Download ALAT Chapter 12

Chapter Twelve
Health and Disease
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Health and Disease
 A major function of the laboratory animal facility
staff is to keep research animals healthy.
 Experimental studies cannot be properly
completed using sick animals.
 Everything an animal technician does is designed
to reduce the danger of disease at the animal
facility.
 It is the purpose of this chapter to acquaint the
new animal technician with the signs of disease
and factors affecting the health of laboratory
animals which are entrusted to his or her care.
Identifying Diseased Animals
 Observe each animal, checking for common
signs of disease.
 Animals found dead must be promptly reported
so valuable tissues & data can be obtained.
 Promptly note signs of sickness so persons
responsible for diagnosis can notify investigator &
treatment started.
 Brightly colored card placed on cage of animal w/
signs of disease, card indicates signs observed.
 Animal health technician to remove dead
animals, observe sick animals, record info. in a
log & inform veterinarian.
Identifying Diseased Animals II
 Veterinarian can advise PI of treatment or
euthanasia.
 While cleaning cage, check for weight loss,
diarrhea, hair coat problems & abnormalities.
 Experiments may cause animal to become sick.
 Report a sick animal when experiment may have
made it sick; this information is helpful to
investigator.
 If an animal seems in pain,
even if expected due to
research experiment, notify
facility veterinarian immediately.
Signs of Disease
 Look for signs of illness.
 Signs vary by species.
 Change in behavior may
be only indication of
illness.
 Report observations.
 Learn terms to describe
signs of disease.
 Learn systems affected to
understand the disease.
Signs of Disease
 Alopecia - usually associated
w/ skin disease, fighting,
parasites or barbering
Barbering is when one animal chews off patches of
hair from another & is done by a dominant animal.
 Anemia - skin or mucous membranes are pale
Gums may appear almost white, usually associated
with blood loss or reduced numbers of erythrocytes.
 Anorexia - animal is not eating
Often noted when animals not drinking due to
inaccessible, broken or disconnected water valve.
Animal ill or in pain may have decreased food intake.
 Bleeding - can be external or internal
You may see fresh blood in cage but not on animal.
Signs of Disease II
 Change in behavior - animal that suddenly
becomes aggressive, quiet or loses interest in
surroundings is usually sick or in pain.
 Circling or head tilt - a rodent spins in a circle
when held by the tail, or an animal walks in a
circle or holds its head to one side. Often
indicates an infection of the middle or inner ear.
 Constipation - no feces being passed because it
is not being moved through the large bowel.
can be caused by lack of feed or water, serious
infections & a number of other disease problems
 Coughing - rapid, forced expelling of air through
the mouth indicates a problem in throat or lungs.
Signs of Disease III
 Diarrhea - passage of watery or loosely-formed
feces; often feces stain perineum or tail region
Bowel infections or parasites can cause diarrhea.
 Discharge - secretion of a wet material from a
body opening often associated with internal organ
infection
 Dyspnea - difficult, labored or rapid breathing
common sign of pneumonia
 Listlessness - lack of alertness in an animal,
animal seems tired compared to others in cage
 Animals in pain also usually seem listless.
Signs of Disease IV
 Loss of weight - decrease of body weight
often associated w/ anorexia due to a serious disease
or can be caused by internal parasites
 Paralysis - inability to move all or part of body
often due to nerve damage or a disease affecting
central nervous system
 Prolapse - organ within body is forced externally
most commonly rectal or vaginal often due to straining
during defecation (bowel movement) or parturition
(giving birth)
 Pruritus - constant or frequent scratching
usually due to irritation of skin because of external
parasites; skin often appears scaly or reddened
Signs of Disease V
 Rough hair coat - change from normal smooth,
shiny hair to a ruffled and dull appearance
can indicate many problems including vitamin
deficiencies, external parasites, internal parasites &
severe infections
one of most reliable indications that animal is ill
 Sneezing - rapid, forced expelling of air through
nose is usually a sign of nasal irritation
 Stunted - animals appear smaller than most
animals of same age; can be due to genetic
composition, infections, parasites or poor
husbandry
 Tumor - abnormal growth
Signs of Disease VI
 Vomiting - passage of gastric contents from
mouth, usually indicates animal has an irritation
in stomach or throat
Vomiting is common in cats/dogs & uncommon in
rodents/ruminants.
 Essential that technicians recognize and report
occurrence of these signs in any animal under
their care.
 It will be easier to communicate clearly, both
verbally and in writing, signs
that you have seen if the above
scientific terms are used.
Causes of Disease
 Concerned with diseases that cause
noticeable illness, also with those
that don’t make animal look sick.
 Such diseases are called sub-clinical.
 Difficult to detect changes can ruin an experiment
by producing altered physiologic data in response
to disease rather than to experiment.
 Disease = any alteration of normal anatomy or
physiology of an animal.
 Disease causes will be classified as follows:
environmental / nutritional / genetic / microbiologic /
parasitic / unknown
Environmental
 Variations of temp, noise, humidity, lighting &
contaminants which produce stress and
alterations of animal’s physiology.
 Most animals are comfortable at about 70°F.
 Animal rooms kept too warm,
cold or which frequently have
temp variations are stressful.
 30% to 70% relative humidity
comfortable for people &
animals under their care.
 Prolonged dry or wet environments can contribute to disease.
Noise, Overcrowding & Light
 Rabbits may jump and hurt themselves, rodents
will not breed, & most animals show alterations in
hormone levels at loud noises.
 If too many animals are in a cage or animals are
in very small cages, they will be stressed.
 Animals become accustomed to specific lighting.
Adjustment to a light/dark cycle is called circadian
rhythm & determines when active & when asleep.
Most animal rooms are set to provide 12 hours of light
and 12 hours of dark.
Breeding animals stop breeding by changes in light
patterns.
Air Exchange, Contaminants & Nutrition
 Odors are evidence a room does not have enough
air changes for number of animals.
 Poor air flow can be caused by major mechanical
problems or as simple as dirty air vent filters.
 Contaminants can enter system by way of air,
water, bedding, & especially feed.
 Nutritional causes of disease - deficiencies or
excesses in quantity or quality of water, fats,
carbohydrates, proteins, minerals & vitamins.
»Levels of essential food components
have been determined.
»If fed proper quantity, needs will be met.
Genetic
 Natural mutations or experimental
 Transgenic & knockout animals have altered
genes, frequently inherit disease problems.
 Some genetic differences affect susceptibility to
diseases & reactions to drugs.
Certain strains have high incidence of breast cancer.
 Spontaneous genetic mutations in research
colonies rarely occur.
 An animal could develop genetic variation that
may be a very important research model in our
future understanding of disease or biology.
(Image) Nude Mice
Microbiologic
 Most microbes do not
cause disease.
 Disease causing microbe = pathogenic organism.
 Pathogenic organisms enter animal through air,
feed, water, or breaks in the skin.
 Microbes often cause cell damage, usually by
release of toxic waste products.
 If signs are not obvious, they are sub-clinical,
requiring special diagnostic laboratory tests to
identify the disease.
 Even without obvious signs, disease will often
to web site;
affect experimental results. Go
http://fig.cox.miami.edu/Faculty/Dana/monera.html
Parasitic
 Parasites live on or in an animal & draw
nourishment from host.
 Animals can be infested with protozoans,
helminthes, lice, mites, fleas, etc.
 In most cases, they exist subclinically, & are often
responsible for altered experimental data.
 Any sign that an animal might have parasites,
such as diarrhea, vomiting, anemia or skin
lesions, should be reported immediately.
Diseases of Unknown Cause
 Many degenerative diseases, cancers & process
of aging itself develop without obvious infectious
or environmental causes.
 Overlapping causes & effects
 Microorganisms may infect an
animal w/ lowered resistance to
infection due to environmental
or nutritional problem.
 Injuries caused by improper restraint or handling
 Allergic responses to experimental immunization
 Experimentally induced tumors
 Try to learn as much as possible from other
people, including veterinarian & investigator.
Transmission of Disease
 Living thing which carries disease = vector.
 Nonliving materials transmit a disease = fomites.
 If cats with contagious disease were removed
from a cage & another cat placed into that
uncleaned cage, 2nd cat could become infected.
 Infectious disease microbes can be transmitted
via hands, air, bedding, cages, water, insects & a
variety of other vectors & fomites.
Transmission of Diseases II
 Many noninfectious diseases inherited.
Some animals have genes causing bleeding disorders.
 Others develop under certain environmental or
nutritional conditions.
Scurvy caused by inadequate amount of vitamin C.
 Genetic predisposition to noninfectious disease
i.e., an allergy to penicillin
 SOPs designed to reduce disease transmission.
Wash hands before leaving an animal room.
Handle small rodents w/ sanitized forceps.
Air should be fresh or filtered.
Properly sanitize cages in water which is 180°F.
Transmission of Diseases III
 Remove animals found dead to reduce disease
transmission.
 Separate sick animals in isolation, separate
cages in separated rooms.
 Place newly received animals in quarantine.
 Determining the cause of disease in any animal
found sick is referred to as diagnosis.
 Identification of a disease from its signs and
symptoms involves a number of special tasks
including culturing for microbes, blood cell
evaluation and biochemistry of serum.
Transmission of Diseases IV
 Exam & dissection of a dead animal = necropsy.
 Sections of organs are removed so pathologist
can examine tissues microscopically.
 The pathologist can often identify & associate
certain tissue changes with a disease.
 Sick animals which have died must be sealed in
waterproof bags, sent to pathology or investigator
& eventually burned in an incinerator.
 To reduce chance of disease, technicians must
maintain laboratory animal facilities “hospital
clean.”
Monitoring Animals
 Cats & dogs are vaccinated,
while monkeys are tested for
tuberculosis at regular intervals.
 Rodent colonies tested through sentinel program.
Sentinels are healthy animals placed in the animal room for
the specific purpose of detecting any disease.
They are left in the room for a period of 1–6 months.
Adding dirty bedding from other cages increases chance of
exposure to any disease present.
Necropsy performed, blood samples checked for antibodies
to rodent diseases & stool samples checked for parasites.
If any diseases is found in sentinels, other animals in the
room are assumed to be infected.
Additional Reading
Harkness, J.E. and J.E. Wagner. The Biology and
Medicine of Rabbits and Rodents, 4th Ed. Lea
and Febiger, Philadelphia, PA. 1995.
Hrapkiewicz, Karen, Leticia Medina, and Donald D.
Holmes. Clinical Laboratory Animal Medicine: An
Introduction, 2nd Ed. Iowa State University Press,
Ames, IA. 1997.