus has been placed on infection prevention and control measures to identify and isolate people with suspected cases of COVID-19, another deadly disease has a much heavier impact on the lives of people living here.

September is the rainy season, when malaria becomes more deadly than ever in the Central African Republic each year. It is the leading cause of death for children under five in the country. During periods when malaria transmission is high, eight out of ten paediatrics consultations in the hospital supported by Médecins Sans Frontières (MSF) in Batangafo are due to complications from malaria, including anaemia and dehydration.

Assessment of health service delivery parameters in Kano and Zamfara States, Nigeria

In 2013, the Nigeria Federal Ministry of Health established a Master Health Facility List (MHFL) as recommended by WHO. Since then, some health facilities (HFs) have ceased functioning and new facilities were established. We updated the MHFL and assessed service delivery parameters in the Malaria Frontline Project implementing areas in Kano and Zamfara States.

In 2016, the US Centers for Disease Control and Prevention (CDC), in collaboration with the Nigeria National Malaria Elimination Program (NMEP), established a 3-year intervention project, Malaria Frontline Project (MFP), with the objectives of strengthening the technical capacity of LGA-level health workers, improving malaria surveillance and facilitating evidence-based decision-making. The project was implemented in Kano and Zamfara States.

Some deficiencies in the list of facilities in DHIS2 and MHFL were uncovered making it difficult to submit and access malaria program data. Also, some facilities were still using the old version of register which did not collect all indicators required by DHIS2. In addition there were a small number of non-functional facilities. Finally the low number of facilities within the PHC category meeting the minimum HR requirement will hamper the countries effort to achieve its goal of universal health coverage. From the foregoing, the study identifies several areas to improve delivery of malaria services specifically and universal coverage in general.

Individual, community and region level predictors of insecticide-treated net use among women in Uganda: a multilevel analysis

ITN use attributable to regional and community level random effects was 39.1% and 45.2%, respectively. The study has illustrated that ITN policies and interventions in Uganda need to be sensitive to community and region level factors that affect usage. Also, strategies to enhance women’s knowledge on malaria prevention is indispensable in improving ITN use.

Genetic diversity and complexity of Plasmodium falciparum infections in the microenvironment among siblings of the same household in North-Central Nigeria

These findings showed that P. falciparum isolates exhibit remarkable degree of genetic diversity in the micro-environment of the household and are composed mainly of multiclonal infections, which is an indication of a high ongoing parasite transmission. This suggests that the micro-environment is an important area of focus for malaria control interventions and for evaluating intervention programmes.

In the past week urban transmission in Goma, a city of at least 2 million inhabitants in eastern Democratic republic of Congo, was documented as a gold miner came home and infected his wife and child. To get a grip on the spread of the disease, DRC is considering another vaccine, not without some controversy. WHO provides detailed guidance on all aspects of response. On the malaria front we have learned more about malaria vectors, natural immunity and reactive case detection.

Ebola Challenges: Vaccines, Urban Transmission

The current Ebola vaccine being deployed to over 150,000 people in North Kivu and Ituri Provinces was itself an experimental intervention during 2016 when it was first used in the largest ever outbreak located in West Africa. BBC reports that, “World Health Organization (WHO) data show the Merck vaccine has a 97.5% efficacy rate for those who are immunised, compared to those who are not.”

The proposed addition of a Johnson and Johnson vaccine would be in that same experimental phase if introduced in DRC now. It has been proven safe as well as effective in other primates. The challenge is that even though the Merck vaccine supplies are near 500,000, this is not enough to cover the potential needs in an area with over 10 million people, although Merck is still producing more. At present, BBC says, “Those pushing for the use of the new Johnson & Johnson vaccine, had proposed using it to create a protective wall, vaccinating people outside the outbreak zone.” In addition, the new national response team is concerned that “Only about 50% of cases of Ebola in the Democratic Republic of Congo are being identified.”

Finally, there is the issue of community mistrust of government workers and challenging logistics. “There are also concerns that the new vaccine – which requires two injections 56 days apart – may be difficult to administer in a region where the population is highly mobile, and insecurity is rife.”

If efforts at vaccination are needed soon in Goma, up to 2 million doses might be needed. Reuters reports that, “Congolese authorities were racing to contain an Ebola epidemic on Thursday, after a gold miner with a large family contaminated several people in the east’s main city of Goma before dying of the hemorrhagic fever.” Readers may recall that the West Africa outbreak of 2014-16 in Guinea, Sierra Leone and Liberia accelerated greatly after infected people went to major cities in search of help.

The miner is the second ‘imported case into Goma, which borders Rwanda, but because his family lives there, he has already infected his wife and one of his 10 children. Contacts are being traced and monitored, but this urban and border threat is one of the factors that led WHO to finally declare the current outbreak a public health emergency.

Malaria

As we move toward malaria elimination Reactive Case Detection (RCD) has been proposed as an integral part of these efforts with the hopes that is can be conceived of as a way of gradually decreasing transmission, according to an article in Malaria Journal. In fact, the value of RCD may be limited as follows:

• RCD alone can eliminate malaria in only a very limited range of settings, where transmission potential is very low
• In other settings, it is likely to reduce disease burden and help maintain the disease-free state in the face of imported infections

Another article looks at “natural exposure to gametocytes that can result in the development of immunity against the gametocyte by the host as well as genetic diversity in the gametocyte.” The researchers learned that there can be variations in immune response depending on season and geography. This information is helpful in planning malaria elimination interventions.

On the vector front a baseline susceptibility testing was conducted in 16 countries in sub-Saharan Africa for neonicotinoids. “The target site of neonicotinoids represents a novel mode of action for vector control, meaning that cross-resistance through existing mechanisms is less likely.” The findings will help in the preparation for rollout of clothianidin formulations as part of national IRS rotation strategies by PMI and other partners.

Researchers also called on us to learn more about malaria vectors in other parts of the world. In order to eliminate Plasmodium falciparum from the Caribbean and Central America program planners should consider local vector characteristics such as An. albimanus. They found that, “House-screening and repellent IRS are potentially highly effective against An. albimanus if people are indoors during the evening.”

Vectors are also of concern on the edges of malaria transmission, particularly in South Africa, one of the ‘elimination eight’ countries of the Southern Africa Development Community. Researchers examined the, “potential role of Anopheles parensis and other Anopheles species in residual malaria transmission, using sentinel surveillance sites in the uMkhanyakude District of northern KwaZulu-Natal Province.” They found Anopheles parensis is a potential but minimal vector of malaria in South Africa “owing to its strong zoophilic tendency.” On the other hand, An. arabiensis was found to be the major vector responsible for residual malaria transmission in South Africa. Since these mosquitoes were found in outdoor-placed resting traps, interventions are needed to control outdoor-resting of vector populations.

NTDs of Concern

During the week, the member states of the African Union renewed their commitment to fight and permanently eliminate Neglected Tropical Diseases. Africa.com reported that, “Achievements to date include 1 billion people treated against at least one NTD and 37 countries have completed the removal of at least one NTD.”

Although some reports have discounted the idea of trachoma in Namibia, there may be reason to re-examine the situation. On Twitter Anthony Solomon notes that Namibia needs #trachoma prevalence surveys. A just-completed joint Ministry of Health & Social Services/@WHO mission found active trachoma & trichiasis in Zambezi & Kunene Regions.

The Times of India draws attention to snakebite. It says that “Under-reported and inadequately treated, fatalities in India are estimated at close to 50,000 a year, the world’s highest.”

Overall we can see that the concept of ‘neglect’ has several uses. There is neglect if half of Ebola cases are undetected. There is neglect if we do not understand malaria vectors in low transmission areas. Finally, there is neglect if we do not conduct up-to-date disease surveys to determine whether a disease is present or not. Elimination of tropical diseases is challenging when key processes are neglected.

On World Population Day (July 11) one often thinks of family planning. A wider view was proposed by resolution 45/216 of December 1990, of the United Nations General Assembly which encouraged observance of “World Population Day to enhance awareness of population issues, including their relations to the environment and development.”

A relationship still exists between family planning and malaria via preventing pregnancies in malaria endemic areas where the disease leads to anemia, death, low birth weight and stillbirth. Other population issues such as migration/mobility, border movement, and conflict/displacement influence exposure of populations to malaria, NTDs and their risks. Environmental concerns such as land/forest degradation, occupational exposure, population expansion (even into areas where populations of monkeys, bats or other sources of zoonotic disease transmission live), and climate warming in areas without prior malaria transmission expose more populations to mosquitoes and malaria.

Ultimately the goal of eliminating malaria needs a population based focus. The recent WHO malaria elimination strategic guidance encourages examination of factors in defined population units that influence transmission or control.

Today public health advocates are using the term population health more. The University of Wisconsin Department of Population Health Sciences in its blog explained that “Population health is defined as the health outcomes of a group of individuals, including the distribution of such outcomes within the group.” World Population Day is a good time to consider how the transmission or prevention of malaria, or even neglected tropical diseases, is distributed in our countries, and which groups and communities within that population are most vulnerable.

World Population Day has room to consider many issues related to the health of populations whether it be reproductive health, communicable diseases or chronic diseases as well as the services to address these concerns.

by Brooke Farrenkopf

With the malaria team made up of public health nurses and an infectious disease specialist in Kumasi

I participated in a study on urban distribution of long lasting insecticide treated bednets (LLINs) as part of the USAID/PMI VectorWorks Project of the Johns Hopkins University Center for Communication Programs aided by a JHU Global Health Field Placement Scholarship. I conducted qualitative interviews to support a programmatic study on the challenges associated with mass distributions in urban contexts and helped develop report recommendations for developing the guidelines for future campaigns in urban areas. I am sharing my findings here.

As noted VectorWorks is funded by the US President’s Malaria Initiative and works to improve access to long-lasting insecticide treated nets (LLINs) in 12 countries in Asia and Africa. VectorWorks Ghana, through collaboration with the National Malaria Control Program (NMCP) and partners, supports the following distribution campaigns:

• School-based distribution, occurring every May for grades 2 and 6
• Continuous facility-based distribution at ANC and EPI visits
• Point mass distribution campaigns, occurring every 3 years

In Kumasi, Takoradi, and Tamale, a point mass distribution campaign had already occurred. The campaign in Accra occurred while I was in Ghana, and I was able to visit the distribution sites and the health facilities where a portion of the LLINs were stored. Here, I was able to see some of the logistical challenges associated with the urban context.

I was also able to see the solutions put in place by the local malaria teams. One solution to improve program delivery was the development of a coupon coding system. As each community member attended the distribution site to receive a LLIN, Ghana Health Service (GHS) staff had to match their registration coupon with the coded coupon in the book. The coding system organized the coupons and identified members who had not attended distribution.

Mass distribution campaigns are the most effective method to rapidly increase long-lasting insecticidal net (LLIN) coverage.  Mass distribution in urban areas with characteristically large and heterogeneous populations of high population density comes with higher costs and difficult logistics. Many inhabitants are not indigenous to the area and are of varied religious, occupational, and socioeconomic backgrounds. Urban areas commonly have large mobile working class populations that are difficult to access. These characteristics are unique to urban areas and introduces the need for improved guidelines in urban areas.

VectorWorks Ghana Team

To date, the National malaria Control Program (NMCP) guidelines for point mass distribution in Ghana have made no distinction between urban and rural areas and have therefore not addressed these differences. This study intended to provide information to refine these guidelines.

Most interviews were conducted in hospitals and health facilities where the members of the malaria teams were located. The interviews were conducted in-person in the four largest metropolitan areas in Ghana: Kumasi, Greater Accra, Takoradi, and Tamale. I helped develop and follow a question guide that covered each phase of the distribution focusing on the challenges, solutions, and recommendations associated with each phase of distribution.

Most common challenges with implementation in urban communities:

• Reaching community members during registration
• Completing registration within the period of days provided and the volunteers allocated, because the population was too dense to reach all of the households and many community members were not at home during registration
• Beneficiary dissatisfaction with universal health coverage definition of sufficient LLIN coverage {one net per two people in each household}

Most common recommendations for future distributions:

• Greater inclusion of sub-metro teams in development of the micro plan
• Increase the resources to recruit and remunerate more volunteers and supervisors to enable more distribution sites, help control crowds, and allow fewer days for each phase
• Intensify social mobilization and allow sub-metros to help develop this plan to utilize local resources, especially to improve understanding of universal health coverage definition of one net per two people and to inform about logistics
• Increase the number of registration days
• Conduct a utilization study to understand coverage of LLIN use and barriers to  consistent use.

I was able to speak with public health nurses, malaria experts, and district health directors, and hear their insight on how to improve future campaigns. My favorite anecdotes included examples of how teams developed innovative solutions to improve campaign efficiency or strategically access hard to reach populations.

The observations and recommendations by the respondents themselves should guide future LLIN campaigns in urban settings in Ghana.

References

• VectorWorks (2017) Johns Hopkins center for Communication Programs. http://ccp.jhu.edu/projects/malaria-vector-control/
• de Beyl CZ, Koenker H, Acosta A, Onyefunafoa EO, Adegbe E, McCartney-Melstad A, Killian A (2016) Multi-country comparison of delivery strategues for mass campaigns to achieve universal coverage with insecticide-treated nets: what works best? Malaria Journal, 15(1): 1.
• Stakeholder Review of Experiences in urban Long-Lasting Insecticidal Net (LLIN) campaign distributions (2012). Malaria Consortium Africa.

As the world increasingly urbanizes, we need to address the role of urban ecosystems and the evolution of disease vectors and organisms.  Marina Alberti and colleagues explained that …

“Recent studies show that cities might play a major role in contemporary evolution by accelerating phenotypic changes in wildlife, including animals, plants, fungi, and other organisms. Many studies of ecoevolutionary change have focused on anthropogenic drivers, but none of these studies has specifically examined the role that urbanization plays in ecoevolution or explicitly examined its mechanisms.”

In their own study they looked at “five types of urban disturbances including habitat modifications, biotic interactions, habitat heterogeneity, novel disturbances, and social interactions.” The researchers learned that, “clear urban signal; rates of phenotypic change are greater in urbanizing systems compared with natural and nonurban anthropogenic systems.” They concluded that there is need to continually “uncover insights for maintaining key ecosystem functions upon which the sustainability of human well-being depends.”

Of particular concern in the area of tropical health are the unique urban manifestations of diseases like yellow fever, dengue and malaria. Although Zika virus, for example, was first discovered in forests, it has adapted to an urban cycle involving humans and domestic mosquito vectors in tropical areas where dengue is endemic. Musso and Gubler in their review further explain that although there may be sylvatic cycles of Dengue, “Arboviruses such as DENV have adapted completely to humans and can be maintained in large tropical urban centers in a mosquito-human-mosquito transmission cycle that does not depend on nonhuman reservoirs.”

Weaver et al. note that Zika in spreading to Asia, “emerged on multiple occasions into urban transmission cycles involving Aedes (Stegomyia) spp. Mosquitoes.” In addition it can be hypothesized that phenotypic changes in Asian lineage ZIKV strains made rare disease outcomes such as congenital microcephaly and Guillain-Barré more common and visible.

According to Estelle Martin and co-researchers, “Puerto Rico, a major metropolitan center in the Caribbean, has experienced increasingly larger and clinically more severe epidemics following the introduction of all four dengue serotypes.” They found that Dengue serotype 4 replaced earlier strains and that “this epidemic strain progressed rapidly, suggesting that the epidemic strain was more fit, and that natural selection may have acted on these mutations to drive them to fixation.”

In addition to virus evolution, mosquito changes have been documented by Caroline Louise and colleagues in “One of the world’s largest urban agglomerations infested by Ae. aegypti … the Brazilian megalopolis of Sao Paulo.”  They detected microevolution despite a short observational period and stress the implications of the “rapid evolution and high polymorphism of this mosquito vector on the efficacy of control methods.”

“The adaptation of malaria vectors to urban areas is becoming a serious challenge for malaria control,” is a major concern of Antonio-Nkondjio and co-workers. They found, “rapid evolution of pyrethroid resistance in vector populations from the cities of Douala and Yaoundé,” Members of this team also learned that the M form of Anopheles gambiae predominated in the centre of urban agglomerates in Cameroon. Previously it was known that larval habitats polluted with decaying organic matter as found in densely populated urban agglomerates, were unsuitable for Anopheles gambiae. The recent study showed that the “M form showed greater tolerance to ammonia (arising from organic matter) compared to the S form. This trait may be part of the physiological machinery allowing forest populations of the M form to colonize polluted larval habitats.”

The evolutionary response of vectors and disease organisms to urban environments needs continued monitoring. Urban disease control and elimination efforts must adapt to such adaptations in the disease process.

According to the UN Food and Agriculture Organization (FAO), about six years ago following a global food crisis, a United Nations high-level task force called for a paradigm shift in urban planning, to one that encourages urban and peri-urban food production. By including urban agriculture in urban land use considerations, planners hoped to achieve benefits ranging from improved food security, economic development to greener environments.

FAO recognizes that there are complex political issues involved in meeting the vision of promoting urban agriculture, including basic access to land, water and other resources, before the benefits can be realized. The issue is further complicated by malaria in some urban environments.

Prathiba De Silva and John Marshall observed that, “Malaria transmission in urban and periurban areas is highly focused around vector breeding sites, which tend to be more numerous in areas of lower socioeconomic status. Control strategies should therefore adopt an element of spatial targeting rather than targeting a wide urban area uniformly. Vector breeding sites are common in areas with slum-like conditions and in areas where urban agriculture is practiced.”

In another study Christophe Antonio-Nkondjio and colleagues concluded that, “The data confirm high selection pressure on mosquitoes originating from urban areas and suggest urban agriculture rather than pollution as the major factor driving resistance to insecticide.” Similarly, Seidahmed et al. observed

— Urban gardens along the banks of the Niger River in Bamako, Mali —

different urban agriculture land use patterns between urban and peri-urban areas as well as differences in insecticide resistance.

These studies suggest that urban planners not only need to consider urban agriculture in land use planning but also need a strong working relationship with public health authorities. Both need to work on pesticide use issues. Green cities can be places that help feed their populations, but they can also be places that a strong focus on local land use can be used to prevent malaria.

The Times of India reports that, “Malaria is no longer restricted to just monsoon months as in the past. Spurred on by widespread construction activity and the resulting poor sanitation, the disease has becomes a round-the-year feature in Mumbai, killing less people but afflicting more.”

An increase was noted: “In all, 76,755 contracted the ailment in 2010, 74% more than the 2009’s figure of 44,035,” but with fewer deaths (better case management?), but it is not clear whether these cases were parasitologically diagnosed.

A member of the medical association attributes the increase, especially the off-season rise, to human activity – construction projects. The official stated that, “Construction sites have puddles of water in which mosquitoes breed. Since construction work goes on throughout the year, so does the breeding. This obviously increases the incidence of malaria.”

Worry was also expressed about, “resistance developed by the Anopheles albimanus mosquito that the civic body’s insecticide fumigation has no effect on it.” This has led the city to consider using “bacillus thuringiensis variety israelensis” for control.

Ironically, in pointing out that, “Another reason for the spread of malaria, which is caused by a parasite called plasmodium, during non-monsoon months is that plasmodium can stay in the body for a long period,” the article raises the possibility that the upswing may not be fully due to new transmission.

Aside from these possible limitations on the validity of the data,  the potential for increased transmission is worrisome, especially in a part of the world that has received less (but increasing) attention from the Roll Back Malaria Partnership. The map from the 2008 World Malaria Report shows the extent of the problem in Asia.

India has a double problem with malaria, hosting both P. vivax and P falciparum.  A recently published article reports that while the national control program has introduced artemisinin-based combination therapy for P. falciparum as a first-line treatment, the older drugs, chloroquine (CQ) and Sulphadoxine-Pyrimethamine (SP) are still available. Unfortunately Shrabanee Mullic and colleagues found that, “In Jalpaiguri District the overall failure rate of CQ was 61% and of SP 14%, which was well above the WHO recommended cut-off threshold level (10%) for change of drug policy.”

Other research in India examined vector control with positive effects. “A study was conducted to evaluate the preventive efficacy of insecticide-treated mosquito nets (ITMNs) and mosquito repellent (MR) in a malaria-endemic foothill area of Assam, India, with forest ecosystem.” The researchers found that, “The total vector population in the three intervention sectors decreased significantly compared with that of the non-intervention one.”

Overall, malaria in India is a complex phenomenon with different forms of the parasite, different ecological settings and different levels of government involved. More attention is needed to address this complex situation is malaria is ever to be eliminated.

Africa is one of the fastest urbanizing regions of the world. Estimates are that nearly 40% of Africans live in urban areas today. This number is expected to exceed 50% by 2030. UN Habitat reports in State of the World’s Cities that African urbanization is often focused on the major cities like the capital, with major slum development, not a place where anopheles mosquitoes are comfortable.

Studies have shown that malaria is not generally an urban disease because dense, congested and dirty urban settings do not favor the breeding of anopheles mosquitoes. When malaria occurs in urban areas, it is often found in very focal transmission sites, for example, in places where urban agriculture is practiced.

Luanda in Angola presents a good example of the urban phenomenon as seen in the chart.  Although much of the surrounding country to the north and east are highly endemic areas, Luanda itself was found to have a prevalence of only 3.5%.  There are variations as expected with the somewhat less dense suburbs having greater, but still not high levels of prevalence.

What is important is that this city contains up to half of the country’s 16+ million inhabitants and is growing. Ironically, while prevalence is low, national strategy documents cite malaria as a cause of nearly one-quarter of child deaths in Luanda.  Clearly there are diagnostic challenges.

Unfortunately the absence of malaria in urban areas does not preclude spending money on malaria treatment, as was documented in Nairobi. We documented a similar challenge in Lagos, Nigeria where prevalence among children aged 1-6 years was only 0.9%, but community members had spent thousands of dollars in preceding weeks on antimalarial medicines to treat fevers that they suspected as being malaria.

Moving forward toward malaria elimination will require countries to account for increasing urbanization.  Increased use of diagnostic tools will be required to ensure appropriate and targeted use of anti-malarial drugs.  Vector control activities will need to be strategic and focus specifically on anopheles’ verified breeding sites.

While increasing urbanization may result in proportionately fewer people at risk from malaria, population growth generally will unfortunately guarantee that large rural populations remain at risk.  National malaria strategies need to take these varying ecologies into account if they are going to eliminate malaria.