RHINOTRACHEITIS:  This widespread and common virus disease is very nasty in that if it doesn't cause death of the cat it can create life-long problems with upper respiratory disorders.  Coughing, sneezing, discharge from the nares, fever and poor appetite may plague the cat all its life.   Chronic tearing and crusty eye discharge are common and create a rather pathetic look to any cat affected.  Vaccines are quite effective in preventing this disease.

CALICIVIRUS:  This is a rather highly contagious upper respiratory virus that creates long term.  Moderate fever, poor appetite and ulceration of the tongue, mouth and lips can provoke weight loss and lethargy in a cat.  Each cat seems to vary in the intensity of signs shown and degree of affliction.  These affected cats can be carriers and will be a source of infection for other susceptible cats.

FELINE INFECTIOUS PERITONITIS (FIP):   This viral infection that is invariably fatal once a cats starts to show signs of it, can take years to cause trouble.  It is most common in young adult cats and is transmitted by other affected cats.  Two types of the disease are noted.  One is called the DRY TYPE of infection where the cat displays a high fever and impairment of internal organs such as the kidneys, liver, lungs and intestines.  These cats simply do not improve no matter what supportive measures are provided.  Likewise the WET FORM of the disease creates a fluid discharge within the abdomen and occasionally in the chest that displays a golden, dense liquid with flakes of proteinaceous debris floating within the fluid.  These cats loose weight rapidly, refuse to eat well and run a high fever.   Vaccination can be protective but, again, must be administered before any exposure takes place.  If an unknown carrier of the disease is vaccinated and develops the disease a year or so later, it seems common to either blame the vaccine or think the vaccine didn’t work.  The vaccine needs to be given prior to any exposure.

FELINE LEUKEMIA VIRUS (FeLV):  This virus, for which there is a very effective vaccine, is transmitted by cat-to-cat contact.  It severely limits the cat’s immune systems ability to ward off all sorts of infections.  Cats affected with FeLV may be carriers of the virus for long periods without displaying any ill effects.  Occasionally, if stressed by surgery or being lost outside or injury, a cat that is harboring the virus… and seemed to be healthy… will develop clinical signs.  Sick cats may have periods of time when they will seem healthy only to have relapses of illness.  It is commonly fatal over a period of time.

FELINE IMMUNE DEFICIENCY VIRUS (FIV):  This disease in cats is similar to the Human Immune Deficiency Virus (HIV) seen in humans.  But the FIV virus is found only in felines.  The evidence seems to indicate that this disease is spread mainly through the bite of an infected cat.  Like FeLV this disease suppresses the immune system’s strength so affected cats are likely to develop all sorts of infections in the urinary tract, respiratory tract, intestine and kidneys.  There is an intranasal inoculation that some veterinarians have been using for several years to help protect cats against Feline Immune Deficiency virus.  Although it is licensed and tested, some veterinarians aren't convinced it is as protective as many of the other feline vaccines.  Some veterinarians highly recommend it for areas where FIV cases are common and where any specific cat may be at high risk of being exposed to cats that potentially could be harboring the virus.

CHLAMYDIA:  This tiny organism (Not a virus) is highly contagious and creates inflammation of the eyes and nasal passages.  Signs include sneezing, ocular discharge, nasal drainage, sneezing, tearing and salivation and coughing.  It has the potential to be transmitted to humans, too.  There are specific antibiotics that seem to work well against this disease.

RINGWORM: also called a DERMATOPHYTE INFECTION:   Fungal infections of the skin of the cat are fairly common, especially in young cats and those with long hair.  Most of the cases of ringworm (which is NOT a worm at all) is due to an organism called Microsporum canis (M canis). It can also cause cutaneous infection in other species including dogs and humans.  Trichophyton mentagrophytes and Microsporum persicolor (acquired by contact with infected wild rodents) are the two other fungal species that commonly affect cats.  Cats may become infected either by direct contact with an infected animal or by exposure to contaminated objects such as grooming tools, clippers or bedding. Fungal spores are hardy and can survive in the environment and cause infections for approximately two years.   Some cats have severe skin disease while other cats have only very minor lesions or no lesions at all and look completely normal. That means that there can be feline carriers of cutaneous fungal infections that can act as a source of infection for other cats. Typical skin lesions are discrete, roughly circular, non-itchy, areas of hair loss, particularly on the head, ears or extremities of the paws. The hairs surrounding affected areas often appear broken. The affected skin is usually scaly and may look inflamed. However, ringworm can look very similar to many other feline skin diseases, such a flea allergic dermatitis, symmetrical alopecia and feline acne. On occasion the claws can become infected.  Topical and ingested medications can help eliminate cutaneous fungal infections but must be used long enough to totally eliminate all fungal organisms.

TOXOPLASMOSIS:   This disease of cats and other mammals is caused by a parasitic protozoan, Toxoplasma gondii. Protozoa are single-celled organisms but are not in the same classification as bacteria. They are among the simplest creatures in the animal kingdom. Cats that hunt and consume raw meat will have the greatest chance for contracting Toxoplasmosis. Ingestion of tissue cysts in infected prey or in other raw meat is probably the most common route by which cats are exposed to Toxoplasma.  Although infection with Toxoplasma is fairly common in cats, actual disease caused by the parasite is relatively rare.  Cats are able to shed Toxoplasma in their feces for a few weeks after they are first infected with the parasite. And as in humans with the disease, cats rarely have symptoms when first infected.  A cat can remain healthy appearing and yet have the organism within their bodies. There are no good tests available to determine if your cat is passing Toxoplasma in its feces.

Acutely infected cats might display lethargy, depression, poor appetite, lesions in the retinas of the eyes, weight loss and fever.  Liver and lung abnormalities may occur.  Any cat that displays a brain disorder such as incoordination,  sensitivity to light, constricted pupils, circling, personality changes or other central nervous system abnormalities should be evaluated for Toxoplasmosis.

Immunocompromised persons who are undergoing immunosuppressive therapy or those with an immunosuppressive disease such as AIDS should take special precautions against exposure to cat feces because of potential infection with Toxoplasma oocysts in the cat’s stool

Cats acquire Toxoplasma infection by eating any of the three infective stages of the parasite: cyst, oocyst, or tachyzoite. Following ingestion of the cysts in infected prey animals such as rodents or birds, the intra-intestinal infection cycle begins. This cycle occurs only in members of the cat family. The organisms multiply in the wall of the small intestine and produce oocysts for two to three weeks. The oocysts are then excreted in large numbers during this time is the cat’s stool.  Within five days, if conditions are right, the shed oocysts can sporulate and become infectious for other animals and humans. Once sporulated, the oocysts are highly resistant to environmental conditions and can survive for many months.

Most healthy exposed cats shed oocysts during acute infection with Toxoplasma, but will not shed them after the acute infection is over. In a few cats that do re-excrete oocysts after another exposure to Toxoplasma, the number of oocysts shed is smaller and may even be insufficient to transmit the parasite effectively.

Congenital infection is much less common in cats than it is in humans and some farm animals.  The diagnosis of Toxoplasmosis is challenging and requires serial sample of blood to see if the animal is developing immune proteins, which implies that Toxoplasma organisms are stimulating the immune system.  Treatment for Toxoplasmosis generally entails administration of an antibiotic, or even two antibiotics at the same time, and is generally effective in arresting the disease in cats.

At present there is no vaccine for Toxoplasmosis in cats. Because of the potential for human exposure to infective oocysts in an infected cat’s feces, special circumstance should be discussed with your physician if you are pregnant, immune compromised or are taking immunosuppressive medications such as anti-cancer medication or cortisone.

CAMPYLOBACTER:  A bacteria, Campylobacter jejuni is most often associated loose, sometimes bloody stool in cats, dogs, guinea pigs and other domesticated species, as well as in humans. Many infected cats show no signs of illness even with the bacteria present in the intestinal tract. Most affected cats are less than 6 months of age. Diarrhea (sometimes bloody) is the sign seen most often, but in most cases where Campylobacter are discovered there are other pathogenic organisms present as well.  The organism can survive in the environment for 3 days or more.  Infection in humans is usually through the food chain; infection from cats is rare but it does happen. Any severe loose stool, especially with blood present, should be evaluated by a veterinarian.

INTESTINAL PARASITES:  The most common are roundworms and tapeworms.  You can view them and read about intestinal worms here.   
Protozoal intestinal parasites can be a hazard as well, and Giardia commonly cause loose, gassy stool and abdominal cramping, especially in young kittens.  Easily overlooked, Giardia infestations may need special stains in a professional veterinary laboratory for positive identification.  Learn more about Giardia here.