Which of the following correctly describes vector-borne diseases?

Vector-borne diseases are defined by their reliance on a specific agent, often an insect or another organism, that is responsible for carrying and transmitting the pathogen to a host. This vector is crucial for the lifecycle of the pathogen, as it facilitates the spread from one organism to another. The presence of this carrier is what differentiates vector-borne diseases from other types of infectious diseases that may spread through other means, such as direct contact or airborne transmission.

In contrast to the other choices, vector-borne diseases can infect a wide range of hosts, including mammals, birds, reptiles, and humans. They are indeed transmissible to humans, as evidenced by many well-known diseases like malaria, dengue fever, and Lyme disease. Furthermore, not all vector-borne diseases are controllable; their management often depends on environmental factors, vector populations, and the efficacy of public health interventions. Thus, the correct answer emphasizes the essential role of the vector in the transmission process.