Health and DiseaseHealth and Disease

LAT Chapter 9

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Chapter 9Disease TerminologyDisease Terminology

Infectious Disease: caused by living agents that invade the

bodies of animals, often causing them to become ill Infected animals are called hosts. Dealing with microscopic

organisms difficult, detected only after signs of disease develop.

Contagious Diseases: transmitted directly or indirectly, from

an infected animal to a healthy one Most infectious diseases are contagious.

Direct contact = infected animals must touch one another.

Indirectly = airborne or aerosol transmission

Horizontal transmission = within the same generation

Vertical transmission = 1 generation to next = mother to offspring

Chapter 9FFomites / omites / VVectors / ectors / CCarriersarriers

F - Inanimate objects that provide a mechanical means of infectious disease transmission. Cages, bedding, feeding pans, scrub brushes, boots, clothing, gloves and

dust particles

V - Living organisms that transmit disease. Insects such as fleas or ticks, animal technicians carrying diseases from

room to room

C - Animals that can transmit infectious diseases to other animals without ever showing signs that they, themselves, have the disease. Hamsters, for example, show no signs of the viral disease lymphocytic

choriomeningitis (LCM) when they carry the disease. People who handle hamsters infected with this virus can become ill with the disease. Mice exposed to such hamsters frequently develop serious clinical disease.

Graphic from: http://caplter.asu.edu/explorers/protocol/arthropods/background.htm

Chapter 9Zoonosis Zoonosis

• Disease transmitted from humans

to animals / animals to humans

= zoonosis, or zoonotic disease. tuberculosis & nonhuman primates turtles & salmonellosis. cats and dogs & ringworm rabies, herpes B, lymphocytic choriomeningitis (LCM), toxoplasmosis, herpes

simplex virus

• Table 9.1 - casual contact zoonoses• Table 9.2 - active contact zoonoses• Epizootic: a sudden disease outbreak that affects a large number of

animals (an epidemic in humans)• Enzootic: disease occurs in several members of a population or

colony (endemic in humans)

For more information:http://medicine.bu.edu/dshapiro/zoo1.htm

Chapter 9Noninfectious DiseaseNoninfectious Disease

Nutritional Diseases: dominant animal may prevent

subordinate from access to food skin conditions, changes in hair coat, growth changes, malformation

of bones, and reduced reproductive capacity.

Hereditary Abnormalities: passed from parent to offspring by

way of genes Certain ones intentionally maintained in inbred animals.

Technicians who work with strain that has inherited problems should

learn about the characteristic unusual responses.

Congenital Diseases: animal is born with disease

Degenerative Diseases: diseases associated with aging

Chapter 9Noninfectious DiseaseNoninfectious Disease

Genetic Abnormalities Discovered in

Mice

From: Biology of the Laboratory Mouse, by The Jackson Laboratory,(Dover Publications, 1968), pp.100-101

Chapter 9CancerCancer

• Unregulated, disorganized proliferation

• Neoplasm = “new growth”

• Chronic irritation, radiation, and certain chemical agents, drugs, and viruses can induce tumor formation.

• Several genes linked to breast and colon tumors.

• Tumors may either be malignant or benign. Benign tumors are not extensively invasive.

Malignant tumors, on the other hand, often spread rapidly, are very invasive, even to other areas of the body (metastasis) and are more life-threatening.

• Many strains of rodents have a predisposition to develop specific types, which makes them useful animal models.

Chapter 9Diagnosing DiseaseDiagnosing Disease

• Diagnosis: Diagnosis is usually based on clinical signs and symptoms, laboratory

test results, and findings from a complete necropsy. A prognosis is a prediction of the probable course of a disease and the

chances of recovery.

• Morbidity and Mortality: The morbidity rate is the number of sick animals expressed as %. Mortality refers to the number of animals that die from a disease. Sick animals that seem near death are said to be moribund.

• Determining Severity: Visible disease signs = overt or clinical No clinical signs = infection is said to be subclinical. Severity depends on # of host cells involved, extent of damage and

importance of the structures.

Chapter 9Classifying Disease Classifying Disease

Etiology - refers to their cause or origin

Anatomically - body system where symptoms occur

Acute - rapid onset and brief duration

Chronic - gradual onset and long duration

Peracute - sudden onset and violent

Local - confined to a small area

Systemic - affect a large part of the body Agents carried through the body by bloodstream Bacterium = bacteremia / virus = viremia Septicemia is term for proliferation of infection in blood. Lesion = local area of damage.

• Gross lesions can be seen with the naked eye.

• Microscopic lesions can be seen under the microscope.

Chapter 9Body DefensesBody Defenses

Signs of inflammation are:

1. Heat

2. Redness

3. Swelling

4. Pain

5. Loss of function

• Certain foreign organisms are not easily destroyed by a local inflammatory response. Large numbers of dead cells, bacteria, and phagocytes may

accumulate, resulting in the production of pus (e.g. abscess).

Relatively long period of inflammation is required for all the bacteria to be killed and for an abscess to heal.

For more information go to: http://www.atherogenics.com/science/therapeutic.html

Chapter 9Invading OrganismsInvading Organisms

• If organisms escape from a local area, they spread throughout body causing septicemia. Simultaneous exposure of many organs to bacterial infection, toxins, or

waste products => death. Lymphatic system drains excess fluids and debris from tissues.

• The lymph nodes trap many bacteria, viruses, and damaged cells.• Swollen lymph nodes are a clinical sign of disease.

• After antigen exposure, immune system produces lymphocytes and antibodies against specific foreign substance that initially stimulated their production. Acquired (developed), active immunity to that substance Antigen-specific antibodies can be identified in diagnostic tests. Controlled exposure to antigens is the principle behind vaccination

against bacterial, viral and allergic diseases.

Chapter 9Allergy or HypersensitivityAllergy or Hypersensitivity

• Instead of helping, allergic immune response causes additional tissue damage. One reaction is called anaphylactic shock.

• Some organisms are adapted to surviving in an animal host despite the immune response. Parasites, such as intestinal roundworms, are a classic example.

• Newborns have temporary level of passive immunity. Antibodies acquired through mothers’ milk or across the placenta.

Passively transferred antibodies protect for the first few weeks of life until old enough to produce own antibodies.

• Only infection or vaccination can stimulate a long-lasting active immune response.

For more information: http://news.bbc.co.uk/hi/english/health/medical_notes/a-b/newsid_372000/372558.stm

Chapter 9SummarySummary

• Unvaccinated, disease-free animals have no immunity from prior exposure. As health status of laboratory animals improves, quality of care and

observation provided by laboratory animal technicians must also improve.

• Host’s immune system usually recognizes a disease agent as foreign and mounts some type of defense.

• Host may be successful or unsuccessful in fighting off disease. depending on # of organisms or concentration of agent to which it was

exposed, the nature of the agent, and way host reacts

• If successful, host lives after recovering; if unsuccessful, it may die. If the host lives, it may or may not develop immunity.

Chapter 9Preventing & Curing DiseasePreventing & Curing Disease

• Preventive medicine way to avoid disease. Requires barriers between hosts and organisms or immunization

before infection occurs.

• Antibiotics or anti-inflammatory drugs, often required to help combat disease.

• Many diseases are no longer common problems in rodents born and raised in barriers. Wild rodents and cockroaches occasionally get in. Imported primates and other wild animals, often contain exotic disease

organisms.

• Be on alert for outbreaks and zoonotic health problems.• Cleanliness and sanitation are still backbone of disease

prevention and control.

Chapter 9Prevention & Control of DiseasePrevention & Control of Disease

1. Quarantine

2. Sanitation and hygiene

3. Periodic examination

4. Appropriate immunizations

5. Proper waste disposal

6. Upkeep of physical facilities

7. Isolation procedures

Chapter 9Identifying & Treating DiseasesIdentifying & Treating Diseases

• Physical Exam - In most cases, exam is a quick visual check to be sure the animal is eating, drinking and behaving in a normal manner. Cage should be observed for signs of blood, abnormal feces or

excessively wet or dirty bedding. Physical examination is the single-most important step in evaluating

the health of an animal.

• Observe closely, before attempting to restrain animal, so that its movement and breathing can be assessed prior to the excitement of restraint.

• TPR - body temperature, pulse rate and respiration rate • Physical exam includes close inspection of eyes, ears, mouth,

nose, hair coat, legs, feet and tail for evidence of clinical signs.

Image from NIH Orientation

Chapter 9AbscessesAbscesses

• Swellings filled with purulent material (pus) are a mixture of

dead bacteria, liquefied tissue, and white blood cells. Most common just under skin, at site of puncture wounds.

Bacteria are deposited under skin and the skin closes over them.

White blood cells to fight the infection.

White blood cells release substances that digest and liquefy some of

the tissue, the bacteria, and themselves.

Treatment usually consists of surgically opening abscess to drain

purulent material.

• Abscess cavity is flushed and antibiotics are administered until the wound

heals.

Early treatment helps prevent spread of organisms.

For more information: http://www.marvistavet.com/html/body_bite_wound_abscess.html

Chapter 9Alopecia Alopecia

• Loss of hair

• Reasons - excessive grooming, metabolic dysfunction, external parasites, and nutritional disorders

• Pattern of hair loss is important in determining the cause. In rodents, a dominant animal often chews hair off the head, neck, and

back of cagemates, a behavior called barbering.

Fungal ringworm infections cause hair loss in circular pattern.

Areas of alopecia on both sides of the body are common in several metabolic diseases.

External parasites, such as fleas, mites, or lice and nutritional deficiencies of some vitamins and minerals common cause => skin surface is not normal.

Overall thinning from hair shed in spring and fall.

Chapter 9External Parasites/ConjunctivitisExternal Parasites/Conjunctivitis

• Infestations with fleas, lice, and mites often result in alopecia caused by scratching.

• Seen around the neck, between rear legs, and on back, cranial to tail. Mites - microscope is required.

• Ear mites, most common in dogs, cats, rabbits, ferrets. Can trigger bacterial infections in the outer ear.

• Insecticide treatment =>possible toxicity. Multiple treatments destroy newly hatching parasites.

• Conjunctivitis is a redness or inflammation of tissue around eyes. Cause - air irritants, infections, or allergies. Viruses and bacteria can also cause conjunctivitis. If only one eye is involved, the cause may be an injury.

For more information: http://www.cornellcollege.edu/biology/insects/mattmeriah/f.htm

Forms in the Flea’s Lifecycle

Chapter 9Mastitis / Hoof or Nail Mastitis / Hoof or Nail

Mastitis: infection of the mammary glands

• Occurs during early nursing period or just after weaning.

• Swollen, firm and hot, and may even turn blue or black

• Treatment: take young away and administer antibiotics. A foster mother or bottle feeding may be necessary if the young cannot eat

solid food.

Overgrown Hoof or Nail Diseases: from poor husbandry

• Common in sheep, goats, rabbits, cats and dogs.

• Birds develop overgrown nails and beaks.

• Treatment: clipping the claws or trimming hooves. Animals on concrete floors seldom have this problem.

Chapter 9Disease of Internal OrgansDisease of Internal Organs

Enteritis: intestinal inflammation => diarrhea Enteritis can be caused by bacteria, viruses, endoparasites,

spoiled food, or contaminated water.

Salmonella, canine parvovirus, feline panleukopenia, MHV, roundworms, tapeworms, hookworms, and coccidia

Spoiled food and contaminated water from the direct action of bacteria, mold, fungi or their chemical toxins.

Pneumonia: infection of the lungs Caused by a variety of bacteria, viruses, or other organisms.

Signs = shallow, labored breathing, coughing, general weakness.

Antibiotics are used to treat, not effective against viruses.

Good nursing care important aspect of treatment, and effective quarantine and isolation programs help control the spread.

Graphic from: http://www.bioan.dk/Projekter/salmonella.htm

Salmonella

Chapter 9Behavioral DisordersBehavioral Disorders

• Trauma usually results from some inappropriate behavior. Social hierarchies => dominant and submissive.

Minor fights usually occur when animals are first put together.

Once social hierarchy is established, fighting usually subsides.

NH primates may fight to near death to establish dominance.

• Self-mutilation: behavioral disease results in trauma Seen mostly in NH primates, but can occur in any species.

Self-mutilation can result from frustration and boredom.

Large male monkeys may mutilate themselves if placed in direct eye contact with one another.

Enrichments such as hard nylon balls, food puzzles, swing chains, tiered perches, polished metal mirrors.

Soft background noise used to reduce stress and aggression.

Chapter 9Behavioral Disorders (continued)Behavioral Disorders (continued)

• May be caused by behavior of people.

• Ensure cages are well kept, designed and maintained. Sharp edges or protruding wires result in cuts or injures.

• Improper handling also causes disease problems.

• Rabbits lifted improperly can easily sustain broken backs while

kicking in an attempt to find firm footing.

• Rats or gerbils can have the skin stripped from the tail if lifted

improperly by the tip of the tail.

• These types of animal injuries are best prevented by assuming a

responsible, humane attitude and nourishing it with a good

education in the proper restraint, handling, and care of animals.

Image from NIH Orientation

Chapter 9Additional ReadingAdditional Reading

1. Bhatt, P.N., Jacoby, R.O., and New, A.E. Viral and Mycoplasmal Infections of Laboratory Rodents. Academic Press, Orlando, FL, 1986.

2. Fox, J.G., Cohen, B.J., and Loew, F.M. Laboratory Animal Medicine. Academic Press, Orlando, FL, 1984.

3. Harkness, J.E. and Wagner, J.E. The Biology and Medicine of Rabbits and Rodents, 4th. Ed. Lea and Febiger, Philadelphia, Pennsylvania 1995.

4. Hrapkiewicz, K., Holmes, D.D. Clinical Laboratory Animal Medicine. Iowa State University Press, Ames, IA, 1997.

5. Outteridge, P.M. Veterinary Immunology. Academic Press, Orlando, FL, 1986.

6. Siegmund, O.H. et al., eds. The Merck Veterinary Manual, 7th Ed. Merck and Co., Inc., Rahway, NJ, 1991.

7. Hillyer, E.V. and Quesenberry, K.E. Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery, W.B. Saunders, Philadelphia, PA, 1997.

8. Manning, P.J., Ringler, D.H. Newcomer, C.E. The Biology of the Laboratory Rabbit, 2nd. Edition, Academic Press, San Diego, CA, 1994.