Spontaneous lung pathology in a captive common marmoset colony (Callithrix jacchus)

Abstract

Data on spontaneous pathology are substantially scarce for common marmosets, compared to other laboratory animals, but is essential for the interpretation of histological findings in the context of toxicological and experimental studies. Especially if common marmosets are used as experimental animals in respiratory research, detailed knowledge on the spectrum, occurrence, and incidence of spontaneous histopathological pulmonary lesions in this non-human primate species is required. In this study, lung tissue of 638 common marmosets from the marmoset colony of the German Primate Center was examined histologically. The analysis revealed a high incidence of predominantly mild and multifocal interstitial pneumonia (32.99 %) of unknown etiology in most cases. Only few marmosets exhibited lobar pneumonia (1.41 %) and bronchopneumonia (0.94), which were mainly caused by bacterial pathogens such as Bordetella bronchiseptica and Klebsiella pneumoniae. Lung immaturity and atelectasis were common histological findings in newborn marmosets. Typical background lesions included anthracosis (8.15 %), hemosiderosis (1.72 %), extramedullary hematopoiesis (11.6 %), mineralization (10.97 %), and inflammatory cell foci (10.34 %). In addition, three cases of pulmonary arteriopathy (0.47 %) and 1 case of foreign-body granuloma (0.16 %) were detected in the marmoset study cohort. The high prevalence of circulatory disturbances (congestion, edema, hemorrhage) and changes in air content (secondary atelectasis, alveolar emphysema) could partly be explained by euthanasia-related artifacts or agonal changes. The present study provides a comprehensive overview of the range and incidence of spontaneous pulmonary histopathology in common marmosets, serving as valuable reference data for the interpretation of lung lesions in toxicological and experimental marmoset studies.

Figure 1

Mild subacute multifocal to coalescing interstitial pneumonia in an adult male common marmoset. Alveolar septa are thickened by infiltrates of lymphocytes, plasma cells, macrophages, and few neutrophils. There is concurrent congestion and evidence of minimal multifocal hemorrhages. HE, scale bar $=$ 100 $\mathrm{\mu }\mathrm{m}$.

Figure 2

(a, b) Severe diffuse acute to subacute fibrinopurulent lobar pneumonia in a female juvenile common marmoset. Alveoli are filled with degenerate neutrophils, macrophages, fibrin, edema fluid, and necrotic debris. HE, scale bar $=$ 100 $\mathrm{\mu }\mathrm{m}$ (a). Grossly, there is abundant suppurative exudate on the cut surface of the affected lung lobes (b). In this specific case, bacterial culture was negative.

Figure 3

Pulmonary lymphoma in a female juvenile common marmoset. Pleomorphic lymphoblasts with considerable mitotic activity infiltrate the lung parenchyma. HE, scale bar $=$ 50 $\mathrm{\mu }\mathrm{m}$.

Figure 4

Pulmonary anthracosis in an adult male common marmoset. Dark-brown-to-black pigment is located in perivascular and peribronchiolar areas. There is mild concurrent pulmonary congestion. HE, scale bar $=$ 50 $\mathrm{\mu }\mathrm{m}$.

Figure 5

Perivascular inflammatory cell focus in an adult male common marmoset. Plasma cells, lymphocytes, and macrophages are the predominant cell type in this lesion. HE, scale bar $=$ 20 $\mathrm{\mu }\mathrm{m}$.

Figure 6

Lung immaturity with cuboidal alveolar epithelium in a female newborn common marmoset. There is intra-alveolar evidence of amniotic fluid aspiration. HE, scale bar $=$ 50 $\mathrm{\mu }\mathrm{m}$.

Figure 7

(a, b) Focal subpleural fibrosis with mineralization in an adult female common marmoset. HE, scale bar $=$ 100 $\mathrm{\mu }\mathrm{m}$ (a). The corresponding macroscopic picture is characterized by multifocal subpleural plaque formation (b).

Figure 8

Foreign-body granuloma in an adult female common marmoset. A hair fragment is surrounded by multinucleated giant cells and macrophages. HE, scale bar $=$ 20 $\mathrm{\mu }\mathrm{m}$.