Fading kittens
© University of Glasgowhttp://www.gla.ac.uk/companion/fadingkits.htm

There are many causes of fading kittens. 

Parasites (both external and internal)

Feline calicivirus 
Feline coronavirus/feline infectious peritonitis 
Chlamydophila felis (formerly Chlamydia psittaci) 
Neonatal isoerythrolysis 
Bordetella bronchiseptica 
Hemobartonella felis 
Feline herpesvirus 
Feline leukaemia virus 
Feline panleukopenia virus/parvovirus 
Toxoplasma gondii 

Parasites 

Heavy flea, louse, roundworms or hookworm infestations can cause severe anaemia and weight loss in newborn kittens. It is sometimes difficult to determine whether young kittens have worms and a faecal examination is required. Sometimes, only one or two worm eggs are seen in the faeces but this is enough to confirm a diagnosis. One must remember that two or three roundworms or hookworms are enough to kill a newborn kitten. 

Prevention: treat queen before mating and treat other cats and/or dogs in household, and the household itself. In kittens, an oral solution such as piperazine (Pip-cit) is suitable and should be given every 2 weeks from 2 weeks of age, until the kittens are 12 weeks of age.

Bordetella bronchiseptica (Kennel cough)

Bordetella bronchiseptica has been reported as the cause of death due to bronchopneumonia in kittens up to 8 weeks of age. 
Diagnosis: oropharyngeal swab, swab of nasal discharge, tracheal wash or sample of pneumonic lung into charcoal Amies bacterial transport medium to Companion Animal Diagnostics, University of Glasgow, or Liverpool Veterinary School. B. bronchiseptica may be difficult to isolate from carrier cats because low numbers of organisms are shed and are easily overgrown by other flora, so selective media such as charcoal-cephalexin agar (Oxoid, Unipath, UK) or Bordet-Gengou agar may be used to suppress undesirable bacterial overgrowth. Note that Liverpool Veterinary School is where much Bordetella expertise is. Characterization of isolates can be performed by ribotype analysis. Blood samples can be taken for antibody detection. 
Post-partum shedding of B. bronchiseptica has been demonstrated in seropositive queens from which no Bordetella could be isolated prior to kittening, suggesting a carrier state. Bacterial shedding has been known to occur for as long as 19 weeks and is not always controlled by antibiotic therapy.
Treatment: First choice: Ronaxan 20mg (Merial) bid for 5 days. Second choice: Trimethoprim-sulfadiazine for 5-7d (i.e. one Tribrissen 20 (Schering-Plough) per day or one Trimacare 20 (Animalcare Ltd) per day). Never divide these tablets as the cats froth at the mouth after dosing and don't use in cats under 1kg. Note that B. bronchiseptica is NOT susceptible to penicillins.
Prevention: vaccinate in-contact dogs with Intrac (Schering-Plough). Intrac is not licensed for use in the cat. Nobivac Bb for cats is expected on the UK market relatively soon. Pre-pregnancy screening will not detect all carriers, prophylactic antibiotic cover before pregnancy may or may not eliminate the organism.
The primary route of infection is via oro-pharyngeal and nasal secretions and excretions from infected hosts, so isolate infected animals from uninfected animals and disinfect hands, food bowls, etc. Minimize overcrowding, stress, intercurrent disease. Ensure adequate ventilation.

Chlamydophila felis (formerly Chlamydia psittaci)

Probably not a cause of feline abortion or stillbirth. However, can cause nasty conjunctivitis in very young kittens in which systemic treatment with oxytetracycline and doxycyclines are not recommended because of tooth discolouration.
Prevention: vaccination ameliorates clinical signs but increases the chances of a cat becoming a chronic carrier, however MDA should protect kittens until 7-9 weeks of age.

Feline calicivirus (FCV)

FCV is less severe than FHV infection, but is still a cause of fading kittens, and cat flu in kittens over 2-3 weeks old.
Signs: fading - post mortem shows thymic atrophy, congested lungs, the body will probably be underweight for the kitten's age. FCV commonly causes lingual ulceration. Kittens over 2-3 weeks old show sneezing, anorexia, depression and oculonasal discharge.
Virus shedding: in oropharyngeal secretions, shedding is continuous.
Transmission: mainly direct, but FCV can survive up to 7 days in the environment so fomite transmission is possible.
Prevention: test breeding queens by virus isolation from an oropharyngeal swab. FCV is shed continuously, with a half-life of 75 days. Preferably breed using only negative queens. If not possible, MDA lasts up to 2-3 weeks, so kittens can be early weaned and kept in isolation from infected individuals. Use bleach diluted 1:32 in water with washing up liquid to disinfect. Serious cat breeders should try to prevent this virus from entering their household by testing all new cats and prospective mates of their cats before admitting them into their premises. Vaccines do not protect against the majority of field strains, although Merial and Fort Dodge claim that their strain protects against more field strains than the usual F9 strain.

Feline herpesvirus

A more severe infection than FCV, causing neonatal death and cat flu. Affected kittens can be left with lifelong chronic sinusitis.
Signs: fading - post mortem shows thymic atrophy, congested lungs, the body will probably be underweight for the kitten's age. Histopathology shows acidophilic intranuclear inclusion bodies. Kittens which survive to 14 days may have very swollen eyes, with corneal ulceration or even ruptured eyeballs under their still closed eyelids. Kittens over 2-3 weeks old show typical cat flu signs: sneezing, anorexia, depression, oculonasal discharge and pneumonia.
Virus shedding: in oropharyngeal secretions, shedding is intermittent and occurs about a week following stress, lasting 1-2 weeks.
Transmission: mainly direct, FHV can only survive up to 12-18 hours in the environment, fomite transmission is possible only within a household.
Prevention: put queens into isolation 2-3 weeks before kittening to deliberately stress them so that their viral shedding is over by the time kittening occurs and MDA will be higher. 
The amino acid l-lysine is said to compete with arginine for capsid construction and thus to decrease FHV shedding.
Test breeding queens by virus isolation from an oropharyngeal swab but bear in mind that FHV shedding is intermittent and occurs post-stress. Cats entering a disease-free colony should be quarantined for 3 weeks and virus isolation attempted at least twice a week before being allowed to mix with the other cats. Vaccination does not prevent induction of a carrier state, so a carrier cat may never have shown clinical signs. Clean contaminated food bowls, etc. using bleach diluted 1:32 in water with washing up liquid to disinfect.

Feline infectious peritonitis (FIP)/ Feline coronavirus

A report by Scott in the 1970s implicated FIP as a cause of neonatal death, it is now believed that the cause in that report was probably taurine deficiency. FIP can cause death in kittens from about 8 weeks old, usually effusive form of FIP, but from 12 weeks of age non-effusive form also possible. Typically occurs from 4 weeks a stress such as rehoming, neutering, perhaps even vaccination. 
Signs: effusive FIP: ascites, loss of body fat, anorexia, mild pyrexia (T 103-104), kitten often quite bright. Non-effusive: weight loss, ocular or CNS signs, icterus, anorexia, pyrexia.
Virus shedding: mainly in the faeces, transiently in saliva.
Transmission: by sharing litter trays. FCoV lasts in the environment in dried up cat litter for up to 7 weeks. Not transmitted transplacentally.
Prevention: by isolating the kittens with the queen from birth. At 5-6 weeks, as maternally derived antibody wanes, remove the queen who may be a source of virus and keep the litter in complete isolation from the rest of the household. Instruct the owner on barrier nursing, using sodium hypochlorite (domestic bleach) on the litter trays at least twice a week. Test the kittens for FCoV antibodies at over 10 weeks of age to confirm that they have not been infected. Primucell vaccination, where available, needs to be used in conjunction with early weaning and isolation as it is given at 16 weeks of age and will only work on FCoV naive cats.
In FCoV seropositive kittens prevention of FIP is by avoiding stress, where possible. Signs to alert you to the possibility of FCoV infection are a history of diarrhoea any time from 5-6 weeks of age - often intractable - sometimes with third eyelid protrusion, and uneven size of littermates / stunting. Isolate the kitten and restest antibody titre monthly, once seronegative it will be out of danger.

Feline leukaemia virus

FeLV is not usually a cause of neonatal mortality, but can cause abortion and stillbirths. 
Virus shedding: primarily in saliva.
Transmission: transplacental and direct, FeLV does not survive for more than minutes outside the cat.
Prevention: - all breeding queens and toms should be regularly tested FeLV negative.

Haemobartonella felis

Kittens fade from a few days to weeks of age, are profoundly anaemic. May be extremely pyrexic (T. 105-107oF). 
Transmission: by fleas, possibly transplacental.
Diagnosis: send an EDTA sample and airdried blood smear to our laboratory.
Prevention: - essentially very good flea control. Screen breeding queens for H. felis and treat those affected with doxycycline 5-10 mg/kg/day for at least 7 days. 


Feline panleukopenia (parvovirus)

Toxoplasma gondii

Uncommon cause of neonatal mortality in kittens. 
Oocyst shedding: from cats only, lasts two weeks. Oocysts must sporulate before becoming infective, therefore are not infectious until 48 hours post shedding. 
Transmission to kittens: transplacental or via suckling.
Prevention: do not feed raw or undercooked meat to pregnant seronegative cats. May choose to breed with only seropositive animals which have already been exposed and are therefore immune.