Which of the following best represents an example of infectious disease spreading via a vector?

A. Agent, Host, Environment: The epidemiologic triangle consists of:

• • Agent – The cause of disease (e.g., bacteria, viruses, toxins).

  • Host – The person or animal affected by the disease.

  • Environment – External factors that influence disease transmission (e.g., climate, sanitation, population density).

B. Agent, Condition, Variable: "Condition" and "Variable" are not standard components of the epidemiologic triangle. The correct term is host (the affected person or animal).

C. Agent, Host, Condition: "Condition" is not part of the triangle. The environment is a crucial factor that influences the spread of disease.

D. Agent, Host, Disease: "Disease" is an outcome rather than a component of the epidemiologic triangle. The triangle focuses on the factors that contribute to disease spread, including the environment.

A. Ticks: Ticks are ectoparasites that attach to the outside of the host rather than living inside the body.

B. Protozoal: Protozoa (e.g., Giardia lamblia, Entamoeba histolytica) are endoparasites that live inside the host, affecting the digestive system.

C. Mites: Mites (Sarcoptes scabiei) are also ectoparasites and do not cause internal gastrointestinal infections.

D. Roundworms: Roundworms (Ascaris lumbricoides) are endoparasites that live in the intestines and can cause gastrointestinal symptoms and malnutrition.

E. Tapeworms: Tapeworms (Taenia solium, Taenia saginata) are also endoparasites that reside in the intestines and can cause weight loss and abdominal discomfort.