Last Updated on April 11, 2026 by admin
Cats are skilled at hiding discomfort, which means many illnesses progress before owners notice anything is wrong. Understanding the most common conditions that affect cats—and their early warning signs—helps you seek veterinary care at the right time and keep your cat healthier for longer.
Common Infectious Diseases
Cats are susceptible to a range of viral and bacterial infections, some of which can be prevented through vaccination.
Feline Upper Respiratory Infection (URI)
Upper respiratory infections are among the most common illnesses in cats, especially in shelters and multi-cat households. They are caused by a combination of pathogens—most commonly feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV), sometimes complicated by secondary bacterial infections. Symptoms include sneezing, nasal and eye discharge, conjunctivitis, and lethargy. Most cases resolve with supportive care; severe cases may require antibiotics for secondary infections, antiviral eye drops, or nebulization therapy. Many cats infected with FHV-1 carry the virus for life and may have recurrent flare-ups during stress.
Feline Leukemia Virus (FeLV)
FeLV is a serious retrovirus transmitted through saliva, nasal secretions, and other bodily fluids—primarily through close contact such as mutual grooming or shared food bowls. It suppresses the immune system and can lead to anemia, lymphoma, and other life-threatening conditions. An effective vaccine is available and recommended for cats with outdoor access or exposure to unknown cats. Indoor-only cats with no exposure are considered low-risk.
Feline Immunodeficiency Virus (FIV)
FIV weakens the immune system over time, leaving cats vulnerable to secondary infections. It is transmitted primarily through deep bite wounds, making intact male cats that roam outdoors the highest-risk group. FIV-positive cats can live for years with careful management and regular veterinary monitoring, but they require prompt treatment of any secondary infections. No widely available vaccine currently exists for FIV in the United States.
Rabies
Rabies is a fatal viral disease affecting the central nervous system. Cats can be infected through bites from infected wildlife. Vaccination is legally required for cats in most US states and many other jurisdictions, and it is the only reliable protection against this disease. Any cat that may have been exposed to wildlife should be evaluated by a veterinarian immediately.
Common Non-Infectious Diseases
Diabetes
Diabetes mellitus is most common in middle-aged to older cats and is strongly associated with obesity and a sedentary lifestyle. It occurs when the body fails to produce or respond to insulin, leading to chronically elevated blood sugar. Symptoms include increased thirst, frequent urination, weight loss despite good appetite, and a plantigrade stance (walking flat on the hocks). Treatment typically involves twice-daily insulin injections and a low-carbohydrate, high-protein diet. With good management, some cats achieve diabetic remission.
Chronic Kidney Disease (CKD)
CKD is one of the most common diseases in older cats, affecting an estimated 30–40% of cats over age 10. The kidneys gradually lose their ability to filter waste and maintain fluid balance. Early signs include increased thirst and urination; as CKD progresses, cats develop weight loss, poor coat quality, decreased appetite, vomiting, and lethargy. CKD is not curable, but it can be managed with dietary modification (phosphorus-restricted, kidney-supportive food), subcutaneous fluid therapy, medications to control nausea and blood pressure, and regular monitoring.
Vomiting and Inflammatory Bowel Disease (IBD)
Occasional vomiting from hairballs or dietary indiscretion is common and usually not serious. Frequent or chronic vomiting, however—particularly when accompanied by weight loss, diarrhea, or decreased appetite—warrants investigation. Causes range from food sensitivities and parasites to IBD, hyperthyroidism, or intestinal lymphoma. Diagnosis often requires ultrasound and intestinal biopsies. Treatment depends on the underlying cause but may include dietary changes, steroids, or other immunosuppressive medications.
Cancer
Cancer is unfortunately common in cats. Lymphoma is the most frequently diagnosed type and can affect the intestines, mediastinum, kidneys, and other organs. Squamous cell carcinoma affects the skin—often on the nose, ears, or eyelids—particularly in cats with white or light-colored faces. Mammary tumors are highly malignant in cats; spaying before the first heat significantly reduces risk. Treatment options include surgery, chemotherapy, and radiation depending on the type and stage.
Parasites
Fleas
Fleas are the most common external parasite in cats. They cause intense itching, skin irritation, and in severe infestations, anemia. Flea allergy dermatitis (FAD) is one of the most common causes of skin disease in cats—even a single flea bite can trigger a reaction in sensitized animals. Fleas also transmit tapeworms. Year-round flea prevention using a veterinarian-recommended product is the most effective strategy; treating the environment (vacuuming, washing bedding) is equally important since 95% of the flea population lives in the home, not on the cat.
Tapeworms
The most common tapeworm in cats (Dipylidium caninum) is transmitted by swallowing infected fleas during grooming. Segments resembling rice grains may be visible around the cat’s rectum or in feces. Treatment is a dewormer prescribed by a veterinarian; flea control is essential to prevent reinfection.
Roundworms and Hookworms
Roundworms (Toxocara cati) are very common, especially in kittens, who can acquire them from their mother’s milk. Heavy infections cause vomiting, diarrhea, and a pot-bellied appearance. Hookworms can cause anemia and are more significant in kittens than adults. Both are treated with deworming medications. Regular fecal testing and routine deworming are standard parts of cat wellness care.
Giardia
Giardia is a protozoan parasite transmitted via contaminated water or feces. It causes soft, watery, or mucoid diarrhea. Diagnosis is by fecal testing; treatment involves antiparasitic medications (typically fenbendazole or metronidazole). Environmental decontamination is important to prevent reinfection.
Urinary Tract Issues
Feline Lower Urinary Tract Disease (FLUTD)
FLUTD is a broad term for conditions affecting the bladder and urethra, including feline idiopathic cystitis (FIC), urinary stones, and urethral plugs. FIC—the most common form—is strongly linked to stress and is more common in indoor cats, overweight cats, and cats in multi-cat households. Symptoms include straining to urinate, frequent trips to the litter box with little urine produced, blood in the urine, and urinating outside the box. Male cats are at risk of urethral obstruction, which is a life-threatening emergency requiring immediate veterinary care. Management of FIC focuses on reducing stress, encouraging water intake (switching to wet food), and environmental enrichment.
Urinary Tract Infections (UTIs)
True bacterial UTIs are less common in cats than in dogs, and are most often seen in older cats, cats with diabetes, or cats with structural abnormalities. Symptoms overlap with FIC. Diagnosis requires urine culture; treatment is targeted antibiotic therapy based on sensitivity results.
Skin Conditions
Ringworm
Ringworm is a fungal infection (Microsporum canis) that causes circular patches of hair loss, scaly or crusty skin, and sometimes itching. It is highly contagious to other cats, dogs, and humans. Diagnosis is by fungal culture; treatment involves antifungal medication (topical and/or oral) and thorough environmental decontamination.
Skin Infections and Dermatitis
Bacterial skin infections (pyoderma) can occur secondary to wounds, allergies, or parasites. Allergies—to environmental allergens, food, or flea bites—are a common cause of skin inflammation, itching, and over-grooming. Diagnosis may involve skin scraping, culture, or allergy testing. Treatment depends on the cause and may include antibiotics, antifungals, steroids, or allergen-specific immunotherapy.
Eye and Ear Issues
Eye Infections and Conjunctivitis
Conjunctivitis (inflammation of the membrane lining the eyelids) is common in cats and is often related to upper respiratory infections—particularly FHV-1, which has a strong tropism for eye tissue. Symptoms include redness, discharge, squinting, and sensitivity to light. Treatment depends on the cause and may include topical antibiotics, antiviral drops, or systemic medication.
Ear Infections
Ear infections in cats are often caused by ear mites (Otodectes cynotis), yeast, or bacteria. Symptoms include head shaking, pawing at the ear, dark discharge, and odor. Diagnosis is by ear cytology; treatment may include ear cleaning, topical medication, and treatment for underlying conditions such as allergies.
Glaucoma and Cataracts
Glaucoma (increased intraocular pressure) can cause pain, redness, and cloudiness, and may lead to blindness if untreated. Cataracts cause a cloudy or bluish appearance to the lens and can impair vision. Both conditions require veterinary evaluation; treatment may involve medication or surgery.
Zoonotic Diseases
A few cat-associated illnesses can be transmitted to humans, though the risk is generally low with basic hygiene:
- Cat scratch disease is caused by Bartonella henselae bacteria carried by infected fleas and transmitted to cats. People typically acquire it through scratch or bite wounds from infected cats. Symptoms include fever, swollen lymph nodes, and fatigue. Most cases resolve without treatment.
- Toxoplasmosis is a parasitic infection transmitted through contact with infected cat feces in the litter box (or contaminated soil). Most people experience no symptoms, but it can cause serious complications in pregnant women and immunocompromised individuals. Pregnant women and immunocompromised people should avoid changing litter boxes; others should clean boxes daily (oocysts take 1–5 days to become infectious after shedding) and wash hands thoroughly.
- Salmonellosis can occur through contact with infected cat feces. Practice hand washing after handling cats and cleaning litter boxes.
- Ringworm (as noted above) can be transmitted directly from an infected cat to a person.
Prevention and General Care
The foundation of preventing common cat illnesses is a combination of regular veterinary care, vaccination, parasite control, and attentive observation at home.
Core vaccines recommended for most cats include feline herpesvirus/calicivirus/panleukopenia (the FVRCP combination) and rabies. FeLV vaccine is recommended for cats with outdoor access. Your veterinarian will advise on a schedule appropriate for your cat’s age, lifestyle, and risk factors.
Year-round parasite prevention is important for cats with any outdoor exposure. Annual wellness exams—and twice-yearly exams for cats over age 7—allow early detection of conditions like CKD, diabetes, and dental disease before they become severe. Because cats hide illness well, any change in behavior, appetite, litter box habits, weight, or coat quality is worth a call to your veterinarian.