Fig. 11

Histological cross- and tangential sections of P. falciformis in the lung parenchyma. a, b. Viable P. falciformis adults (asterisks) coiled in the lung parenchyma and surrounded by a mild leukocyte reaction (many macrophages, occasional multinucleate giant cells, some lymphocytes and eosinophils) (black arrows) and smooth muscle hyperplasia. The alveolar walls are moderately expanded by the above described inflammatory cell population, with occasional alveolar wall rupture (arrowhead) and emphysema. c, d Detail of the marked areas in a and b. The parasites have a thin smooth cuticle (c) and pseudocoelom, coelomyarian-polymyarian musculature (m), intestine (i) with granular pigment and large uterus (u) filled with developing larvae (lv). The leukocyte reaction is also visible (black arrow in c). e, f. Free P. falciformis larvae (with thin walls and granular content) (black arrowhead in f) are present in the bronchiolar (b) and peribronchiolar spaces, associated with prominent inflammatory reaction consisting of many macrophage (some laden with hemosiderin) (asterisk in f), epithelioid cells and multinucleate giant cells (red arrowhead in f) and few eosinophils and fibroblast. Degenerated parasites (black arrow in e) induce a marked inflammatory response consisting of ill-defined granulomas (asterisks in e) and a locally-extensive interstitial lympho-histiocytic and eosinophilic pneumonia (arrowheads in e); H&E staining, ×20 (a, b and f), ×40 (c), ×100 (d) and ×10 (e). Scale-bars: a, b, f, 100 μm; c, 50 μm; d, 25 μm; e, 200 μm