Q&A: Diagnosing Tropical Diseases

Tropical diseases encompass all diseases that occur solely, or principally, in the tropics. In practice, the term is often taken to refer to infectious diseases that thrive in hot, humid conditions, such as malaria, leishmaniasis, schistosomiasis, onchocerciasis, lymphatic filariasis, Chagas disease, African trypanosomiasis, and dengue.

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In this article:
Neglected tropical diseases
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

Neglected tropical diseases

The people who are most affected by these diseases are often the poorest populations, living in remote, rural areas, urban slums or conflict zones. Neglected tropical diseases persist under conditions of poverty and are concentrated almost exclusively in impoverished populations in the developing world.

Lacking a strong political voice, people affected by these tropical diseases have a low profile and status in public health priorities. Lack of reliable statistics and unpronounceable names of diseases have all hampered efforts to bring them out of the shadows. They include dengue, rabies, blinding trachoma, Buruli ulcer, endemic treponematoses (yaws), leprosy (Hansen disease), Chagas disease, human African trypanosomiasis (sleeping sickness), leishmaniasis, cysticercosis, dracunculiasis (guinea-worm disease), echinococcosis, foodborne trematode infections, lymphatic filariasis, onchocerciasis (river blindness), schistosomiasis (bilharziasis), soil-transmitted helminthiases (intestinal worms).

Neglected tropical diseases affect more than 1 billion people, primarily poor populations living in tropical and subtropical climates. They are frequently clustered together geographically and individuals are often afflicted with more than one parasite or infection. More than 70% of countries and territories that report the presence of neglected tropical diseases are low-income or lower middle-income economies.

MCQ: clinical scenario

While working with a missions organisation in Africa a doctor is asked to see a 28 year old male with fresh bleeding per rectum. The man gives a history of increasing fever, headache and constipation. On inspection he is noted to have a relatively slow pulse rate and pinkish spots are seen on his abdomen.

The most likely diagnosis is:

a) Lyme disease
b) Brucellosis
c) Typhoid fever
d) Listeriosis
e) Psittacosis

MCQ: answer

The correct answer is C

MCQ: explanation

Typhoid fever is a disease largely of developing countries where sanitary conditions are insufficient to stop its spread. Typhoid fever is a protracted disease that is associated with bacteraemia, fever, and chills during the first week; widespread reticuloendothelial involvement with rash, abdominal pain, and prostration in the second week; and ulceration of Peyer patches with intestinal bleeding and shock during the third week. Typhoid fever may lead to an erosion of the blood vessels in Peyer's patches that without appropriate treatment may result in gross blood in the faeces in 10 to 20% of the patients. Severe intestinal hemorrhage may complicate approximately 2% of the cases late in the course of untreated typhoid fever. Such intestinal bleeding may precede perforation, another complication of typhoid fever.

Reference(s)
1). WHO: Tropical diseases. Available online: https://www.who.int/topics/tropical_diseases/en/
2). WHO: Why are some tropical diseases called "neglected"?. Available online: https://www.who.int/news-room/q-a-detail/why-are-some-tropical-diseases-called-neglected