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Shelter Snapshot: Steps to contain disease outbreak
Is the shelter you work with prepared to manage an infectious disease outbreak? From before an outbreak to after its contained, here are the steps you need to take.
Photo: Shutterstock.comYou're a kind-hearted practicing veterinarian, helping out shelter pets in your area. But is the facility you work with ready when a worst-case scenario happens?
The effects of animal shelter outbreaks are far-reaching and ultimately devastating. They include loss of life, increased suffering, loss of often-limited financial resources, loss of a shelter's reputation and increased compassion fatigue in shelter staff, among others. In order to prevent the tragic effects of disease outbreaks, prevention policies should be developed with a preemptive mindset, assuming that infectious disease could enter the shelter at any time. So once a break in protocol or another misstep has allowed a disease to spread through the shelter, what's the best strategy to mitigate the costs associated with that outbreak? Walk through these six steps to come out clear on the other side.
Step 1: Plan ahead
Every shelter should write an outbreak response plan at a time when shelter management is not in crisis, where decisions could be driven by emotions. It's helpful to have a specific plan for common infectious diseases, but it's vital to have a broad-based plan that can be used in any investigative process. At the start of an outbreak, the cause of disease may not be known, and the plan must be flexible enough that it can be changed as new information is brought to light. Rapid response can significantly mitigate losses.
Step 2: Stop the spread of disease
The primary step after a disease has been identified is to stop movement from within, into and out of the shelter. Restricting movement and practicing strict biosecurity until an initial risk assessment and triage can be performed is an effective way to limit further spread. By limiting movement, it will allow some flexibility in available staff time, which can be used for disinfection, treatment of ill animals and (re)training. If preventing intake is not possible, a clean break is necessary to prevent exposing unaffected animals. Either a secondary facility will be needed or decontamination of part of the primary facility must be completed to allow intakes to be separated from the shelter population. Staff, supplies and animals cannot move between the “dirty” area and the “clean” area of the shelter, or a clean break will not be maintained.
Step 3: Diagnose the pathogen (if possible)
At a minimum, perform a cursory examination of every exposed animal for the purposes of initial triage. When developing a differential diagnosis list, it's important to consider who's affected, how many animals are affected and what clinical signs you're observing. Spreadsheets of all affected animals can provide a useful tool to help provide perspective on the situation.
It's often recommended that 5 to 10 percent of the population undergo diagnostic testing in order for a causative agent to be identified. Testing performed will depend on the clinical signs present, available resources and differential diagnoses being considered. Necropsy is often a good testing option if appropriate, relative to the level of illness and mission of the organization.
Want more? A webinar on this topic previously recorded by Dr. Dykstra is available to Association of Shelter Veterinarians (ASV) members
on their website.
Step 4a: Assess the level of risk for the shelter as a whole …
An important part of assessing the risk for the shelter as a whole includes reviewing any protocols related to sanitation, animal movement, stress reduction, intake and any other procedures or protocols related to animal husbandry. Although written protocols are important, it's also vitally important to ensure the protocols are being followed as written. A breakdown in staff training could have fatal complications in the shelter. Other means of assessing population risk include reviewing applicable shelter data, such as length of stay, determination of an attack rate per risk factor and plotting an epidemic curve.
Step 4b: … and the level of risk for each animal
An individual risk assessment involves consideration of individual immune status, vaccination status, proximity to an infected animal, and cleanliness of the living environment. Knowledge of these factors helps to divide the population into four groups based on risk:
> Those infected or displaying clinical signs of disease
> Those exposed to and at risk of the disease
> Those exposed but not at risk of developing infection
> Those not exposed.1
The initial physical exam and diagnostics allow for identification of those that are part of the first group. Examining the living conditions, proximity to infected animals and staff adherence to disinfection protocols can help determine which animals belong to the fourth group. Those not exposed should be maintained in a manner that prevents exposure and are assumed to have the same risk as an animal that enters the facility during a non-outbreak period.
Determination of which animals belong in the second and third groups depends largely on the pathogens involved and the resources available. Point-of-care antibody titer testing is relatively inexpensive with high diagnostic accuracy for canine distemper virus (CDV) and canine parvovirus (CPV)2-4and more moderate accuracy for feline panleukopenia virus (FPV).5,6 Samples can also be sent to the major commercial laboratories for titer testing. While more expensive than point-of-care testing, sending samples out may be a practical option for shelters that do not encounter frequent outbreaks or for private practitioners providing consultation services in outbreak scenarios.
Those with a negative titer are high risk and need to be quarantined for 14 days (CPV, FPV) or four to six weeks (CDV).7 To avoid unnecessarily long quarantine periods, antibody titer testing for CDV can be combined with polymerase chain reaction (PCR) testing to potentially move more animals through the shelter, especially if the consulting veterinarian becomes involved later in the course of the outbreak.8 It's often recommended that dogs exposed to CDV be released with a medical waiver following quarantine because of the variability in incubation period.
Juveniles (younger than 5 months old) with a positive titer can be bathed and immediately placed in rescue, foster care or adoption with a waiver. Antibody in juveniles could be due to a waning maternal antibody or vaccination so it's important to get these animals out of the shelter as soon as possible.9 Because of the impact of maternal antibodies on vaccination, always consider juveniles at some risk of developing disease even with positive titers. Adults with a protective antibody titer can be safely moved to adoption or rescue and are considered low risk.
As with any diagnostic test, false positive and false negative results are possible for various reasons. In addition, the lack of a positive antibody titer does not mean an animal is susceptible, nor does a positive titer mean an animal is immune. Interpret all results with the understanding that some level of risk will always be present no matter the diagnostic results.
When resources limit the availability of laboratory or point-of-care tests, individual risk assessment decisions must be made on a case-by-case basis. The presence of protective antibody titers has been correlated with being neutered, relinquished by an owner and over 6 months of age.10 Also, any adult in the population known to have received a modified life virus vaccination at least one week prior to exposure could be considered low risk for CPV, FPV or CDV. Risk assessment based solely on signalment is inaccurate and difficult but is sometimes necessary due to a lack of resources.
Serology is less helpful in managing outbreaks caused by upper respiratory tract disease (URTD) pathogens. These are often managed by reviewing risk factors and changing shelter management procedures or protocols in order to decrease the incidence of disease. Population-level changes that decrease stress and lower pathogen load in the environment are generally more successful than the management of individual cases.
Step 5: Manage the situation to work through the outbreak
Decontamination of the area with multiple cycles of mechanical cleaning, disinfection and complete drying is necessary as animals are moved according to risk assignment.4 Choose disinfectants based on effectiveness against the most environmentally sturdy pathogen present (or suspected), and follow dilutions and contact times precisely (more details, tips and tricks here). Strict biosecurity measures that prevent fomite transmission and interspecies spread should be followed. Furthermore, proper personal protective equipment can prevent cross contamination and help protect staff from possible zoonosis.
Consider measures that improve individual and population disease resistance. It may be prudent to administer antiparasitics and vaccinations to animals in the population. Providing proper nutrition and mitigating stress will help individual immune response. Decreasing overcrowding will also decrease the pathogen load in the environment, limit new exposures, decrease stress and allow for easier animal movement. In the case of a very serious illness or one with the potential for zoonotic transmission, it may be advisable to provide empirical treatment to new arrivals or animals potentially exposed.
Recent adopters, foster parents, employees, volunteers, local veterinarians and potentially the local media need to be informed of the outbreak and given accurate information. Not providing timely, accurate information can lead to rumors and a loss of organizational reputation. Not alerting local veterinarians or other animal care facilities may lead to secondary outbreaks and further loss of life.
Step 6: Look ahead
Following an outbreak, it's necessary to review procedures and identify the factors that allowed the disease to spread. Review your shelter's procedures and protocols to ensure all measures are being taken to prevent a future outbreak. A review of the epidemiology of the cause of the outbreak may help identify areas for improvement. Protocols need to be amended as necessary, and staff training needs to be completed immediately to prevent additional outbreaks. As with every aspect of shelter medicine, prevention is the goal of these measures.
1. Hurley KF. Outbreak management In: Miller L, Hurley K, eds. Infectious disease management in animal shelters. Ames, Iowa: Wiley-Blackwell, 2009;39-48.
2. Gray LK, Crawford PC, Levy JK, et al. Comparison of two assays for detection of antibodies against canine parvovirus and canine distemper virus in dogs admitted to a Florida animal shelter. J Am Vet Med Assoc 2012;240:1084-1087.
3. Litster A, Pressler B, Volpe A, et al. Accuracy of a point-of-care ELISA test kit for predicting the presence of protective canine parvovirus and canine distemper virus antibody concentrations in dogs. Vet J 2012;193:363-366.
4. UCDavis Koret Shelter Medicine Program. Canine: Parvovirus (CPV). Available online: http://www.sheltermedicine.com/library/canine-parvovirus-cpv#8 (Accessed 2Aug2017).
5. DiGangi BA, Gray LK, Levy JK, et al. Detection of protective antibody titers against feline panleukopenia virus, feline herpesvirus-1, and feline calicivirus in shelter cats using a point-of-care ELISA. J Feline Med Surg 2011;13:912-918.
6. Mende K, Stuetzer B, Truyen U, et al. Evaluation of an in-house dot enzyme-linked immunosorbent assay to detect antibodies against feline panleukopenia virus. J Feline Med Surg 2014;16:805-811.
7. Newbury S, Larson L, Schultz R. Canine distemper virus In: Miller L, Hurley KF, eds. Infectious disease management in animal shelters. Ames, Iowa: Wiley-Blackwell, 2009;161-172.
8. University of Wisconsin School of Medicine and Public Health Video Library; Shelter Medicine Series: Canine Distemper-A Year of Outbreaks. Available online: http://videos.med.wisc.edu/uwvetmedsheltermedicine (Accessed 2Aug2017).
9. Larson L, Newbury S, Schultz R. Canine and feline vaccinations and immunology. In: Miller L,Hurley KF, eds. Infectious disease management in animal shelters. Ames, Iowa: Wiley-Blackwell, 2009;61-82.
10. Sabshin SJ, Levy JK, Tupler T, et al. Enteropathogens identified in cats entering a Florida animal shelter with normal feces or diarrhea. J Am Vet Med Assoc 2012;241:331-337.
"Shelter Snapshot" is a collaborative column between the Association of Shelter Veterinarians (ASV) and dvm360.com to help inform veterinarians and team members involved in veterinary shelter medicine and in related aspects of veterinary general practice. To learn more about the ASV and to find the “Guidelines for Standards of Care in Animal Shelters,” Position Statements on a variety of topics, and other resources, visit sheltervet.org.