Causes of fading puppy and kitten syndrome - Veterinary Medicine
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Causes of fading puppy and kitten syndrome
Getting a grasp on the many things that can prove fatal in puppies and kittens can help you save these neonates struggling for their lives.


While less common because of vaccination programs, canine parvovirus type 2 infection, canine distemper, and infectious canine hepatitis are all capable of causing neonatal illness and death in puppies.4 As routine vaccinations perhaps become less common, these diseases should be kept in mind and considered as differential diagnoses at necropsy.


Kittens are susceptible to a multitude of viruses (Table 2) that can cause neonatal illness and death. Feline herpesvirus type I and calicivirus are most common.1 These infections may be transient, but failure to control hypoglycemia and hypothermia or secondary bacterial infection can result in rapid decline. Feline leukemia virus, transmitted by the dam or other in-contact cats, results in thymic atrophy and slow wasting of kittens.1 Coronavirus infections are also common in ill kittens, causing diarrhea and feline infectious peritonitis. Panleukopenia, while uncommon because of vaccination programs, can also result in kitten deaths. The most common time frame for viral infections in kittens is from 3 to 4 weeks of age, but kittens can be affected in their first week of life.1

Intestinal parasites

Intestinal parasitism is a frequent complicating factor in fading puppy and kitten syndrome. Because roundworms and hookworms are transmitted transplacentally, most pups are born with these parasites.31,32 Roundworm larvae are also transmitted in the milk during nursing in both kittens and puppies. Marked illness can occur before the patent period. In pups, the pulmonary migration phase of the larvae shortly after birth may prove fatal. Hookworm larvae are also transmitted transplacentally and through the dam's milk in kittens and puppies.31,32 Marked infestation can result in deterioration and fatal anemia at as early as 2 to 3 weeks of age.1,23 Death can occur before a patent infection develops, so do not rely on fecal examination for diagnosis.23

Protozoan parasites, primarily Giardia species, Coccidia species, and, in kittens, Tritrichomonas foetus, are major causes of diarrhea in the young. While rarely fatal, they can contribute to illness and can put a neonate at higher risk of additional infection. Toxoplasma gondii infection is an uncommon cause of illness in kittens, resulting in fever, neurologic and respiratory signs, and death in three to 12 days.18


Clearly, the causes of fading puppy and kitten syndrome are many. In clinical cases, multiple factors often play a role, so a complete evaluation and thorough support of the neonate are important in determining a cause and in effecting a successful outcome. Evaluating and treating affected neonates are covered in the next two symposium articles.

Joni L. Freshman, DVM, MS, DACVIM
Canine Consultations
3060 Woodview Court
Colorado Springs, CO 80918

*Breeders Assitant—Tenset Technologies, Cambridge, UK,; WinCanis Pedigree—Willowind,; BreedMate—Wild Systems P/L, New South Wales, Australia,
**The veterinary diagnostic laboratories at Colorado State University, University of California-Davis, and University of Florida-Gainesville.
***Canine parvovirus isolation is available at the Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University.


1. Bucheler J. Fading kitten syndrome and neonatal isoerythrolysis. Vet Clin North Am Small Anim Pract 1999;29:853-870.

2. Moon PF, Massat BJ, Pascoe PJ. Neonatal critical care. Vet Clin North Am Small Anim Pract 2001;31:343-365.

3. Anderson AC. Reproductive ability of female beagles in relation to advancing age. Exp Gerontol 1965;1:189-192.

4. Johnson CA, Grace JA, Probst MR. The effect of maternal illness on perinatal health. Vet Clin North Am Small Anim Pract 1987;17:555-566.

5. Chandler ML. Canine neonatal mortality, in Proceedings. Soc Therio Annu Meet 1990;243-253.


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