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Cat Viral Infections

Chlamydia | Influenza | Feline Infectious Enteritis | Feline Leukaemia | Feline Immunodeficiency Virus | Feline Infectious Peritonitis | Rabies | Feline Spongiform Encephalopathy

For a virus to get energy and reproduce, it needs a host body, and not all viruses will cause disease. In the cat pathogenic viruses are responsible for conditions such as feline enteritis, cat flu and rabies. Some viruses, such as the one responsible for enteritis, are very resilient and will survive for long periods, while others such as cat flu, are easily destroyed by disinfectants. Some viruses produce severe disease very quickly, while others like feline immunodeficiency virus (FIV) have a long incubation period.

You can protect your cat from a lot of serious viral infections by vaccination, but not every where will inoculate against rabies and feline infectious peritonitis. Both of these vaccines are available world wide but are not necessarily licensed. In the United Kingdom, the rabies vaccine is only used on animals intended for export. If quarantine regulations are lifted in the United Kingdom, it is likely that the rabies vaccine will become compulsory. Cat  flu and feline enteritis are effectively protected against by means of vaccination.

Infections are not necessarily the same as disease.  Disease is any impairment of the normal functioning of the animal, and is usually caused by infection. For example, cats will become infected with feline coronavirus, but may not show any signs of disease or illness. Infections are not always contagious.


Chlamydia organisms fall midway between viruses and bacteria and are responsible for a disease in the upper respiratory tract in the cat, with symptoms that are familiar to flu. Minor outbreaks cause the eyes to become inflamed and produce a nasty discharge. Severe attacks cause nasal discharge and a loss of smell and appetite. Chlamydia organisms are susceptible to similar antibodies to which bacteria are sensitive. A vaccine has been available since 1991and most cases are found in households with pedigreed breeding animals, but is has been known to occur in other cats as well.

Influenza (Viral Rhinitis)
This illness affects the upper respiratory tract, it's caused by two main viruses, feline calicivirus and feline herpesvirus. Both cause coughing and sneezing. Discharge from the nose and eyes cause distress for the cat, and a sore throat discourages eating and drinking. Feline calicivirus causes ulceration of the nose, mouth and tongue. Feline herpesvirus can cause the nose, windpipe and lungs to become inflamed, resulting in a lot of coughing and sneezing. Your cat stands a greater chance of survival if it is kept warm and comfortable and encouraged to eat and drink. Antibiotics will help prevent the risk of secondary infections but will not attack the primary virus. Vaccination is the best preventative measure.

Feline Infectious Enteritis
This disease is also known as feline panleukopaenia and feline parvovirus. The first symptom is a very high fever. The virus attacks rapidly dividing cells, particularly in the bowel. Symptoms include depressed behaviour, loss of appetite, vomiting, and a desire to drink but an inability to do so. Diarrhoea is not always present. Rapid dehydration sets in followed by coma and death. The rapidity of the disease means that death can occur two or three days after vomiting starts or even within 24 hours. This disease is highly infectious. Treatment is supportive; keep the cat warm and free from draughts, and administer re-hydration as advised by the vet.

Feline Leukaemia Virus (FeLV)
This virus was first noticed by breeders in the 1970s. People originally thought this disease could be hazardous to humans, but this is not the case. The virus can only be transmitted to other cats. All cats are affected similarly and rapidly when they come into contact with the virus. It was found that a larger than expected portion of the normal domestic cat was affected and many of these cats lived in to old age. This made a nonsense of early veterinary advice that cats with feline leukaemia virus should be euthanased immediately.

Some cats do succumb to other untreatable infections as the virus attacks the cat's immune system, while other cats are less affected. If you have one cat that has the virus, in a multi-cat household, the cat with the virus should be removed, as it can be transmitted through saliva and blood. The infected cat could move to a house that has no other cats. Testing for the virus is done through a blood sample. It is possible for a cat to test positive and then, two weeks later, to show a negative result, only having had a passing contact with the virus. A vaccine for this virus has been available since 1992.

Most breeders will have their cats neutered, or young breeding cats, regularly tested to show that they are FeLV-negative. Females are only mated to made which also regularly test negative, so that the kittens are automatically negative too. They can then be protected by vaccination. Many breeders leave this to the new owners. If a kitten is an only pet, then this can be left until the kitten is a litter older.

Feline Immunodeficiency Virus (FIV)
This is similar to the human immunodeficiency virus (HIV) which may lead to acquired immunodeficiency syndrome. The feline version cannot be passed to humans, and the human version cannot be passed to cats.

FIV progressively breaks down the cat's immune system. This leads to the cat becoming vulnerable to infections. The cat may appear well, but will slowly be affected my many minor illnesses which become untreatable. No vaccination exits at present.

Feline Infectious Peritonitis (FIP)
The virus that causes this disease is found in many cats and normally only occasionally causes a transient diarrhoea. In about 10% of cats the virus leaves the intestines and invades the blood vessels which causes severe inflammation. The membrane which lines the abdominal cavity is called peritoneum, and once the blood vessels have become inflamed and infected, treatment is very difficult and often unsuccessful.  The disease can be triggered in almost all age groups, even young kittens.

Wet FIP is the most common form of the disease. Onset is rapid. Just 24 hours after being lively, of good appetite and with normal litter-tray motions, a wet FIP sufferer will be lethargic, will not eat much and have sickness and diarrhoea. The coat is often dull, but the most obvious sign will be a hugely distended fluid-filled abdomen. There is no cure. Euthanasia is the only option.

Dry FIP is less common and is difficult to diagnose. The signs are similar to those above. Terminally, the cat may have jaundice and show symptoms similar to cat flu, physical disorientation, blindness due to haemorrhages in the eyes and fits.

The presence of the virus is detected in antibody tests. Over 80% of show cats are seropositive, showing they have had some contact with the disease. It is thought that a stressful situation, such as introducing a new cat into the house or a long journey, may tip a cat with pre-existing viral condition into the full blown virus.

FIP does not seem to be as infectious as was first thought. The virus is carried in the cats saliva and faeces. Litter trays should be disinfected regularly using cleaning products recommended by your vet. Keeping cats in small, easily managed colonies, observing strict hygiene and maintaining a stress free environment should reduce the possibility of the disease flaring up. The virus will not survive long outside the host, and is killed with disinfection agents. There is no vaccine available in the United Kingdom at the moment, although it is available in other European countries.

All mammals can get rabies, and the bite of an infected animal is dangerous. Once infected the cat may show signs of huge alteration in appetite, voice and be very aggressive. An inability to drink gives rabies its other name, hydrophobia - fear of water. Other signs are, foaming at the mouth, swelling of the skull, jaw paralysis and disorientation.

Treatment is possible but must be given as soon it is suspected that it has been bitten by an infected animal. There is very little hope of any infected mammal surviving once the incubation period of the disease has passed and the symptoms are showing. Vaccination is available and standard in countries where rabies exists but, at present, in the United Kingdom it is only obtainable for animals that are to be exported.

Feline Spongiform Encephalopathy

This disease is caused by a sub-viral protein that is capable of reproducing itself. It is similar to the bovine form (BSE) that has occurred in the United Kingdom, but no where else. The disease seems to be fatal in cats and is not diagnosable before death. It seems to have been transmitted as a result of eating cattle infected with BSE or sheep with scrapie. The cat develops abnormal behaviour, it stops grooming itself, it drools with muscle tremors and an abnormal head posture. However, positive diagnosis is only possible on post-mortem examination.


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