What disease is indicated by a fever, nasal discharge, difficulty swallowing, and the horse standing with its head extended?

Strangles is characterized by a fever, nasal discharge, difficulty swallowing, and the distinctive posture of the horse standing with its head extended. The fever is typically one of the first signs to appear, followed by the development of nasal discharge, which can be thick and purulent due to the presence of the Streptococcus equi bacteria, responsible for the infection.

Difficulty swallowing occurs as the lymph nodes in the throat become inflamed and swollen, causing discomfort and obstructing the horse's ability to eat and drink normally. Horses often adopt a position with their heads extended in an attempt to relieve pressure on their throat or discomfort associated with the swollen lymph nodes.

Other diseases mentioned can show similar symptoms but do not align as closely with the specific combination of signs for strangles. While equine influenza can cause fever and nasal discharge, it typically does not involve the specific swallowing difficulties or the characteristic head position seen in strangles. Colic primarily affects the gastrointestinal system and presents with signs related to abdominal pain rather than respiratory symptoms. West Nile virus does not typically present with the combination of symptoms described but instead is more associated with neurological signs, such as incoordination or changes in behavior.

Thus, the combination of symptoms in this case points definitively to