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Deadly Diseases

The female Anopheles mosquito may well be the most dangerous creature on Earth. When she lands on human skin, she sucks up blood through her needle-shaped mouth and injects saliva into the wound. If this saliva contains Plasmodia parasites, the victims will soon suffer severe fever, violent shivering, and profuse sweating — the telltale symptoms of malaria.

"Malaria" is a misnomer. Drawn from the Italian mala aria, or "bad air," the name reflects the historical belief that the disease is caused by miasmas, or noxious exhalations from rotting matter or stagnant water. In 1889, a tiny parasite was revealed as the disease-causing agent, and eight years later, the mosquito was identified as the parasite-carrying agent.

When a mosquito carrying malaria bites her victim, she injects parasites into the bloodstream, where they migrate to the liver and other organs and incubate. A malaria victim may show no symptoms for weeks or months during this incubation. Then the parasites return to the bloodstream and invade the red blood cells. Rapid multiplication of the parasites ruptures the red cells, releasing more parasites into the bloodstream and causing the characteristic symptoms. If the person does not receive prompt and effective drug therapy, damage may occur to the brain and other organs, sometimes leading to death.

Malaria is largely a geographical disease, endemic to tropical climates in Africa, Asia, and South America. An estimated 350 million to 500 million people worldwide are infected with malaria each year; of the more than one million who die, two-thirds are children. An African child under 5 suffers on average six bouts of the recurring illness each year.

In the United States, malaria was historically a problem in the southeastern states. Begun in 1947, the National Malaria Eradication Program (the precursor of the Centers for Disease Control, or CDC) applied the insecticide DDT to the interior surfaces of rural homes and entire properties where malaria was reportedly prevalent. About 4.6 million houses were sprayed, and five years later, malaria was considered eliminated in the United States.

A remarkable man named Fred Soper first took on malaria in Brazil in the 1930s. With the passion and determination of a field general directing an army, Soper eliminated the Anopheles gambiae mosquito from the country within a decade, stopping a deadly outbreak in its path. His success raised hopes that malaria could be eliminated worldwide. By 1948, 55 nations had signed up for the Global Malaria Eradication Program Soper would go on to lead.

With DDT as their tool, Soper's mosquito warriors were successful in sharply curtailing malaria or eliminating it entirely from nearly 40 countries, including Taiwan, many Caribbean nations, the Balkans, and parts of North Africa. But just as they seemed to be on the brink of victory, their luck ran out. First, mosquitoes began to develop resistance to DDT, and then, in 1962, Rachel Carson's Silent Spring identified the harmful effects of DDT on ecosystems. The chemical was subsequently banned in the United States. While this action benefited the environment, it hurt Soper and his team's international efforts to combat malaria, in which only a small amount of DDT was used indoors. To this day, researchers continue to look for a chemical comparable to DDT in its mosquito-killing effectiveness.

Despite decades of research work, a successful vaccine for malaria remains elusive. Scientists hope that the genetic decoding of the malaria parasite may offer helpful points of intervention for interrupting its life cycle. Meanwhile, several current research efforts seem promising, largely bolstered by the Bill & Melinda Gates Foundation (The Bill & Melinda Gates Foundation is a funder of the Rx for Survival project).

People residing in non-malaria-endemic areas are normally safe in their home countries, although a few cases are reported each year of "airport malaria," in which a mosquito, hitching a ride on an aircraft, causes disease. Travelers to malarial areas have a high risk of catching a serious infection because they lack the natural immunity that provides local residents some protection.

Tourists can take an antimalarial drug as an effective preventative. (If taken for a long time, some of these drugs have long-term side effects, and are therefore not recommended for residents of malaria-endemic regions). Doctors may prescribe a course of medication for travelers that covers the immediate time before, during, and after a visit to a malaria area. Several medications, including doxycycline, atovaquone/proguanil, mefloquine, and primaquine, have proven effective.

But malaria is one of nature's most resilient killers, and the Plasmodium parasite is becoming resistant to these older medications. A promising new drug, artemisinin, has been synthesized from a plant used as a treatment in China for centuries. Demand for artemisinin currently far outstrips supply, and costs of the treatment remain beyond the reach of many malaria victims.

About 99 percent of mosquitoes carrying the malarial parasite are night biters, so for travelers and native populations alike, netting treated with insecticide for sleeping areas is crucial. In the absence of an effective mosquito-elimination method, netting can prevent many of the one million malaria deaths of children under 5 each year, and save many adults from unnecessary illness and death as well.

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What Are Neglected Tropical Diseases?

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It's likely you've heard of malaria, HIV-AIDs and tuberculosis. These three diseases continue to have a massive impact on human health across the globe. You may not be familiar, however, with schistosomiasis, Chagas disease, leishmaniasis or trachoma, which fall under the umbrella of "neglected tropical diseases" (or NTDs for short).

What Are Neglected Tropical Diseases?

NTDs comprise a range of illnesses mostly caused by viruses, fungi, bacteria and parasites. Together, these include at least 20 conditions that severely impact the most vulnerable people in the world. Schistosomiasis, for example, is caused by parasitic worms released by freshwater snails. Over 200 million people worldwide are affected by it, according to the WHO, with nearly 12,000 deaths occurring from the disease each year.

Maria-Gloria Basáñez, a professor and chair of neglected tropical diseases at Imperial College London, underlines that these diseases overwhelmingly impact the "bottom billion of the world's population".

"They have a disproportionate impact on the most marginalized and vulnerable sections of these populations, namely women and children," says Basáñez.

How Dangerous Are These Tropical Diseases?

Mortality linked to NTDs is often lower than other diseases, but Basáñez states they can lead to a huge burden of disability, which in turn impacts economies. Trachoma for instance — which is caused by the bacterium Chlamydia trachomatis — can lead to irreversible blindness, and is thought to have impaired the vision of at least 1.9 million people. It's known as the leading cause of infectious blindness in the world. Onchocerciasis and neurocysticercosis, meanwhile, are caused by parasitic worms, and can lead to epilepsy.

There are 179 countries across the globe that have reported at least one case of NTDs in 2021, but the disease burden is concentrated in just 16 countries. Poverty underpins many of the affected areas, and NTDs can perpetuate that cycle, Basáñez adds.

Read More: Dengue Fever Is on the Rise — a Ticking Time Bomb in Many Places Around the World

Why Don't NTDs Get More Attention?

The reasons why NTDs are neglected are complex. Over the last two decades, international organizations, health organizations and governments have increasingly taken notice of tackling these diseases. Yet, despite these efforts, funding, medical support, research and development, as well as awareness, continue to lag behind those of other diseases, Basáñez says.

"I think there is a big gap between awareness and the international commitment, because [NTDs] affect the poorest of the poor," she adds.

Part of the challenge, Basáñez continues, is that these diseases tend to be endemic — concentrated in specific locations or countries without sudden increases in the number of cases — without much outbreak and epidemic potential, meaning that they tend to fall under the radar.

"It's an example of out of sight and out of mind," says Basáñez. "So, it's really important that we keep the visibility up in all the ways that we can."

Is Climate Change a Factor?

led by the WHO, international organizations, health authorities, governments and others aim to eliminate NTDs by 2030. Tackling them is ever more important due to climate change, which could result in a geographic spread and change in infection rates, according to researchers. For example, shifting precipitation and temperature are linked to changes in the distribution of diseases such as dengue, chikungunya and leishmaniasis.

How climate change might impact other NTDs is still unclear and a point of active research, notes Basáñez.

"We have two issues: How the ecology of the insects and the snails [and other vectors] that are involved in the transmission of some of these diseases is going to change," she adds. "And how our infrastructure and resources are going to be affected."

Read More: Climate Change is Likely to Increase the Risk of Infectious Diseases

How Can We Treat Neglected Tropical Diseases?

Tackling NTDs comes from a range of angles. Fundamentally, many of these diseases are linked to a lack of access to clean water, sanitation and healthcare; addressing these is paramount to reducing their impact. So, too, says Basáñez is ensuring distribution and coverage of preventive treatments for some NTDs, and access to diagnosis, treatment and management for others.

Still, progress is marching forward towards the overall goal of preventing and eliminating NTDs by 2030; around 80 million fewer people required NTD interventions between 2020 and 2021. By the end of 2022, 47 countries across the globe had eliminated at least one of these diseases, according to a recently published global report by the WHO.

New treatments are also under development to help those impacted. In 2021, researchers at the London School of Hygiene & Tropical Medicine identified new compounds that can target the parasitic worms that cause schistosomiasis, raising hopes its elimination could be on the horizon.

"You need to keep the momentum, keep the incentive and the populations engaged with these treatment programs," Basáñez says. "They are going to be needed for a long time."

Eliminating NTDs is still a ways off, with multiple challenges along the way. Researchers like Basáñez remain hopeful that progress can be made with concerted action. "I firmly believe that people should be informed, better acquainted, better engaged at all levels in the population, both in non-endemic countries and endemic countries."

Read More: Genetically Modified Mosquitoes May Protect The World From Disease

Malaria: A Disease Of Poverty

619 000 people die annually from malaria. Over 95% of malaria cases and deaths from the disease are in Africa. Malaria slows economic growth and development and perpetuates a vicious cycle of poverty. 25 April is World Malaria Day.

247 million new cases of malaria were recorded in 2021.

Ólafur Halldórsson has caught malaria four times in only one year. The Icelander, who for the past five years has run an orphanage in Kenya, says that the first time was the worst. "I was brought to a local hospital and treated with chloroquine. I was unconscious for a week and suffered horrible side-effects and was virtually blind and deaf when I woke up."

Ólafur Halldórsson who runs the orphanage in Oyugis, Kenya. Photo: Björt sýn.

He was transferred to a more sophisticated hospital in a dire condition and survived.

"Since then, I have caught it three more times, but I know the symptoms and I have drugs in stock. Only three pills are needed and you are good," says Halldórsson.

"It is so sad that this disease kills people in the hundreds of thousands because it is easily curable. And sadly, many of those who die are children."

Children under 5 accounted for about 80% of all malaria deaths in the African Region of WHO, the World Health Organization.

One of the targets of the Global Goals

Photo: Adoscam-Creative Commons Attribution-Share Alike 4.0

The fight against malaria is one of the targets in the Global Goals for Sustainable Development (or Sustainable Development Goals). The objective is to reduce mortality rates by at least 90% and eliminate malaria in at least 35 countries by 2030 and to prevent a resurgence of malaria in all countries that are malaria-free.

 The impact of malaria is not only felt in terms of the human suffering and death it causes, but also by the significant economic cost and burden – to families, households and national economies.

"Malaria and poverty are intimately connected. As both a root cause and a consequence of poverty, malaria is most intractable for the poorest countries and communities in the world that face a vicious cycle of poverty and ill health", according to the Earth Institute of the University of Colombia.

For a few dollars

Photo: Björt sýn.

"The necessary drugs cost a few dollars or euros but the local people cannot afford it," Halldórsson explains.

"They simply are too poor or they live in remote areas where there are no hospitals or doctors."

Malaria is a life-threatening disease spread to humans by some types of mosquitoes. It is mostly found in tropical countries. It is preventable and curable.

Despite recent setbacks in malaria control, the global burden of malaria has been reduced over the last 2 decades thanks to investments in research and development. Rapid diagnostic tests, insecticide-treated nets and therapies have been the backbone of the malaria response since 2000. Continued investment in the development and deployment of next-generation tools will be key to achieving the 2030 global malaria targets.

New hope

Photo: Björt sýn.

A number of malaria vaccines are currently in development. Many of them target the malaria parasite before it enters the human liver where it can quickly multiply.

WHO already recommends broad use of the RTS,S/AS01 malaria vaccine among children living in the regions with moderate to high malaria transmissions. In addition, new diagnostics are on the way and there are several promising developments in the field of antimalarial medicines.

World Malaria Day 2023 is marked under the theme "Time to deliver zero malaria: invest, innovate, implement".

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