Divulgação, Notícias

Active search for locally unknown diseases in “non-endemic” countries and regions

Lessons learned from work to reveal Visceral Leishmaniasis in previously unknown focus in Northern Somalia


By Dr. Mikko Aalto


Visceral Leishmaniasis children with their mothers: In the back row Registered Nurse Fadumo Osman, Dr Mikko Aalto and Dr Abdiaziz Ahmed Mohamed

All clinicians know that some patients get the right diagnosis and consequently the right treatment almost automatically.

And that for others there are two equally important factors that hinder finding the correct diagnosis.

First, many clinicians are unfamiliar or even have never heard about some diseases, even if they are common in some geographic areas.

Secondly, some diseases need special samples and tests which would not be done, unless the clinician suspects actively exactly that special disease. Lumbar puncture for meningitis and spleen aspiration for visceral leishmaniasis (VL) are examples where even the sample would not be taken if the clinician does not suspect especially meningitis or VL.

On contrary, a bone marrow aspiration can be done when the clinician suspects any hematologic disease, and a good pathologist or hematologist would then see the Leishmania amastigotes even if some type of leukemia was suspected clinically.

The same problem arises when a standard sample, like venous blood or urine sample is taken as a routine, but the necessary specific test is not part of the local routine pattern of tests.

Examples are pregnancy test, random blood sugar and malaria rapid diagnostic test (RDT), causing missing of life threatening diseases, like ectopic pregnancy, diabetic ketoacidosis or falciparum malaria.

It becomes even more difficult when the test needed is not available in the health care system, maybe in the whole country. This is the case e.g. with leishmaniasis RDTs. They are provided free of charge by WHO and other organizations, but only in countries and geographic areas where there is proven presence of VL. This practice is one of the causes why VL remains undiagnosed in many tropical areas if there is no active search for it.

The same applies to many other diseases, like Ebola Virus Disease (EVD), African and American Trypanosomiases and their respective RDTs. If they are not available at least at the first referral level, they remain undiagnosed, with disastrous effects both for patients and public health.

It is important to note that while many new tests like serologic RDTs and new genomic tests improve and speed up diagnostics, they can do it at the cost of forgetting other more broad spectrum tests.

Thin and thick blood films used to be the gold standard for first line test for acute fever. Besides malaria they used to reveal also borreliosis, trypanosomiasis, sickle cell disease and leukemia.

Now the widespread use of malaria RDTs has lead to abandoning the more time consuming microscopy leading to a situation that these other diseases now need to be actively suspected.

Also relying on genomic tests can lead to forgetting of old culture based tests, which can detect completely unsuspected pathogens like Histoplasma capsulatum when the culture conditions were optimized for Leishmania donovani complex, or Kingella kingae when culture conditions are optimized for Staphylococcus aureus and other more common pathogens.

The question of clinicians not being familiar with important diagnoses is a more complex one.

Even in developed countries the medical education tries to cover the diseases more common in that country, and of disease prevalent in the tropics malaria can be the only tropical disease covered somehow appropriately in medical training. So diseases like leishmaniases, schistosomiases or liver flukes can receive no attention at all in medical education in arctic and temperate climate countries.

In least developed countries there are problems in the level of medical education in general and lack of chances for continuous education.

In countries with worst situation in [health] public and private health care systems the common feature is prolonged armed conflicts and their devastating effects on the whole human civilization in affected countries.

Finding solutions to these shortcomings might be less complex than analyzing their causes.

Horizontal programs which try to improve the level of Health Centres (HC) and Maternal and Child Health Clinics (MCHC) and first referral level hospitals can complement effectively the great successful vertical programs targeting specific diseases like tuberculosis, malaria, maternal and child mortality and others. As the number of important diagnoses on the first levels of health care is at least in hundreds, it cannot be expected that as many vertical programs could be created to solve the problems even at this level.

And as important the work to develop the whole civilization in the least developed countries is, we cannot wait until it bears fruit in offering a decent health care and nutrition to the most disfavored populations.

Free or affordable quality health care should be provided by international efforts to those populations which are completely unable to do it by themselves now and in the foreseeable future.

Stopping the use of resources by developed countries to armed conflicts in least developed countries would alone provide ample financing and resources to these tasks.

Finally, it is not reasonable to wait for the health care system of the least developed countries to be able to find and report to WHO and international community the diseases which are thought even not to exist in those countries.

The experience from working out the presence of visceral leishmaniasis in a previously unknown focus in Northern Somalia shows how important it is to actively search for such diseases in geographic areas where the disease is both unknown and even thought not to exist.

Inspired by the experience in Northern Somalia an active search for finding visceral leishmaniasis also in Tanzania, a “non-endemic country” was started in March 2019.

The first diagnosis of visceral leishmaniasis, without any travel history, was done in the same year, in this “non-endemic country”, although all classical confirmatory tests were not done.

Again it is only after working out the first diagnosis, with limited local experience and resources, that external help can be expected for Tanzania from WHO and international VL research community.

So, the final conclusion is that there is a need of international support for active search of so called neglected tropical diseases and similar diseases at least in the least developed countries.

Mikko Aalto primary research interests include malaria, leishmaniasis, and the control of their vectors (CV PDF)

Author suggested readings:

  1. Visceral Leishmaniasis, Northern Somalia, 2013–2019. Aalto MK, Sunyoto T, Yusuf M, Mohamed A, Van der Auwera G, Dujardin J. Emerg Infect Dis. 2020;26(1):153-154. https://dx.doi.org/10.3201/eid2601.181851
  2. First report of the visceral leishmaniasis vector Phlebotomus martini (Diptera: Psychodidae) in Tanzania. Clark JW, Kiosk E, Odemba N, Ngere F, Kamanza J, Oyugi E, Kerich G, Kimbita E, Bast JD. J Med Entomol. 2013 Jan;50(1):212-6.

DOI: https://doi.org/10.1603/ME12147

  1. Map: Status of endemicity of Visceral Leishmaniasis
  2. https://www.who.int/leishmaniasis/burden/Status_of_endemicity_of_VL_worldwide_2016_with_imported_cases.pdf?ua=1