Tropical Diseases in Africa – Sleeping Sickness

by Shravya Murali – Art in Tanzania internship

Human African Trypanosomiasis, also known as ‘Sleeping Sickness’ is a neglected tropical disease, and a recurrent public health problem in Sub-Saharan Africa. The deadly sleeping sickness has robbed tens of thousands of lives of individuals in Africa annually, and about 65 million people continue to be at risk of falling prey to it. Fortunately, internationally coordinated efforts have led to a drastic drop in death rates after 2000, with the reported cases of infection being 992 in 2019. It is vital to sustain these global efforts to eradicate the disease for the safety of millions residing in Sub-Saharan Africa.

How does sleeping sickness spread?

This life-threatening disease is spread to humans via bites from tsetse flies that carry the parasite (Trypanosoma brucei) causing the disease. Tsetse flies are exclusively found in Africa, specifically in the south of the Sahara. While there are about 30 species or sub-species of the tsetse fly, only six are known to be able to transmit the sleeping sickness parasite to humans.

However, this disease can also spread from an infected individual to another individual via:

  1. Contaminated needles (i.e., sharing of needles with an infected individual)
  2. Sexual contact – reported to have resulted in the spread of the disease between humans in some cases.
  3. Pregnancy – The parasite is able to cross the placenta, thereby spreading from mother to fetus.
  4. Mechanical transmission – The parasite may spread from human-to-human through other insects that feed on blood.

What are the effects of the disease?

The disease can manifest in two forms caused by different subspecies of the Trypanosoma brucei sleeping sickness parasite – T.b.rhodesiense and T.b.gambiense. The former is commonly associated with the presentation of a painful inflammation, known as ‘chancre’, at the site of the bite. The latter rarely results in a chancre although this has been occasionally observed in infected travellers from non-endemic regions. The “Winterbottom’s sign”, or swollen lymph nodes, is more commonly observed in infections caused by T.b.gambiense.

Regardless of the subspecies of the parasite, the disease comprises of two stages at which it can be clinically diagnosed – the early stage, and the late stage. Furthermore, the symptoms are usually common, causing difficulties in identifying the subspecies that resulted in the disease.

In the early stage, the parasite is found in the blood and the lymphatic system. Its symptoms commonly include:

  • Restlessness
  • Fatigue
  • Headache
  • Itchiness
  • Joint pain

Signs such as weight loss, intermittent fevers that occur could for a day up to a week, and swelling of the liver and spleen, are usually indicative of an early-stage infection.

In T.b.gambiense infections, the disease progresses slowly as it proceeds from the early stage to the late stage after about 300 to 500 days. On the other hand, T.b.rhodesiense infections advance quicky from the early to the late stage in only around 21 to 60 days.

The late stage is known to be riskier as the parasite enters the central nervous system and results in inflammation of the brain – a condition known as meningoencephalitis – which causes neuropsychiatric problems and tends to be fatal. Some of the neuropsychiatric issues include reversal of the sleep-wake cycle (hence the name “Sleeping Sickness”), hallucinations, anxiety, aggression, and mania. The patient may also enter coma, and if left untreated, this stage leads to death.

How is sleeping sickness treated?

The sleeping sickness, after infection, is normally treated by administered specific drugs depending on the stage of infection. For early-stage infection, pentamidine or suramin is used. Both drugs produce unwanted side-effects and can only be used for early-stage infections. While suramin can result in allergic reactions, pentamidine, is commonly well-tolerated by patients. In the late stage, melarsoprol, eflornithine, and nifurtimox are usually used. While melarsoprol can be used to treat both gambiense and rhodesiense infections, it is obtained from arsenic, hence resulting in serious side effects such as reactive encephalopathy – altering brain function. Eflornithine and nifurtimox are less toxic, but the former is only effective against gambiense infection, while the latter has not been studied for its effectiveness against rhodesiense infections. Hence, the current treatments against late stage rhodesiense infections are still inadequate, drawing an urgent need for sufficient treatment considering the quick progression of infection caused by this subspecies.

What could be done to prevent the disease?

Due to the lack of drugs or vaccines to allow for immunity against sleeping sickness, the only way to prevent the disease currently is to avoid contact with tsetse flies. In countries where tsetse flies are found, the following precautions can be taken:

  • Checking vehicles before travelling in them, as tsetse flies are drawn to motion and dust from vehicles in motion.
  • Wearing fully covered clothing, such as pants and shirts with long sleeves.
  • Ensure that clothes worn are of neutral colours or blend with the environment, as tsetse flies are attracted to colours that stand out in the environment.
  • Avoiding bushes, where the tsetse flies often reside.
  • Using insect repellent to prevent bites from other blood-sucking insects other than tsetse flies that can spread the disease – as tsetse flies are not significantly affected by insect repellents.

The World Health Organisation (WHO) aims to completely eradicate the African Trypanosomiasis by 2030, with international research organisations coordinating to study potential treatments that are more effective, and drugs that may help prevent the disease. At the same time, it is also important that individuals play their part in avoiding transmission of the disease by taking the necessary precautions for the safety of all.

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