A seven-day-old angus bull calf with a history of diarrhea was necropsied by the submitting veterinarian. The small intestine, liver, kidney and the lymph node were submitted as fresh and formalin-fixed tissues to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) for further testing. The tests requested by the submitting veterinarian included microscopic evaluation (histopathology), bacterial culture and sensitivity, and polymerase chain reaction (PCR) testing for viruses.
There were no gross findings reported on the submittal form by the veterinarian. On microscopic examination, the major finding was the lesion in the small intestine. This lesion consisted of inflammation that was composed of a mixed-inflammatory cell population including macrophages, lymphocytes, plasma cells and neutrophils that were primarily within the lamina propria but also extended to the submucosa. The intestinal glands often contained necrotic debris and the intestinal villi were moderately blunted and fused. On the surface of the intestinal villi were numerous protozoal organisms (Figure 1) that were morphologically consistent with Cryptosporidium sp. Other significant findings included a neutrophilic abomasitis, tubulointerstitial nephritis, interstitial pneumonitis, randomly distributed histiocytic and neutrophilic hepatitis and draining neutrophils in the mesenteric lymph nodes.
The parasites in the small intestine was a finding consistent with a diagnosis of cryptosporidiosis. However, the presence of large numbers of neutrophils in the small intestine and abomasum was highly suggestive of a concurrent bacterial infection. The distribution and composition of the inflammation observed in the liver, kidney and lung were changes consistent with a disseminated bacterial infection (bacteremia) secondary to the inflammatory lesions in the small intestine and/or abomasum. Bacterial culture of the small intestine consisted of primarily E coli. Furthermore, the absence of Coronavirus and Rotavirus and the presence of Cryptosporidium sp. were confirmed with PCR of the small intestine.
Transmission of Cryptosporidia is primarily fecal-oral, but environmental contamination can spread the organism. Treatment, when necessary, is primarily symptomatic with antibiotics indicated in the event of a secondary bacterial infection. Cryptosporidia are very resistant to temperature and chemical disinfection; therefore, individual housing of calves and strict sanitation are necessary to reduce the level of contamination in the environment. Cryptosporidiosis is a zoonotic pathogen, and appropriate hygiene precautions should be exercised when caring for infected individuals.
Cryptosporidium sp. is a ubiquitous protozoal pathogen. Although it often causes a self-limited infection in immunocompetent animals, the very young or immunocompromised hosts suffer from intractable diarrhea. Cryptosporidia attach to surface epithelial cells of the stomach, small intestine, or colon and can cause subacute or chronic, sometimes bloody, watery diarrhea. There is associated dehydration and electrolyte loss. In susceptible individuals, infections can be fatal, particularly in the presence of other pathogens.
For more information about TVMDL’s test offerings, visit tvmdl.tamu.edu or call 1.888.646.5623.
REFERENCES
Barka, N., Blackwell’s Five-Minute Veterinary Consult: Ruminant; Scott R.R. Haskell, DVM, editor. 2008 pgs. 268-269.