Wright's stain, 400x

Several pulmonary parasites can be identified from lung fluid samples (tracheal lavages, bronchioalveolar lavages, tracheal swabs or biopsies). Parasitic larvae which can be isolated in these samples include Filaroides sp., Aelurostrongylus abstrusus, Crenosoma vulpis; and some oocysts such as Capillaria aerophila as well as Paragonimus sp. These parasites are often associated with an infiltration of eosinophils. The parasite illustrated in this microphotograph is a Filaroides osleri larva found at the bronchial bifurcation. It affects dogs. The parasite stimulates an inflammatory response and subsequent formation of nodules. When a strong  infiltration of eosinophils is found in a sample and parasites are not seen, it is recommended to do a coprology which includes a Baermann test which may allow the identification of larvae present in the feces (and which may have been coughed up from the respiratory tract and swallowed). Other ways of isolating and identifying such parasites are by a scraping or a biopsy of the nodules in the bronchi of affected animals. Allergic bronchitis or pneumonia can be associated with parasitic infections, though dirofilariasis or asthma can also be associated with eosinophilic inflammation.