Malaria is caused by the parasite Plasmodium falciparum, which is transmitted by mosquitos. The World Health Organization (WHO) estimates that in 2020, there were 241 million cases and 627,000 deaths worldwide, 94% of cases and 96% of deaths occur in sub-Saharan Africa. Tragically, malaria claims the life of a child under the age of five every minute.
As mosquito habitats have expanded with global warming, people are more likely to contract the malaria parasite. The WHO advises vector control to reduce the number of mosquitos and so lessen the likelihood of mosquito bites, as well as chemoprevention to prevent illness in the absence of an effective vaccine.
The parasite Toxoplasma gondii, a close cousin of Plasmodium, infects 2 billion people worldwide and is the cause of the foodborne illness toxoplasmosis. Babies and persons with compromised immune systems, such as those with AIDS or cancer, are more vulnerable to the disease. Studies also suggest that Toxoplasma parasites have long-term effects on a person’s personality and behaviour due to their ability to nest in the human brain, and they may play a role in schizophrenia and bipolar disorder.
Despite the tireless efforts of scientists to eradicate these two parasite-borne diseases, the drugs currently available to treat them are suboptimal, and few alternatives exist, if any.
Undesirable side effects
Treatment for toxoplasmosis often has serious side effects such as liver toxicity and suppression of the bone marrow, which is involved in the production of blood cells, putting immunocompromised individuals at even greater risk. In addition, there are no drugs that can kill Toxoplasma when the parasite establishes itself as a latent infection in the muscle and brain. Even when drugs do exist, cost can be a factor – one option, Daraprim, made news in 2015 after Turing Pharmaceuticals hiked the price from $13.50 to $750 per tablet in the United States, threatening access for vulnerable patients.
In places where malaria is endemic, artemisinin-based combination therapies (ACTs) are now the first-line treatments. Artemisinin is a plant extract that originated in traditional Chinese herbal therapy and was first synthesised by Dr. Tu Youyou, who received the 2015 Nobel Prize. However, a major worry is the spread of resistance to both artemisinin and alternative drug combinations, initially in south-east Asia and recently in Rwanda and Uganda. Resistance occurs when a medication loses its potency and can no longer completely cure the infection it was designed to treat.
A drug-development strategy that can save significant time and money in the “repurposing” of treatments initially approved for other illnesses or conditions. A well-known example is Sildenafil, originally developed to treat chest pain caused by coronary artery disease. While it failed clinical trials, scientists discovered that one of the drug’s side effects was erection, and it was purposed as Viagra, which…
La suite est à lire sur: theconversation.com
Auteur: Mohamed-Ali Hakimi, Research director in parasitology, Inserm
