The red, somewhat ulcerated, ovoid lesions at left are punched-out Peyer's patches caused by a parvovirus infection.

Canine Parvovirus (CPV) has an affinity for the rapidly dividing cells of the intestine, lymphoid tissues and the bone marrow. CPV thus leads to:

• Intestinal crypt cell necrosis,
• Damaged or "punched-out" lymph tissue (Peyer's patches in the case of the intestine)
• Leukopenia