What clinical signs are caused by pinworms (Oxyuris sp.) in affected animals?

Pinworms, particularly Oxyuris species, are known to cause specific clinical signs primarily associated with irritation and discomfort in the rectal and perianal areas. The most notable sign in affected animals, especially horses, is pruritis or intense itching around the tail base. This itching leads to frequent scratching, which can result in excoriations or abrasions of the skin, and may also cause broken hair at the tail base due to the animal’s persistent attempts to relieve the itch.

The other choices describe symptoms more commonly associated with different conditions. For instance, diarrhea and fever are typically linked to gastrointestinal infections or other digestive issues. Weight loss and lethargy are more general signs that could indicate a variety of health problems, including parasitic infections or systemic illnesses, but are not specifically indicative of pinworm infestations. Lastly, respiratory distress and coughing are signs that are typically associated with respiratory tract conditions rather than a pinworm infection, which primarily affects the intestines and anal area. Thus, the clinical signs caused by Oxyuris sp. clearly align with pruritis, excoriations, and broken hair at the tail base, making this the correct choice.