Tropical Health Matters

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.

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.

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.

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.