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Common Diseases of Laboratory Animals

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andy zanetti

on 15 October 2014

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Transcript of Common Diseases of Laboratory Animals

References
Chapter 9 – Laboratory Animal Technician (LAT)

Chapter 13 – Laboratory Animal Technologist (LATG)

Handbook of Clinical Signs in Rodents and Rabbits


Disease 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


Fomites, Vectors and Carriers
Fomites
- Inanimate objects that provide a mechanical means of infectious disease transmission.
➝ Cages, bedding, feeding pans, scrub brushes, boots, clothing, gloves and dust particles

Vectors
– Living organisms that transmit diseases.
➝ Insects such as fleas or ticks, animal technicians carrying diseases from room to room

Carriers
- 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.

Zoonosis
Disease transmitted from humans to animals / animals to humans
= zoonosis, or zoonotic disease.
➝ tuberculosis & nonhuman primates
➝ giardia & dogs
➝ rat bite fever & rats
➝ MANY OTHERS: rabies, herpes B, lymphocytic choriomeningitis (LCM), toxoplasmosis, herpes simplex virus ...

Noninfectious Diseases
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


Classifying Diseases
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.


Signs of Inflammation
Heat
Redness
Swelling
Pain
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.


Common Diseases of Laboratory Animals
Andrea Zanetti, DVM Ms PhD
Resident Veterinarian
Department of Animal Resources
University of Southern California

Prevention & 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


Identifying & 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 (LARGE ANIMALS)

Physical exam includes close inspection of eyes, ears, mouth, nose, hair coat, legs, feet and tail for evidence of clinical signs.


Abscesses
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 area dministered until the wound heals.
➝ Early treatment helps prevent spread of organisms.

Skin and Fur
Alopecia - Loss of hair
✓ 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
.

Fur mites
✓ Clinical signs include - excessive scratching, hair loss, and skin lesions caused by self-trauma.
✓ Diagnosis - tape test, PCR
✓ Treatment selemectin

Idiopathic ulcerative dermatitis
✓ Often mistaken for trauma due to fighting
✓ Occurs primarily over the dorsal surface of the body (scapular region)
✓ Exact cause is not known
✓ No treatment

Fighting wounds
✓ Group-housed animals
✓ Wounds may be found in many superficial body locations
Gastrointestinal
Malocclusion
➝ Incisor overgrowth (congenital or the result of trauma)

Enteritis: intestinal inflammation =>
diarrhea

➝ Enteritis can be caused by
Bacteria (Helicobacter)
Viruses (Mouse Hepatitis Virus, Mouse Parvovirus, Epizootic Diarrhea of infant Mice, Mouse Norovirus)
Endoparasites
Protozoa (Tritrichomonas muris, Trichomonas spp, Chilomastix spp, Entamoeba muris, Giardia muris and Spironucleus muris)
Others: spoiled food, or contaminated water.

Rectal prolapse
➝ Many causes
➝ treatment - supportive pain relief medication
Nutritional
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.


Gastrointesinal
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.


Respiratory
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 that 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.

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 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.



Respiratory

Pneumonia
: infection of the lungs
➝ Caused by
Bacteria
Chronic respiratory disease or murine respiratory mycoplasmosis - Mycoplasma pulmonis
Antibiotics are used to treat, not effective against viruses.
Viruses
Sendai virus - No treatment

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

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

Respiratory
Pasteurellosis

Pasteurella multocida

Common in rabbits but difficult to treat

Some animals are asymptomatic carriers

May spread by aerosol transmission or direct contact

Signs include: mucopurulent nasal and ocular discharges, sneezing, exudate staining of the forelegs, head tilt, localized abcesses and genital infections.


Bacterial Pneumonia -
Bordetella bronchiseptica
and Streptococcus pneumonia
Clinical signs are triggered by stress conditions
Dyspnea, nasal discharges, anorexia, rough haircoat are common signs
Acute death may occur in naive colonies
Treatment with antibiotics
Malocclusion
Associated with
premolars and molars rather than incisors
Clinical signs include decreased feed intake, chronic weiht loss, and heavy salivation
The fur of the cheeks and neck may be wet and have green tint.
Treatment consist of filing the teeth

Antibiotic-induced enterotoxemia
Prolonged therapy with antibiotics promotes changes in endogenous bacterial flora growth and leads to hemorrhage and epithelial slough of the gastrointestinal tract.
Pododermatitis
Bumblefoot
- granulomatous cellulitis

Developed in animals housed in rough surfaces or wire floors

The feet are often swollen and painful

Mild lesions may be treated by changing housing conditions and antibiotics

Severe cases often do not response to treatment
Scurvy
Vitamin C deficiency

Affected animals lose their appetite and are reluctant to move
may also have swollen and painful joints
Necropsy shows hemorrhages in the muscle tissue and joints

Laboratory chow formulation contains sufficient vitamin C but improper storage can cause vitamin breakdown and high temperature can accelerate this loss.
Feed should be used within 90 days after milling and should be stored in a temperature controlled environment

Supplementation may be required for pregnant and sick animals
Skin and Fur
Ectoparasites

Ear mite (Psoroptes cuniculi)

Fur mite (Cheyletiella parasitovorax and Listrophorus gibbus)

Common in pet rabbits but not in laboratory animals

Treatment with anti-parasitic drugs
Gastrointestinal
Gastric trichobezoars (
Hairballs
)
➝ Common in rabbits
➝ Rabbits are unable to vomit due to strong cardiac sphincter and therefore cannot eliminate hairballs.
➝ Clinical signs include anorexia, weight loss, depression, a palpable abdominal mass, absence of feces or production of abnormal shaped fecal pellets.
➝ Difficult diagnosis
➝ Death due to starvation metabolic disturbances.
➝ Common treatment focus on enhancing the passage of hairball by administrating mineral oil using a feeding tube or providing a laxative paste or additional roughage in the diet.
➝ Surgery is usually performed in pet rabbits, but uncommon i laboratory animals


Mucoid enteropathy
➝ Not well-understood
➝ Seen in 3- to 10-week-old rabbits that have recently been under stress.
➝ Clinical signs include mucus in the drop pan, abdominal distention, dehydration, wet and stained perianal fur, tooth grinding, and sloshing sound when the abdomen is palpated.
➝ Reducing stress, practicing good sanitation, and increasing dietary fiber seem to foster prevention.
➝ Treatment is primarily symptomatic and rarely successful.

Coccidiosis
Common protozoan of conventionally housed rabbits.
Clinical signs include poor weight gain, sticky feces, and profuse, watery and something bloody diarrhea.

Diagnosis by fecal flotation
.
There is no effective treatment but sulfa drugs may hep eliminate signs of the disease, more important are good hunsbandry practices.

Multisystemic
Measles

Usually occurs following contact with infected humans.
Vaccination important before working with nonhuman primates
Clinical signs include skin rash, nasal and ocular discharges, conjunctivitis, facial edema, eyelid inflammation, and pneumonia
Treatment - supportive care

Cercopithecine Herpesvirus 1
(CHV-1, formerly known as Herpes B virus)

Old World monkeys are carriers
Asymptomatic in rhesus, cynomolgus, and other macaques
Oral lesions or ulcers are the most common signs of infection
Health concern to people handling nonhuman primates (zoonotic and can be fatal to humans)
Human infection occurs through cuts or bite wounds and contact with macaque fluids (such as blood and urine) that are splashed to the eyes.
PPE are very important preventive measurement to prevent human infection.
Gastrointestinal
Diarrhea
➝ Common problem

Most common agents include bacteria (Salmonella, Shigella, etc) and protozoan (Giardia sp, Balantidium coli, Entamoeba hystolicta) infections (all zoonotic).
➝ Antibiotic for bacteria; metronidazole for protozoan and electrolyte replacement (for in both)


Acute gastric dilation (
Bloat
)

Cause by overeating, changes in feeding regimen, stress or administration of anesthetic agents
➝ Clinical signs include distension of abdomen, colic, dyspnea, vomiting, weakness, seizures, shock and without immediately treatment death
➝ Treatment consist of gastric decompression by stomach tube and corrective fluid therapy





Respiratory
Atrophic rhinitis

Inflammation of upper respiratory tract.
Bordetella bronchiseptica and Pasteurella multocida
Disease is associated with stress due to overcrowding, inadequate ventilation, and poor sanitation
More severe in young animals
Classical lesions (bone atrophy of nasal turbinates and distorsion of the nasal septum).
Addition of sulfonamides or antibiotics to the food helps with prevention
A vaccine is available


Respiratory
Enzootic pneumonia

Mycoplasma sp other bacteria and viruses may complicate the disease

Pneumonia is chronic and mild

Persistent, dry cough, respiratory distress and lung lesions detected at necropsy

Antibiotics may help control the disease


LAM
General Mice/Rat Guinea Pig Rabbit Monkey Pig
Participation is highly appreciate!!!!!!
Respiratory
Tuberculosis
➝ Old world primates are highly susceptible

➝ Mycobacterium tuberculosis

➝ Contracted from humans in laboratory animals

➝ Prevention by TB testing every 6-12 mo

➝ Inhalation is the most common route of infection

➝ Signs include weight loss and general unthriftiness. Other signs, diarrhea, pneumonia and skin ulcerations.


Most effective control include quarantine, TB testing and elimination of tuberculin reactors

➝ Highly zoonotic (PPE is very important for prevention of human cases)





What are the five cardinal signs of inflammation?
Cercopithecine Herpesvirus 1 (CHV-1, formerly known as Herpes B virus) is a highly pathogenic virus and cause fatal disease to humans. The disease is transmitted to humans by........
Bloat in nonhuman primates is caused by...
Bordetella bronchiseptica and Pasteurella multocida are the causative agent of what disease in pigs?
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