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Objective—To evaluate the possibility of swine becoming infected with Salmonella Typhimurium when housed for 2 to 6 hours in an environment contaminated with Salmonella, similar to a lairage situation prior to slaughter.

Animals—40 crossbred market pigs with an approximate body weight of 92 kg.

Procedure—Five trials were conducted (8 pigs/trial) in simulated lairage conditions. Superficial inguinal, ileocecal, and mandibular lymph nodes, cecal contents, distal portion of the ileum, and fecal samples were obtained from each pig after 2 (n = 10), 3 (10), and 6 (5) hours of exposure to an environment contaminated with feces defecated by 10 pigs intranasally inoculated with nalidixic acid-resistant Salmonella Typhimurium (χ4232). In addition, 5 control pigs that were not exposed were also evaluated in the same manner.

Results—Feces deposited on the floor by intranasally inoculated swine were mixed with water to form slurry with a resulting load of approximately 103 colonyforming units of Salmonella Typhimurium/g of material. Eight of 10, 6 of 10, and 6 of 6 pigs exposed to the slurry for 2, 3, or 6 hours, respectively, had positive results for at least 1 sample when tested for the specific strain of Salmonella Typhimurium.

Conclusions and Clinical Relevance—Pigs can become infected during routine resting or holding periods during marketing when exposed to relatively low amounts of Salmonella organisms in the preslaughter environment. Intervention at this step of the production process may have a major impact on the safety of pork products. (Am J Vet Res 2001;62:1194–1197)

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in American Journal of Veterinary Research


Objective—To determine the effect of intranasal exposure to live leukotoxin (LktA)-deficient Mannheimia haemolytica (MH) at the time of feedyard arrival on nasopharyngeal colonization by wildtype MH in calves.

Animals—200 calves.

Procedure—Calves from Arkansas (AR calves; n = 100; mean body weight, 205 kg) were purchased from an order buyer barn. Calves from New Mexico (NM calves; n = 100; mean body weight, 188 kg) were obtained from a single ranch. Calves were transported to a feedyard, where half of each group was exposed intranasally with LktA-deficient MH at the time of arrival. Calves were observed daily for respiratory tract disease (RTD), and nasal swab specimens were collected periodically to determine nasopharyngeal colonization status with MH. Serum samples were assayed for antibodies to MH.

Results—15 AR calves had nasopharyngeal colonization by wild-type MH at the order buyer barn, whereas none of the NM calves had nasopharyngeal colonization. Intranasal exposure to LktA-deficient MH elicited an increase in serum antibody titers against MH in NM calves, but titers were less in NM calves treated for RTD. Exposure of NM calves to LktA-deficient MH offered protection from nasopharyngeal colonization by wild-type MH.

Conclusions and Clinical Relevance—Exposure of calves to LktA-deficient MH elicited an increase in serum antibody titers against MH and decreased colonization of the nasopharynx by wild-type MH. Earlier exposure would likely allow an immune response to develop before transportation and offer protection from nasopharyngeal colonization and pneumonia caused by wild-type MH. ( Am J Vet Res 2003;64:580–585)

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in American Journal of Veterinary Research


To identify management factors affecting the risk of animals developing vesicular stomatitis (VS).


Case-control study.


Horses, cattle, and sheep with suspected vesicular stomatitis on 395 premises in Colorado, New Mexico, Utah, and Arizona.


Data were collected during the VS outbreak of 1997. Diagnosticians interviewed livestock owners and completed a supplemental questionnaire. Cases were defined as those premises that had a completed questionnaire and had ≥ 1 animal positive for VS. Control premises were all premises investigated that had a completed questionnaire and on which the animals had been tested but VS was not detected.


Animals that had access to a shelter or barn had a reduced risk of developing VS (OR, 0.6; 95% confidence interval [CI], 0.35 to 0.99). This effect was more pronounced for equine premises (OR, 0.5; 95% CI, 0.3 to 0.9). Conversely, during an adjusted analysis on equine premises, risk of developing disease was increased slightly where animals had access to pasture (OR, 2.01; 95% CI, 1.1 to 3.7). On all premises where owners reported insect populations were greater than normal, odds of developing disease were significantly increased (OR, 2.5; 95% CI, 1.47 to 4.47). Premises with animals housed < 0.25 miles from running water were more than twice as likely to have clinical signs of VS (OR, 2.6; 95% CI, 1.32 to 5.0).

Conclusions and Clinical Relevance

These results support reports of others that suggest biting insects are a vector in VS virus transmission. Management practices to reduce exposure to biting insects might reduce the risk of VS. (J Am Vet Med Assoc 1999;215:1263–1268)

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in Journal of the American Veterinary Medical Association


Objective—To measure the relationship between gross lesions in swine carcasses observed at a processing plant and Salmonella contamination and to determine whether nonexpert assessments of lesion status would correspond with swine pathologists' judgments.

Animals—Carcasses of 202 conventionally raised and 156 antimicrobial-free pigs in a Midwestern US processing plant examined from December 2005 to January 2006.

Procedures—4 replicates were conducted. For each, freshly eviscerated carcasses were identified as having or lacking visceral adhesions by a nonexpert evaluator and digital carcass photographs were obtained. Swab specimens were obtained from carcasses before the final rinse stage of processing, and bacterial culture for Salmonella spp and Enterococcus spp was performed. Subsequently, carcass photographs were numerically scored for lesion severity by 3 veterinary pathologists. Results were used to test the ability of lesion detection to predict bacterial contamination of carcasses and the agreement between judgments of the inexperienced and experienced assessors.

Results—The probability of Salmonella contamination in carcasses with lesions identified at the abattoir was 90% higher than that in carcasses lacking lesions, after controlling for replicate identity and antimicrobial use. The receiver operating characteristic curve and Cohen κ indicated close agreement between lesion detection at the abattoir and by the 3 pathologists.

Conclusions and Clinical Relevance—Findings indicated the presence of lesions could be used to predict Salmonella contamination of swine carcasses and that a nonexpert processing-line assessment of lesions could be used to discriminate between healthy and chronically ill swine before their entry into the human food supply.

Full access
in American Journal of Veterinary Research