Fading kitten syndrome (FMS) refers to neonatal death (death within the period of birth until weaning.) Kitten mortality is highest during the first week of life, accounting for >90 percent of deaths. Estimates show a 10 percent rate of stillbirth and a 10 percent mortality rate by day two of life.

An extremely perceptive caregiver might be attuned to the signs of FKS and this may increase the kitten's chance of survival. For example, low birth weight kittens, kittens with congenital abnormalities, and kittens who are poor nursers are at higher risk for FKS. People who rescue and foster pregnant cats and/or foster kittens should take time to learn to spot the signs of FKS as the offspring of stray and feral cats are particularly prone to this condition. Since FKS is so common, many people involved in feline rescue advocate for spaying rescued pregnant cats.

What Is Fading Kitten Syndrome?

Fading kitten syndrome is not a disease, but rather a collection of signs that develop in neonatal kittens. It has many underlying causes and leads to rapidly declining health. Unfortunately, one of the very first signs is the unexplained death of a very young kitten. Because of this, FKS has been compared to sudden infant death syndrome (SIDS) in human babies.

Signs of Fading Kitten Syndrome in Cats

There are some indications that a kitten may be at risk for developing fading kitten syndrome. The signs to watch for include:

Extremely low birth weight: Kittens that develop FKS are often the smallest of the litter. They have a low birth weight and are not as active as their litter-mates.

Kittens that develop FKS are often the smallest of the litter. They have a low birth weight and are not as active as their litter-mates. Inability to nurse properly: Healthy kittens nurse almost immediately after birth. A fading kitten is often not strong enough to grasp and suckle the mother cat's nipple. During the first 72 hours or so of nursing after birth, healthy kittens that are nursing well receive special milk called colostrum. This colostrum provides essential nutrients and antibodies. Colostrum gives the kitten passive immunity. allowing them to grow and thrive until they can receive vaccinations and stop nursing. If a kitten fails to nurse and needs to be bottle-fed it will not receive colostrum and is more likely to develop FKS.

Healthy kittens nurse almost immediately after birth. A fading kitten is often not strong enough to grasp and suckle the mother cat's nipple. During the first 72 hours or so of nursing after birth, healthy kittens that are nursing well receive special milk called colostrum. This colostrum provides essential nutrients and antibodies. Colostrum gives the kitten passive immunity. allowing them to grow and thrive until they can receive vaccinations and stop nursing. If a kitten fails to nurse and needs to be bottle-fed it will not receive colostrum and is more likely to develop FKS. Abandonment: Mother cats sense when there is a weak kitten and may abandon it in favor of her other kittens. This is an instinctual reaction designed to protect the healthier kittens.

Mother cats sense when there is a weak kitten and may abandon it in favor of her other kittens. This is an instinctual reaction designed to protect the healthier kittens. Hypothermia (low body temperature): Since newborn kittens can't regulate their own body temperature, they depend on their mom for warmth. Therefore, abandoned kittens or kittens that do wander away from mom, rapidly develop hypothermia. Hypothermic kittens are lethargic. Its mouth and gums will be a bluish shade rather than a healthy pink. This can rapidly be fatal unless human intervention occurs.

Illustration: Wenjia Tang. © The Spruce, 2018

Causes of Fading Kitten Syndrome

There are many causes of FKS and treatment depends on the underlying reason.

Disease or malnutrition of the mother cat during gestation: If this is the queen's first litter of the season, she may not have access to the amount of food required to grow healthy kittens. Depending on the environment, a queen can have up to five litters of kittens within a year. This is physically taxing on the female cat, causing malnourishment and illness. This combination does not bode well for late-season kittens, resulting in higher rates of stillbirth, congenital abnormalities, and kittens with FKS. This is why it's so imperative to take a suspected pregnant cat to the veterinarian for a prenatal check-up. Your vet will discuss your options and how to take care of a pregnant cat.

If this is the queen's first litter of the season, she may not have access to the amount of food required to grow healthy kittens. Depending on the environment, a queen can have up to five litters of kittens within a year. This is physically taxing on the female cat, causing malnourishment and illness. This combination does not bode well for late-season kittens, resulting in higher rates of stillbirth, congenital abnormalities, and kittens with FKS. This is why it's so imperative to take a suspected pregnant cat to the veterinarian for a prenatal check-up. Your vet will discuss your options and how to take care of a pregnant cat. Infectious diseases: There are a number of viral and bacterial infections that quickly affect an entire litter of kittens. Keep litters of stray or feral queens completely separate from your household cats. If possible, donate your time or money to local feral and rescue cat organizations that help spay and neuter stray cats.

There are a number of viral and bacterial infections that quickly affect an entire litter of kittens. Keep litters of stray or feral queens completely separate from your household cats. If possible, donate your time or money to local feral and rescue cat organizations that help spay and neuter stray cats. Neonatal isoerythrolysis: This occurs when the queen and kitten have different blood types. The kitten's red blood cells are destroyed by antibodies they receive from the mother cat's colostrum.

This occurs when the queen and kitten have different blood types. The kitten's red blood cells are destroyed by antibodies they receive from the mother cat's colostrum. Fleas and other parasites: When fleas bite, they ingest blood and secrete saliva, so an infestation on a newborn kitten can lead to severe anemia or transmit parasites, both of which are potentially fatal. Kittens are susceptible to other infectious agents including protozoal infections, intestinal parasites, and ticks.

Treatment and Prevention

Since FKS is not an actual disease, but a collection of signs, it cannot be entirely prevented. The best course of action is to treat the specific signs and hope for the best. Consult a veterinarian right away if you notice any abnormal signs in a newborn kitten, especially lethargy, lack of nursing, and/or difficulty breathing. The kitten will be examined and tested for any infections or parasites. The vet will prescribe a course of action to treat any infection, prevent hypothermia, malnutrition, and dehydration. In the unfortunate event that the kitten does not survive, know that you did your best to help them and try to direct your attention to the mother cat and other kittens to make sure they are healthy and thriving.