Public Health Importance of Emporiatrics: A Review

What's In A Mosquito Bite? How Warmer Climates Spread Disease

Living on the edge of wetlands on the Italian island of Sardinia, Anna Rita Cocco is mourning the loss of her elderly father who died in a coma within weeks of a fatal mosquito bite.

"My father was full of life and used to walk for miles each day. I was expecting him to die at some point, but not suffering like that, taken from me by a mosquito," she said her late father, Bernardino, who died aged 80.

Italy was only declared malaria-free by the World Health Organization (WHO) in 1970, but now other lesser-known mosquito- or tick-borne diseases are on the rise.

A complex mix of global warming, changes in land use and more movement of people and goods are contributing to the spread of illnesses - such as dengue or Lyme disease - to new regions in a worsening trend, the UN panel of scientists says.

Migratory birds infected by mosquitoes and flying over 2,000 miles (3,200 km) from Senegal in west Africa have been identified as carriers of the West Nile virus that killed Cocco's father in Sardinia, where summers are becoming hotter.

The Mediterranean island, and northern areas of Italy where the virus is also spreading, are both suffering more extreme events of floods and droughts.

Abundant water helps mosquitoes to breed, while more drought and fewer trees constrict the migratory birds' ecosystems, forcing them into closer contact with each other, enabling some diseases to spread.

"People don't seem to be aware of the threat," said Cocco.

Habitat changes in Senegal 

Epidemiologists identify habitat change as one of the main factors behind the intercontinental leap of the West Nile virus.

First identified in 1937 in the West Nile region of Uganda, the disease has spread within Africa and to other continents. Almost 3,000 people have died in the United States alone since a first outbreak in New York in 1999. 

In the red clay houses of Maka Diama village in northwest Senegal, women make soap from plants that grow in a nearby river, which they sell to tourists and local hotels, and cook rice grown in surrounding paddy fields.

Recent years have seen huge changes in this wetland region teeming with crocodiles and migratory birds, most notably a leap in rice production, driven by government efforts to reduce Senegal's reliance on imported rice.

Barrages built near the coast to retain and safeguard freshwater supplies from salty sea water have slowed river flows, and fertilisers used for rice paddies have encouraged the growth of river plants.

This push for greater food self-sufficiency has tripled rice production to 1.3 million tonnes over a decade. But changes in land use have upset the delicate wetland habitats, helping mosquitoes which lay eggs in stagnant water.

"There are so many mosquitoes here these days," said Arame Diop, one of the village soap-makers. "Far more than there used to be." Diop's family already sleep under mosquito nets to avoid malaria, which is endemic in Senegal.

Assane Gueye Fall, an entomologist at the National Livestock and Veterinary Research Laboratory in the capital, Dakar, said Senegal's policies sought to improve food and water security.

"But to solve a problem, they created another," he said of what he called the "explosion of mosquitoes" and of disease.

Carried on a wing

The long-distance carriers of West Nile are birds that receive the virus from bites by infected mosquitoes and then fly on their migratory routes, to be bitten once more by mosquitoes that then spread illness to people and other animals, mainly horses.

Flamingos, herons, storks and birds of prey are among many migratory species found in the wetlands of the Djoudj National Bird Sanctuary, a UNESCO World Heritage Site near Maka Diama.

Navigating his boat slowly, captain Ibrahima Ndao, the park conservationist, explained how abrupt changes in land use are impacting the wetlands. Pelicans are swooping all around, catching fish for their young.

"There has been a significant expansion of paddy fields around the reservoir. But we have to make sure that the birds' environment is preserved," he said.

"If the space of their environment is reduced it's easier for illnesses to spread," said Ndao, pointing out increased growth of plants along the banks, including those used by the women of Maka Diama to make soap.

Ndao stressed the importance of a "one-health approach" that looks at human and animal health as one issue.

In the capital Dakar, Babacar Ngor Youm, head of Senegal's National Parks within the Ministry of Environment and Sustainable Development, said "political choices" must be made to raise food production despite risks of harmful side-effects.

Food sovereignty is necessary "as the Ukraine war showed," he said, referring to a rise in world food prices after Russia invaded its neighbour.

"With urbanisation comes deforestation … and if there's less space for the birds, illnesses spread more quickly," said Youm, who previously worked on an outbreak of avian flu in Djoudj park.

As in Europe, Senegal is also losing natural habitats through desertification exacerbated by climate change, forcing animals into closer contact with human communities.

Bridging the knowledge gap

Vector-borne diseases - such as malaria, dengue, Zika, yellow fever and West Nile - are seen by WHO as an increased threat in Africa, potentially affecting over 800 million people, some 70 per cent of the population.

West Nile virus has gained a foothold in an increasing number of countries, from Australia to Venezuela.   

Because it is easy to confuse West Nile with a generic flu or other mosquito-borne illnesses, patients rarely get tested.

As a result, the impact of the virus in Africa is virtually unknown. Local populations also build resistance to the disease. With little information, it is also difficult to build models of how it might spread in Europe and elsewhere.

West Nile is often asymptomatic or mild, but one out of 150 people who contract the virus can develop severe neurological complication including meningitis, paralysis and even death.

In 2022, 12 European nations reported 1,335 locally acquired cases of West Nile virus - with a few others brought in by international travellers - and 104 deaths. It was the highest number of cases since a peak of more than 1,500 in 2018.

Italy suffered most in the European Union in 2022 with 51 deaths, ahead of 33 in Greece and five in Romania, according to the European Centre for Disease Prevention and Control.

A public health campaign is alerting people, and authorities are stepping up tests of birds and mosquitoes.

The main vector is the mosquito Culex, but what makes West Nile potentially endemic is that it can be transmitted by more than 50 species of mosquito and by ticks, said entomologist Fall in Dakar. By contrast, dengue, for example, relies on one or two species.

There is no West Nile vaccine available for humans, although one has been developed for horses.

"The expansion of West Nile cannot be stopped," said Fall. "This is why we need collaborative research between Africa and Europe."

"And prevention in animals and in humans must be considered as one."

This story was supported by the European Journalism Centre Global Health Project.

This story was published with permission from Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, climate change, resilience, women's rights, trafficking and property rights. Visit https://www.Context.News/.

Ask An Expert: Is The Threat Of Malaria Increasing?

Malaria has been around for a long time, and yet it's constantly evolving. The mosquitoes that transmit malaria have a remarkable ability to adapt and overcome our best defenses. In the face of growing insecticide resistance, as well as climate change, our foundation continues to invest in the transformative science needed to save lives.

Laura Norris has spent the past 17 years studying malaria's ever-evolving path, first as a microbiologist and currently as a senior program officer at the Gates Foundation. She shares crucial information about malaria today and how the latest innovations can help beat this deadly disease.

Why is malaria still such a problem? 

In 2021, there were an estimated 247 million malaria cases, including 619,000 deaths. Those figures, shocking on their own, are even more heartbreaking when you consider that three-quarters of those deaths were among children under age 5—and that poverty and inequality are huge factors in transmission of the disease. While many higher-income countries have eliminated malaria, it is still abundant in low- and middle-income countries. Children in those areas are more likely to have other complicating factors, such as malnourishment. And while good preventive and curative treatments exist, many places lack the kind of health care required to provide them.

Is climate change making malaria worse? 

There's a lot of concern about malaria and climate change, and with good reason. Mosquitoes thrive in warm weather, and the world is getting warmer, which can extend disease transmission seasons. Changes in temperature, humidity, and rainfall are altering the malaria map. The United States recently reported its first locally acquired malaria infections in decades. Elsewhere, increasing rates of malaria infection are placing an increasing burden on health care systems and profoundly disrupting the ability to prevent, test for, and treat malaria.

Malaria is unforgiving, surging in the face of extreme weather events—like the horrific flooding in Pakistan last year and the more recent cyclone in Mozambique—as well as conflicts, disease outbreaks, and population displacements, which are all becoming increasingly common in the face of climate change. For these reasons, it is more important than ever to work toward eradication with urgency. Malaria eradication may be one of the most cost-effective climate adaptations we can make. 

Who is most at risk as the threat of malaria evolves?

Ninety-five percent of malaria cases are in Africa. India is another hotspot. While the infection rates there are fairly low compared to countries in Africa, its population is so large that the case numbers are quite high. Population is so large that the case numbers are quite high.

Until recently, malaria was primarily a problem in rural places. The types of mosquitoes that traditionally transmit malaria prefer breeding sites with clean water and vegetation, like ponds, slow-moving streams, and rice paddies. You don't find those in cities. But in 2012, researchers began seeing an invasive species of mosquito called Anopheles stephensi in urban areas in Djibouti, Ethiopia, Sudan, and Nigeria. Djibouti had about 73,000 cases of malaria in 2020, compared to just 27 cases before An. Stephensi's arrival.

An. Stephensi will lay eggs in artificial containers, including wells, cisterns, fountains, water barrels, and even abandoned tires—all common in urban areas. And these mosquitoes are very efficient at transmitting malaria. One model predicted that An. Stephensi alone could put 126 million people around the world at risk of the disease.

Could malaria come back in places it was eliminated?

While malaria generally has not returned to areas where it has been previously eliminated, reemergence can occur under certain environmental conditions. That's part of the reason why the goal is worldwide eradication. Mosquitoes don't concern themselves with international borders. Countries need strong health surveillance systems so they can respond rapidly to new cases, even if new cases are unlikely.

That's why all countries need strong health surveillance systems so they can respond rapidly to new cases, even if they are unlikely.

Is insecticide resistance in mosquitoes contributing to the malaria threat?

Insecticide resistance has become a huge problem, not just for malaria but also for other mosquito-borne diseases. Over the past few decades, insecticide-treated bed nets and indoor residual spraying have been the main defenses against malaria. Together, they have saved millions of lives. It's truly a global success story. But these highly effective malaria-control efforts have relied on a very small number of insecticides, particularly one type, called pyrethroids. The problem is that anytime you put selective pressure on an insect population, that population develops new defenses over time. Resistance emerges. That means an insecticide that could once reliably kill mosquitoes isn't as reliable anymore.

What's being done to combat insecticide resistance?

One way to stave off insecticide resistance is to keep a step ahead of the mosquitoes and their evolving defenses. A number of organizations have been working on developing new insecticides, with promising results. For example, two new types of bed nets have entered the market that are treated with a pyrethroid and a second ingredient, either pyriproxyfen or chlorfenapyr. Pyriproxyfen reduces the number of offspring that a female mosquito has; chlorfenapyr targets the mosquito's energy centers at a cellular level. The combination of two insecticides acts in a very different way than a pyrethroid alone and provides a way to address the problem of resistance. WHO issued recommendations for the use of these new dual-AI nets in 2023.

One brand of these bed nets, called IG2, was studied in a two-year trial involving more than 39,000 households in Tanzania. The trial found that IG2 nets reduced malaria cases by nearly half compared to pyrethroid-only bed nets. Similar results were seen in another study conducted in Benin.

Can vaccines help protect people from malaria?

First-generation malaria vaccines are remarkable technical accomplishments. The world's first WHO-recommended and prequalified malaria vaccine, RTS,S/AS01E, is already being used alongside existing tools with the potential to save thousands more children from malaria. Meanwhile, another first-generation vaccine, R21/Matrix-M, may soon become the second vaccine to be recommended by WHO and will help to increase vaccine supply for endemic countries.

However, we cannot end malaria with the vaccines and other tools we have today, which is why our foundation is helping to fund the development of monoclonal antibodies, a single injection of which could give a person a full season's worth of protection against malaria, as well as self-replicating RNA vaccines that have the potential to be manufactured quickly and in large quantities.

What other innovations could help protect against mosquito-borne disease?

One new idea our foundation is funding involves a way to breed male mosquitoes to carry a gene that doesn't allow their female offspring to survive into adulthood. Male mosquitoes don't transmit malaria, so these specially bred males can be released to mate with wild females, which can cause the mosquito population to plummet.

Attractive targeted sugar baits also have a lot of potential. This innovation takes advantage of the fact that mosquitoes feed on sugar in addition to blood. It uses a device the size of notebook paper that contains date syrup laced with insecticide. The mosquito stops by for a drink and is killed by the insecticide.

Can malaria still be eradicated?

Yes it can, despite the challenges. With smart strategies and investments, the world can put an end to malaria. The tools at our disposal are at the cutting edge of innovation and are poised to transform the way we prevent and treat malaria.

Beyond that, many of us in the malaria field are especially encouraged by the work of institutions and researchers on the African continent, which are developing capacity for more molecular research and improved surveillance. More of that growth is needed, but the amount of research that has been shifting to labs in Africa is really promising. Here at the foundation, one of the things we want to focus on next year is how to boost local private-sector investment in malaria control. The need for greater innovation highlights just how important these kinds of locally based efforts are.

Mosquito Spraying To Close New London County State Forest

GRISWOLD, CT — The state Department of Energy and Environmental Protection (DEEP)'s Mosquito Management Program sprayed for mosquitoes in the Mt. Misery area of Pachaug State Forest in Griswold on Thursday afternoon.

Entrances to the state forest will be closed beginning at 2 p.M. Thursday, and the forest and nearby roads will be closed for the evening, re-opening at 8 a.M. Friday.

The end of mosquito season is approaching, and there have been no cases of Eastern Equine Encephalitis (EEE) in humans so far this season. However, the risk level in the eastern part of the state for EEE virus remains elevated.

Mosquitoes collected earlier this month in New London County tested positive for EEE and West Nile Virus. EEE has been detected in the following towns this year: Canterbury, Griswold, Hampton, Killingly, Ledyard, Mansfield, Plainfield, Stonington, Thompson, Tolland, Voluntown, Willington, and Woodstock. No human or animal cases have been reported in Connecticut in 2023.

EEE is a rare but serious illness in humans. Four to eight cases are reported in a typical year in the U.S. EEE is the most severe mosquito-transmitted disease in the U.S., with approximately 40 percent mortality and neurological impairment in most survivors.

To reduce the risk of being bitten by mosquitoes, the DEEP recommends residents:

Minimize time spent outdoors between dusk and dawn when mosquitoes are most active.

Consider the use of mosquito repellents containing an EPA-registered active ingredient, including DEET, Picaridin, IR3535, oil of lemon eucalyptus, para-methane-diol (PMD), or 2-undecanone when it is necessary to be outdoors.

Wear shoes, socks, long pants, and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are more active. Clothing should be light-colored and loose-fitting and made of tightly woven materials that keep mosquitoes away from the skin.

Be sure door and window screens are tight-fitting and in good repair.

Use mosquito netting when sleeping outdoors or in an unscreened structure and to protect infants when outdoors.

For information on EEE, West Nile Virus, and other mosquito-borne diseases, what can be done to prevent getting bitten by mosquitoes, the latest mosquito test results, and human infections, visit the Connecticut Mosquito Management Program website at https://portal.Ct.Gov/mosquito

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