Evidence of Chlamydia infection of small intestinal epithelial cells was found in 4 4-14-day-old nursing piglets and 2 22-30-day-old weaned piglets. Each nursing piglet was from a different South Dakota swine farm experiencing preweaning diarrhea. The first weaned piglet was 1 of 7 live piglets from a Minnesota swine farm that were having problems with postweaning weight loss and a mild cough; diarrhea had not been noted by the owner. The second weaned piglet was from an Iowa farm experiencing diarrhea beginning 5 days after weaning. Three piglets were submitted alive and necropsied at the diagnostic laboratory. Three piglets were necropsied by the herd veterinarians, who submitted fresh and formalinfixed samples to the laboratory.Increased fluidity of the colonic contents was the only macroscopic change in the intestinal tracts of 5 piglets. The submitting veterinarian reported that a pseudomembrane was adhered to the ileal mucosa of the sixth piglet. In 3 nursing piglets, the lymphatics in the cranial two-thirds of the small intestinal mesentery were filled with chyle, indicating absorption from the small intestine. Immunofluorescent antibody (IFA) staining detected porcine rotavirus antigen in small intestinal enterocytes of 1 nursing and 1 weaned piglet but not in sections ofintestine from the other 4 piglets. Transmissible gastroenteritis virus (TGE) antigen was not found in IFA-stained frozen sections of small intestine from all piglets. Viral particles were not found by electron microscopic examination of negatively stained colonic contents. Bacterial culture procedures for enteric pathogens and IFA staining for K88, K99, and 987P pilus antigens of enterotoxigenic Escherichia coli did not yield significant results.Microscopic examination revealed mild to moderate necrotizing enteritis in the distal jejunum and ileum of the 4 nursing piglets and 1 weaned piglet. Mild to moderate villous atrophy with attenuation, necrosis, and sloughing of the villous epithelium was present in affected areas of the small intestine (Figs. 1, 2). A variable amount of detritus and fibrin partially covered the mucosal surface, and abnormally high numbers of neutrophils were in the lamina propria of 3 piglets. Microscopic lesions in the small intestine from the rotavirus-positive weaned piglet consisted of moderate villous atrophy and attenuation of the villous epithelium; inflammation and epithelial necrosis were minimal. In hematoxylin and eosin (HE)-stained sections of distal jejunum and ileum from all piglets, the supranuclear region of many enterocytes contained large vacuoles. Basophilic round bodies < 1.0 µm in diameter were within these vacuoles (Fig. 2). Neither bacterial colonization of the brush border of enterocytes nor developmental stages of Isospora suis were found.

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The bovine respiratory disease complex (BRDC) is the most common disease problem in feedlot cattle, accounting for 65-75% of feedlot morbidity and mortality. The annual cost of BRDC to the cattle industry has been estimated at $167.2 million to $232.4 million (Perino, 1992). BRDC is caused by a complex interaction of stresses and microorganisms on the host animal. In most outbreaks, it is not possible to diagnose with certainty which infectious agents are present by clinical examination alone. Diagnosis of infectious causes of BRDC has primarily been done on tissue samples obtained from postmortem examinations. This method has resulted in a low diagnosis rate for viral infections. In addition, antibiograms done on bacterial isolates from the lungs of treated dead cattle or chronically ill cattle are of questionable value since these samples were obtained from "treatment failures". We have adopted a new program combining nasal swabs and tracheal swabs to improve viral diagnosis rates and provide more meaningful sensitivity data on bacterial isolates. The goal of this program is to provide more timely and accurate information so informed decisions can be made on treatment, vaccination, and herd health programs when BRDC outbreaks occur.