ALAT Chapter 13 Colony Health Surveillance PDF

ALAT Chapter 13 Colony Health Surveillance Good research depends on the availability of healthy research animals. Keeping animals healthy is a major function of the laboratory animal facility staff. To safeguard the health of the animals, and therefore their quality as research subjects, animal faci...

ALAT Chapter 13 Colony Health Surveillance Good research depends on the availability of healthy research animals. Keeping animals healthy is a major function of the laboratory animal facility staff. To safeguard the health of the animals, and therefore their quality as research subjects, animal facilities operate a program of animal health surveillance. • Health Surveillance • Health surveillance begins before the animals are received • in the facility. When animals are ordered from an approved • vendor or transferred from another institution, the receiving • institution’s animal procurement form requires the • shipper to provide a summary of the health status of the • animals prior to shipping. The scope of the testing information • required will vary from institution to institution • and by species. • Large animals, such as rabbits, cats, dogs, swine, and NHPs, • should be procured from approved commercial vendors. • The veterinarians will have an animal care program encompassing • diagnostic testing (e.g., fecal testing, blood • work) and prophylactic treatments for pathogens, such as • endo- and ectoparasites. In addition, an entry order will • be established to isolate animals procured from different • vendors. Each laboratory animal facility should have a • health surveillance program specifically developed for the • species being housed. The health surveillance program • begins with selecting vendors that can provide healthy • animals suitable for the research requirements. Laboratory • animal care technicians first become involved in the health • surveillance program when animals are received into the • facility. They check incoming animals immediately upon • arrival and perform preventive measures as specified by • Animal Observation • The quality of husbandry provided to the animals is one • of the most important factors in health surveillance and • disease prevention. Laboratory animal care technicians are • often the first to notice that something is not quite right • with an animal. Early detection is essential to avoid the • spread of disease in a colony and promote animal welfare. • Of course, depending on the research, the animals may • be meant to become sick (e.g., preclinical studies for HIV • or cancer models). • Animal observations should be consistent and appropriate • for the species and for the study. Many studies induce • disease, so animal care staff should be aware that • poor condition may be a product of the experimental • manipulation. For example, mice that are experimentally • infected with influenza will lose weight. Listed below are • some of the signs that can indicate health problems in • laboratory animals. Observations: General Body Condition & Posture Stunted growth refers to animals that appear much smaller than most animals of the same age. Causes include genetics, infection, parasites, or poor husbandry. Weight loss is often associated with anorexia due to a serious disease. Insufficient or incorrect feed and endo- or ecto-parasites can also cause weight loss. Swelling, lumps, or growths anywhere on the body may indicate a tumor or a disease-related accumulation of fluid. Abnormal posture or movement, such as hunching or circling (Figure 13.1). Paralysis is the inability to move all or part of the body, often due to nerve damage or disease affecting the central nervous system. Behavior change is often the only indication that something is wrong with the animal. An animal that suddenly becomes aggressive, quiet, or loses interest in its surroundings is usually sick or in pain. Observations: Condition of Skin, Fur, or Feathers A dirty, unkempt, or ruffled hair coat can indicate many problems, including vitamin deficiencies, external parasites, internal parasites, and severe infections. This sign is one of the most reliable indications that an animal is ill.  Piloerection, the involuntary erection or bristling of fur or feathers, over the entire body indicates the animal feels cold and may be ill.  Alopecia is the loss of hair or feathers in patches or widespread areas. It can be associated with a skin disease, fighting, parasites, or barbering (Figure 13.2).  Red, swollen, or irritated skin can indicate illness or injury.  Evidence of trauma, such as bite wounds or other injuries, need immediate attention.  Pruritus is a constant or frequent scratching due to skin irritation and can be caused by external parasites. The skin often appears scaly or red.  Bleeding can be external, such as a torn nail, bite wound, or cut, or internal, such as from the bladder, bowel, or uterus. Look for fresh blood in the cage as well as on the animal.  Pale skin on the ear lobes can indicate anemia.  Yellow tinged skin can indicate liver issues. Observations: Mucus Membranes Pale gums (gums that are normally pink are almost white) usually indicates anemia caused by blood loss or lack of iron. A bluish tint to the lining of the mouth, nose, eyelids, vagina, or rectum is referred to as cyanosis. An animal with cyanosis is not receiving enough oxygen and requires immediate attention Observations: Eyes, Ears, & Nose  Discharge, redness, and odor.  Scratching or pawing may indicate pain or irritation.  Abnormal eye size, either too small or too large.  Squinting or swelling.  Porphyrin: Red staining around the eyes and nose in mice or rats is caused by a substance called porphyrin. Porphyrin is secreted by a tear gland, known as the Harderian gland, located behind the eye. Rats normally may have some staining, but over-secretion and lack of grooming (due to illness or stress) can cause excessive accumulation, indicating a potential health problem. Observations: Jaws & Teeth Overgrown or abnormally aligned teeth (malocclusion) can interfere with chewing in rodents and rabbits. Broken or missing teeth (any species). Observations: Perineal Area Vaginal discharge and swelling of the vulva may indicate that the animal is in heat (estrus), or it may be a sign of infection. Prolapse of the rectum, vagina, or uterus occurs when internal tissue is pushed through a body orifice. It is typically caused by straining during defecation or as a complication of giving birth. Diarrhea is the passage of watery or loosely formed feces. Often the animal will have feces or blood staining the perineum or tail region. Infections of the bowel or parasites of the intestinal tract can cause diarrhea. This can also be the direct effect of research studies for colon cancer or irritable bowel syndrome. Constipated animals pass dry, scanty feces because there is a lack of proper movement in the large bowel. Causes include inadequate feed or water intake and serious infections. Observations: Tail Sloughing of the skin (degloving) is usually due to incorrect handling. Lost tail tips can be due to trauma or amputation. Observations: Feet Ulceration and inflammation of the feet is often due to housing on rough floor surfaces. The nails, claws or hooves of the animal should be trimmed to prevent lameness or difficulties with movement Lameness (difficult walking) is often caused by trauma or infection. Pale skin on feet indicate anemia in rodents. Yellow tinged skin can indicate liver issues. Observations: Respiration Coughing, sneezing, rapid, shallow or labored breathing (dyspnea) are all signs of problems in the nasal passages, throat, or lungs. Nasal discharge is often associated with infection of internal organs. Observations: Aquatic Animals In addition to many of the points above, the following signs may also indicate injury or illness in an aquatic animal: Lethargy (drifting with the current or lying on the bottom) Abnormal equilibrium (loss of buoyancy control, swimming with either head or tail pointed down) Abnormal respiration (unusually rapid, slow, or erratic opercular movements) Piping (gasping for air at the water surface) Flashing (rubbing on or bumping against tank surfaces) Darting (a lack of schooling or shoaling behavior) Excessive mucus production Fin erosion (ragged fins or holes in fins) Gas bubbles on or in the skin Bristling scales Abnormal coloration, depigmentation, or missing scales Causes of Diseases • The term “disease” means any alteration of the normal anatomy or physiology of an animal. The signs of disease may be classified as clinical or subclinical. • Clinical signs are evident to an observer; you can look at the animal and see that it is ill. • Subclinical signs are not apparent to the observer; however, the animal may be suffering despite having no visible signs. These hidden signs can alter the study by changing an animal’s physiologic functions and thereby affecting scientific data. • It is vital that animal care technicians are aware of the potential diseases associated with the species they are caring for. • Early detection is important for the care and health of individual animals and for safeguarding the entire colony. • Any animals that may be sick should be reported to a supervisor. • If the illness could be due to an infectious pathogen, the animals may be removed from the general colony and placed in isolated housing to reduce the possibility of infection transmission. Malnutrition • Nutritional causes of disease include deficiencies or excesses in the quantity or quality of water, fats, carbohydrates, proteins, minerals, and vitamins in the diet. • Different species have different nutritional needs, so it is important to provide appropriate diets for all animals within the colony. • For example, guinea pigs lack the enzyme needed to produce vitamin C, so guinea pig diets must contain vitamin C supplements. • The nutritional content of commercially prepared diets is based on extensive research on dietary formulations. If animals are fed the proper diet in the right quantity and have free access to water, their nutritional needs will usually be met. • In some research studies, animals are fed a diet with a nutritional imbalance or supplements in order to induce disease for research purposes. Technicians should be aware of any clinical signs expected in these animals so they can alert the research or veterinary staff when these signs become evident, perhaps necessitating special husbandry procedures. Infection Bacteria, viruses, fungi, and other microorganisms that cause disease are said to be pathogens. • Pathogen: an infectious agent that causes a disease. • Nonpathogenic organisms: Microorganisms that do not cause disease. • Contagious pathogens: When infectious organisms are easily transmitted among animals, the pathogen is said to be contagious. • Host-specific pathogens: Some pathogens attack only particular species, known as the host, and not others. These agents are said to be host-specific. For example, a virus that infects cats may not affectdogs or humans. Even closely related species may not be infected with the same organism. Some mouse viruses do not infect rats. • Other pathogenic microorganisms will infect numerous species, like the fungus that causes ringworm. • In general, pathogens in the environment can infect an animal through air, feces, feed, water, or through contact with skin or fur. • If the pathogen invades the body and survives the counterattack by the immune system, it will multiply in the host’s body. The infection may disrupt normal cellular processes, which manifest as disease in the host. The disease state caused by the pathogenic organisms is typically evident to the laboratory animal care technician by observation. • To identify a subclinical disease, it is necessary to perform diagnostic testing. Infestation • Parasites are organisms that draw nourishment from a host animal. The presence of parasites is called infestation. • Animals can be infested with protozoans (which are single-celled organisms); helminths (which are worms); or arthropods, such as lice, mites, and fleas. • Though some parasites may cause death, in many cases parasitism is subclinical. Nevertheless, even subclinical disease can result in altered research data. • You should immediately report any sign that an animal may have parasites, such as diarrhea, vomiting, skin lesions, or paleness in normally pink tissues, such as the gums or eyes. Environment • Environmental causes of disease can include variations of temperature, noise, humidity, overcrowding, lighting, and ventilation. • Changes in these environmental parameters can produce stress and alterations of the animal’s physical or biochemical functions, which are collectively referred to as the animal’s physiology. While such changes do not typically cause disease in an otherwise healthy animal, they can alter the body’s immune system, hormone balance, and metabolism, thereby affecting research outcomes. • Environmental factors, such as low rates of room air exchange, may permit pathogenic microorganisms to be spread among the animals. • Proper cage density is an important environmental factor. One of the greatest challenges in a rodent breeding colony is preventing overcrowding. With so many pups born to a litter and growing so rapidly, a nursery cage can quickly become overcrowded, especially if multiple litters are present. This situation is stressful to all the animals in a crowded cage, and a young litter may be injured or even killed if older pups are still present in the cage. • For aquatic animals, maintaining good water quality is paramount to maintaining animal health. Contaminants • Contaminants can enter an animal’s body through the air, water, bedding, and feed. • In a well-run animal facility, these sources of contamination are carefully monitored to avoid any substances harmful to the animals. • One potential source of contamination is mold in bedding, caging equipment and facility areas. Mold may produce chemicals toxic to the animals. • For aquatic housing, cleaning agents and disinfectants are a major source of water contamination. Tank components should be thoroughly rinsed before placing the clean tanks back into circulation. Other Causes of Disease Degenerative changes in body tissues The process of aging. Improper restraint or handling Allergic responses may develop due to vaccinations, drugs, or insect stings. If investigators are studying cancer, technicians will often see experimentally induced or spontaneous tumors. Frequently, more than one factor may combine to cause disease. For example, an animal weakened by an inadequate diet is more vulnerable to bacterial infection. In this case, the nutritional deficiency allowed the infection to take place. Transmission of Infection • In a laboratory animal facility, infectious organisms are transmitted to an animal in a variety of ways. It is important to understand the route of infection in order to control transmission of pathogens. • Vectors: A vector is an organism that transmits a pathogen, but does not cause disease itself. An example of a natural vector is the mosquito. Mosquitoes carry the organisms that cause malaria inside their bodies. The mosquito does not develop malaria, but it passes these organisms to humans through its bite. • Contact: A person can pick up a pathogen by direct physical interaction with an infected animal, perhaps on a glove or a sleeve. The pathogen is then passed to a healthy animal during handling, potentially infecting that animal. • Fomites: Nonliving items or materials that transmit an infectious organism are called fomites. If an infected mouse is removed from a cage and another mouse is placed into that unclean cage, the second mouse is at risk for becoming infected. The contaminated bedding serves as a fomite for this pathogen. • Some organisms require direct contact between two animals to be transmitted and cannot survive in the environment. Others are transmitted indirectly through fomites or vectors and are stable in the environment (meaning that they remain infectious). • Pathogens can be inhaled into the respiratory tract, swallowed into the gastrointestinal tract, rubbed or splashed into the eye, or inserted into the body through the skin by either a puncture or an existing wound. • High-quality husbandry is the most important part of disease prevention. Proper husbandry practices can significantly reduce pathogen transmission, so it is important to follow strict practices when performing daily care. • • • • • Smaller rodents, such as mice, should be handled with gloved hands or forceps provided the gloves or forceps are sanitized before handling animals in another cage. To sanitize gloves between cages, spray gloved hands with a disinfectant and rub over all glove surfaces before opening a new cage. To prevent the spread of organisms from room to room, facilities may have SOPs to change out PPE between rooms. For example, an outer pair of gloves and shoe covers may be discarded upon exiting a room, and a new pair of each would be donned at the entrance of the next room. Another way to minimize the risk of pathogen transmission is to designate a facility work flow from clean rooms to dirty rooms. Everyone should wash their hands before leaving an animal area. All animal cages should be properly cleaned and/or sanitized according to facility procedures. Many facilities autoclave cages and feed prior to their use. In many facilities, and especially in barrier conditions, incoming room air is passed through a HEPA filter to avoid introducing airborne organisms. In addition, pest control programs reduce the possibility of transmission of pathogens by removing potential vectors for disease. Sentinel Animals • Since many pathogens can cause subclinical disease, a sentinel testing program is needed to diagnose and monitor the health status of the colony. • Animals are designated as sentinels and are tested to detect viruses, bacteria, and parasites that are present within the colony. Sentinel status is indicated on the animals’ cage cards. • New sentinel animals are rotated into the colony on a schedule to maintain appropriate screening of colony animals. • A representative number of the sentinels are tested and necropsied periodically, typically every three months. • There are two types of sentinel programs, direct and indirect. Most facilities use indirect sentinel testing since it is more effective in time and expense in large colony settings. • • • In a direct sentinel program, sentinels are placed in cages with the colony animals. In an indirect sentinel program, the sentinels are housed in separate microisolation cages in the animal room. On cage changing days, small samples of soiled bedding are collected from the cages of the colony animals and placed in the sentinels’ cages. The soiled bedding exposes sentinel animals to any organisms that are excreted by the colony animals through urine, feces, or saliva. At the end of the sentinel period, diagnostic tests are performed to screen for specific pathogens. If sentinel animals test positive for any of these pathogens, the colony animals will likely test positive also. A typical indirect program uses one cage of sentinels per rack, with two to three animals per cage. The sentinel cage is often placed in a specific location on the rack, such as a lower corner. • Another method of colony health surveillance is environmental testing. In rodent rooms, this may involve testing dust and air filters; with aquatic facilities, this can involve testing solid waste from tanks, or particulates filtered from system water. Using molecular biology techniques, such as polymerase chain reaction (PCR), minute quantities of pathogens can now be collected, amplified and analyzed in the same manner as samples taken from sentinel animals. Because such small samples can be taken for this kind of testing, both environmental pathogen surveillance and direct testing of sentinels can be conducted more frequently and cost effectively. • Zebrafish: A growing number of zebrafish facilities have a sentinel program in place. As with rodents, these animals are housed with the rest of the colony and periodically euthanized for necropsy and pathological examination. • However, rather than direct and indirect rodent sentinels, zebrafish sentinels will receive pre- and post-filtration water. • In a recirculating water system, the pre-filtration sentinels are exposed to water that has already passed through the colony and into the main dirty sump. Water is then filtered and disinfected by ultraviolet radiation. The post-filtration sentinels are then exposed to this clean, filtered water. By exposing these animals to the water in the system, both before and after filtration, animal care staff can determine if there is an infection within the colony AND if the water filtration and disinfection processes are functioning correctly. • Sentinel animals do not eliminate the need for other methods of colony health surveillance. Indirect sentinel testing, for example, will typically detect only those pathogens transmitted by indirect contact. Pathogens that are transmitted by direct contact between animals may be missed. • Sentinel programs are not used for large animals. Instead, large animals are observed on a daily basis for any signs of disease, stress, and discomfort. If a disease is suspected, blood and other biological fluids may be tested for specific pathogens. Diagnosis of Disease • When animals become sick, the nature and cause of the disease must be investigated. This process is referred to as diagnosis. Often the diagnosis can be determined through a detailed history of clinical signs and a thorough physical examination. When these initial evaluations do not yield a diagnosis, testing can help determine the cause of the illness. Diagnostic tests may involve: • amplifying pathogen DNA by PCR for analysis. • culturing microorganisms from a biological sample of the animal, such as urine, feces, or wound drainage. A swab of the sample is placed on plates or tubes of artificial nutrients to see if bacteria or viruses grow. • evaluating blood cells for changes in number or appearance, which indicate a disease process. • measuring chemicals in the serum, which is the liquid portion of blood. These tests are sometimes known as serum chemistry, clinical chemistry, or a biochemistry panel. Detecting Parasites Testing for internal and external parasites should be performed at regular intervals on rodents. • Cellophane tape test: Used to detect some types of pinworms, a common helminth parasite found in the mouse intestinal tract. The adhesive side of a piece of clear cellophane tape is applied to the perineal area, which is the area below the tail of the animal, and over the anus. The cellophane tape is then placed onto a microscope slide. The slide is viewed through a microscope to see if pinworm eggs are present. • Fecal flotation is another method used to detect internal parasites. In the fecal flotation test, a small stool sample is mixed with water or other liquid solution and strained. When left to stand for some time, any parasite eggs that may be present will float to the surface. The top layer of this fluid is then transferred onto a glass slide, and examined under a microscope. The type of parasite can be determined by the appearance of the eggs, as the eggs of each species have distinctive characteristics. • Pluck Test: Historically, the most common evaluation for ectoparasites in rodents is performed by a pluck test. A small sample of hair is plucked or removed from an animal using a piece of cellophane tape. The tape can be placed onto a microscope slide and viewed for any external parasites. • PCR tests are used to detect a multitude of pathogens. • In large animal species, parasites can be seen by directly examining the animal’s skin and hair. • Gill clips or skin scrapes: used for aquatic animals, samples are examined microscopically Vaccinations • Many facilities routinely vaccinate large animals against specific diseases. • Ferrets are generally vaccinated against canine distemper. • Laboratory cats and dogs, especially those held for long-term studies, may be given the same vaccinations that are recommended for companion animals. • Decisions about the use of vaccines are made by the veterinary staff after consulting with the investigator. Tuberculosis Testing in NHPs • Facilities housing NHPs should have a regular surveillance program to screen for tuberculosis (TB). Most cases of TB in NHPs are likely due to human exposure, either in their country of origin or from infected facility staff. • TB is a highly infectious bacterial pathogen, so once it is in an animal room; it can spread rapidly among animals. • Personnel are subsequently at risk for acquiring the infection from the animals. • TB testing is based on the injection of a purified and noninfectious material, called tuberculin, into the skin, generally the eyelid. Typically the injection site is examined by qualified personnel 48 or 72 hours after administration. Positive reactions may be suggestive of TB and require further testing for diagnosis. • All NHPs should be tested for TB when they arrive at the facility, during the quarantine period, and at regular intervals thereafter. An example of a typical schedule for TB testing is a first test administered within 7 days of arrival, two subsequent tests administered at 2-week intervals, and then testing every 6 months thereafter. • Staff working with these species must also be tested periodically. Each facility will have a schedule in place that meets its own needs. Isolation • Isolation areas house animals known to be, or suspected of, carrying infectious diseases that could spread to other laboratory animals or laboratory personnel. Isolation areas should be separate from other areas in the facility. • If an animal is suspected of being sick due to an infectious disease, the veterinary staff may place it in isolated housing conditions away from the general colony. Isolating infected animals helps protect the colony from the risk of disease transmission. • There are occasions when an animal room is designated as an isolation room because an infectious outbreak has been detected in some of the animals in the room. In this situation, all inhabitants of that room must be isolated from the colony. • Isolation rooms, like quarantine rooms, should operate on a negative pressure air supply to prevent any disease organisms from being carried out of the room on air currents. • Husbandry tasks for isolation areas should be done late in the day to reduce the risk of spreading pathogens from these animals to other rooms. • Stringent hand hygiene should be practiced • Any protective clothing work in the vivarium should be discarded or cleaned by facility laundry services. Dead Animals • Dead animals should be removed from the animal room to reduce the possibility of disease transmission from the carcasses. • Facility procedures or special instructions may dictate that these animals be necropsied before disposal. • Carcasses should be sealed in biohazard bags and placed in cold storage until evaluation. Never use a freezer to store a carcass to be necropsied. Freezing destroys the structure of the tissues and interferes with microscopic examination. • During necropsy, appropriate tissue samples are collected and preserved in dilute formalin to prevent decay of the tissues. The preserved tissues are examined microscopically by a pathologist, an individual trained to identify and associate changes in tissue with a disease. • All dead animals, but especially those that were sick, must be carefully removed from the facility. Their tissues should be handled in a manner that prevents the transmission of pathogens. Carcasses and tissues should not be discarded with other waste materials from the facility. Instead, these items should be disposed of using the appropriate equipment, such as an incinerator or tissue digester, to prevent the transmission of infectious organisms to humans or other animals. Summary • Laboratory animals are susceptible to many diseases that can affect the research data obtained from the animals. • As an ALAT, you should understand how disease is spread and the ways to prevent disease outbreaks through sound husbandry practices. • It is particularly important to be aware of signs of disease in animals under your care, so that other personnel can be quickly alerted to intervene. • When working with animals that have an illness, you should try to learn about the disease from other persons in the facility, including veterinarians and investigators. Ask questions about what causes the disease, how it can be spread, and how it can be managed.