Psittacosis: This diagnosis is likely due to the patient's exposure to chickens. Psittacosis is a bacterial infection caused by Chlamydophila psittaci, which can be transmitted to humans from infected birds, including chickens. The patient's age and exposure history make this a plausible diagnosis.

Influenza: Given the patient's age, influenza is a common cause of recurrent fever, especially during flu season.
Avian Influenza: Although less common, avian influenza (bird flu) can be transmitted to humans who come into contact with infected birds, making it a possible diagnosis.
Campylobacteriosis: This bacterial infection can be acquired through contact with chickens or their feces, leading to symptoms like fever.

Salmonellosis: This bacterial infection can be severe in older adults and is associated with contact with chickens or their feces. Missing this diagnosis could lead to severe consequences, including sepsis.
E. coli Infection: Certain strains of E. coli can cause severe infections, including those acquired from animal exposure. Older adults are at higher risk for complications.
Histoplasmosis: Although more commonly associated with exposure to bird or bat droppings, histoplasmosis can cause recurrent fever and is important not to miss due to its potential severity.

Q Fever: Caused by Coxiella burnetii, Q fever is a rare zoonotic disease that can be transmitted from animals, including birds, to humans. It's less likely but should be considered in the differential due to the patient's exposure to chickens.
Cryptococcosis: This fungal infection is more common in immunocompromised individuals but can be acquired from exposure to bird droppings. It's a rare consideration but important in patients with recurrent fever and appropriate exposure history.