Which of the following is NOT considered an external parasite?

An ascarid is not considered an external parasite because it is a type of internal parasite. Ascarids are a group of roundworms that live primarily in the intestines of their hosts, such as livestock and other animals, where they feed and reproduce. They can lead to health issues such as malnutrition or blockages if present in significant numbers.

In contrast, ticks, fleas, and botflies all fall into the category of external parasites. Ticks and fleas attach themselves to the skin of the host and feed on blood, potentially transmitting diseases in the process. Botflies lay their eggs on the host's skin, and the larvae burrow into the flesh, causing harm to the host from the outside.

Understanding the distinction between internal and external parasites is crucial for effective parasite management in livestock. Recognizing that ascarids are a type of internal parasite helps clarify the broader context of animal health and disease prevention.