Interaction of Bordetella bronchiseptica, Pasteurella multocida, and fumonisin B1 in the porcine respiratory tract as studied by computed tomography

Abstract

The interaction of Bordetella bronchiseptica, toxigenic Pasteurella multocida serotype D, and the mycotoxin fumonisin B(1) (FB(1)) was studied. On day 0 of the experiment, 28 artificially reared 3-day-old piglets were divided into 4 groups (n = 7 each): a control group (A), a group fed FB(1) toxin (B), a group infected with the 2 pathogens (C), and a group infected with the 2 pathogens and fed FB(1) toxin (D). The B. bronchiseptica infection [with 10(6) colony-forming units (CFU)/mL] was performed on day 4 and the P. multocida infection (with 10(8) CFU/mL) on day 16. From day 16 a Fusarium verticillioides fungal culture (dietary FB(1) toxin content 10 mg/kg) was mixed into the feed of groups B and D. In groups C and D, clinical signs including mild serous nasal discharge, sneezing, panting, and hoarseness appeared from day 4, and then from day 16 some piglets had coughing and dyspnea as well. Computed tomography (CT) performed on day 16 demonstrated lung lesions attributable to colonization by B. bronchiseptica in the infected groups. By day 25 the number of piglets exhibiting lesions had increased, and the lesions appeared as well-circumscribed, focal changes characterized by a strong density increase in the affected areas of the lungs. The gross pathological findings confirmed the results obtained by CT. These results indicate that, when combined with dual infection by B. bronchiseptica and P. multocida, dietary exposure of pigs to FB(1) toxin raises the risk of pneumonia and increases the extent and severity of the pathological changes.

Figure 1

Lung lesions at the level of the 4th thoracic vertebrae on day 16 as shown by computed tomography (CT) of the lung of a piglet in group D infected with Bordetella bronchiseptica and Pasteurella multocida sero-type D and fed fumonisin B₁ (FB₁).

Figure 2

Demonstration of the progressively focal character of the lung lesions in serial CT scans of a piglet in group C on days 16 (A), 25 (B), and 39 (C) at the level of the 6th thoracic vertebra.

Figure 3

Diffuse inflammation extending to a lung lobule in the pulmonary parenchyma (A) and chronic inflammation of the pulmonary parenchyma extending to most of the left anterior, intermediate, and posterior lobes, accompanied by adhesive pleuritis (B), in piglets in group D.

Figure 4

Inflammatory and necrotic foci surrounded by a fibrous capsule in the pulmonary parenchyma of a piglet in group C. Hematoxylin and eosin (H&E); original magnification ×20.

Figure 5

Alveolar and interstitial edema in the lung of a piglet in group D. H&E; original magnification ×100.