Which aquatic pest is known to transmit diseases to humans?

Certain species of mosquitoes are well-known vectors for transmitting diseases to humans. These mosquitoes can carry and spread various pathogens, including viruses and parasites that cause significant health issues. For instance, species like Aedes aegypti and Anopheles gambiae are notorious for transmitting diseases such as dengue fever, Zika virus, and malaria, respectively.

In contrast, while water fleas, freshwater snails, and algae can be associated with aquatic ecosystems, they do not pose a direct threat to human health through disease transmission in the same way that mosquitoes do. Water fleas primarily serve as food for fish and do not infect humans. Freshwater snails can be hosts for certain parasitic worms, but they do not actively transmit diseases to humans in the way mosquitoes do. Algae may contribute to harmful algal blooms that can produce toxins affecting water quality, but they do not directly transmit diseases to humans either. Hence, the distinctive role of certain species of mosquitoes as disease vectors makes them the correct choice in this context.