What constitutes a pathogen?

A pathogen is defined as a microorganism that can cause disease in its host. This includes bacteria, viruses, fungi, and parasites, all of which have the potential to disrupt normal biological functions and lead to illness. Understanding pathogens is crucial in mosquito control, as certain species can transmit diseases like West Nile virus or Zika virus to humans and animals.

In this context, the definition aligns with the role of pathogens in public health and vector control practices. Recognizing what constitutes a pathogen allows practitioners to develop effective strategies to manage and reduce disease transmission associated with mosquito populations.

The other choices represent different concepts that do not relate to the definition of pathogens. For instance, a disease-fighting agent refers to something that helps to combat disease rather than causing it, while immune cells are part of the body's defense system against pathogens rather than pathogens themselves. Similarly, treatments for infections are designed to eliminate or control pathogens rather than being classified as pathogens.