Respiratory syncytial and parainfluenza type 3 viruses coexisting with Pasteurella multocida and Mannheimia hemolytica in acute pneumonias of neonatal alpacas
Introduction
Alpaca farming is the most important activity for traditional small herders throughout the Peruvian Andes. Reared at more than 3800 m elevation above sea level, these animals are the main, and in many cases the only, source of food and income for a vast rural population (Bustinza et al., 1988, Wheeler, 1991) whose herds are continuously devastated by massive neonatal mortality produced by infectious diseases, especially enteric and acute pneumonia (Rosadio et al., 1990, Ramírez, 1991).
Respiratory infections in alpacas are believed to result from the interaction of multiple factors including pneumonic pathogens, immune status of the host and the extreme Andean climatic conditions (Rosadio et al., 1990). Failure of passive immune transfer has been associated with fatal enteritis or pneumonia in this species (Garmendia et al., 1987), however, the definitive etiology of most of the lower respiratory tract infections is still poorly characterized. None the less, serologic studies have demonstrated that llamas and alpacas have been exposed to Parainfluenza virus 3, Bovine Diarrhea virus, Bovine Herpesvirus 1, Respiratory Sincytyal virus and Influenza virus A (Rivera et al., 1987, Rosadio et al., 1993) as well as to Mycoplasma spp. (Hung et al., 1991).
In 2004, Victorio et al. reported the presence of neutralizing antibodies to BRSV (80%) and PI3 virus (67.5%) in serum samples of 354 apparently healthy adult alpacas collected after a pneumonia outbreak from 30 different small herders in Cusco Department. In the present study, we report gross, microscopy and microbiological analysis of 24 lungs from 7 to 39 day old alpacas dying of acute pneumonia collected during the 2004 and 2005 birth seasons at 2 experimental research stations (n = 21) and a large cooperative farm (n = 3) in Southern Peru. Following the results of Victorio et al. (2004), we used the direct immunofluorescence test to monitor the tissues from each affected lung for the presence of PI-3 and BRSV antigens. Additionally, bacterial isolation under aerobic conditions on the same tissues revealed massive predominance of Pasteurella multocida and Mannheimia haemolytica, confirming the previously reported prevalence of these bacteria in acute pneumonia cases in Peru (Rosadio et al., 1990).
Section snippets
Animals
A total of 24 dead neonates (crias) aged 20 ± 9 days old (5–39 days) and weighing 7 ± 1 kg with a presumptive diagnosis of pneumonia and/or having respiratory difficulties were collected from the two “La Raya” Research Stations in Puno (n = 13) and Cuzco (n = 8), as well as from a cooperative farm (n = 3) in Puno. All the neonates were affected suddenly and, with the exception of 2, did not receive antibiotherapy prior to the fatal outcomes. Most of the dead carcasses (n = 21) were necropsied within 12 h
Gross and histopathological changes
Most of the animals were found dead or dying, and clinical information of the disease process was generally not available. In one neonate, however, we observed weakness, prostration with dyspneic respiration and stertoruos sounds at auscultation, but no nasal or ocular secretion or coughing occurred prior to death.
In 13/24 of the cases, gross alterations of the lungs were associated with extensive fibrinous necrotizing pneumonia (n = 3) or purulent necrotic pneumonia (n = 10) compromising both
Discussion
Acute pneumonia is the second cause of mortality among Andean alpaca neonates, but the definitive etiologic agent has not been determined. The results of this study show the presence of pneumotropic viruses (BRSV and PI3), in conjunction with P. multocida and/or M. haemolytica, in a range of pathological pneumonic lesions in alpaca neonates, supporting preliminary serological evidence for the presence of multiple agents within acute alpaca pneumonias in Peru (Rivera et al., 1987, Hung et al.,
Conclusions
Our investigation indicates that acute pneumonia in Andean alpacas shows some gross and histopathology similarities to identical illness in calves and lambs. It also suggests that the etiopathogenesis complex of acute pneumonia and resultant fatality could be a result of pathogenic interaction between virus (BRSV, PI-3) and bacteria (P. multocida and/or M. haemolytica). The study does not discard the participation of other potential pathogens, such as Mycoplasma sp. or Bovine Herpesvirus 1,
Acknowledgments
This project was partially financed by the Consejo Superior de Investigaciones Universidad Nacional Mayor de San Marcos, INCAGRO (subproyecto PIEA 00286), FINCyT (contrato 008-2007) and CONOPA Research Institute. Special thanks to W. Garcia, D. Pezo, S. Morales, M. Arainga and K. Guzman (Universidad de San Marcos), Julio Cubas and Jose Luis Apaza (Rural Alianza EPS) for materializing samples collection and J.C. Wheeler for assistance in writing the manuscript.
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