Which parasite can cause demodicosis in dogs?

Demodicosis in dogs is specifically caused by Demodex mites, which are a type of ectoparasite. These mites are normally present on the skin of healthy dogs in small numbers, but certain conditions, such as a weakened immune system, can lead to an overgrowth of these mites and subsequent skin disease, or demodicosis.

Demodicosis manifests in various forms, including localized and generalized, often resulting in symptoms like hair loss, redness, and secondary bacterial infections. Understanding this helps highlight the unique relationship between the host's immune response and the presence of these mites.

Other parasites listed, such as fleas, ticks, and heartworms, do not cause demodicosis. Fleas and ticks primarily cause irritation and can transmit other diseases, while heartworms affect the cardiovascular system. Since Demodex mites are the specific cause of demodicosis, they are the correct answer.