Neglected tropical illnesses and their postage stamps

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All diseases are not equal. While some get more attention, others are neglected. This unequal treatment is often due to either a threat-perception, our ability to make a change, or simply because fewer people talk about them.

Further, modern medicine has always had its focus on disease-threats in the northern hemisphere. For instance, tuberculosis because it was common, and malaria as it could spread. As explorers, followed by merchants, and then colonialists from the North explored new lands in Latin America, Asia and Africa, they came across many unusual diseases. These unusual diseases from the tropics, led to their amalgamation as “tropical medicine”.

What if…

If perhaps colonialists were from the tropics, “temperate medicine” could be a speciality. We do have a 1961 term “polar medicine“, that started with polar expeditions. Today we better describe it as “wilderness medicine“. So “tropical medicine” or “tropical diseases” is perhaps a branch of medicine, typified by its geography.

In 2005, World Health organisation, identified about 20 of “tropical” diseases as neglected. Today, these are collectively called NTDs or neglected tropical diseases. Lets explore philately related to some of these NTDs

Swollen limb due to Lymphatic Filariasis

Filariasis is an ancient disease, well documented in ancient, as well as medieval texts. A typical manifestation is a hard, painless, swollen leg or an arm, that stays on for years. At times it is more hidden, either as a swollen scrotum, or a white milky urine. By the end of the 19th century, we knew that is because of a worm-parasite, that blocks our lymph channels. These worms produce tiny, microscopic wormlets that sometimes escape from the tissues to reach in our blood. Then in-turn mosquitoes pass on these wormlets (or microfilaria) from one person to another.

Onchocerciasis – or “river blindness” – is another filarial disease caused by Onchocerca volvulus. Also known as river-blindness, as the organisms manage to enter the eyes. Onchocerciasis affects eyes and skin. This neglected disease is seen in countries of Sub-saharan Africa and South America.

Human African Trypanosomiasis or the sleeping sickness

Trypanosoma infection in the countries around Congo Basin, leads to an illness known as “sleeping sickness”. The parasite, spreads from one person to another through a fly (we know as tse-tse fly or glossina species.

The story of Yellow fever

Today, if any person from outside Africa or South America needs to visit these parts of the world, she needs a Yellow fever vaccine. This tropical disease causes fever and jaundice. For years it was confused with malaria, but we could not find any malarial parasites in the blood. In 1880s, Carlos Finlay a Cuban physician discovered that this disease is spread by Ades mosquito. This theory was accepted more than 20 years later by Walter Reed, who embarked on a mission to eliminate Ades mosquito in central America.

We could isolate the yellow fever virus in 1927, and developed its vaccine in 1936. This work was led by Max Theiler, a South Africa born scientist.

Leishmaniasis: Cutaneous (Sore) and Visceral (Kala Azar)

An illness that led to a boil like skin lesion (or sore) was known since ancient and medieval times. This carried many names such as tropical sore, Allepo sore, Delhi sore, Bagdad sore etc. Another illness where patients had fever, large spleen and darkening of their skins was also observed by Britishers in Bengal and Assam. This was locally known as Kala-Azar (or Black condition).

In the year 1900, a Scottish pathologist William Boog Leishman, who was then serving in the British Indian Army discovered an organism in spleen of a dead soldier. Same organism was also described independently, by an Irish doctor Charles Donovan, who was then working in Madras Medical College. The organism was hence called Leishmania donovani, and the disease as Leishmaniasis. In next few years, the same type of organism was also seen in tropical sores, connecting the two diseases under the same same as Leishmaniasis. This organism was Leishmania tropica.

Chagas Disease and Trypanosoma Cruzi

This is a peculiar disease, from South America. Patients have fever and skin lesion, that goes away. However, many months or years later they developed slowing of heart, and difficulty in swallowing due to its late effects. In 1909, Carlos Chagas identified an organism from bugs. These tritomine bugs were found in the mud walls of typical houses in rural Brazil. This organism was similar to Trypanosoma, that was seen in Africa.

While it is treatable, this disease still affects about 6 million people in South America. Since the organism was identified on 14th April 1909, the date is observed as world Chagas disease day.

Schistosomiasis

Schistosoma are flukes, that usually cause disease in animals. We know such diseases as Zoonoses. This disease occurs in various forms in different parts of the world, as a disease of urinary bladder, or liver or of intestines.

The german parasitologists Theodor Maximilian Bilharz and Carl Theodor Ernst first discovered a schistosoma in 1851. This was from urine of a patient who had fever and bloody urine. This organism was Schistostoma haematobium. Schistosomiasis is known as bilharzia or bilharziosis in many countries.

Many years later in 1902, Patrick Manson discovered an organism in Central America. This was Schistostoma mansoni. The organism has a peculiar life-cycle that involves flukes, snails, water and human beings.

Bitten by a snake

Interestingly, WHO also lists snake bites as a NTD. While snakes are ubiquitous, and have many species and sub-species, their neglect comes from little scientific advancement in its treatment. Part of this neglect is because anti-snake venom or anti-sera are species specific. The species of venomous snakes vary by region, hence need for a different anti-sera. Vital Brazil Mineiro da Campanha, known as Vital Brazil a Brazilian physician-immunologist gave these concepts.

Today we use such multi-species (or polyvalent) anti-snake venoms in many parts of the world, including India. Vital Brazil went on to produce anti-venom against scorpions and various other species of snakes. He helped establish Butantan institute in Sao Pualo, a leading global center for anti-snake venoms in Brazil.

Neglect of tropical diseases

Today Health narrative is based on what is common, and how well it is funded. So some diseases end up as poor cousins of others. We often estimate how many person-years of life is lost by a disease – and amongst infections, malaria, HIV and tuberculosis rank high. The diseases with a limited geography do-not end up making their mark. They are often not on the global or even a regional health agenda. It is a number game after all.

Nations in the tropics will probably need to figure these out themselves, and take care of the neglect. Probably colonialism is gone, or not yet from the health-care agenda.