• Many viruses pose a health threat for cats and kittens.kitten image by AGphotographer from Fotolia.com
  
  Cats are susceptible to a number of viruses that can affect their health adversely. In some cases, vaccines may be available to prevent infection, but many have neither vaccines nor cures. PetEducation.com says that cats usually must rely on their own immune systems to fight these viruses.
  
  

Feline Leukemia

• Infection by the feline leukemia virus, or FeLV, leads to a host of health complications for cats, including various types of cancer and problems with the immune system. The virus is present in bodily fluids, such as saliva, feces and urine. Cats become infected by grooming, sharing food or water bowls, or coming nose-to nose with other infected cats, according to PetEducation.com. A bite from a cat with FeLV also can transmit the virus.
  
  Cats with FeLV do not always exhibit symptoms, though fever, diarrhea or swollen lymph nodes may develop. Weight loss, anemia, infections, digestive ailments, respiratory problems and eye infections also may occur.
  
  

Feline Immunodeficiency Virus

• Feline immunodeficiency virus, or FIV, is similar to FeLV in that both are retroviruses that attack a cat's immune system. Unlike FeLV, FIV infections do not occur typically from grooming or sharing food and water bowls. Instead, most cats get FIV through bites from infected cats. According to PetEducation.com, infection occurs in three stages. In stage one, cats may have swollen lymph nodes, skin infections or intestinal problems. During stage two, which can last for years, cats typically are asymptomatic. In stage three, the infected cat's immune system has been so damaged that it cannot fight off infections. Cats in stage three may have skin, respiratory tract or intestinal infections. They may also suffer cancer. Watch for lack of appetite, swollen lymph nodes, fever, weight loss and lack of energy.
  
  

Feline Infectious Peritonitis

• The feline coronavirus causes feline infectious peritonitis, or FIP. Two types of feline coronavirus exist: feline enteric coronavirus, which does not cause disease, and feline infectious peritonitis virus, which causes FIP. In cats with FIP, white blood cells infected with the feline infectious peritonitis virus, or FIPV, help the virus spread throughout the cat's body. Cornell University's College of Veterinary Medicine warns that this can cause inflammation in the kidney, brain or abdomen. Since FIP is a progressive disease, it is fatal. Transmission occurs through exposure to an infected cat's feces or saliva, though most infections are passed from an infected female to her kittens, according to Cornell. Symptoms include fever, weight loss, lack of appetite, a rough coat, depression, anemia, a pot-bellied appearance or difficulty breathing.
  
  

Panleukopenia

• Panleukopenia, also known as feline distemper, is a common and widespread virus that can be fatal for cats. Transmission of panleukopenia occurs from exposure to an infected animal's urine or feces, or through contact with fleas. Pregnant cats also can transmit the virus to her kittens in utero. Symptoms include vomiting, diarrhea, seizures, fever, appetite loss, depression and dyhydration. A vaccine exists to help prevent the spread of panleukopenia. PetEducation.com suggests having kittens vaccinated at regular intervals to safeguard them from infection.