Loção Catnip é tão eficaz quanto Deet para repelir mosquitos, segundo estudo

Uma loção de erva-dos-gatos produzida localmente provou ser “tão eficaz quanto o Deet” como repelente de mosquitos em testes realizados em Uganda.

Catnip, ou Nepeta cataria, é uma erva comum da família das mentas. The chemical in the plant that causes feline euphoria – nepetalactone – also has insect-repelling properties but this has not previously been commercialised.

New tools are vital in the fight against malaria, the disease spread by mosquitoes that infects about 282 million people a year and killed 610,000 in 2024 – the majority of them young children in African countries. Existem preocupações sobre o aumento da resistência aos insecticidas, bem como aos medicamentos de primeira linha utilizados para tratar a doença.

In a study presented at the Society for Experimental Biology conference in Florence on Tuesday, a team working between Uganda and Wales found mosquitoes seeking a blood meal were less likely to land on people wearing lotions made from catnip.

Dr Simon Scofield, a senior lecturer at Cardiff University, said: “We found that a 6% catnip oil was just as effective as Deet, and the 2% catnip oil was only marginally less effective than that.

“Deet is out of the price bracket for most rural Ugandan subsistence farmers, so buying commercially available mosquito repellents is just not practicable.

“We wanted to make a repellent, which is highly efficacious, but also allows local people to be involved in the production cycle so that it costs a minimal amount of money,” he said.

Se os gatos locais eram ou não mais propensos a seguir os usuários de loção não fazia parte da pesquisa, admitiu Scofield. “We did not conduct any experiments to see if it is attractive to cats, but given that the active ingredient [nepetalactone] has well-known cat-attractive properties, I would expect they would quite like it,” he said.

Na primeira parte da avaliação, testes laboratoriais confirmaram que o óleo de erva-dos-gatos poderia ser um repelente eficaz de insetos. Researchers then successfully tested the catnip repellent in the field in eastern Uganda by checking how many mosquitoes landed on volunteers’ legs over an evening.

Some volunteers used Deet (the world’s most widely used and effective insect repellent), some used a lotion with 2% concentration of catnip, others a 6% catnip lotion, while others used placebo creams.

A pesquisa também estabeleceu que a loção poderia ser produzida localmente por uma empresa comunitária. So far it has been distributed for free, using grant funding, but the next phase of the project will see production increased and the lotion sold to create a sustainable income for workers.

“Once we know that we can sell and distribute the repellent at a low cost, that should generate a self-sustaining system where the money is flowing back to everybody at each stage in the development,” said Scofield.

A loção Deet (N,N-Dietil-meta-toluamida) usada para comparação no ensaio contém 15% de Deet e é a mais amplamente disponível em Uganda. Os viajantes do Reino Unido que visitam regiões endémicas de malária são aconselhados a usar repelentes mais fortes com pelo menos 50% de Deet.

Swai Kyeba, a research entomologist from the Ifakara Health Institute in Tanzania who was not involved in the study, said: “New vector-control tools are necessary in the fight against malaria, especially those that are cheap and locally produced, to help improve accessibility.

“No entanto, um desafio com repelentes tópicos é a baixa adesão porque requerem aplicação regular. É por isso que continuam a ser uma ferramenta complementar na luta contra a malária.”

Ele pediu mais pesquisas sobre as famílias de Uganda que usam os repelentes atualmente disponíveis, antes que a produção de loção de erva-dos-gatos fosse ampliada.

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