Objective—To examine effects of co-infection with
porcine reproductive and respiratory syndrome virus
(PRRSV) and Bordetella bronchiseptica in pigs.
Animals—Forty 3-week-old pigs.
Procedure—30 pigs (10 pigs/group) were inoculated
with PRRSV, B bronchiseptica, or both. Ten noninoculated
pigs were control animals.
Results—Clinical signs, febrile response, and
decreased weight gain were most severe in the group
inoculated with both organisms. The PRRSV was isolated
from all pigs in both groups inoculated with
virus. All pigs in both groups that received PRRSV had
gross and microscopic lesions consistent with interstitial
pneumonia. Bordetella bronchiseptica was cultured
from all pigs in both groups inoculated with that
bacterium. Colonization of anatomic sites by B bronchiseptica
was comparable between both groups.
Pigs in the group that received only B bronchiseptica
lacked gross or microscopic lung lesions, and B bronchiseptica
was not isolated from lung tissue. In the
group inoculated with B bronchiseptica and PRRSV, 3
of 5 pigs 10 days after inoculation and 5 of 5 pigs 21
days after inoculation had gross and microscopic
lesions consistent with bacterial bronchopneumonia,
and B bronchiseptica was isolated from the lungs of 7
of those 10 pigs.
Conclusions and Clinical Relevance—Clinical disease
was exacerbated in co-infected pigs, including
an increased febrile response, decreased weight gain,
and B bronchiseptica-induced pneumonia. Bordetella
bronchiseptica and PRRSV may circulate in a herd and
cause subclinical infections. Therefore, co-infection
with these organisms may cause clinical respiratory
tract disease and leave pigs more susceptible to subsequent
infection with opportunistic bacteria. (Am J Vet Res 2000;61:892–899)
Objective—To determine effects of intranasal inoculation
with porcine reproductive and respiratory syndrome
virus (PRRSV) or Bordetella bronchiseptica on
challenge with nontoxigenic Pasteurella multocida in
Animals—Seventy 3-week-old pigs.
Procedure—In experiment 1, pigs were not inoculated
(n= 10) or were inoculated 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 were 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
Results—Pasteurella multocida was not isolated
from tissue specimens of pigs challenged with P multocida
alone or after inoculation with PRRSV.
However, in pigs challenged after inoculation with B
bronchiseptica, P multocida was isolated from specimens
of the nasal cavity and tonsil of the soft palate.
Number of bacteria isolated increased in pigs challenged
after coinoculation with PRRSV and B bronchiseptica,
and all 3 agents were isolated from pneumonic
lesions in these pigs.
Conclusion 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 multocida. Coinfection with PRRSV and B
bronchiseptica predisposed pigs to infection of the
upper respiratory tract and lung with P multocida.
Porcine reproductive and respiratory syndrome virus
and B bronchiseptica may interact to adversely affect
respiratory tract defense mechanisms, leaving pigs
especially vulnerable to infection with secondary
agents such as P multocida. (Am J Vet Res 2001;