North American Veterinary Licensing Examination (NAVLE) Practice Test

Choosing neonatal isoerythrolysis as the most likely diagnosis for a litter of one-day-old kittens presenting with hemolytic symptoms is grounded in the understanding of the disease's pathophysiology. Neonatal isoerythrolysis occurs when a mother cat with a different blood type than her kittens produces antibodies against her kittens' red blood cells, most commonly in type B queens nursing type A kittens. These maternal antibodies are transmitted through the colostrum, leading to the destruction of the kittens' red blood cells shortly after birth, hence causing hemolytic symptoms such as anemia, jaundice, and lethargy.

Neonatal septicemia could cause clinical signs but would typically present with systemic signs of infection rather than specifically hemolytic symptoms in neonates. Liver disease in very young kittens is generally less common, and while it can cause similar symptoms, it does not specifically explain the hemolysis seen at this age. Pyruvate kinase deficiency can lead to hemolytic anemia but is much less common and typically presents with more chronic cases rather than a sudden incidence in a litter of one-day-old kittens. Therefore, neonatal isoerythrolysis fits best with the clinical picture described.