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  • Author or Editor: Richard B. Rimler x
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Abstract

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.

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 inoculations.

ResultsPasteurella 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; 62:521–525)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether Pasteurella multocida toxin (PMT) affects growth of the proximal portion of the humerus of young pigs.

Animals

20 colostrum-deprived, cesarean-derived pigs.

Design and Procedure

5 groups (n = 4/group) of pigs were formed. Group-1 pigs received 0.1 ml of phosphate-buffered saline solution for 4 weeks; group-2 pigs received 0.05 μg of PMT/kg of body weight at 14 and 21 days; group-3 pigs received 0.05 μg of PMT/kg at 28 and 35 days; group-4 pigs received 0.1 μg of PMT/kg at 14 and 21 days; and group-5 pigs received hyperimmune serum (from a sow given purified toxin) on days 13, 20, 27, and 34, and 0.1 μg of PMT/kg on days 14, 21, 28, and 35.

Results

All pigs given 0.1 μg of PMT/kg without serum died or were euthanatized, as were 4 pigs given 0.05 μg of PMT/kg. These pigs had increased serum interleukin 1 and 6 bioactivities. Pigs surviving 0.05 μg of PMT had decreased weight gain, rough coat, marked atrophy of the ventral concha (as determined by turbinate perimeter ratios), and small stature. The surviving pigs also had reduced area and decreased proliferation indices in physeal chondrocytes on the basis of bromodeoxyuridine immunoreactivity. Control and serum-treated pigs gained weight, had no clinical effects, had similar physeal areas, and had higher cell proliferation indices.

Conclusions

PMT inhibits endochondral bone formation by reducing physeal area and chondrocyte proliferation in vivo. Hyperimmune serum neutralizes the effects of toxin on weight gain, clinical appearance, physeal area, and chondrocyte proliferation.

Clinical Relevance

PMT may affect growth of the skeletal system. Antiserum to PMT is protective. (Am J Vet Res 1996;57:848–852)

Free access
in American Journal of Veterinary Research