Appendicitis
Arabian fading syndrome
Atypical myoglobinuria
Aural (ear) haematoma
Aural (ear) plaques
Auricular chondritis
Autotomy
Avascular necrosis of the femoral head (Legg-Calvé-Perthes disease)
Avian bornavirus infection (avian ganglioneuritis – proventricular dilation disease)
Atresia coli