Abstract :
The etiopathogenesis of acute pneumonia, the second most important cause of mortality
among neonatal alpacas in Peru, is still poorly understood. The objective of this study was to
characterize gross and histopathology lesions, as well as to identify viruses [parainfluenza
type 3 (PI-3) and/or bovine respiratory syncytial (BRS)] by direct inmunofluorescence
test, and isolate bacteria [Pasteurella multocida (Pm) and/or Mannheimia haemolytica (Mh)]
from 24 fatal acute pneumonia cases of alpaca neonates 7–39 days old. At necropsy
the gross lesions corresponded to moderate purulent focal bronchopneumonia or severe
necrotic purulent fibrinous (n = 13), and moderate to severe pulmonary congestion and/or
pulmonary edema (n = 11). Histopathological analysis revealed: acute severe and diffuse
necrotizing, fibrinous, suppurative bronchopneumonia (n = 3), acute mild to moderate and
focally diffuse suppurative bronchopneumonia (n = 10) and acute moderate to severe diffuse
congestion and pulmonary edema (n = 11). Among these 24 fatal cases, 22 yielded virus
identification and/or bacterial isolation. Eight of these 22 cases were positive for only one
pathogen (5 for viruses and 3 for bacteria), 10/22 were positive for 2 pathogens RSV plus
bacteria (n = 7), PI-3 plus bacteria (n = 2) and 1 for both bacteria and 4/22 were positive for
3 pathogens [RSV, PI-3 plus bacteria (n = 3) and PI-3 plus both bacteria (n = 1)]. Among the
affected lung tissues, virus was identified 19 times (13 positive for RSV, 9 for PI-3, and 3/19
for both viruses) whereas bacteria were isolated 14 times [P. multocida (n = 8), M. haemolytica
(n = 6), and both bacteria (n = 2)]. The presence of multiple pathogens was observed
in 14/22 positive cases with an observation of virus–bacteria association in 13/14 of the
cases. The coexistence of RSV-Pm was the most frequently observed (6/13) followed by the
simultaneous presence of RSV-Mh (4/13) and PI-3 Pm or Mh (4/13). These results appear to
indicate that acute pneumonia in alpaca neonates may well result from virus and bacterial
interactions in a similar way to pneumonic lesions of other ruminants.
