Veterinary Healthcare - Controlling disease transmission in animal shelters: Part 2 (Proceedings)
Controlling disease transmission in animal shelters: Part 2 (Proceedings)


Whenever there is a disease outbreak, one of the first control measures should be a thorough, first-hand review of sanitation procedures. Staff often take short cuts when cleaning, especially if they are under staffed or if the shelter is overcrowded. Proper sanitation involves both cleaning and disinfection. Proper cleaning involves the removal of all dirt and organic debris from all surfaces, including bars, walls and tops of cages, in addition to washing with hot water and a detergent or degreaser. Proper disinfecting inactivates the remaining pathogens. Effective chemical disinfection requires the removal of all dirt and organic debris first, use of the appropriate chemical to inactivate the pathogen, proper preparation, dilution, application and storage of the product according to the manufacturer's instructions, allowing the correct surface contact time and in some cases, rinsing the disinfectant from all surfaces and allowing the surface to dry before replacing the animal in the cage. Staff should receive training and the proper equipment to ensure the safe and effective application of the chemical.

Every effort should be made to minimize disruption of the animal's life and routine when cleaning. This is of particular importance for cats. In one study, rehousing induced herpes activation in 83% of 14 cats. While cages should be cleaned (removal of soiled papers, obvious dirt, litter boxes, fecal material, etc,) every day, disinfecting can be done less frequently if animals remain in the same cage for the duration of their stay. However, disinfection must always take place before a new animal is placed in a cage. Cages can be cleaned while the animal remains in place, but they must be removed for proper disinfecting. Cages and enclosures should not be hosed down while the animals are in them.

The three most common disinfectants used in shelters in the US are sodium hypochlorite (or common household bleach), quaternary ammonium products (otherwise known as quats or A-33, Parvosol, Kennelsol, etc)) or potassium peroxymonosulfate, commonly known as Trifectant or Virkon. There is a lot of confusion about the use and effectiveness of these products. There are various studies that indicate that although several quaternary ammonium products may be labeled as parvocidal, they are not (Eleraky 2002). The quats are not reliable against calici virus either. The only product of the three that reliably kills Microsporum canis is sodium hypochlorite (concentration 5.25%), but it must be diluted 1:10, whereas the normal dilution for routine use is 1:32. Whenever dealing with parvo or calici virus, or when unsure of the identity of the pathogen, sodium hypochlorite or potassium peroxymonosulfate should be considered the disinfectant of choice. The random mixing of some disinfectants and failure to follow instructions can result in dangerous fumes being formed. Appropriate safety equipment (protective eye wear, boots, aprons, gloves, etc) should always be used when handling any chemical disinfectant.

For a sanitation program to be effective, procedures should be observed and reviewed with staff periodically to ensure that proper cleaning, proper dilutions and applications of disinfectants and other guidelines are being followed. Since one of the most common means of disease spread in shelters is via fomites, or inanimate objects, volunteers, staff and the public should all be made aware of their potential role in spreading disease through this method. To reduce fomite transmission, attention must be paid to washing hands frequently, disinfecting cleaning utensils, food and water dishes, toys, ropes and muzzles, medical and anesthesia equipment, pens, pencils, temporary holding cages, litter boxes, restraint and grooming equipment and so on. Shelters are encouraged to use disposables such as food trays, litter boxes and other equipment whenever possible. Animals should have but not share toys. Water bowls should be thoroughly disinfected each time a new animal is introduced to an enclosure. Commercial dishwashers are of considerable value because hot water over 170F in dishwashers is effective against many organisms. Bedding, towels, uniforms, etc should be laundered in hot water, detergents and bleach.

Cleaning equipment should be kept in the same room rather than moved around. Juvenile and healthy animal rooms should be cleaned before rooms with sick animals. Staff should change clothing or wear protective aprons and gloves when cleaning multiple areas, but especially after cleaning sick rooms. Ventilation vents should be vacuumed and kept clean. The use of foot baths (Trifectant is the best disinfectant to use) is recommended if they are properly maintained, meaning they must be properly cleaned and refilled daily or more frequently if heavily soiled; otherwise their use should be discouraged because they may actually contribute to disease transmission. Hand sanitizers (70% alcohol) should be placed in animal and public areas. Although they won't kill parvo or calici virus, their use may help reduce disease spread.

In an ideal situation, each animal would be placed in a double sided run with a guillotine door or assigned an adjacent empty cage to move into while their cage is cleaned. If this is not possible each cat should be assigned their own transport cage for the duration of their stay; the cage should be used to house the cat whenever cleaning or other procedures have to be performed requiring transport of the cat. Squirt and spray bottles are useful for spot cleaning cat cages, although some chemicals may cause them to squint or sneeze if they are sprayed too closely to the cat or improperly diluted. The practice of tethering dogs to a cage occupied by another dog or letting them run loose in the common area while cleaning their cages should be discouraged. If double sided kennels or two cages per dog are not available, alternatively, utilizing a system that leaves one cage in a run empty and moves each dog down into the cage adjacent to theirs while cleaning the just vacated cage helps minimize general all- around disease exposure. This "move down one" system, while not perfect, is a realistic compromise to minimize disease transmission.

A comprehensive health care program for shelter animals consists of a physical examination at the time of entry to the shelter, immediate isolation of sick, debilitated and injured animals, administration of appropriate vaccinations upon admission, routine prophylactic deworming for roundworms and hookworms, treatment of external parasites, disease testing and euthanasia when necessary to alleviate pain and suffering. Shelters that can afford to routinely screen cats for feline leukemia (FeLV) and feline immunodeficiency virus (FIV) and dogs for heartworms are encouraged to do so, although it may not always be the best use of resources in a high turnover shelter. Animals who are sick and injured should receive immediate medical attention and offered appropriate analgesia for painful conditions and injuries. If these animals cannot be offered appropriate care and treatment, they should be transferred to veterinary hospitals for care or be euthanized humanely by trained personnel with an intravenous or intraperitoneal injection of sodium pentobarbital. Intracardiac injections should be utilized only if the animal is anesthetized, deeply sedated, unconscious or comatose.

Another component of the health care program should include daily rounds to monitor overall health and behavior, and to make placement and disposition decisions in a timely fashion. Animals in adoption areas who develop health and behavior problems should be quickly moved to other appropriate areas. Foster care and rescue group programs provide excellent ways to reduce the population and provide an opportunity for animals with minor problems to be cared for outside of the shelter until they are well enough to be adopted. It removes them as a threat to the health and well being of the other animals in the facility .It also provides the community an opportunity to get involved in the life of the shelter and help save animal lives. Foster care should be considered a vital component of shelter health care programs, but they must be administered properly to ensure their success.

Vaccinations are just one component of a disease control program. They are ineffective without other control measures! While no single vaccination protocol is effective in every shelter due to the varying circumstances encountered in every shelter, one general rule should be to vaccinate animals at the time of entry to the shelter with a modified live vaccine. Other decisions can be made as to which animals will be vaccinated, which products to use, etc. Vaccines have specific roles to play in disease outbreaks. Respiratory vaccines may lessen the severity of disease, reduce or induce shedding, but they do not prevent infection. This is one reason why vaccination is limited in its ability to control respiratory disease outbreaks in shelters. On the other hand, the parvo and canine distemper vaccines are excellent products to use during an outbreak because they provide fairly rapid and complete protection against infection.

Vaccination is not equivalent to immunization. In any given population of vaccinated animals, some animals will not be successfully immunized due to a variety of host and vaccine factors. Vaccine mishandling by staff is frequently overlooked as a cause of vaccine failure, i.e., failure to keep refrigerated, failure to mix or administer properly, etc. Other reasons for vaccine failure include maternal antibody interference, the animal may already be exposed and incubating disease, there can be a lag time between vaccination and antibody production of about 7 days in some cases, and many animals are too debilitated and/or immune compromised to respond.

Vaccine recommendations for shelter animals vary from recommendations for the private sector. The American Animal Hospital Association (AAHA) and American Association of Practitioners (AAFP) both recognize the unique conditions encountered in shelters and devised separate shelter vaccination policies. Shelters often begin vaccinating animals at a younger age, and may vaccinate every 2 weeks instead of 3 because the animals have greater exposure to disease. They may also continue vaccinating past the recommended age of four months in dogs and three months in kittens. Unlike private practices, shelters should vaccinate animals who are injured, debilitated, running a mild fever or pregnant because the risk of contracting disease is so much higher than any risk from side effects or reactions.

Different products may be used in shelters than would be in common use in a private practice. Feline herpes and calici virus modified live intranasal vaccines can be useful in low stress, low turnover shelters because they may be given at a younger age (three weeks in some cases) and they can induce an immune response faster than conventional vaccination. The disadvantage is that they may cause side effects that mimic clinical disease. Avoid use of the intranasal panleukopenia vaccine though, especially in young kittens. The new recombinant canine distemper vaccine has been shown to overcome maternal antibodies, withstand viral challenge within 4 hours of administration, and is very safe, making it a very good vaccine to use in a shelter. The bordetella vaccine for cats and the intranasal parainfluenza and bordetella kennel cough vaccine for dogs may be used more frequently in shelters as well.

The role of vaccination in animal shelter health care programs is still poorly understood due to lack of data. However, the suggested core vaccination protocol for cats in shelters is modified live feline panleukopenia, calici and herpes virus (FVRCP) vaccine administered subcutaneously at admission and boostered every 2 weeks until the animal reaches 4 months of age. The suggested canine core vaccination protocol is modified live distemper, hepatitis, parainfluenza and parvo virus (DHPP) vaccine administered subcutaneously at admission, along with an injectable or intranasal parainfluenza and bordetella vaccine also given at admission and boostered every 2 weeks until the animal reaches 4 to 5 months of age. Rabies vaccination should be administered by a licensed veterinarian to long term residents and before animals are released from the shelter.

All animals should be dewormed prophylactically for roundworms and hookworms for the health benefits to the animal and because of concerns about visceral and cutaneous larval migrans, two zoonotic diseases caused by these parasites. The Centers for Disease Control (CDC) and Companion Animal Parasite Council (CAPC) have issued guidelines for deworming that should be used. The guidelines recommend immediate deworming using a broad spectrum product and reworming at 2 week intervals until 3 months of age, once a month from 3 to 6 months of age and then routine screening and deworming as indicated. (See or for complete recommendations.) There are many good broad spectrum products on the market so treatment will not be discussed here, but a bath should be considered part of a complete and thorough treatment protocol, especially if Giardia is suspected.

It is beyond the scope of this paper to discuss disease testing in depth or treatment protocols for shelters. Fecal flotation tests should be performed on a few sentinel animals for surveillance purposes or when animals have diarrhea or are unthrifty. Shelters that group house cats, neuter before adoption, adopt to households with multiple cats and treat diseased and injured animals should consider retro virus testing to be mandatory.

While the AAFP retro virus testing guidelines recommend that no healthy cat be euthanized based on the results of a single positive test, many shelters cannot afford to retest and have so many other healthy cats waiting for adoption that they do indeed euthanize based on the results of a single test. Heartworm screening of dogs in endemic areas is recommended if affordable. Parvo tests look for virus antigen and thus it is important to understand parvo viral shedding patterns and how vaccination may affect the test results. Dogs shed virus from day 3 post infection and for 12-14 days afterward only. False negatives may be obtained when antibody binding to the antigen occurs, and it is believed that weak positives may be obtained due to vaccination. Testing for feline infectious peritonitis (FIP) is not recommended in the shelter environment as the tests are not specific for FIP. Tests for infectious diseases should be interpreted in conjunction with the clinical signs, a history of exposure and an understanding of the sensitivity and specificity of the tests. More information may be obtained at

Vigorous individual animal and environmental treatment is recommended for fleas, ticks and any other external parasites. Traditional treatment protocols must often be adapted for shelters to reflect the fact that limited resources are available, large numbers of animals must be treated or there is a risk of spreading disease to other shelter animals. The three general scenarios for treatment of shelter animals with infectious disease include either placing them in a foster care home, transporting them off-site to a veterinary hospital or keeping them in an isolation room designed for implementing biosecurity measures for in-house treatment. Overcrowded or poorly designed shelters that treat diseased animals in rooms with other healthy animals because their isolation areas are full endanger the health of all the animals in the facility. This practice is strongly discouraged.

One of the most arguably effective and controversial population control methods to use during a disease outbreak in an animal shelter is to euthanize all diseased, in contact and exposed animals. This method is seldom used in shelters to the extent it is used in large animal herds because of ethical and moral repercussions from staff, the media and the public to such a drastic measure. No one likes to euthanize shelter animals, but when all other methods of reducing the shelter population (adoption, foster care, rescue) to manageable numbers that permit humane care have been exhausted, euthanasia of sick and unadoptable animals should at least be considered. Animals who are housed in crowded facilities are stressed and have a poor quality of life if they are sick, injured or in pain or cannot move about freely, rest, play, eat, defecate and sleep in peace. They are much more prone to develop disease and behavior problems when they are prohibited, due to circumstance, from exhibiting normal behaviors. Although the trend for shelters to build clinics and hospitals is increasing, most shelters still do not have the resources to provide appropriate treatment and intensive nursing care and are therefore ill equipped to offer the quality of care necessary to alleviate animal suffering. Although shelter medicine is regarded as herd health, attention must be paid to the quality of life of each individual animal. Euthanasia is a valuable tool that should be considered for use to prevent animal suffering, manage disease outbreaks and reduce population numbers when other methods are not available, have failed, or would be inappropriate in a shelter.

Shelter medicine is a field of veterinary medicine that has attracted a great deal of attention in the last few years. Effective disease control in shelters requires a multi disciplinary approach that often uses new methods and ways of thinking to handle unique situations. Shelters are not hospitals but the animals that are entrusted to their custody deserve the best care the veterinary profession can offer them. Key components of a disease control plan include understanding the interplay of host, environmental and agent factors, and the impact of disease transmission, shelter design, stress and sanitation on the actual veterinary health care program. Prevention of disease is much more cost effective than treatment in shelters, but there are often many factors beyond the control of management that cause prevention programs to falter. When this happens, prudent veterinarians should take steps to fully investigate the circumstances, seek out and consult with experienced shelter veterinarians and universities in order to implement appropriate remedial strategies. Increased interest in shelter medicine has resulted in research that is creating protocols for health care and disease prevention that increase the welfare for these animals and enhances the ability of shelters to find new homes for stray, relinquished, unwanted and abandoned animals.

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