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Unexpected Findings in Unrelated Mortalities: Red Angus Calf and White Tailed Deer

 

by Drs. Korana Stipetic and Belinda Thompson

Two unrelated cases were submitted to Animal Health Diagnostic Center at Cornell College of Veterinary Medicine for general investigation of death after acute illness. A female, six day old, nursing, Red Angus calf died despite antibiotic treatment and IV fluid therapy. The referring veterinarian consulted with Veterinary Support Services (VSS) while the animal was still alive and a couple of hours later after it died, and was not going to pursue a necropsy.  However the non-specific febrile illness, per-acute clinical decline and death were reasons cited during consultation to pursue a more definitive diagnosis.

The submitting veterinarian’s necropsy findings for the calf revealed small amount of fibrin in the abdominal space and a more significant amount of pleural fluid (image 1), very enlarged mesenteric lymph nodes and a mottled liver that seemed more firm than normal (image 2).  Tissues fixed in 10% neutral buffered formalin and fresh tissues collected during the post-mortem exam were submitted for histopathology, bacteriology and virology testing.

The AHDC Veterinary Support Services veterinarian developed a specific testing plan that included histopathology on fixed tissues, aerobic culture on a cerebrospinal fluid, liver, spleen, lung and intestinal tissues, and anaerobic culture on an intestinal swab submitted in anaerobic transport media, cerebrospinal fluid in anaerobic transport media and liver and tissues. The diagnostic plan also included submission for Salmonella culture on a fresh spleen and intestine and fluorescent antibody tests for Clostridial organisms performed on heart tissue.

The second case was a female white-tailed deer from a private hunting preserve that died of suspected pneumonia. The owners had recognized some weight loss but no other clinical signs ante-mortem. Two weeks previously, another deer had presented with signs thought to indicate pneumonia and died. A post-mortem examination and limited diagnostic submissions revealed pulmonary edema due to an unknown cause with Bibersteinia trehalosi isolated from the lungs and Escherichia coli isolated from the kidneys, despite a lack of marked inflammatory cell infiltrates in those tissues. The veterinarian called to request advice on how to stop the deaths in these deer and was encouraged to perform a post-mortem exam on the second deer, since the findings in the previous case were not fully explained, and there was at least one more deer in poor condition.  Gross necropsy findings included severe coalescing cranio-ventral pneumonia with fibrous adhesions to the ribcage (images 3 and 4), one heart valve with irregular thickening, and very dark blood (image 5). Fresh tissue samples and tissues fixed in 10% neutral buffered formalin were submitted.

The VSS veterinarian designed a specific plan that included histopathology testing for fixed tissues, aerobic culture on thoracic fluid, lung and liver samples, Leptospira fluorescent antibody test on kidney, fungal and Mycoplasma cultures on a lung and heart valve tissues, a mineral panel and selenium testing on liver, and virus isolation on lung. Glass slides of exudate from thoracic cavity were made for gram stain and acid fast staining.

Histologic examination for the Red Angus calf samples revealed multifocal random necrosis in the liver, spleen, lymph node, and small intestine, consistent with hematogenous dissemination of bacteria. Bacterial culture results indicated many Listeria monocytogenes in the cerebrospinal fluid, liver, spleen, and lung, which confirmed the diagnosis of bacteremia due to systemic infection with Listeria monocytogenes.

Histologic findings for the white-tailed deer included coalescing areas of necrosis effacing airways, consistent with Mycoplasma bovis infections. Results of aerobic culture revealed many Listeria monocytogenes organisms in animal’s thorax and few in the lung, heart valve and liver.  Trueperella pyogenes, Biberasteinia trehalosi, and Mycoplasma spp were also isolated from both lung and heart valve tissue, and Trueperella pyogenes was also isolated from the liver and thoracic fluid.  In addition, myocardial necrosis and mineralization with fibrinous endocarditis and myocarditis was described. Both hepatic iron and zinc concentrations were higher than the normal range published for deer, but neither were thought to be high enough to result in clinical toxicosis.  The selenium concentration was within the normal range published for supplemented deer.

The findings indicating septicemic listeriosis in both of these unrelated cases are interesting.  Septicemic listeriosis is most common in simple stomached animals and in immunosuppressed individuals.  Neonatal ruminants may develop septicemic listeriosis if they become exposed to Listeria in utero, ingest the organism from their environment, or ingest the organism in suckled milk or due to manure contamination of the udder of their dam while suckling.  Septicemic listeriosis is described in neonatal suckling ruminants while their dams remain clinically normal.  In the case of the deer with septicemic listeriosios, post-mortem results are consistent with a chronic respiratory infection that could have led to immunosuppression and increased susceptibility to Listeria septicemia.

Both submitting veterinarians consulted with VSS regarding the various risks for Listeria accumulation in forages, feedstuffs, and decaying organic material in the environment or in feeding and watering facilities. These cases highlight the importance of post-mortem examination and multiple fresh and fixed tissue submissions. Combination of histologic findings and ancillary testing results revealed unexpected but important cause for management concern in both facilities and provided guidance for future management plans.

Reference

The Merck Veterinary Manual On-line
http://www.merckmanuals.com/home/infections/bacterial-infections/listeriosis

White Tail Deer Heart White Tail Deer Lung
Image 1. Red Angus Calf Thorax and Abdomen Image 2. Red Angus Calf Liver
White Tail Deer Thorax Red Angus Calf Liver
Image 3. White Tail Deer Thorax Image 4. White Tail Deer Lung
Red Angus Calf Thorax and Abdomen  
Image 5. White Tail Deer Heart