Common Diseases of Dogs and Cats for Technicians

Introduction

A technician does not diagnose disease, but a technician is often the first person to notice it. You take the history, see the bloody diarrhea in the kennel, count the breathing rate, and teach the owner how to give insulin. You also decide, in the first minute, whether a patient goes into the general ward or into isolation.

This guide covers the diseases of dogs and cats that come up most often in practice and on the VTNE: parvovirus, distemper, FeLV, FIV, FIP, kennel cough, leptospirosis, diabetes mellitus, hyperthyroidism, chronic kidney disease, Cushing and Addison disease, feline lower urinary tract disease, intervertebral disk disease and heart disease. For each one you will learn the cause, how it spreads, the signs you will see, and what the technician monitors and teaches. "Common animal diseases" and "pathophysiology" are both knowledge statements on the VTNE outline.¹⁹

Key facts

How the VTNE tests this

• Recognize the classic signs of a disease from a short case (signalment plus signs), then choose the nursing action. Domain 5 Task A; K3, K4.¹⁹
• Choose the isolation and PPE plan for a contagious or zoonotic patient, and the right disinfectant for the agent.
• Monitor the right parameter: blood glucose in a diabetic, sleeping respiratory rate in a cardiac dog, urine output in a blocked cat. Domain 5 Task B.¹⁹
• Educate the client on home care: insulin injections, SQ fluids, cage rest, keeping an FeLV-positive cat indoors. Domain 5 Task C.¹⁹
• Calculate a simple value, such as a breathing rate per minute or a disinfectant dilution.

Core concepts

Infectious diseases: think "how does it spread?"

For every infectious disease, ask three questions. How does it spread? How long does it survive in the hospital? Can it infect people? The answers decide where the patient is housed, what you wear and what you clean with.

Canine parvovirus (CPV) attacks rapidly dividing cells in the gut and bone marrow. Signs begin as lethargy, anorexia and fever, then progress to vomiting and hemorrhagic (bloody) small bowel diarrhea within 24 to 48 hours.¹ Infected dogs shed virus in feces within 4 to 5 days of exposure, often before signs appear, and for about 10 days after recovery.¹ Diagnosis is usually confirmed with a fecal antigen test, and Merck advises immediate isolation of suspected or confirmed cases.¹

Canine distemper is a paramyxovirus related to measles. Dogs show fever, nasal discharge, pneumonia and diarrhea, sometimes followed by neurologic signs such as muscle twitching (myoclonus) and seizures, including "chewing-gum fits".² Survivors may develop hyperkeratosis (thickening) of the footpads and nose and enamel hypoplasia of the teeth.² Some infected dogs shed virus for several months.²

Feline leukemia virus (FeLV) is one of the most common infectious causes of disease in cats worldwide.³ Point-of-care ELISA tests detect the viral antigen p27. Tears and saliva should not be used to test for FeLV antigen.³ Cats should be tested before FeLV vaccination, and infected cats should be kept strictly indoors.³

Feline immunodeficiency virus (FIV) spreads through saliva, mainly by biting. Outdoor cats, male cats and older cats are more likely to be infected.⁴ Cats can look healthy for months or years, but remain infected for life.⁴ The screening test detects antibodies.⁴

Feline infectious peritonitis (FIP) is an immune-mediated disease caused by feline coronavirus (FCoV). FCoV spreads by the fecal-oral route or fomites, most often from queens to kittens, but only about 5% to 12% of infected cats go on to develop FIP.⁵ Risk factors include multicat housing, young age, purebred lineage and recent stress.⁵ The effusive ("wet") form causes fluid in the abdomen or chest; the noneffusive ("dry") form does not.⁵ Antiviral drugs now show promise for treatment, although they are not available in every country.⁵

Kennel cough (infectious tracheobronchitis) has several causes, including Bordetella bronchiseptica, canine parainfluenza virus, canine adenovirus 2 and canine influenza.⁶ The typical sign is a "goose honk" cough, often followed by retching, that is easy to trigger by gently pressing on the trachea. Most cases are self-limiting, and hospitalized dogs should be housed in isolation.⁶

Leptospirosis is a bacterial disease that ranges from mild infection to acute kidney injury, respiratory disease or death in dogs.⁷ Doxycycline is the main drug used, and polyvalent vaccines are available. Occupational exposure is a risk factor for people.⁷

Sources: Merck Veterinary Manual chapters on each disease.^{1,2,3,4,5,6,7}

Endocrine diseases: hormones too high or too low

Diabetes mellitus causes polyuria (increased urination), polydipsia (increased thirst), polyphagia (increased appetite) and weight loss. The renal threshold for glucose is about 180 mg/dL in dogs and about 280 mg/dL in cats, so above those levels glucose spills into the urine.⁸ Cataracts are common in dogs, not cats, with poorly controlled diabetes.⁸ Insulin is given SC, usually every 12 hours; dogs on twice-daily insulin get two equal meals, each given just before the injection.⁸ Remission is possible in cats; in dogs, diabetes is usually lifelong.⁸ Up to 25% of diabetic patients are euthanized on the day of diagnosis, often for reasons that client education can prevent, which makes the technician's teaching role central.⁸

Hyperthyroidism is a common endocrine disease of mature and senior cats. Signs include hyperactivity, excess vocalization and weight loss despite a good appetite.⁹ Treatment options are radioiodine, antithyroid medication (methimazole), thyroidectomy and an iodine-deficient diet. Methimazole is lifelong if it is the only treatment.⁹

Hyperadrenocorticism (too much cortisol) occurs mostly in dogs aged 7 to 12 years. About 85% of dogs have the pituitary-dependent form, called Cushing disease, and 15% have a cortisol-producing adrenal tumor.¹¹ Look for polyuria and polydipsia, polyphagia, a "potbelly", panting, muscle weakness and symmetric alopecia. Trilostane is the usual treatment and is given with food.¹¹

Addison disease (hypoadrenocorticism) is a lack of mineralocorticoid and glucocorticoid. It occurs mostly in young to middle-aged dogs, more often in females.¹² An addisonian crisis brings hypovolemia, hypotension, severe hyperkalemia with a slow heart rate (bradyarrhythmia), hypoglycemia and vomiting or diarrhea. A low sodium to potassium (Na:K) ratio is a key laboratory clue, and IV fluid therapy is the mainstay of emergency treatment.¹²

Kidney, bladder, spine and heart

Chronic kidney disease (CKD) is staged with the IRIS system, using creatinine and SDMA in a stable, hydrated patient.¹⁰ Polyuria and polydipsia are not seen until about two thirds of the nephrons are lost.¹⁰ Systemic hypertension is a common complication that can damage the kidneys, eyes, brain and heart, so blood pressure is part of every CKD recheck.¹⁰ Renal diets, low in phosphorus with modest amounts of high-quality protein, lengthen survival. Fluids can be given SC at home when needed.¹⁰

Feline lower urinary tract disease (FLUTD) shows as hematuria (blood in urine), pollakiuria (frequent small voids), stranguria (straining) and periuria (urinating outside the litter box). Most cats with these signs have feline idiopathic cystitis, which is linked to stress. Management includes reducing stress, litter box care, canned food and pheromones.¹³ A straining male cat is an emergency until proven otherwise, because urethral plugs cause most obstructions and severe hyperkalemia can cause life-threatening arrhythmias.¹⁴

Intervertebral disk disease (IVDD) is most common in chondrodystrophic breeds such as the Dachshund, French Bulldog, Beagle and Shih Tzu. Miniature Dachshunds have a lifetime risk of about 20%.²⁰ In a paralyzed dog, the most important prognostic finding is deep pain perception, tested by pinching a toe or the tail and watching for a behavioral response such as turning the head. A reflex withdrawal of the limb does not count.²⁰ Dogs with pain and mild to moderate deficits often recover with 2 to 3 weeks of cage rest.²⁰

Heart disease differs by species. In dogs, myxomatous mitral valve disease (MMVD) is the most common heart disease, and most dogs have a murmur for years before signs appear.¹⁶ In cats, hypertrophic cardiomyopathy (HCM) is most common and is often silent. Cats in heart failure breathe fast and hard; cough is uncommon. Some cats develop systemic thromboembolism (a clot that often blocks blood flow to the hind limbs).¹⁷

Sources: Merck Veterinary Manual; ACVIM MMVD consensus.^{8,9,10,11,12,13,14,15,16,17,20}

Procedure or technique: admitting a patient with a contagious disease

1. Screen at the door. A young, unvaccinated dog with vomiting and diarrhea, or a coughing dog, stays out of the lobby. Ask the client to wait in the car or move straight to an exam room set aside for this.
2. Test early. For a suspected parvovirus case, run the fecal antigen test as soon as possible so isolation can start.¹
3. House in isolation. Suspected or confirmed parvovirus and hospitalized kennel cough patients go to isolation.^1,6 Keep dedicated equipment (thermometer, stethoscope, bowls) in the room.
4. Wear the right PPE. Gown, gloves and foot covers for every entry. For leptospirosis, add eye protection and handle urine carefully because people can be infected through body fluids.⁷
5. Monitor and record. Temperature, hydration, body weight, vomiting and stool, and urine output. Report trends to the veterinarian.
6. Clean and disinfect. Remove organic matter first, then apply a disinfectant that works on the agent. For parvovirus use a product proven against nonenveloped viruses, such as bleach at 1:32 with 10 minutes of wet contact.¹⁸
7. Discharge with teaching. Parvovirus survives in the environment for a long time and dogs shed it for about 10 days after recovery, so advise the owner on cleaning and on keeping the dog away from unvaccinated dogs.¹

Flowchart: where does this patient go?

Species differences

• Diabetes: cataracts develop often in poorly controlled diabetic dogs but not in cats. Remission is possible in cats, while diabetes in dogs is usually lifelong.⁸
• Heart failure: in dogs, panting can mask the fast breathing of pulmonary edema, so a sleeping rate counted at home is more useful; cats in heart failure rarely cough.^15,17
• Endocrine: hyperthyroidism is a common disease of mature and senior cats; in dogs, thyroid carcinoma is the primary cause. Cushing disease as described here is a disease of middle-aged to older dogs, and Addison disease occurs most commonly in dogs.^9,11,12
• IVDD: clinical disk disease is rare in cats and horses.²⁰
• Retroviruses and FIP: FeLV, FIV and FIP are cat diseases. Parvovirus, distemper and kennel cough are covered here for dogs.

Calculation

Safety, legal and client education

• Zoonosis: leptospirosis can infect staff and owners. Teach owners to wear gloves when cleaning up urine and to wash hands.⁷
• Vaccination: distemper, parainfluenza and CAV-2 vaccines protect against kennel cough agents; leptospirosis vaccines should match the serovars found locally.^6,7 Kittens get FeLV vaccine as part of the initial series and one year later.³
• Diabetes teaching: client communication is a key part of success, and home monitoring is often best.⁸ Show the owner how to handle the insulin and give the injection, and how to feed with each dose.
• Heart teaching: teach the owner to count the sleeping respiratory rate, because a rise above baseline is the best predictor of impending decompensation.¹⁶
• FeLV and FIV positive cats: keep them indoors to protect them and other cats.^3,4
• Bleach safety: bleach is caustic and corrosive. Wear gloves and follow the label and the hospital protocol.¹⁸

Common mistakes and exam traps

Quick review

1. Parvovirus: fecal-oral, nonenveloped, isolate, bleach 1:32 for 10 minutes.
2. Distemper: aerosol, respiratory then neurologic signs, hard pad.
3. FeLV: saliva and grooming; p27 antigen test; never test tears or saliva.
4. FIV: bite wounds; antibody test; outdoor, male and older cats at risk.
5. FIP: mutated FCoV; wet form has effusions; multicat homes and young cats.
6. Kennel cough: honking cough; isolate if hospitalized.
7. Leptospirosis: urine-borne zoonosis; gloves and eye protection.
8. Diabetes: PU/PD, polyphagia, weight loss; insulin SC with meals.
9. Hyperthyroid cats lose weight while eating well.
10. CKD: IRIS stage by creatinine and SDMA; check blood pressure.
11. Addison crisis: hyperkalemia, bradycardia, low Na:K; Cushing: potbelly and PU/PD.
12. Heart: MMVD in dogs, HCM in cats; sleeping respiratory rate above 30 is a warning.