Effects of intranasal inoculation with Bordetella bronchiseptica, porcine reproductive and respiratory syndrome virus, or a combination of both organisms on subsequent infection with Pasteurella multocida in pigs
Sl. Brockmeier et al., Effects of intranasal inoculation with Bordetella bronchiseptica, porcine reproductive and respiratory syndrome virus, or a combination of both organisms on subsequent infection with Pasteurella multocida in pigs, AM J VET RE, 62(4), 2001, pp. 521-525
Objective-To determine effects of intranasal inoculation with porcine repro
ductive and respiratory syndrome virus (PRRSV) or Bordetella bronchiseptica
on challenge with nontoxigenic Pasteurella multocida in pigs.
Animals-Seventy 3-week-old pigs.
Procedure-In experiment 1, pigs were not inoculated [n = 10) or were inocul
ated with PRRSV (10), P multocida (10), or PRRSV followed by challenge with
P multocida (10). In experiment 2, pigs were not inoculated (n = 10) or we
re inoculated with B bronchiseptica (10) or PRRSV and B bronchiseptica (10)
; all pigs were challenged with P multocida. Five pigs from each group were
necropsied 14 and 21 days after initial inoculations.
Results-Pasteurella multocida was not isolated from tissue specimens of pig
s challenged with P multocida alone or after inoculation with PRRSV. Howeve
r, in pigs challenged after inoculation with B bronchiseptica, P multocida
was isolated from specimens of the nasal cavity and tonsil of the soft pala
te. Number of bacteria isolated increased in pigs challenged after coinocul
ation with PRRSV and B bronchiseptica, and all 3 agents were isolated from
pneumonic lesions in these pigs.
Conclusions and Clinical Relevance-Infection of pigs with B bronchiseptica
but not PRRSV prior to challenge with P multocida resulted in colonization
of the upper respiratory tract and tonsil of the soft palate with P multoci
da. Coinfection with PRRSV and B bronchiseptica predisposed pigs to infecti
on of the upper respiratory tract and lung with P multocida. Porcine reprod
uctive and respiratory syndrome virus and B bronchiseptica may interact to
adversely affect respiratory tract defense mechanisms, leaving pigs especia
lly vulnerable to infection with secondary agents such as P multocida.