Researchers have discovered how Trichoderma asperellum, a fungal pathogen, kills the larvae of female anopheles mosquitoes, which spread malaria1.
The researchers found that the spores of the pathogen first attach to the outer layer of the larvae, after which they degrade it and secrete specific toxins. Such toxins eventually trigger the death of the larvae.
The fungus, the researchers say, could potentially be used as an effective bio-control agent, opening up a new direction in mosquito vector control and disease management.
T. asperellum is widely used in agriculture to combat pathogenic microbes that infect various plants. However, the effects of this fungus on the larvae of anopheles mosquitoes was unknown.
To explore this, scientists from the Ramakrishna Mission Vivekananda Centenary College in West Bengal, India, treated the larvae of anopheles mosquito with the fungal spores and then monitored host-pathogen interactions.
After three hours of interaction, the fungal spores attached themselves on the larval surface by using specific carbohydrate-containing adhesives. The spores then grew and secreted specific enzymes that degraded the cuticle, the outer layer of the larvae. This allowed the spores to puncture the cuticle and enter the larval body.
The fungi then secreted toxins that reduced the levels of phenol oxidase inside the larval body. Since this enzyme is associated with larval immunity, a decrease in its levels weakened the larval defence. This, in turn, promoted further growth of the pathogens, ushering larval death.
