Effect of porcine reproductive and respiratory syndrome virus on subsequent Pasteurella multocida challenge in pigs

Abstract

This trial was conducted to evaluate the effect of Porcine reproductive and respiratory syndrome virus (PRRSv) on a subsequent challenge with Pasteurella multocida in pigs. Sixteen, 3-4 week-old piglets, from a PRRSv and Aujeszky disease virus (ADV) free herd were used. Animals were equally and randomly allocated in four groups which were treated according the following schedule: Group I: negative controls; Group II: inoculation with only PRRSV; Group III: inoculation with PRRSV and P. multocida; Group IV: inoculation with ADV and P. multocida (positive controls). PRRSV and ADV were inoculated intranasally, at the doses of 10(4.6) and 10(4.5) TCID50/ml, respectively. Five days later, pigs from groups III and IV were inoculated intranasally, with two ml of a 10(9) CFU/ml suspension of equal parts of P. multocida, strains A52 and A24. No lesions were observed in piglets of group I. Microscopically, interstitial pneumonia was identified in all piglets of groups II and III and 3/4 piglets from group IV. Bronchopneumonia was detected in 3/4 of the piglets from group III and in all animals of group IV which, additionally, showed meningo-encephalitis and purulent rhinitis. Macroscopically, only piglets of groups III and IV had lung consolidation. However, much lower pneumonic scores (2.3%) were observed in group III, where 3 of 4 piglets were affected. On the other hand, all piglets of group IV showed some degree of pulmonary consolidation, with a mean score of 13.7%. Based on these results, it appears that the role of PRRSV as a initiator of secondary diseases is still undefined, but is probably mild. There was no clear interaction between PRRSv and Pasteurella multocida under the conditions and strains tested here.

Pathogenesis of Porcine Reproductive and Respiratory Syndrome Virus-induced Increase in Susceptibility to Streptococcus suis Infection

“…28 The characteristics of isolate VR-2385 have been described previously. [1][2][3][4][5][6][7][8][9][10][11]14,28 Six randomly selected pigs from each group were necropsied on day 10 of the study. The remaining pigs were euthanatized when they became moribund or on day 28 of the study (Table 1).…”

“…27 In other experiments, a synergistic effect could not be demonstrated between PRRSV and bacterial infections. 1,3,19 Differences in experimental design, PRRSV strain, 9 S. suis strains, and host genetic factors 11 may influence the outcome of coinfection studies. For example, exposure of PRRSV-infected pigs to different S. suis strains resulted in different clinical manifestations and severity of disease, indicating that the strain of bacteria can influence the clinical disease induced in a coinfection model.…”

Pathophysiological changes occurring duringEscherichia coliendotoxin andPasteurella multocidachallenge in piglets: relationship with cough and temperature and predicitive value for intensity of lesions

“…As concluded by the authors of this trial, a daily monitoring of cough and a better record of the lung lesion volume could improve the predictive value of this symptom regarding the intensity of the pulmonary disease. Hyperthermia has also been monitored during swine respiratory infections involving Pasteurella multocida but the relationship between the body temperature and lung lesions was not investigated [6,9,15].…”

“…It was suggested that a daily monitoring rather than a weekly recording procedure would have strengthened this study. Hyperthermia has also been monitored during swine respiratory infections involving Pasteurella multocida but the relationship between the body temperature with lung lesions was not investigated [6,9,15]. Finally, the relationships between the cough, body temperature and other pathological parameters, scarcely measured in clinical conditions, as the magnitude of the pulmonary inflammatory process and the pulmonary functional changes, have never been investigated so far.…”

Biology and Diseases of Swine

“…The role of PRRS in exacerbating pasteurellosis is still uncertain and probably has only a mild effect (Carvalho et al, 1997). Vaccination and medicated feed (tetracyclines, tylosins) and water may be beneficial.…”