Which insect is usually associated with rats in the transmission of diseases?

Fleas are typically associated with rats in the transmission of diseases. They are known vectors for various pathogens that can infect both animals and humans. When rats infest an area, they often carry fleas that can jump onto humans or other animals, potentially spreading diseases such as the bubonic plague, murine typhus, and other illnesses.

The relationship between rats and fleas is significant because fleas can thrive in rat nests and can reproduce quickly, increasing the chances of disease transmission. This association enhances the risk of outbreaks in environments where rat populations are high.

Choosing the correct answer highlights the importance of understanding the roles that specific pests play in disease ecology, particularly how secondary pests like fleas interact with primary hosts like rats. While other options may involve interactions with other pests, they do not hold the same specific and notable connection to the transmission of diseases linked directly to rats as fleas do.