Case Report: Cow with necrotic ear tips of unknown origin

Honorable Mention, Cases and Abstracts Category
Hailey Harroun, Colorado State University

SIGNALMENT:
Species: Bovine
Breed: Angus
Age: 8yr
Sex: Female
Reproductive Status: open, 4mo calf at side
Presenting Complaint: Bloody, crusted ear tips, with hair loss and tissue loss

HISTORY:
Only cow in a herd of 30 displaying signs of hair loss on both ear tips with necrosis and loss of tissue. Remaining tissue is thickened and crusted with blood. Ears do not seem particularly painful or pruritic. Cow is currently nursing 4 month old calf, on a diet of alfalfa-mix hay, current on all vaccinations (IBR, BVD, PI3, BRSV, Clostridium). It is currently the end of December, but weather has not been cold enough to indicate frostbite. This condition has been present for two weeks duration, and seems to be progressing, with more necrosis and shortening of ear tips.

PREVIOUS HISTORY OF ILLNESS: none

PHYSICAL EXAM:
Body Weight: 1500lb
Temp: 101F
Heart Rate: 60bpm
Respiration: 25

Skin:normal, except ears
Musculoskeletal:normal
Circulatory:normal
Mucous Membranes:normal
Respiratory:normal clear lung sounds
Digestive:normal rumen and intestinal sounds
Genital/Urinary:normal
Eyes/Ears:eyes normal; ears crusted, bloody, appears to be loss of tissue on the tips
Neurologic:normal
Lymph Nodes:normal

Affected ears
DIFFERENTIALS:

• Squamous cell carcinoma
• Fungal infection
• Bacterial infection (Staphylococcus, Streptococcus)

DIAGNOSTICS:
A wedge biopsy of the more severely affected right ear was taken from the ear tip, approximately 4mm deep and 3 mm wide. The sample was placed in formalin and sent to the Washington Animal Disease Diagnostic Laboratory (WADDL) at Washington State University.
The laboratory report concluded that no fungal, bacterial or viral agents were found in the sample. The only histologic findings were moderate cellular neutrophilic infiltrates, necrosed tissue and hemorrhage.
The pathologist's top three differentials for these findings were:

• Frostbite
• Fescue toxicity
• Cellulitis associated with septicemia

DIAGNOSIS:
As stated in the history, the ambient temperatures for the past two weeks have not dropped below 30 degrees Fahrenheit. For an adult cow native to the area and accustomed to temperatures as low as negative 10 degrees Fahrenheit, this makes frostbite extremely unlikely. Fescue toxicity is also low on the differential list, as fescue is not native to northeastern Washington, and is not present in any pastures on the ranch. All hay is purchased locally, and does not contain fescue. Septicemia can be ruled out because the cow is not systemically ill, has no fever, is BAR and seems otherwise unaffected by the condition of her ears.
The cow's ears were cleaned with sterile water and an antiseptic drying agent was applied. The etiologic process of this condition remains a mystery. The ears eventually healed and the pinna of both ears are about half normal length.