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Health and Disease
LAT Chapter 9
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Chapter 9
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Disease Terminology
Chapter 9
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
Fomites / Vectors / Carriers
Chapter 9
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
Zoonosis
Chapter 9
• Disease transmitted from humans
to animals / animals to humans
= zoonosis, or zoonotic disease.
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tuberculosis & nonhuman primates
turtles & salmonellosis.
For more information:
http://medicine.bu.edu/dshapiro/zoo1.htm
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)
Noninfectious Disease
Chapter 9
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
Noninfectious Disease
Chapter 9
Genetic
Abnormalities
Discovered in
Mice
From: Biology of the Laboratory Mouse, by The Jackson Laboratory,(Dover Publications, 1968), pp.100-101
Cancer
Chapter 9
• 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.
Diagnosing Disease
Chapter 9
• 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.
Classifying Disease
Chapter 9
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


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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.
Body Defenses
Chapter 9
Signs of inflammation are:
1. Heat
For more information go to:
2. Redness
http://www.atherogenics.com/science/therapeutic.html
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.
Invading Organisms
Chapter 9
• 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.
Allergy or Hypersensitivity
Chapter 9
• 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
Summary
Chapter 9
• 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.
Preventing & Curing Disease
Chapter 9
• 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.
Prevention & Control of Disease
Chapter 9
1. Quarantine
2. Sanitation and hygiene
3. Periodic examination
4. Appropriate immunizations
5. Proper waste disposal
6. Upkeep of physical facilities
7. Isolation procedures
Identifying & Treating Diseases
Chapter 9
• 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
Abscesses
Chapter 9
• 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
Alopecia
Chapter 9
• 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.
External Parasites/Conjunctivitis
Chapter 9
• 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.
Forms in the Flea’s Lifecycle
 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
Mastitis / Hoof or Nail
Chapter 9
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.
Disease of Internal Organs
Salmonella
Chapter 9
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
Behavioral Disorders
Chapter 9
• 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.
Behavioral Disorders (continued)
Chapter 9
• 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
Additional Reading
Chapter 9
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.