A 33-year-old farmer presents to the clinic with symptoms of recurrent wheezing and coughing after working in a barn where hay is stored. He has no prior history of asthma, and is not taking any medications. On physical examination, there are bibasilar crackles on auscultation of the lungs, the heart sounds are normal, JVP is 2 cm above the sternal angle, and there is no peripheral edema.His laboratory investigations are normal with no increase in eosinophils on the CBC. The chest x-ray (CXR) reveals patchy lower lobe infiltrates, and a normal cardiac silhouette. Which of the following is the most likely diagnosis?