Tropical Health Matters

The World Health Organization has prepared an important document entitled “Health is the Argument for Climate Action: COP29Health is the Argument for Climate Action: COP29 Special Report on Climate Change and Health”. Malaria and other vector borne diseases are highlighted.

The report addresses diseases carried by mosquitoes by stating that, “Climate change increases the transmission of deadly infectious diseases such as dengue, malaria, West Nile virus” and others which are temperature and rainfall dependent. In particular, malaria transmission is intricately connected with temperature and rainfall patterns, and extreme weather events have been shown to cause rapid spikes in cases.”

Climate change not only effects environmentsClimate change not only effects environments where these diseases thrive, but impacts the livelihoods of populations, reducing their ability to pay for prevention and treatment. Migration and displacement also may result increasing vulnerability to disease.

Two of the report’s recommendations have special bearing on malaria. One is the need to “develop and implement innovative financing mechanisms, such as a global health insurance scheme for climate-vulnerable nations” and communities. A second is the importance of “Strengthen(ing) health surveillance systems, particularly in low-income countries, to better track and respond to climate-related health impacts.”

Recognizing the climate dependence of malaria will be a crucial step in eliminating the disease.

The 2024 World Malaria Day Theme of “Gender, Health Equity, and Human Rights” cannot be divorced from the inequities of climate change wherein the countries that contribute the least to the problem suffer the most, including the deleterious effects of changing malaria geographics. The current severe drought in Zambia, Zimbabwe, and Malawi is a case in point.

As a recent headline in VOA news states, “UN officials in Zambia to assess worst drought in 20 years.” The government has declared a drought officially where it “has affected a total of 8 provinces across the country with highest impacts in Southern, Central, Eastern, North-western, Western, and Lusaka Provinces.”

Drought should not be confused with a “normal” dry season. What we are seeing in Southern Africa now is an extended dry period in what should have been the rainy season. A study in Mali suggests that adult malaria-carrying mosquitoes “have endured the dry season by aestivating—the hot-weather equivalent of hibernating.” Unfortunately, an extended dry period of a drought may be more difficult to endure for the adults, but possibly the eggs are more resistant. Additional studies paint a more complicated picture.

Weather cycles intensify with climate change. El Niño, which can lead to droughts also produces warming in higher elevations so there tends to be an increase in malaria transmission in areas in the highlands.

Research in Zambia published just two years ago reported increasing trends of malaria in areas covering over 47% of all health facilities, while a declining trend was seen in areas covering 27% of health facilities. The decreasing trend was noticeable in the south, where malaria risk is lowest, and current drought conditions higher. The authors stress the need for continued geographic surveillance and implementation of control strategies geared to the conditions in each area.

A systematic review of the effects of climate change identified “vector borne disease (including malaria, dengue and West Nile Virus)” as a major concern as well as “nutrition-related effects (including general malnutrition and mortality, micronutrient malnutrition, and anti-nutrient consumption),” which compromises the ability of children to fight disease. The review found different impacts of drought ranging from increase mortality a year after a drought, to the disappearance of some vector species. The lesson is that each country needs to monitor their situation carefully. For Zambia, UNICEF reports that, “significant number are children, at risk of food insecurity, acute malnutrition, and disease.”

Research on drought effects on malaria arose from a study that examined the effects of drought on malaria infection (genetic) complexity and transmission in lizards (Plasmodium mexicanum and Sceloporus occidentalis). The authors noted that, “relationship between rainfall and parasite prevalence is somewhat more ambiguous.” Thus, the authors recommended that more information is needed about human malaria parasites and drought since “drought may cause shifts in human disease outcomes independent of any changes to prevalence.”

The United Nations challenges us by observing that, “Due to the complex relationship between malaria and climate change, gaps in knowledge still exist in the mechanisms of the linkage.” Changes in temperature, rainfall, and humidity need to be monitored for effects on vectors, parasites, and human movement. The current situation requires a more nuanced and complex approach to interventions if malaria elimination can be achieved while also preventing gender discrimination, promoting health equity and preserving human rights.

A new study from Kenya addresses one of the major challenges to malaria elimination. The authors note changing vector behaviour towards early morning biting has been established. Children are observed to come to school early, as do mosquitoes that have “peak landing between 06:00 and 07:00.” They also found that mosquitoes continue their activity until 11:00. The An. funestus mosquitoes they collected “were either fed or gravid, potentially indicative of multiple bloodmeals within each gonotrophic cycle, and had a sporozoite rate of 2.05%.” this is of particular concern because school aged children are not always prioritized in various malaria control interventions.

In Cambodia researchers found that “20% of collected Anopheles were active during the day, with increased day biting during the dry season.” Ellie Sherrard-Smith and colleagues explain that bednets and indoor residual spray are intended to work best when people are indoors and sleeping. They caution that, “Mosquito bites taken outside of these times contribute to residual transmission which determines the maximum effectiveness of current malaria prevention.” Their review documented that on average 21% of mosquito bites in Africa take place outside bedtime.

A study in Tanzania by Nicodem J Govella et al. noted that the use of insecticide-treated nets for malaria control has been associated with shifts in mosquito vector feeding behaviour including earlier and outdoor biting on humans. They concluded that efforts highlighting the need for control methods that target early and outdoor biting mosquitoes are now required.

In short, various changing factors ranging from climate and mosquito genetics to even the existing interventions like bednets that we use to control the biting of malaria carrying mosquitoes, threaten our ability to eliminate malaria. New vector control measures are urgently needed as is expansion of other interventions like malaria vaccines.

The United States has been assisting in the fight against malaria and tropical diseases throughout the tropics. The question now arises is it ready to tackle these diseases on the home front?

In recent months CBS News reported that “Malaria cases in Florida and Texas are first locally acquired infections in U.S. in 20 years,” according to CDC. Local transmission of these 8 cases is the key concern because there are always imported cases from travelers to malaria endemic areas throughout the year. This has led to better planning of mosquito control activities. All of the Florida cases were found in Sarasota County. Although Anopheles mosquitoes still existed in the environment, they had not been infected in recent years.

Likewise Pensacola News Journal noted that, “Rising evidence is pointing to the possibility that leprosy has become endemic in the southeastern U.S. with Florida being named among the top reported states.” The paper explains that these Leprosy cases in central Florida account for nearly 20% of the national total, and that the state is considering instituting contact tracing.

Chagas disease may affect up to 300,000 people from Florida across to California, but an Emerging Pathogens Institute report shared in the Apopka Voice, explained that most cases remain undetected. While Chagas primarily affects people who have immigrated from Latin America, researchers are discovering locally acquired cases because the vector, the kissing bug, has been found in 29 states, and thus local transmission now occurs.

An article in PLoS NTDs explains that Zika, Dengue, and Chikungunya viruses are spread in the southern and Gulf Coast states by members of the Aedes mosquito family, aided by changes in weather and climate patterns. Just as in other countries where NTDs are endemic, the US experience of these diseases also sees that, “poverty equates to substandard housing that exposes residents to insect vectors, a lack of access to sanitation and water, and degraded environments.”

Local, State and National health agencies in the US are starting to awaken to the fact that diseases which we thought were eliminated back in the mid-19^th-century are making a comeback. At a minimum, funding and training are needed to equip our Health Departments with environmentally appropriate vector control measures, appropriate treatment regimens, and disease surveillance tools to tackle the same problems that are threatening the lives of people throughout low- and middle-income countries throughout the world.

In the past week, news has featured challenges to malaria elimination around the globe. Starting in Papua New Guinea which accounted for accounted for 86% of all cases in the Western Pacific Region in 2020. While there are 39% fewer cases in the region since 2000, there was an increase of 300,000 cases between 2019 and 2020. It is mainly in the six countries of the Greater Mekong subregion where progress has been steady.

Moving east to the Brazilian Amazon, one finds wildcat gold mining operations are not only destroying Native American ecosystems but are carving huge holes in the earth which are perfect breeding conditions for mosquitoes. This means that malaria cases among the Yanomami indigenous people living in the Brazilian Amazon have increased by more than 12 times since 2014.

Also within South America, one finds that although Paraguay was certified by the World Health Organization (WHO) as free of local transmission of malaria in 2018, experts are warning that travelers entering the country from areas with malaria transmission could easily reintroduce the disease. Hence vigilance is urged.

Crossing next to sub-Saharan Africa, one reads of studies showing an increasing link between malaria and agriculture across the region. As population expands in the region, more food, water and agricultural commodities are required. Irrigation and deforestation to clear land for agriculture increase the risk of childhood malaria in sub-Saharan Africa. The experts recommend that African ministries of agriculture, health, and environment need to collaborate on safer development policies and practices, not only to curb malaria, but the devastating effects of climate change.

Finally continuing back to Asia, one finds what might be termed an epidemiological conflict between Nepal, which is nearing malaria elimination for 2025, and its southern neighbor India, which is a source of imported malaria. Although the number of indigenous cases is nearing zero, health authorities fear that imported cases of of malaria from India are so high that local transmission could be reignited.

Malaria is clearly a global health problem. Collaboration and coordination across continents is needed to eliminate the scourge.

The Lancet has published the 2021 update of the important climate countdown series in time for the upcoming UN Framework Convention on Climate Change 26th Conference of the Parties (COP26) in Glasgow. Interestingly in that 44-page Lancet climate paper malaria is mentioned several times, but basically the same example of increased months of transmission in highland areas repeated. Specifically…

“The number of months with environmentally suitable conditions for the transmission of malaria (Plasmodium falciparum) rose by 39% from 1950–59 to 2010–19 in densely populated highland areas in the low HDI group, threatening highly disadvantaged populations who were comparatively safer from this disease than those in the lowland areas (indicator 1.3.1).”

Hopefully the malaria community will use the other information in the report to explore and document additional malaria-climate issues including…

• Desertification reducing mosquito habitats
• Climate heightened conflicts putting more people at risk of malaria
• Translating economic losses into difficulty paying for health systems to support malaria programs
• Increased zoonotic transmission of malaria (e.g. knowlesi) threatening elimination
• Rising sea levels affecting mosquito habitats

Malaria is an ideal exemplar condition to demonstrate the effects of climate change by having definitive effects on the host, the vector and the parasite. These issues need immediate attention if malaria elimination targets are to be maintained and achieved.

Today’s news and abstracts look at a variety of issues ranging from overall malaria funding funding needs to the effect of climate change on different types of mosquitoes and the diseases they carry (e.g. malaria vs dengue). We also examine the need for surveillance among nomadic groups and the use of cell phones in a saliva based malaria testing system. Please click the links below to read more on each subject.

Rwanda: Government Needs U.S.$70 Million to Fill Malaria Financing Gap

By Nasra Bishumba: The Government needs $73 million to bridge the funding in the funds needed to fight malaria between 2020 and 2024, The New Times can reveal. The Rwanda National Strategic Plan 2020-2024 to fight malaria drawn up in June this year indicates that although the implementation requires Rwf295bn ($280 million), the government already has funding commitment to the tune of $206.8m (equivalent to 74 per cent).

According to the strategic plan, a copy of which The New Times has seen, this leaves a gap of $73m which it hopes to mobilize from different sources. With these funds, the government is seeking to protect at least 85 per cent of the population with preventive interventions and to work towards promptly testing and treating suspected malaria cases by 2024. To achieve this, the biggest chunk of the funds will be invested in malaria prevention to a tune of $186m, an equivalent of 66 per cent of the entire budget.

Climate Change May Shift Risks of Mosquito-borne Diseases

By Asher Jones: More dengue, less malaria. That may be the future in parts of Africa on a warming planet, depending on where you live. New research says it’s all about which mosquitoes will thrive. And the methods to control one don’t necessarily work on the other.

The mosquito that spreads malaria prefers relatively cool temperatures of 25 degrees Celsius (77 degrees Fahrenheit). The dengue mosquito does best at 29 degrees Celsius (84.2 degrees Fahrenheit). Because of this difference in optimal temperatures, “We would actually predict that climate change might have opposing effects [on disease transmission],” said Erin Mordecai, assistant professor of biology at Stanford University and lead author on the study. “Climate change might make it less suitable for malaria to be transmitted but more suitable for dengue to be transmitted.”

Africa’s Nomadic Pastoralists and Their Animals Are an Invisible Frontier in Pandemic Surveillance

@ASTMH The effects of COVID-19 have gone undocumented in nomadic pastoralist communities across Africa, which are largely invisible to health surveillance systems despite the fact that they are of key significance in the setting of emerging infectious disease. We expose these landscapes as a “blind spot” in global health surveillance, elaborate on the ways in which current health surveillance infrastructure is ill-equipped to capture pastoralist populations and the animals with which they coexist, and highlight the consequential risks of inadequate surveillance among pastoralists and their livestock to global health. As a platform for further dialogue, we present concrete solutions to address this gap.

Mobile phone-based saliva test wins NIH prize

Cornell researchers’ concept for a quick, non-invasive, mobile phone-based system to detect infectious diseases, inflammation and nutritional deficiencies in saliva was awarded a $100,000 National Institutes of Health Technology Accelerator Challenge prize. The NIH’s prize challenge encourages the development of new, non-invasive diagnostic technologies important for global health. For the group’s saliva-based test, a small 3D-printed adapter is clipped to a mobile phone and synced with a mobile app. The app uses the phone’s camera to image test strips to detect malaria, iron deficiency and inflammation, with results in under 15 minutes.

The proposal builds on the FeverPhone and NutriPhone platforms developed by the team at Cornell’s Institute for Nutritional Sciences, Global Health and Technology (INSiGHT). The technologies, funded by the NIH and the National Science Foundation, evaluate infections and nutritional status using blood. According to Mehta, technologies using salivary biomarkers could revolutionize how conditions such as malaria and iron deficiency are identified and addressed, especially in settings where access to primary health care and traditional, laboratory-based tests is limited.

Monsoon infections: How to tell the difference between dengue and malaria? Watch out for these symptoms

While both diseases are mosquito-borne and cause similar symptoms such as fever, joint/muscle pain, headaches, and fatigue, some differences between their symptoms can help you identify the specific infections. Unique symptoms of Malaria: Stomach problems such as vomiting, Diarrhoea, Dry cough, Shivering, Spleen enlargement Unique symptoms of Dengue: Pain behind the eyes, Swollen glands, Rashes

We are sharing more updates from newsletters and journal abstracts found online. Issues include mapping malaria in connection with climate change, COVID-19 possibly inhibiting reporting o malaria cases, co-infection with coronavirus and malaria or dengue, Plasmodium knowlesi in northern India, and the effect of sanitation campaigns on infectious diseases. Click on links to read details.

Malaria kills 400,000 people a year, A new map shows where climate change will make it worse

A new study examines the impact of climate change on malaria in Africa. The maps reveal which areas will become more – or less – climatically suitable. Of an estimated 228 million cases of malaria worldwide each year, around 93% are in Africa. This proportion is more or less the same for the 405,000 malaria deaths globally.

That’s why there are huge efforts underway to provide detailed maps of current malaria cases in Africa, and to predict which areas will become more susceptible in future, since such maps are vital to control and treat transmission. Mosquito populations can respond quickly to climate change, so it is also important to understand what global warming means for malaria risk across the continent.

If it is too warm or too cold, then either the malaria parasite or the mosquito that transmits the parasite between humans will not survive. This suitable temperature range is relatively well established by field and laboratory studies and forms the basis for current projections of the impact of climate change on malaria. Yet, surface water is equally crucial as it provides habitat for the mosquitoes to lay their eggs. See original article in Nature Communications.

Malaria Situation in the Peruvian Amazon during the COVID-19 Pandemic

Malaria Situation in the Peruvian Amazon during the COVID-19 Pandemic. This article was originally published in Am J Trop Med Hyg. (2020 Sep 3. doi: 10.4269/ajtmh.20-0889). Online ahead of print. The Peruvian Ministry of Health reports a near absence of malaria cases in the Amazon region during the COVID-19 pandemic.

However, the rapid increase in SARS-CoV-2 infections has overwhelmed the Peruvian health system, leading to national panic and closure of public medical facilities, casting doubt on how accurately malaria cases’ numbers reflect reality. In the Amazon region of Loreto, where malaria cases are concentrated, COVID-19 has led to near-complete closure of the primary healthcare system, and diagnosis and treatment of acute febrile illnesses, including malaria, has plummeted. Here, we describe the potential association of COVID-19 with a markedly reduced number of reported malaria cases due to the reduced control activities carried out by the Peruvian Malaria Zero Program, which could lead to malaria resurgence and an excess of morbidity and mortality.

Dengue, malaria a new threat for Covid patients

Doctors in at least two Delhi hospitals have reported patients with twin infections of Covid-19 and dengue or malaria, a trend that could become worrying since the double disease may be deadlier, and the region is entering its most critical season for mosquito-transmitted diseases. The anecdotal reports tie in with latest findings that suggest a high prevalence of co-infections of diseases such as malaria, dengue and leptospirosis, which together have several symptoms that overlap with a symptomatic Covid-19 illness. Andhra villages see big drop in dengue, malaria, typhoid cases after pilot sanitation drive. Andhra govt data shows cases of seasonal diseases like dengue, typhoid, acute diarrhoea & malaria fell 97.4%, 96%, 81.7% and 50.4%, respectively, after the sanitation drive.

Now, months after the launch of the drive called ‘Manam Mana Parishubhratha’ (Our Cleanliness and Us), these villages have recorded a massive drop in the numbers of patients reporting with seasonal diseases like dengue, typhoid, malaria and acute diarrhoea. a 50.4% decrease in malaria cases (601), said the data.

AIIMS study finds zoonotic malarial parasite in acute febrile illnesses patients.

A zoonotic disease is a disease that can be spread/jump from animals to humans and vice versa. AIIMS researchers have sounded a note of caution after finding the presence of monkey malarial parasite ‘Plasmodium knowlesi’ in the north Indian population while doing a study on patients with acute febrile illnesses (AFI) and pathogens causing them.

The presence of the zoonotically transmitted malaria parasite was found during the study of acute febrile illnesses and causative pathogens in certain patients admitted in AIIMS from July 2017 to September 2018. The All Indian Institute of Medical Sciences (AIIMS) researchers from the Department of Biochemistry, along with clinicians from the Department of Medicine, were involved in the study on the pathogens causing severe fever.

From time-to-time we will feature a collection of news and abstracts available “today.” Here are five stories available on 31st August 2020.

Med-tech on a leash: The many diseases that can be detected by dogs

Malaria, a parasitic disease, which is transmitted to humans by Anopheles mosquitoes, can also be detected by our canine friends. In 2019, English researchers presented the results of a study conducted in The Gambia, which involved training dogs with socks that had been worn by children infected with malaria, who otherwise had no symptoms.
The experiment proved to be so successful that researchers are now planning on using this method to test for asymptomatic cases of the disease….

New Malaria Transmission Patterns Emerge In Africa.

An international study reveals how future climate change could affect malaria transmission in Africa over the next century. Malaria is a climate sensitive disease; it thrives where it is warm and wet enough to provide surface water suitable for breeding by the mosquitoes that transmit it. For more than two decades now, scientists have suggested that climate change may alter the distribution and length of transmission seasons due to new patterns of temperature and rainfall. The burden of this disease falls primarily on Africa. In 2018, out of an estimated 228 million cases of malaria worldwide, 93% were in the African continent.
Detailed mapping of malaria transmission is vital for the distribution of public health resources and targeted control measures.

In the past, rainfall and temperature observations have been used in malaria climatic suitability models to estimate the distribution and duration of annual transmission, including future projections. But factors affecting how rainfall results in water for mosquito breeding are highly complex, for example how it is absorbed into soil and vegetation, as well as rates of runoff and evaporation. A new study, led by the Universities of Leeds and Lincoln in the UK, for the first time combined a malaria climatic suitability model with a continental-scale hydrological model that represents real-world processes of evaporation, infiltration and flow through rivers. This process-focused approach gives a more in-depth picture of malaria-friendly conditions across Africa….

Covid has spelt a lockdown for routine health services in India

Official data are now available to show the extent to which routine health services in India were unavailable and the scale of its impact. The number of fully immunised children fell by over 15 lakh in the three-month period from April to June compared to the same months last year. The number of institutional deliveries fell by about 13 lakh. The registered number of TB patients undergoing treatment fell to almost half of what it was last year. People seeking cancer treatment as outpatients fell by over 70%. Hard-won progress on several national health goals, including the programme to bring down infant and maternal mortality or those to treat TB, malaria and non-communicable diseases such as heart diseases, diabetes and cancer,

Insecticide resistance in indoor and outdoor-resting Anopheles gambiae in Northern Ghana

The overall results did not establish that there was a significant preference of resistant malaria vectors to solely rest indoors or outdoors, but varied depending on the resistant alleles present. Phenotypic resistance was higher in indoor than outdoor-resting mosquitoes, but genotypic and metabolic resistance levels were higher in outdoor than the indoor populations. Continued monitoring of changes in resting behaviour within An. gambiae s.l. populations is recommended.

Highlighting the burden of malarial infection and disease in the neonatal period: making sense of different concepts

Review of neonates from 14 malaria-endemic countries found pooled prevalence in this specific age group. Importantly, their results suggest a prevalence of congenital malaria of 40.4/1000, and a prevalence of neonatal malaria of 12/1000, Interestingly, the authors also confirmed congenital malaria to be more frequent in settings with unstable malaria transmission, a finding in line with the hypothesis of the importance of the immunity background in the risk of congenital malaria.

A flooded street in Santa Clara de Nanay, April 2, 2012 (courtesy of Asociación Benéfica Prisma)

Josh Colston of the Division of Infectious Diseases and International Health, University of Virginia School of Medicine, Charlottesville, presented his findings on the connection between floods and enteric pathogens in Peru at the 2019 meeting of the American Society of Tropical Medicine and Hygiene. Below he has shared us with a summary of his work and findings. A link to the recently published work is also provided.

Climate change represents an impending global public health threat since extreme weather events like floods can cause injury and drowning, toxic exposure, and the spread of infectious diseases. Poor people living in unplanned settlements with inadequate infrastructure are most vulnerable to these impacts. Outbreaks of gastroenteritis often occur following floods and can be particularly serious for young children. But there are many different bugs that can cause this illness and it’s not yet known which of them are most prone to contaminating floodwater. However, a newly published paper in the International Journal of Environmental Research and Public Health may shed some light thanks to a small piece of serendipity in an otherwise devastating natural disaster.

Location of the study site

The 2010-2012 La Niña event (the colder counterpart of El Niño) caused huge disruption to weather patterns over several continents. The Amazonian region of Peru around the city of Iquitos was particularly badly hit by heavy rains. It’s a low-lying area particularly prone to flooding since it’s situated at the confluence of several Amazon tributaries. Waterways are the main transport routes in the region, so most of the population lives close to the banks of the rivers. Following months of heavy rainfall in late 2011 and early 2012, three of the rivers – the Ucayali, Marañón, and Nanay – burst their banks, causing widespread flooding and forcing many locals to abandon their homes and evacuate to drier areas. By the end of the disaster, an estimated 50,000 people had been made homeless.

It just so happened that, in a quiet fishing town on the outskirts of Iquitos called Santa Clara de Nanay, an epidemiologic surveillance study was being carried out. Around 300 babies had been recruited and field workers were taking regular measurements and biological samples to see how they were growing and what bugs they were catching. Using a special epidemiologic method known as ‘causal inference’ researchers were able to compare the samples of the infants’ poop before, during and after the flood to see how the rates of infection changed.

Estimated prevalence rates of four viruses and three bacteria before, during and after the flood

Interestingly, two viruses showed substantial upticks during the flood. Rates of rotavirus were 5 times, and sapovirus 2.5 times the normal level for that time of year. What’s more, the rotavirus cases seemed to be caused by unusual virus strains that were not common in the area and which are less preventable by vaccine. Meanwhile, three bacteria – Campylobacter, Shigella and a type of E. coli called ST-ETEC – showed smaller increases. It’s common to catch Campylobacter from poultry and, since a lot of households in Santa Clara keep chickens in their yards, it’s possible that the mini-outbreak was cause by floodwater washing chicken droppings out of the coops and into the wider environment.

What’s clear from this and other recent studies, is that we need to start thinking bigger when it comes to drainage and sanitation solutions. Traditional low-cost, household-level improvements to water sources and sanitation facilities may not be up to the task in the face of climate events that may suddenly and unexpectedly expose entire communities to large amounts of untreated sewage. Investments in more ambitious, municipal-level water, wastewater, and drainage infrastructure – the kind that historically brought about massive, society-wide child health improvements in high income countries – may be the only sure route to climate resilience.