While the world currently battles to lower the incidence of Covid-19, prospects for reducing the transmission of a far deadlier disease, malaria, may have improved. Any progress in this area could prove particularly beneficial for sub-Saharan Africa.
There are over 200mn incidents of malaria each year
Annually, the disease kills c400k people every year, making it one of the deadliest transmittable diseases. This is particularly the case for infants – globally it is the fifth most common cause of death for under-fives, and two-thirds of all malaria casualties are in this age group. For lower-income countries, malaria ranks as the sixth most common cause of death overall, with 40 deaths per 100k population per annum.
Top 10 causes of death in low-income countries
Source: WHO, World Bank
The economic costs of malaria are high
Even for survivors, the disease can prove debilitating, both when first caught and through subsequent attacks. Factor in the reduced productivity of carers, and malaria carries significant social and economic costs for the global economy. Some estimates show that families can spend up to 25% of their income on treatment of malaria and its after-effects (such as anaemia), while 10% of lost schooldays in Africa can be attributed to malaria (either of the child or a family member). A study by Gallup & Sachs (2000) showed that countries with endemic malaria had income levels in 1995 that were only 33% of those in countries that do not suffer from malaria. Countries with a severe malaria burden grew 1.3% less per year, compared with those without, while a 10% reduction in the incidence of malaria lifted annual GDP growth by around 0.3ppts.
Why is malaria so difficult to control?
It is estimated that up to US$5.8bn needed to be spent annually in order to reduce the incidence of malaria by 40% between 2015 and 2020. The current spending rate is around US$3bn, which is largely allocated towards R&D, provision of mosquito nets and anti-malarial drugs.
The annual cost of eliminating malaria
Source: Council for Foreign Relations, WHO
There are several reasons why malaria has proven so difficult to control, let alone eradicate.
- Firstly, contracting the disease once does not confer immunity on the individual. The malaria parasite can take different forms. Within the human body, it shifts from the liver to the blood stream. These factors make it hard for the immune system to effectively deal with the threat, and also complicate the challenge of developing an effective vaccine.
- Secondly, the malaria parasite is spread between individuals by a vector, mosquitos, that can have a far wider range, and survive for longer, than the most common ways for transmission of other communicable diseases (contact, aerosols etc).
- Compounding difficulties in controlling malaria has been the increasing prevalence of drug-resistant strains of the disease, which first emerged in Asia in the 1970s and in Africa in the 1980s. Mosquitoes, the parasite vector, have also been showing signs of resistance to pesticides such as pyrethroids, organophosphates and carbamates.
The malaria parasite lifecycle
Fungal warfare could be the answer
A recent paper noted that mosquitos on the Kenyan shores of Lake Victoria that were infected by Microsporidia MB did not carry the malaria parasite. Microsporidia is a naturally-occurring fungal-like organism that lives in the genitals and digestive tract of mosquitos. It seems that mosquitos infected with microsporidia have enhanced immune systems, which may prevent them from acting as a host for the malaria parasite.
Increasing the incidence of Microsporidia infection in the mosquito population (either by releasing spores, or by releasing infected male mosquitos to mate with females) could lower mosquitos’ effectiveness as a vector for the malarial parasite. Studies suggest microsporidia infection is passed from the female to her offspring. Note that male mosquitos do not bite humans.
An alternative solution also involves fungi, but this time with a more sinister outcome for the mosquito. A fungus, Metarhizium pingshaense, which naturally infects mosquitos, can be genetically modified to produce spider venom; initial tests in Burkina Faso showed that the modified fungus killed 99% of infected mosquitos.
Sub-Saharan Africa would be the key beneficiary of any curtailment of malaria
In 2018 there were an estimated 235mn cases of malaria globally, of which 93% were in Africa. Of the estimated 435k deaths due to malaria in 2017, the WHO thinks 93% occurred in Africa. Six countries accounted for more than half of all malaria cases worldwide - all are in the SSA region: Nigeria (25%), the Democratic Republic of the Congo (12%), Uganda (5%), and Côte d’Ivoire, Mozambique and Niger (4% each).
Meaningful reductions in the incidence of malaria in sub-Saharan Africa would have significant economic and societal benefits, particularly for lower-income and rural communities.
Malaria incidence is concentrated in sub-Saharan Africa
Source: WHO, Tellimer Research