AALAS INTRODUCTION TO HAMSTERS

Which statement is true regarding the assessment of pain or distress in hamsters?

- Pain or distress in hamsters is commonly expressed by subtle changes in activity level and behavior. - A hamster with a mild to moderately painful condition may appear and behave normally.

An investigator's responsibilities towards the use of laboratory animals include assuring that staff are properly trained to:

- Perform the animal procedures humanely. - Provide the necessary supportive care to the animals during a procedure. - Provide the necessary supportive care to the animals following a procedure.

Supportive care:

- Provide a source of warmth to hamsters from the onset of anesthesia to the end of anesthetic recovery. - Inject sterile physiological fluid (warmed) to compensate for blood loss during a procedure and depressed fluid intake post-procedure. This procedure should be performed in concert with input from the veterinary staff.

Which occupational health and safety concerns are relevant to performing research on hamsters?

- Risk for developing an allergy to hamsters and for developing asthma. - Staff should participate in the institution's occupational health and safety program. - Risks for bite injuries when handling hamsters. - Risks for zoonotic diseases when working with hamsters.

Which statement is true regarding hamsters that have newly arrived at a facility? Check all that apply.

- The animals should be housed in a quarantine area and may undergo diagnostic testing. - Experimentation on the animals is generally delayed until the end of quarantine.

This peri-procedural care requirement covers:

- properly preparing the animal to humanely undergo the procedure; - supporting the animal's physiological functions during the procedure; and - providing additional supportive care to aid the animal in recovering from the procedure.

Anesthetics:

Gaseous anesthetics Injectable anesthetics

Which statement is true regarding hamsters that have newly arrived at a facility?

- Experimentation on the animals is generally delayed until the end of quarantine. - The animals should be housed in a quarantine area and may undergo diagnostic testing.

Immune System

T-cells Cheek pouches

Inbred strains are typically used for

finely controlled studies that capitalize on genetic isogenicity. Inbred strains with characteristics of human diseases or physiological conditions are generally preferred models for biomedical research.

The Public Health Service Policy requires institutions to have an occupational health and safety program

for individuals working with laboratory animals.

Hamsters do not vomit because they lack the

neurophysiological mechanisms for emesis. Therefore, presurgical fasting is not necessary in hamsters, as it is for nonrodent species.

Hamsters have incisors that are

open-rooted, meaning that these teeth grow continuously throughout adult life. A diet of soft foods, i.e. in liquid or powder form, or a developmental jaw malformation will cause tooth overgrowth. Staff must be alert to detect any signs of this condition and to provide appropriate treatment.

The molars retain fine particles of food and are

prone to dental caries, making the hamster a model for dental research.

Social characteristics

Hamsters are solitary animals by nature and may prefer to be housed separately. If grouped since weaning, cage mates may live peacefully together, although stress has been reported in group-housed hamsters. Fighting may result if unfamiliar adults are mixed together. Females, especially Chinese hamsters (Cricetulus griseus), are more prone to be aggressive toward strangers, except when presented with a male during estrus.

Nocturnalism

Hamsters are very active at night and spend most of their day asleep. During the night, they will explore their cage and make use of enrichment devices, if available. For example, hamsters will run for long periods on exercise wheels.

Which of the following oversees research using hamsters?

USDA, AALAC, OLAW

Most institutions use microisolator cages (filter cage top and solid bottoms) under barrier conditions or in open-topped cages (no filter top) under conventional conditions. Hamster caging must be secure, e.g., with tightly fitting wire lids, because

hamsters are prone to dislodge cage tops and escape through narrow spaces. Hamsters have a solitary nature and so may prefer to be housed individually.

Sedatives + Analgesia:

hese agents are commonly mixed with other drugs in an anesthetic cocktail. Refer to the information accessed from the "Anesthetics" link. Some sedatives also have analgesic effects. When combined with general anesthetics, a balanced anesthesia is attained, and these sedatives enhance analgesia through specific effects. Examples: Medetomedine and xylazine

Removing greater quantities of blood (exceeding 10% of total blood volume) can produce

hypovolemic shock. Repeated collections of smaller amounts of blood will have the same effect. In such procedures, animals should receive warmed, physiological fluids to replace the volume of blood collected. In addition, monitor the animal's hematocrit for anemia.

In hamsters, herbaceous foodstuffs are broken down by microbial action in the cecum, which is a large organ in the hamster. To assimilate

the microbial byproducts of digestion, the hamster regularly eats its own feces, a habit known as coprophagy. Hamsters will consume feces directly from the anus. Stomach digestion and intestinal absorption of this fecal material yields nutrients that are essential to the animal.

Hamsters should have a source of warmth throughout a procedure that lowers their body temperature (e.g., anesthesia, surgery) and afterwards until they recover the ability to

thermoregulate themselves.

Gastrointestinal

Inability to vomit Coprophagy

People can develop an allergy to hamsters after having contact with them for

some time

United States Department of Agriculture (USDA) enforces the Animal Welfare Act and Animal Welfare Regulations for all covered species, including hamsters. These requirements include

standards for husbandry, caging, environmental enrichment, and the use of restraint devices.

Most hamsters are outbred stocks, meaning

that individuals have a high degree of heterozygosity and phenotypic variability.

To ensure the humane treatment of laboratory animals, research involving hamsters is regulated by federal laws. The two main agencies that oversee the enforcement of federal regulations are

the United States Department of Agriculture and the Public Health Service.

USDA Animal and Plant Health Inspection Animal Care Policy Manual, Policy #12, states that alternatives should be considered in the planning phase of

the animal use proposal and alternatives reconsidered at least every three years.

Sebacious scent glands are located on

the dorsal flank (hip region) along the spine. These are present in both sexes, although they are more prominent in males. When the hair is removed, these glands are visible as dark areas of the skin. These glands are stimulated by androgens. The secretions are used to mark territory and are involved in sexual behavior.

These strains are designated:

CHF148 (spontaneous disease model) CHF146 (control)

Anatomy

Cheek pouches Teeth and caries Scent glands

Jugular vein

Performed under anesthesia because of restraint method and the need for animal immobilization.

According to the AVMA, which statement is TRUE for the use of CO2 as a euthanasia agent of hamsters?

Compressed CO2 gas in cylinders is the only acceptable source of carbon dioxide.

Hamsters do not undergo a true hibernation but a pseudohibernation instead. The distinction is that they remain sensitive to

touch and so are readily aroused from their hibernatory state. Under conditions of shortened day length, cool temperatures (8°C, 48°F), less light, and social isolation, hamsters hoard food and enter into pseudohibernation. During this state, the hamster has a decreased body temperature, low respiration rate, and a low heart rate. The animal will arouse every two to three days with short periods of normal alertness and activity.

Quarantine aims to prevent

transmission of diseases between new animals and established colonies, so diagnostic tests may be performed during this period.

Inbred (isogenic) strains of the Syrian hamster (Mesocricetus auratus) are used for

cardiomyopathy studies.

Carbon monoxide

"Carbon monoxide used for individual animal or mass euthanasia is acceptable for dogs, cats, and other small mammals, provided that commercially compressed CO is used and the following precautions are taken: "(1) personnel using CO must be instructed thoroughly in its use and must understand its hazards and limitations; "(2) the CO chamber must be of the highest quality construction and should allow for separation of individual animals; "(3) the CO source and chamber must be located in a well-ventilated environment, preferably out of doors; "(4) the chamber must be well lit and have view ports that allow personnel direct observation of animals; "(5) the CO flow rate should be adequate to rapidly achieve a uniform CO concentration of at least 6% after animals are placed in the chamber, although some species (e.g., neonatal pigs) are less likely to become agitated with a gradual rise in CO concentration; and "(6) if the chamber is inside a room, CO monitors must be placed in the room to warn personnel of hazardous concentrations. It is essential that CO use be in compliance with state and federal occupational health and safety regulations."

Carbon dioxide

"Compressed CO2 gas in cylinders is the only recommended source of carbon dioxide because the inflow to the chamber can be regulated precisely." "Carbon dioxide generated by other methods such as from dry ice, fire extinguishers, or chemical means (e.g., antacids) is unacceptable. "Species should be separated and chambers should not be overcrowded." "With an animal in the chamber, an optimal flow rate should displace at least 20% of the chamber volume per minute. Loss of consciousness may be induced more rapidly by exposing animals to a CO2 concentration of 70% or more by pre-filling the chamber for species in which this has not been shown to cause distress." "Gas flow should be maintained for at least 1 minute after apparent clinical death. It is important to verify that an animal is dead before removing it from the chamber. If an animal is not dead, CO2 narcosis must be followed with another method of euthanasia. Adding O2 to the CO2 may or may not preclude signs of distress. Additional O2 will, however, prolong time to death and may complicate determination of consciousness." "There appears to be no advantage to combining O2 with carbon dioxide for euthanasia."

Barbiturate overdose

"Injectable barbiturates act quickly and smoothly to render rodents unconscious...Pentobarbital is the most commonly used barbiturate for laboratory rodents because of its long shelf life and rapidity of action." Pentobarbital combinations

Dissociative agent combinations

"Lethal doses of dissociative agents such as ketamine are commonly used in laboratory settings. In some species, ketamine alone can result in stimulatory activity prior to sedation and loss of consciousness. In conscious rodents, ketamine and similar dissociative agents should be used in combination with an a2-adrenergic receptor agonist such as xylazine or benzodiazepines such as diazepam."

Inhalant anesthetics

"With inhalant anesthetics, the animal can be placed in a closed receptacle ...[and] the anesthetic can be introduced from a vaporizer. The latter method may be associated with a longer induction time. Vapors are inhaled until respiration ceases and death ensues. Because the liquid state of most inhalant anesthetics is irritating, animals should be exposed only to vapors. Also, sufficient air or O2 must be provided during the induction period to prevent hypoxemia. "In order of preference, halothane, enflurane, isoflurane, sevoflurane, methoxyflurane, and desflurane, with or without nitrous oxide, are acceptable for euthanasia of [rodents]."

Which statement is true regarding the assessment of pain or distress in hamsters?

- A hamster with a mild to moderately painful condition may appear and behave normally. - Pain or distress in hamsters is commonly expressed by subtle changes in activity level and behavior.

Monitoring during anesthesia:

- Analgesia - toe pinch - Respiration - gross changes in rate, character of breathing - Color of mucous membrane and skin - poor oxygenation (blue), poor blood perfusion (pale)

Monitoring post procedure:

- Assess appearance, activity, and behavior as indications of pain and discomfort (see the "Detecting Pain and Distress" lesson). - Assess food and water intake. - Provide floor-level access of food and water post procedure if stretching overhead for these items (in the cage wirelid) may be painful. - Assess wound healing.

Keep in mind that:

- General anesthesia causes disturbances of thermoregulation and other physiological functions. Hamsters are unable to properly thermoregulate for some time after some procedures, including anesthesia and surgery. - During surgery, the animal may experience pain if anesthesia is inadequate at any time during the procedure. - Postoperatively, the animal may experience pain, discomfort, and distress unless treated with analgesics and appropriate supportive care measures. - Due to the interaction of metabolic factors and drug effects that can cause animal mortality, hamsters should receive good supportive care and monitoring during anesthesia, whether or not the procedure involves surgery.

The following is a list of hamster species used in biomedical research. The Syrian and Chinese hamster species are the most commonly used.

- Golden hamster or Syrian hamster, Mesocricetus auratus. (adults 120 g) - Chinese or Striped hamster, Cricetulus griseus (adults 30-35 g) - Armenian hamster, Cricetulus migratorius (approx. 45 g) - European hamster, Cricetus cricetus (adults approx. 350 g) - Siberian or Djungarian hamster, Phodopus sungorus (adults 30-50 g)

Volume recommendations for intravenous fluid administration and blood collection in adult Syrian hamsters

- IV fluid volume (mL) ma. acute admin - 0.3 mL - total blood volume (mL) - 78 ml/kg - safe bleed volume (mL) - 0.55 ml - bleed out volume (ml) - 2.9-5.2 ml

Supportive care aims to:

- Maintain the animal's physiological status as near normal as possible - Minimize animal pain and distress

Lateral saphenous vein (lateral tarsal vein)

1. Accessing the lateral saphenous vein: - Does not require anesthesia. - May be aided by sedation because vein visibility is enhanced by peripheral vasodilation (drug effect). - May be aided by sedation to reduce animal struggling due to distress. 2. Blood collection from the lateral saphenous vein does not involve cannulation of the vein lumen. Instead, the vein is punctured percutaneously and blood is passively collected as it pools on the skin.

Abdominal vena cava Abdominal aorta

1. Performed as a terminal procedure under anesthesia. 2. Vessel access involves a ventral midline incision and reflection of intestines.

Retroorbital sinus

1. Retroorbital puncture is controversial because of the risk of injury to the optic nerve and other nearby structures. 2. This method is considered to be painful and may cause blindness. 3. Generally requires anesthesia. 4. Topical ophthalmic anesthetic is recommended post-procedure.

The assurance must take the form of a written narrative that describes which sources were used to determine that alternatives were not available. Typically, you may be asked to provide the results of a database search including information on:

1. The databases searched. 2. The date the search was performed. 3. The years of citations covered by database searches. 4. The key words and/or search strategy used when searching a database.

Cardiac puncture Carotid artery

1. These two methods require anesthesia. 2. Most often allowed only as a terminal procedure. 3. Check with your institution for guidelines on these routes of blood collection.

The dental formula is

1/1 incisors and 3/3 molars. Like other rodents, hamsters lack canines and premolars.

volume recommendations for the safe administration of fluids acutely in adults (Syrian hamster, average

120g

Recommended needle sizes are

23 to 27 gauge.

The typical acclimation period for hamsters would be

3 to 7 days

What is a procedure?

A procedure is any activity carried out on the animal, such as food or water restriction, behavioral testing, blood collection, or surgery

Which of the following best describes the purpose of the federally mandated "alternatives search" in an animal protocol?

A search for procedures that may replace the use of animals, reduce the number of animals used, or refine the methodology to minimize animal pain or distress. Return to Lesson

Severe pain and distress causes overt clinical signs in hamsters. Laboratory staff working with hamsters should be trained to recognize these abnormalities in:

Activity level: - Depression - Lethargy - Extended sleep Behavior: - Aggressiveness - Self-trauma - Uncoordinated movements/ataxia - Vocalization (chatter or screech) Appearance: - Ruffled fur - Ocular discharge - Hunched posture - Pale mucous membranes - Soiled anogenital area Vital signs: - Respiratory distress - Hyperthermia - Hypothermia Body Condition: - Weight loss - Emaciation - Dehydration Intake: Reduced intake of food and water

Which statement is true regarding the conduct of surgery in hamsters?

Applicable federal mandates require the use of aseptic surgical technique for survival surgery in hamsters.

Analgesics:

Available in two drug types - the opioids and the nonsteroidal anti-inflammatory drugs (NSAIDs). The rapid clearance of many of these drugs in hamsters results in the need for an increased frequency of administration. Examples: Opioid Buprenorphine - 0.05-0.1 mg/kg SQ twice daily NSAID Ketoprofen - 1.0-2.0 mg/kg SQ, once daily

Acceptable:

Barbiturate overdose Dissociative agent combinations

Behavior:

Biting Escapism Feeding behavior Nocturnalism Social characteristics

Which statement is true regarding care procedures for hamsters undergoing surgery?

During the procedure, hamsters should be monitored for depth of anesthesia, body temperature, and cardiovascular and respiratory function.

Escapism

During their active period (at night), hamsters may escape if they determine that their cage is not secure, e.g., via a loosely fitting wire lid. They are adept at chewing through cage materials, including plastic. Therefore, cages must be made secure with the use of strong materials and tightly fitting cage components.

the term euthanasia is derived from

Greek and means "good death." Animals should be euthanized when killed for any purpose, including research. To euthanize a hamster, you must be trained in the concepts of euthanasia, the method to be used, and the proper handling of hamsters. Methods are classified as acceptable or conditionally acceptable, as set by the most current edition of the American Veterinary Medical Association's document, the AVMA Guidelines for the Euthanasia of Animals. The inclusion of conditionally acceptable methods in your protocol may require scientific justification and IACUC approval.

Biting

Hamsters are inclined to bite when startled, frightened, or in pain. A common cause for biting is handling the animal while it is asleep in its cage. Hamsters may sleep very deeply, and a sudden awakening may elicit an aggressive response. It is important to carefully wake the animal and make it aware of your intention to handle it. If a hamster is prone to bite an approaching hand, a small container like a can may be used to scoop up the hamster and remove it from the cage.

Cheek pouches

Hamsters have cheek pouches, or evaginations, that extend along the head to the neck area. Cheek pouch dimensions have been reported to be 35-40 mm by 4-8 mm by 20 mm long. The hamster uses these pouches to carry and store food. A female also uses her cheek pouches to carry or conceal her young. Often, persons unfamiliar with this feature will report that the hamster has swellings or lesions in the throat area when they have observed a hamster with full pouches.

Why is fasting hamsters prior to anesthesia unnecessary?

Hamsters have no risk for respiratory aspiration of stomach contents under anesthesia because they cannot vomit.

Why do hamsters require a source of warmth while undergoing anesthetic procedures?

Hamsters lose body heat rapidly under anesthesia.

Bacteria: Leptospira spp.

Hamsters may be a reservoir for Leptospira spp. bacteria, which are shed in the urine. Transmission occurs by contact with urine and tissues, or inhalation or ingestion of aerosol droplets. Humans with leptospirosis may have influenza-like symptoms, orchitis, rash, skin and mucosal hemorrhage, hemolytic anemia, hepatorenal failure, jaundice, encephalitis, and pneumonia.

Protozoa: Giardia spp.

Hamsters may harbor the protozoan Giardia. Transmission occurs by the fecal-oral route of infective cysts. Humans may have an asymptomatic infection or may have overt clinical signs of anorexia, nausea, abdominal cramps, bloating, and diarrhea. Severe infections may involve bile and pancreatic ducts and damage upper intestinal mucosa.

Monitoring post anesthesia:

Hamsters must be monitored until fully recovered from anesthesia as indicated by the ability to ambulate and maintain core body temperature.

Feeding behavior

Hamsters prefer to be fed on the cage floor. Given the blunt shape of the hamster's nose, this animal is less able to grasp rodent food blocks overhead in the feed hopper of the cage wire lid. With a wire mesh that is sufficiently spaced for their access to the food blocks, hamsters will pull their food into the cage where it can be hoarded. Contamination of food on the floor with wastes is less of a concern in hamsters because they expel their wastes and store their food in separate sites. Hamsters will also hoard food in their cheek pouches.

Metabolism

High rate of metabolism - impact on drug clearance High surface area - impact on hypothermia Pseudohibernation

Acceptable with Conditions:

Inhalant anesthetics Carbon dioxide Carbon monoxide Tribromoethanol

Which site is least traumatic for nonterminal venipuncture in hamsters?

Lateral saphenous vein

Which statement is true regarding anesthesia in hamsters?

Long term anesthesia is appropriately achieved by gas anesthesia using a vaporizer.

Which statement is true regarding anesthesia in hamsters?

Long term anesthesia is appropriately achieved by gas anesthesia using a vaporizer. Return to Lesson

Viruses:

Lymphocytic choriomeningitis virus (LCM)

Helminths: Rodentolepis nana

Rodentolepis nana (also called Hymenolepis nana), the dwarf tapeworm, is found in hamsters. It has both a direct and indirect (via flour beetles or fleas) cycle. R. nana is transmissable to man. Depending on the parasite burden, humans may have no apparent clinical signs or may have nausea, anorexia, vomiting, diarrhea, and central nervous signs (agitation).

Nonvascular Injections

Subcutaneous (SQ or SC) - 3-4 mL in scruff Intraperitoneal (IP) - 3-4 mL Oral (PO) - 20 mL/kg Intradermal (ID) - 0.05 mL/site Intramuscular (IM) - 0.1 mL per site Cheek pouch - 0.1 mL instilled into wall of everted pouch.

Hamsters lack suppressor

T cells and have atypical cytotoxic T cells.

The information that should be provided with the results of a database search for alternatives includes which of the following?

The names of the databases used, the date of the search, the years of citations accessed, and the search strategy

What concept is relevant to the proper conduct of euthanasia?

The selection of an appropriate euthanasia method should address considerations of humaneness to the animal, and safety and esthetics for the staff.

Sedatives:

These agents are commonly mixed with other drugs in an anesthetic cocktail. Refer to the information accessed from the "Anesthetics" link. Sedatives have no effect on consciousness, the perception of pain, or other sensations. When combined with general anesthetics, the result is a balanced anesthesia where muscle relaxation, unconsciousness, and analgesia are enhanced. Examples: Acepromazine, diazepam, midazolam, and zolazepam

Injectable anesthetics are generally used in

a cocktail mixed with one or more sedatives and analgesics. The anesthetic cocktails most commonly used on hamsters in the USA contain ketamine or tiletamine as the anesthetic agent. Bolus injections of anesthetic cocktail may produce a surgical level of anesthesia for periods ranging from 20 to 45 minutes, which is ideal for many surgical procedures commonly performed in hamsters, such as cannula implantation. The duration of surgical anesthesia depends on the drug agents used as well as the strain/stock of hamster. Repeated dosage of injectable agents to provide a long term anesthesia is not recommended because of the resulting fluctuations in systemic blood concentration and therefore in anesthetic effect. In such situations, the repeat doses of anesthetic cocktail are administered only when the animal begins to show evidence of pain. This is a poor practice of anesthesia because a surgical plane of anesthesia is not continuous throughout the procedure. Animal welfare mandates require an avoidance of such unnecessary animal pain and distress. Examples (administered IP): Ketamine 75 mg/kg; Medetomidine 1 mg/kg Ketamine 100 mg/kg; Xylazine 10 mg/kg Ketamine 200 m/kg; Diazepam 5 mg/kg Ketamine 40 mg/kg; Midazolam 2 mg/kg; Butorphanol 0.1 mg/kg

Tribromoethanol is acceptable with conditions as

a method for euthanasia when prepared, stored, and administered at the appropriate dosage."

Animals should be exsanguinated only under

anesthesia.

Surgical procedures in hamsters must be conducted using

aseptic technique. This means that the: instruments must be sterilized, surgeon should wear mask, gown, head covering, and sterile surgical gloves, and surgical site should be appropriately prepared (scrubbed). Nonaseptic methods are not acceptable. Nonaseptic methods are not acceptable.

Assessing pain and distress in hamsters is difficult at times because hamsters, like many other species, commonly

conceal outward signs of moderate pain and distress. In this case, the behavioral changes that reveal a hamster's pain and distress may be subtle and detectable only with specialized behavioral methods.

A cheek pouch is a

muscular sac lined with stratified squamous epithelium. The lining of the cheek pouch may be everted and examined in an anesthetized hamster. This epithelium is thin-walled, highly distensible, highly vascular and largely devoid of lymphatic tissue except for some lymph vessels. Due to the lack of lymphatic tissue, the cheek pouches are immunologically privileged and have been used as sites for tumor induction and implantation. The hamster cheek pouch model is also widely used in drug safety and toxicology testing.

High rate of metabolism - impact on drug clearance

of drugs from the body. Drugs administered at dose rates used in larger species (with lower metabolic rates) would reach lower blood concentrations and exert less pharmacological effect in the rat. As a result, hamsters should receive drug doses that have been scaled to the hamster's metabolism. Through a discipline known as allometry, mathematical formulas have been developed to adjust dose rates between species of disparate size.

Supportive care includes the monitoring of both

physiological parameters and analgesia during anesthetic and surgical procedures. Monitoring of vital signs and potential signs of pain should be conducted throughout the procedure and the recovery period.

Hamsters have a large body surface area (relative to body volume). As a result, hamsters are vulnerable to

profound hypothermia under conditions of sedation and anesthesia. Sedation and anesthesia induce hypothermia due to drug effects on the hypothalamus and a rapid drop in core body temperature. If surgery is being performed, additional heat is lost by convection from an open incision during surgery.

Gaseous anesthetics

provide the best means for long periods of anesthesia due to the continuous administration via inhalation. Since methoxyflurane is no longer available, and the use of ether is not recommended, researchers have access only to those agents that are best administered via a vaporizer. Recommended agents: isoflurane and halothane.

Hamsters are generally housed in

shoebox cages with a solid floor covered with bedding material that absorbs liquid wastes. Bedding has been shown to be preferred by rodents for resting, and it is considered to provide them with comfort, warmth, and the opportunity to burrow. This type of flooring is well suited for breeding because pups are better protected from chilling.