Tropical Health Matters

On August 18, 2024 Aprotim Cory Bhowmik posted this entry on Dengue in the class blog of the course, Social and Behavioral Foundations of Primary Health Care at the Johns Hopkins Bloomberg School of Public Health

Dengue is an illness that we are not too familiar with in the United States, but it can have severe and sometimes deadly effects, including fever, fatigue, body aches, lymphadenopathy, and an increased chance of bleeding. This disease is spread by the Dengue virus, which is carried by the Aedes aegypti mosquito. West Bengal, a state in India, has become infamous for being a hub of Dengue infection. In 2022, with a population of over 100 million people, West Bengal had over 60,000 cases and 30 deaths.

Photo: A clinic with patients being treated for Dengue infection. (Romita Datta, India Today)

Since insect-borne diseases such as malaria are also common in this region, the people have thorough knowledge of how Dengue is spread and how mosquito nets and insect spray can be effective. Despite the daily use of these measures, however, Dengue continues to have a strong hold on the community due to (1) the presence of bodies of water that attract mosquitoes and (2) the presence of unsanitary sites (e.g., trash accumulation).

So, what can be done? The resolution would require steps to eliminate unwanted bodies of water and reduce sites of trash accumulation. Some government departments have addressed these issues:

• Department of Panchayats and Rural Development: surveys 300 households per week on cleanliness for Dengue prevention
• Department of Environment: has projects on pollution, coastal management, and biodiversity–but not Dengue prevention
• Urban Affairs and Municipal Affairs Department: surveys households regularly
• Department of Health: discusses treatment, but not prevention, of Dengue infection

However, these departments have either (1) nonspecific descriptions of their actions to decrease Dengue infection or (2) have no results documented. In order to decrease the incidence of Dengue, it would be prudent to press the most active department — Panchayats and Rural Development– on the results of their surveys and whether cleanliness has actually improved.

Irrespective of these results, there has been no data showing a decrease in Dengue infection in West Bengal as a whole. A reasonable proposal would be to incentivize the cleaning of unsanitary sites and inappropriate bodies of water by giving tax cuts to those that comply and/or levying fines for non-adherence. This reward system is common in many parts of the world, and unless concrete steps like incentivization are taken, Dengue infections will not decrease anytime soon.

Edwin Chng has contributed this posting to the Blog site for the JHU site for the course Social and Behavioral Foundations of Primary Health Care.

Dengue has been endemic in Singapore for many decades, with all four dengue serotypes (DENV-1-4) in active circulation. It presents a significant impact on the economy, with the financial burden of dengue estimated to be US$1.04 billion from 2010 to 2020. (Mosquito Photo credit: http://bitly.ws/twG2)

Despite aggressive conventional vector control measures such as fogging and breeding site elimination, Singapore continues to have persistent outbreaks annually. The number of cases in recent years have also surged. From January to July 2022, 9 deaths and 22,468 cases have been reported thus far – the latter number is more than 4 times the number of cases reported in the whole of 2021. Dengue cases is likely to continue to increase, as the traditional peak dengue season in the country is from June to October each year. (Dengue Cases Graph Photo credit: NEA)

Singapore’s dengue crisis can be attributed to climate change and a recent change in the prevailing serotype. In the past, the dominant strains in Singapore were DENV-1 and DENV-2, hence the Singapore population has lower immunity to the other two strains. As a result, a large proportion of the population remains susceptible to DENV-3, which is emerging as the dominant strain in Singapore.

As such, as per the World Health Organization, dengue vaccination remains an integral part of dengue prevention and control strategy. The vaccine has an efficacy of about 80% against the outcomes of infection, hospitalization and severe infection which is potentially lethal. Unfortunately, the Singapore government has decided not to include it in the national immunization program, hence it is not eligible for government subsidy. As a result, the vaccine which costs a hefty USD450 remains inaccessible to the average Singaporean. (Vaccine Photo credit: http://bitly.ws/twGk).

Various stakeholders including the National Center for Infectious Diseases, primary care physicians and pharmaceutical companies can rally and work together in awareness campaigns and clinical studies. Health economics data from such collaborations can confirm the cost-effectiveness of dengue vaccines and positively influence the government to consider a change in its existing policy to provide subsidies. Increasing its accessibility and affordability to more Singaporeans will definitely contribute significantly to the fight against dengue in Singapore.

Today the issue of water is important for malaria mosquito propagation, both in irrigation and flooding. Artificial skin enables testing of mosquito biting. Fake medicines for malaria and other conditions threaten Africa’s health. Archived RDTs can aid surveillance. Finally there is concern for co-infection with both malaria and dengue leading to severe disease. Follow links below to read details.

Impact of sugarcane irrigation on malaria vector Anopheles mosquito fauna, abundance and seasonality in Arjo-Didessa, Ethiopia

Despite extensive irrigation development in Ethiopia, limited studies assessed the impact of irrigation on malaria vector mosquito composition, abundance and seasonality. This study aimed to evaluate the impact of sugarcane irrigation on species composition, abundance and seasonality of malaria vectors. Adult Anopheles mosquitoes were collected using CDC light traps from three irrigated and three non-irrigated clusters in and around Arjo-Didessa sugarcane irrigation scheme in southwestern Ethiopia.

Overall, 2108 female Anopheles mosquitoes comprising of six species were collected. The ongoing sugarcane irrigation activities in Arjo-Didessa created conditions suitable for malaria transmitting Anopheles species diversity and abundance. This could drive malaria transmission in Arjo-Didessa and its environs in both dry and wet seasons. Currently practiced malaria vector interventions need to be strengthened by including larval source management to reduce vector abundance in the irrigated areas.

Prevalence of and risk factors for severe malaria caused by Plasmodium and dengue virus co-infection

A systematic review and meta-analysis examined co-infection with both Plasmodium and dengue virus (DENV) infectious species could have serious and fatal outcomes if left undiagnosed and without timely treatment. The present study aimed to determine the pooled prevalence estimate of severe malaria among patients with co-infection, the risk of severe diseases due to co-infection, and to describe the complications of severe malaria and severe dengue among patients with co-infection. Relevant studies published between databases between 12 September 1970 and 22 May 2020 were identified and retrieved.

The present study found that there was a high prevalence of severe malaria among patients with Plasmodium and DENV co-infection. Physicians in endemic areas where these two diseases overlap should recognize that patients with this co-infection can develop either severe malaria or severe dengue with bleeding complications, but a greater risk of developing severe dengue than severe malaria was noted in patients with this co-infection.

South Sudan: Flooding deepens a humanitarian crisis in Pibor area

Today, however, the Pibor River has swelled to make parts of the town inaccessible and is threatening the clinic. Many neighborhoods cannot be reached by foot, and a local ferry is too expensive for many who live in the area. A mobile MSF team is providing medical care in hard-to-reach areas. “Our focus is now on malaria, measles and flooding,” said Josh Rosenstein, MSF deputy head of mission. “Today we are reaching out to the community through our daily mobile clinics, treating the most severe illnesses. We’re also implementing our flood contingency plan, which includes building additional flood defenses around the clinic to ensure we can continue to provide medical services, as the water level is rising at an alarming speed.”

Stratifying malaria receptivity in Bangladesh using archived rapid diagnostic tests

Surveillance of low-density infections and of exposure to vectors is crucial to understand where malaria elimination might be feasible, and where the risk of outbreaks is high. Archived rapid diagnostic tests (RDTs), used by national malaria control and elimination programs for clinical diagnosis, present a valuable, yet rarely used resource for in-depth studies on malaria epidemiology. 1022 RDTs from two sub-Districts in Bangladesh (Alikadam and Kamalganj) were screened by qPCR for low-density Plasmodium falciparum and Plasmodium vivax infections, and by ELISA for Anopheles salivary gland antibodies as a marker for exposure to vectors.

Concordance between RDT and qPCR was moderate. qPCR detected 31/1022 infections compared to 36/1022 diagnosed by RDT. Exposure to Anopheles was significantly higher in Kamalganj despite low transmission, which could be explained by low bed net use. Archived RDTs present a valuable source of antibodies for serological studies on exposure to vectors. In contrast, the benefit of screening archived RDTs to obtain a better estimate of clinical case numbers is moderate. Kamalganj could be prone to outbreaks.

New tool mimics human skin to allow detailed study of mosquito biting

eLife: Researchers develop a human skin mimic to study mosquito biting in high resolution without using humans as ‘bait.’ The tool, which uses an artificial blood meal and a surface that mimics human skin, will provide detailed understanding of blood feeding without using human subjects as bait. It can also fit conveniently into a backpack, allowing the study of mosquitoes in laboratory and natural environments.

Blood feeding is essential for mosquitoes to reproduce, but it is during blood feeds on human hosts that they pass on pathogens such as malaria. It consists of a bite ‘substrate’ – a transparent, temperature-controlled surface that mimics body temperature to attract mosquitoes. An artificial meal is applied on top of this and covered with a commonly used membrane that mosquitoes can pierce. The meal resembles blood, allowing mosquitoes to engorge and increase their weight by two to threefold. This bite substrate is then placed in a transparent cage, and an external camera records the mosquitoes’ behaviour. The team tested biteOscope with four medically important species of mosquito.

Counterfeiting of Fake Drugs in Africa: current situation, causes and countermeasures

The more desirable a product is the higher the tendency to replicate it and meet that parcel of consumers that want to join the trend but cannot pay the price. Profit is one of the many reasons that make counterfeit an attractive business for many.  Africa, unfortunately but not surprisingly, is one of the most affected continents, comprehensible since its markets have become a huge target for second generation goods, with a major focus on pharmaceutical drugs.

The World Health Organization (hereinafter, WHO) stated that 42% of all fake medicine reported to them between the years of 2013 and 2017 was linked to the African continent and we expect that these numbers fall short of reality. Africa is seriously affected by it and one clear example is the anti-malarial medication. Anti-malarials and antibiotics are amongst the most commonly reported as fake or substandard medical products.

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.

Various updates were found in newsletters and journal abstracts online today. These looked at mosquitoes – what attracts them to people, how ookinetes move in the midgut, and how perlite from volcanic rock may be a barrier repellent. Nigeria reports that there is no ACT resistance – so far.  And malaria partners join to coordinate actions in Uganda.  Click on links to read details.

Nigeria yet to detect resistance of malaria parasite to ACTs, says ministe

Contrary to reports that Africa has for the first time identified resistance strain of the malaria parasite to the drug of choice, Artemisinin Combination Therapy (ACT), the Minister of Health, Dr. Osagie Emmanuel Ehanire, on Monday said a study conducted in three states of the country showed there is no such phenomenon in Nigeria.  “However, we are still monitoring the situation. We insist that people should conduct a malaria test before using the drug of choice. This we hope will help prevent any kind of resistance of the malaria parasite to ACTs.”

Ministry of Health launches the Malaria Free Uganda Fund

Health Minister Dr Jane Ruth Aceng told journalists in Kampala today that the idea of having this new board was reached after realizing that different entities have been conducting the same malaria control related work. She said that the ministry resolved that mainstreaming responsibility will remove financial and operational bottlenecks that deter them from achieving set targets for elimination of the disease. The fund with a board of 11 members is chaired by Kenneth Wycliffe Mugisha of the Rotarian Malaria Partners-Uganda.

Volcanic Rock Yields a New Kind of Insecticide for Mosquitoes

Insecticide resistance to pesticides has become widespread in mosquito populations, making insecticides less effective over time. Therefore, there is an urgent need for insecticides with alternative modes of action. tested a material derived from volcanic rock, perlite, as a potential non-chemical insecticide against Anopheles gambiae, one of the primary mosquitoes that spreads malaria in Africa. In their new report published in August in the Journal of Medical Entomology, they show that perlite has encouraging potential as a mechanical insecticide. Perlite is believed to act by causing dehydration in the mosquitoes. read more…

Mosquitoes love pregnant, beer-drinking exercisers with Type O blood

Mosquitoes spread Zika, West Nile, Chikungunya, Dengue, and Malaria, resulting in 700 million illnesses a year and a million deaths. Even if you don’t get sick from a mosquito bite, the blood thinner they pump into your flesh before draining your blood causes swelling and itching. This article in Smithsonian Magazine lists the factors that make some people more tempting targets than others to mosquito bites. They include:

• Blood type: “One study found that in a controlled setting, mosquitoes landed on people with Type O blood nearly twice as often as those with Type A.”
• Carbon Dioxide: “people who simply exhale more of the gas over time—generally, larger people—have been shown to attract more mosquitoes than others.”
• Exercise: “mosquitoes find victims at closer range by smelling the lactic acid, uric acid, ammonia and other substances expelled via their sweat”
• Skin bacteria: “scientists found that having large amounts of a few types of bacteria made skin more appealing to mosquitoes”
• Beer: “Just a single 12-ounce bottle of beer can make you more attractive to the insects”
• Pregnancy: “pregnant people exhale about 21 percent more carbon dioxide and are on average about 1.26 degrees Fahrenheit warmer than others”
• Clothing color: “wearing colors that stand out (black, dark blue or red) may make you easier to find”
• Genetics: “underlying genetic factors are estimated to account for 85 percent of the variability between people in their attractiveness to mosquitoes”

Live In Vivo Imaging of Plasmodium Invasion of the Mosquito Midgut

Malaria is one of the most devastating parasitic diseases in humans and is transmitted by anopheline mosquitoes. The mosquito midgut is a critical barrier that Plasmodium parasites must overcome to complete their developmental cycle and be transmitted to a new host. Here, we developed a new strategy to visualize Plasmodium ookinetes as they traverse the mosquito midgut and to follow the response of damaged epithelial cells by imaging live mosquitoes. Understanding the spatial and temporal aspects of these interactions is critical when developing novel strategies to disrupt disease transmission.

Updates from newsletters and journal abstracts found online today. Issues include health and malaria service disruptions from COVID-19, increased mosquito-borne diseases, including malaria, in India and mosquitoes and attractant odors. Click on links to read details.

Continuing vital health services in Guinea-Bissau during COVID-19

ReliefWeb explains that as lockdowns, curfews and transport disruptions prevent many vulnerable people from getting healthcare, communities are stepping into the breach. Community health workers and volunteers are ensuring their peers, friends, and neighbours are protected from disease. “In previous bednet distribution campaigns, we used to identify the families before setting up the distribution points,” said Ivannildo Vieira, a community health worker, “but this year, because of COVID-19 restrictions, it was decided to do door-to-door distributions in order not to gather people in a single distribution area.”

Helping communities protect themselves from diseases like malaria in Guinea-Bissau is no simple task. Located on West Africa’s coast, Guinea-Bissau is one of the world’s poorest and most fragile countries. Malaria is the leading cause of death among pregnant women and children under five. Malaria prevention measures have been complicated by a rapid increase in the number of COVID-19 cases.

Delhi records 24% rise in Dengue, Malaria in 7 days

While Delhi’s healthcare is overwhelmed with tackling the COVID-19 pandemic, another epidemic of vector-borne diseases are knocking at its door. A whopping rise of 24 per cent in Dengue, Malaria, and Chikungunya cases were recorded in the last one week.  The cities/corporations stated that they reported incidents of mosquito-breeding at 44,259 households and served 35,103 legal notices to the violators. Meanwhile, 1,512 prosecutions were launched against the violations.

Is Anopheles gambiae attraction to floral and human skin-based odours and their combination modulated by previous blood meal experience?

Malaria Journal notes that Mosquitoes use odours to find energy resources, blood hosts and oviposition sites. While these odour sources are normally spatio-temporally segregated in a mosquito’s life history, here this study explored to what extent a combination of flower- and human-mimicking synthetic volatiles would attract the malaria vector Anopheles gambiae sensu stricto (s.s.).

Nulliparous and parous A. gambiae s.s. are attracted to combinations of odours derived from spatio-temporally segregated resources in mosquito life-history (floral and human volatiles). This is favourable as mosquito populations are comprised of individuals whose nutritional and developmental state steer them to diverging odours sources, baits that attract irrespective of mosquito status could enhance overall effectiveness and use in monitoring and control. However, combinations of floral and skin odours did not augment attraction in semi-field settings, in spite of the fact that these blends activate distinct sets of sensory neurons. Instead, mosquito preference appeared to be modulated by blood meal experience from floral to a more generic attraction to odour blends. Results are discussed both from an odour coding, as well as from an application perspective.

Malaria Leaves 100 Dead in South Sudan

The East African reports that South Sudan’s Ministry of Health and the World Health Organization (WHO) say at least 100 people died of malaria in the  In a joint report released on Sunday, the two institutions said morbidity and mortality trends in the Protection of Civilians Sites across the country, as of July, indicated rampant deaths due to malaria infections.

Below we highlight some of the news we have shared on our Facebook Tropical Health Group page during the past week.

Polio Persists

If all it took to eradicate a disease was a well proven drug, vaccine or technology, we would not be still reporting on polio, measles and guinea worm, to name a few. In the past week Afghanistan reported 2 wild poliovirus type 1 (WPV1) cases, and Pakistan had 3 WPV1 cases. Circulating vaccine-derived poliovirus type 2 (cVDPV2) was reported in Nigeria (1), DRC (4) and Ethiopia (3) from healthy community contacts.

Continued Ebola Challenges

In the seven days from Saturday to Friday (June 28) there were 71 newly confirmed Ebola Cases and 56 deaths reported by the Democratic Republic of Congo’s Ministry of Health. As Ebola cases continue to pile up in the Democratic Republic of the Congo (DRC), with 12 more confirmed Thursday and 7 more Friday, a USAID official said four major donors have jump-started a new strategic plan for coordinating response efforts. To underscore the heavy toll the outbreak has caused, among its 2,284 cases, as noted on the World Health Organization Ebola dashboard today, are 125 infected healthcare workers, including 2 new ones, DRC officials said.

Pacific Standard explained the differences in Ebola outbreaks between DRC today and the West Africa outbreak of 2014-16. On the positive side are new drugs used in organized trials for the current outbreak. The most important factor is safe, effective vaccine that has been tested in 2014-16, but is now a standard intervention in the DRC. While both Liberia and Sierra Leone had health systems and political weaknesses as post-conflict countries, DRC’s North Kivu and Ituri provinces are currently a war zone, effectively so for the past generation. Ebola treatment centers and response teams are being attacked. There are even cultural complications, a refusal to believe that Ebola exists. So even with widespread availability of improved technologies, teams may not be able to reach those in need.

To further complicate matters in the DRC, Doctors Without Borders (MSF) “highlighted ‘unprecedented’ multiple crises in the outbreak region in northeastern DRC. Ebola is coursing through a region that is also seeing the forced migration of thousands of people fleeing regional violence and is dealing with another epidemic. Moussa Ousman, MSF head of mission in the DRC, said, ‘This time we are seeing not only mass displacement due to violence but also a rapidly spreading measles outbreak and an Ebola epidemic that shows no signs of slowing down, all at the same time.’”

NIPAH and Bats

Like Ebola, NIPAH is zoonotic, and also involves bats, but the viruses differ. CDC explains that, “Nipah virus (NiV) is a member of the family Paramyxoviridae, genus Henipavirus. NiV was initially isolated and identified in 1999 during an outbreak of encephalitis and respiratory illness among pig farmers and people with close contact with pigs in Malaysia and Singapore. Its name originated from Sungai Nipah, a village in the Malaysian Peninsula where pig farmers became ill with encephalitis.

A recent human outbreak in southern India has been followed up with a study of local bats. In a report shared by ProMED, out of 36 Pteropus species bats tested for Nipah, 12 (33%) were found to be positive for anti-Nipah bat IgG antibodies. Unlike Ebola there are currently no experimental drugs or vaccines.

Climate Change and Dengue

Climate change is expected to heighten the threat of many neglected tropical diseases, especially arboviral infections. For example, the New York Times reports that increases in the geographical spread of dengue fever. Annually “there are 100 million cases of dengue infections severe enough to cause symptoms, which may include fever, debilitating joint pain and internal bleeding,” and an estimated 10,000 deaths. Dengue is transmitted by Aedes mosquitoes that also spread Zika and chikungunya. A study, published Monday in the journal Nature Microbiology, found that in a warming world there is a strong likelihood for significant expansion of dengue in the southeastern United States, coastal areas of China and Japan, as well as to inland regions of Australia. “Globally, the study estimated that more than two billion additional people could be at risk for dengue in 2080 compared with 2015 under a warming scenario.”

Schistosomiasis – MDA Is Not Enough, and Neither Are Supplementary Interventions

Schistosomiasis is one of the five neglected tropical diseases (NTDs) that are being controlled and potentially eliminated through mass drug administration (MDA) of preventive chemotherapy (PCT), in this case praziquantel. In The Lancet Knopp et al. reported that biannual MDA substantially reduced Schistosomiasis haematobium prevalence and infection intensity but was insufficient to interrupt transmission in Zanzibar. In addition, neither supplementary snail control or behaviour change activities did not significantly boost the effect of MDA. Most MDA programs focus on school aged children, and so other groups in the community who have regular water contact would not be reached. Water and sanitation activities also have limitations. This raises the question about whether control is acceptable for public health, or if there needs to be a broader intervention to reach elimination?

Trachoma on the Way to Elimination

Speaking of elimination, WHO has announced major “sustained progress” on trachoma efforts. “The number of people at risk of trachoma – the world’s leading infectious cause of blindness – has fallen from 1.5 billion in 2002 to just over 142 million in 2019, a reduction of 91%.” Trachoma is another NTD that uses the MDA strategy.

The news about NTDs from Dengue to Schistosomiasis to Trachoma is complicated and demonstrates that putting diseases together in a category does not result in an easy choice of strategies. Do we control or eliminate or simply manage illness? Can our health systems handle the needs for disease elimination? Is the public ready to get on board?

Malaria Updates

And concerning being complicated, malaria this week again shows many facets of challenges ranging from how to recognize and deal with asymptomatic infection to preventing reintroduction of the disease once elimination has been achieved. Several reports this week showed the particular needs for malaria intervention ranging from high burden areas to low transmission verging on elimination to preventing re-introduction in areas declared free from the disease.

In South West, Nigeria Dokunmu et al. studied 535 individuals aged from 6 months were screened during the epidemiological survey evaluating asymptomatic transmission. Parasite prevalence was determined by histidine-rich protein II rapid detection kit (RDT) in healthy individuals. They found that, “malaria parasites were detected by RDT in 204 (38.1%) individuals. Asymptomatic infection was detected in 117 (57.3%) and symptomatic malaria confirmed in 87 individuals (42.6%).

Overall, detectable malaria by RDT was significantly higher in individuals with symptoms (87 of 197/44.2%), than asymptomatic persons (117 of 338/34.6%)., p = 0.02. In a sub-set of 75 isolates, 18(24%) and 14 (18.6%) individuals had Pfmdr1 86Y and 1246Y mutations. Presence of mutations on Pfmdr1 did not differ by group. It would be useful for future study to look at the effect of interventions such as bednet coverage. While Southwest Nigeria is a high burden area, the problem of asymptomatic malaria will become an even bigger challenge as prevalence reduces and elimination is in sight.

Sri Lanka provides a completely different challenge from high burden areas. There has been no local transmission of malaria in Sri Lanka for 6 years following elimination of the disease in 2012. Karunasena et al. report the first case of introduced vivax malaria in the country by diagnosing malaria based on microscopy and rapid diagnostic tests. “The imported vivax malaria case was detected in a foreign migrant followed by a Plasmodium vivax infection in a Sri Lankan national who visited the residence of the former. The link between the two cases was established by tracing the occurrence of events and by demonstrating genetic identity between the parasite isolates. Effective surveillance was conducted, and a prompt response was mounted by the Anti Malaria Campaign. No further transmission occurred as a result.”

Bangladesh has few but focused areas of malaria transmission and hopes to achieve elimination of local transmission by 2030. A particular group for targeting interventions is the population of slash and burn cultivators in the Rangamati District. Respondents in this area had general knowledge about malaria transmission and modes of prevention and treatment was good according to Saha and the other authors. “However, there were some gaps regarding knowledge about specific aspects of malaria transmission and in particular about the increased risk associated with their occupation. Despite a much-reduced incidence of malaria in the study area, the respondents perceived the disease as life-threatening and knew that it needs rapid attention from a health worker. Moreover, the specific services offered by the local community health workers for malaria diagnosis and treatment were highly appreciated. Finally, the use of insecticide-treated mosquito nets (ITN) was considered as important and this intervention was uniformly stated as the main malaria prevention method.”

Kenya offers some lessons about low transmission areas but also areas where transmission may increase due to climate change. A matched case–control study undertaken in the Western Kenya highlands. Essendi et al. recruited clinical malaria cases from health facilities and matched to asymptomatic individuals from the community who served as controls in order to identify epidemiological risk factors for clinical malaria infection in the highlands of Western Kenya.

“A greater percentage of people in the control group without malaria (64.6%) used insecticide-treated bed nets (ITNs) compared to the families of malaria cases (48.3%). Low income was the most important factor associated with higher malaria infections (adj. OR 4.70). Houses with open eaves was an important malaria risk factor (adj OR 1.72).” Other socio-demographic factors were examined. The authors stress the need to use local malaria epidemiology to more effectively targeted use of malaria control measures.

The key lesson arising from the forgoing studies and news is that disease control needs strong global partnerships but also local community investment and adaptation of strategies to community characteristics and culture.

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.

… Redirecting Resources into the Hands of People Who Slap Mosquitoes Everyday.

Class members from the course “Social and Behavioral Foundations of Primary Health Care” at the Johns Hopkins Bloomberg School of Public Health write a policy advocacy blog as part of their assignments. Here we are sharing the blog posted by elizabethwetzler. read more on this and other SBFPHC blog posts by clicking here.