A uterine infection can cause premature birth and the kittens will usually be underweight, wizened and scraggy. They will either have below normal or above normal temperatures and may be either hyperactive or very lethargic. Although they initially suckle normally, they do not fill out or progress like healthy kittens. They show signs of progressive weakness and stop suckling. With FKS, weaker kittens generally fade earlier; stronger kittens may not start fading for a couple of weeks. Affected kittens fade in spite of efforts to hand-rear them. They become weaker and less resilient, breathing may become more labored and pneumonia may develop. The kitten then dies.
As soon as fading is noticed in a kitten, get your vet to take rectal and throat swabs from the kittens (and vaginal swabs from the mother if possible). If bacteria are present, antibiotics may save the lives of those kittens which have not started to fade. They will need careful temperature control and plenty of fluids to combat dehydration. Many fading kittens do not respond to any treatment and post mortems may identify the cause of the problem.
Blood-type mismatch (Neonatal Isoerythrolysis) occurs when blood-type B mothers have blood-type A kittens (it rarely occurs the other way around). Maternal antibodies from colostrum destroy the kitten’s blood cells. Some kittens may already be in decline from this when taken on by a human fosterer. Symptoms include dark brownish-red urine and severe anemia. Kittens stop nursing after about 3 days, fade and die. Some kittens are less severely affected and appear to thrive, but their tail-tip may die during the first two weeks. Some have been saved by blood transfusion, but blood donor cats are unavailable in many areas and if available may not be affordable in a rescue/shelter situation. it is more common in purebred cats than in the moggy population.