APV targets just about every system, and can be seen in many of the organ systems. As the vital organs fail, the body is unable to process food, crop stasis occurs and the bird dies from dehydration even though the crop is full. Adults may experience weight loss, recurrent bacterial and fungal infections and poor feather formation. They may appear to recover but die months later from renal failure. If birds infected with APV are bred, nesting and laying can appear normal.
Chicks sometimes die in the shell or hatch in a very week state only to die within hours.
Other chicks may hatch just fine and appear to be thriving for as long as 15 days, however, due to a weakening of the vital organs and the immune system, the body cannot support its own growth and the chicks die acutely, within hours with full crops. As the vital organs fail the body is unable to process food, crop stasis occurs and the chick dies of dehydration although the crop is full. Some chicks live longer but fail to thrive. They may have poor muscle tone, swollen abdomens, be unable to fly and never learn to feed themselves. Still others may seem completely normal, other than being slow to grow and feather out.