One of the worst parts of cottaging in the spring is having to flick away the annoying buzz of mosquitoes circling your head. Sure, you can douse yourself in bug spray and light up a mosquito coil, but somehow you still get bit.
While experts haven’t figured out a surefire way to prevent mosquitoes from biting, they have discovered a way to reduce the insect’s population—by poisoning them with human blood.
Researchers out of the Liverpool School of Tropical Medicine (LSTM) have discovered that the drug nitisinone makes human and animal blood deadly to mosquitoes. Nitisinone is an FDA-approved medication used to treat individuals with rare, inherited diseases, such as alkaptonuria and tyrosinemia type 1. This is where the body struggles to metabolize the amino acid tyrosine.
What makes it effective against mosquitoes is that nitisinone blocks an enzyme known as 4-hydroxyphenylpyruvate dioxygenase (HPPD). Researchers found that when mosquitoes ingested human blood containing nitisinone, it blocked the HPPD enzyme in the insects’ bodies, preventing them from digesting the blood, killing them within a few hours.
“Unlike conventional insecticides that target the mosquito’s nervous system, nitisinone targets an entirely different biological pathway in mosquitoes, which offers a new option for managing the growing problem of insecticide resistance,” said Lee Haines, first author on the study and an honorary fellow at LSTM, in a statement.
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In a previous study, researchers at LSTM found that nitisinone was fatal to tsetse flies, a blood-sucking insect that transmits African trypanosomiasis, a parasitic disease fatal to humans and animals. This motivated the researchers to test the drug against mosquitoes.
Researchers collaborated with the Royal Liverpool University Hospital, testing human blood containing nitisinone donated by patients diagnosed with alkaptonuria. The study found that nitisinone lasts in the blood for approximately 16 days and was effective with as little as a daily dose of two milligrams.
One of the most exciting outcomes of the study is that nitisinone could prove to be an effective tool in reducing the spread of malaria. Approximately 600,000 people die per year from malaria, mostly in Africa. It continues to be a leading cause of preventable death, particularly targeting children.
The researchers theorized that if enough people took nitisinone, it could significantly reduce the mosquito population, preventing the spread of malaria. Nitisinone proved effective against all types of mosquitoes, including older females, which tend to be the most common carriers of malaria, and hardier mosquitoes immune to insecticides.
However, the researchers pointed out that nitisinone is not a vaccine. The drug does not protect against malaria infection.
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The World Health Organization (WHO) currently distributes two types of malaria vaccines, but the parasite’s complex lifecycle can make it difficult for the vaccines to be effective. Currently, the WHO reports that the vaccines have caused a 13 per cent drop in mortality among children.
Some researchers have also proposed the use of the antiparasitic medication ivermectin to deal with mosquitoes. It functions similarly to nitisinone, making human blood toxic to the blood-sucking insects. Ivermectin is typically used to treat worm and parasite infections, but can cause health issues if overused, and can kill species other than blood-sucking insects, negatively impacting the environment.
“We thought that if we wanted to go down this route, nitisinone had to perform better than ivermectin,” said Álvaro Acosta-Serrano, study lead at LSTM, in a statement. “Indeed, nitisinone’s performance was fantastic; it has a much longer half-life in human blood than ivermectin, which means its mosquitocidal activity remains circulating in the human body for much longer. This is critical when applied in the field for safety and economic reasons.”
Due to its rare use, nitisinone remains expensive to purchase. The researchers said they hope that by extending the use of the drug, it could increase production and decrease the price.
The research team’s next goal is to figure out what dosage of nitisinone is most effective against blood-sucking insects.
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