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.
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 pigs.


METHODS
Seventy 3-week-old pigs.


METHODS
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 inoculations.


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.


CONCLUSIONS
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.
Brockmeier
S L
SL
Respiratory Diseases of Livestock Research Unit, USDA, Agricultural Research Service, National Animal Disease Center, Ames, IA 50010, USA.
Palmer
M V
MV
Bolin
S R
SR
Rimler
R B
RB
D000818:Animals; D016470:Bacteremia; D001885:Bordetella Infections / Q000150:complications / Q000382:microbiology / Q000662:veterinary*; D016950:Bordetella bronchiseptica / Q000472:pathogenicity*; D008168:Lung / Q000382:microbiology / Q000473:pathology; D009296:Nasal Cavity / Q000382:microbiology; D010160:Palate, Soft / Q000382:microbiology; D014066:Palatine Tonsil / Q000382:microbiology; D010326:Pasteurella Infections / Q000150:complications / Q000473:pathology / Q000662:veterinary*; D016979:Pasteurella multocida / Q000472:pathogenicity*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000382:microbiology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000472:pathogenicity*; D011897:Random Allocation; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000821:virology; D014766:Viremia