Feline leukemia virus (FeLV) also known as lymphosarcoma is the leading viral killer of cats. The virus may spread through saliva contact so may be transmitted by bites or through mutual grooming, sharing food and water and also through urine and feces.  The virus has a limited survival rate outside the infected cat – a maximum of 48 hours, with survival longer in damp conditions.

There is no one hundred per cent effective FelV vaccination. The current vaccine in use is approximately eighty to eighty five per cent effective. It is possible, therefore, that a previously vaccinated cat could contract feline leukemia virus, if exposed to it.  You do not say whether your cat is an outdoor cat, where risk is higher, or an indoor cat exposed to a FelV positive cat.  The possibility of infection could vary according to the circumstances where you believe infection could have taken place.

Feline leukemia virus is a retrovirus that affects a cat’s immune system so it may contract various illnesses in a weakened state.  It is, therefore, difficult to list specific indicators of infection since these may vary from cat to cat. Some cats exposed may show symptoms within a few weeks, others may not show symptoms for some time.

Early symptoms may include weight loss, loss of appetite, fever, vomiting or diarrhea, swollen lymph nodes.  Later indicators may include all of these and also weakness or lethargy abscesses or wounds which are failing to heal.  An infected cat may suffer from frequent infections.  Check your cat’s gums for any sign of persistent gingivitis or for pale coloration. Their breathing may appear to become difficult or may sound noisy.  More frequent urination than normal or unusual thirst may indicate infection.

You know your own cat best, if he or she is behaving in an abnormal manner, for instance not eating even though he or she seems hungry, or seems to be repeatedly suffering different infections then you should not hesitate to have the cat checked out at once by your vet.