Animal Movement and Housing
Housing and movement can have a profound effect on the likelihood of exposure of patients to pathogens. Ideal facilities have no contact between inpatients and outpatients, allow for grouping and segregation of animals with different risks for contagious diseases, prevent direct contact with adjacent animals, reduce the potential for indirect exposures through contact with contaminated environments, and have adequate space so that there is time to properly disinfect all housing and handling environments between use with different animals.
This, of course, is completely dependent on early recognition and effective management of patients with higher risks of transmitting contagious diseases.One major problem frequently encountered in large animal facilities, particularly older facilities, is that construction and design factors often hinder infection control activities. Infection control issues were often not given high priority when designing many older facilities, so a variety of problems are often encountered. These include patient traffic flow problems, requisite mixing of inpatients and outpatients, inability to segregate different cohorts in the population, heavy traffic around important areas (e.g., surgery, isolation), inadequate stall numbers, inadequate isolation facilities, poor ventilation, improper drainage, use of materials that are difficult to clean and disinfect, and design issues that hinder adequate cleaning and disinfection. A variety of challenges come with designing an optimal facility. Many measures used to enhance infection control are inherently inconvenient, and designs that optimize infection control often have a significant impact on building costs and efficient use of the facility. It can be difficult to reconcile ease of operation with the level of infectious disease risk that is desired. However, development and rigorous use of sound infection control protocols can overcome most deficits in design and construction to achieve an acceptable practice standard for minimizing HAIs.
Outpatient Areas
In general, outpatients tend to have a lower contagious disease risk, in terms of both likelihood of shedding infectious agents and their susceptibility to infectious disease. However, “lower” risk does not mean “no” risk, and it is important to design holding areas that minimize contact with other animals while clinicians obtain histories and initial examinations to more clearly categorize patients relative to their contagious disease risk. Ideally, outpatients should have little or no contact with inpatient animals and minimal contact with areas visited by inpatients. However, this is often not entirely possible. For example, it is often impractical to build separate areas for diagnostic imaging of inpatients and outpatients. However, the general principle of separation of inpatients from outpatients should be adhered to as much as possible.
Holding stalls in admission and outpatient examination areas may need to house many animals every day. As such, it is important that a sufficient number of stalls is available to allow appropriate cleaning between use, that there are established mechanisms to allow admitting clinicians to identify high-risk cases, and that this information is promptly conveyed to relevant personnel so that extra precautions can be taken with that patient and the environment with which it has been in contact. Environmental precautions may range from routine cleaning and disinfection to restricting use pending high-level cleaning and disinfection, stall cultures, or patient cultures.
Inpatient Areas
Inpatients pose greater challenges than outpatients because they often have significant risk factors for infectious disease acquisition such as comorbidity, dietary changes, antimicrobial treatment, disruption of natural defense mechanisms, surgery, and placement of invasive devices. Compromised inpatients, particularly certain patient groups (e.g., those with GI disease), may be more likely to shed infectious agents such as S.
enterica. Thus infection control protocols should emphasize the need to reduce the risk of transmission of infectious agents from inpatients to other hospitalized animals and hospital personnel and to minimize risks related to contamination of the hospital environment. A variety of methods can be used to manage this risk, which needs to be balanced with levels of risk aversion and available resources to support infection control efforts.One method of reducing the risk of disease transmission between individuals and groups (i.e., between animals in different wards or those assigned to different services) is to assign animals to different cohorts and then create physical and procedural separation among the different groups. It is important to group animals based on known or suspected infectious disease status or infectious disease susceptibility, as well as to group and separate animals with different disease syndromes (e.g., respiratory disease or GI disease). It is also logical to group and segregate animals that are managed by different clinical services in order to decrease the probability of transmitting infectious agents through indirect contact and to increase the ability to contain a cluster of infections related to one clinical service. Examples include segregating patients managed by surgery and medicine services to help reduce risks for transmission of different contagious agents and managing cattle separately from other large animal patients (especially horses) to reduce risks for Salmonella transmission. In general, managing inpatients as smaller cohorts helps to contain transmission risk, thereby decreasing the likelihood of a widespread outbreak in the entire patient population. Creating smaller cohorts of patients with different risks for contagious disease also facilitates the use of varying levels of infection control precautions for different groups.
The design of some facilities does not allow for the separation of different cohorts in different buildings or wards.
When physical separation of inpatient groups (excluding isolation cases) is impossible or impractical, animals with different disease risks can still be managed differently in a common ward system. One approach is to designate areas within large wards for different cohorts. Another is to identify animals in different risk categories, applying different levels of infection control precautions, but to allow interspersing of animals from different risk categories in the same area. This is similar to the approach for patient isolation used in most human hospitals, but it is only effective for diseases that are not transmitted by aerosols (i.e., it is not generally effective for contagious respiratory diseases such as influenza or EHV) and where there is a reasonable ability to prevent direct (e.g., nose-to-nose contact over stall walls) or indirect (e.g., cross-contamination from stall cleaning supplies) transmission. Physical separation within a ward can be enhanced by the use of chain or rope barricades to identify and minimize access to patients with elevated contagious disease risk status. A key for successful infection control using this type of system is the absolute need for prominent identification of different groups, having defined protocols for each group, and maintaining effective communication about the disease status of these patients. One system that has been used is color labels to indicate infection control status. For example, colored adhesive dots can be placed on stalls or stall cards of all patients; red dots might indicate animals with a known highly contagious disease, yellow dots might indicate that animals are suspected of having an infectious disease or may have increased risk of acquiring infectious disease, and green dots might indicate that animals are considered to have an average or low risk of carrying or acquiring contagious disease agents. This type of system is easy to apply and easy to understand. In addition, more prominent signs can be used to more clearly indicate certain concerns (e.g., Salmonella, MRSA, rabies suspect) to all personnel. One consideration with these more specific labels, however, is whether visitors could obtain confidential and sometimes prejudicial information from visible notices.Isolation of Highest Risk Patients
The most rigorous control of contagious disease hazards requires that transmission potential be absolutely minimized for patients suspected or known to be infected with highly contagious pathogens or pathogens associated with highly consequential diseases. In general, this means that these patients should have no direct or indirect contact with other animals or areas used in the routine care of patients via personnel, fomites, aerosols, or other materials. It also means that human access to these patients and their care environment should be tightly controlled. In general, to achieve this level of isolation, these patients will require housing in a separate, specially designed unit.
Most isolation protocols in large animal medicine focus on a limited number of pathogens. Protocols for large animal facilities tend to focus heavily on animals clinically affected by S. enterica, viral respiratory pathogens, and S. equi, and more recently on horses with neurologic disease because of the risks related to EHV-1. Whether these protocols are adequate or excessive for control of other pathogens is debatable, and a broader scope is likely required in many facilities. That said, protocols that reduce the risk of transmission of one agent generally reduce the transmission potential of other agents, particularly if there are similarities regarding transmission routes or risk factors for exposure and infection.
Large animal isolation protocols need to consider a variety of issues, including indicators for isolation, cleaning and disinfection, personnel movement and barrier precautions, patient contact and movement, manure disposal, and supply stocking. Defining methods for identifying animals that need to be isolated and establishing specific criteria for handling these animals are critical steps, and these methods must be properly communicated to all individuals associated with patient or facility care.
Developing protocols for rapid identification of patients that represent a contagious disease hazard is critical to the success of any infection control program. The best isolation units are not effective if unoccupied. Specific disease and syndrome criteria for isolation should be developed to facilitate prompt isolation of appropriate individuals, typically in advance of confirmation of the presence of an infectious agent. Isolated animals should be kept physically separate from the rest of the hospital population at all times if possible. This means that isolation units should be designed so that animals will rarely if ever need to leave the unit, except for an emergency procedure such as surgery. Stocks, examination areas, and scales should be available. A major deficiency of many large animal isolation facilities is the inability to use mechanical hoists and slings to safely manage recumbent, profoundly ataxic patients, which is important because of concerns regarding herpesvirus myeloencephalitis resulting from EHV-1 infections. Ideally, there should be minimal contact of personnel with isolated animals and their stall environment. The ability to monitor patients in isolation using viewing windows or by remote electronic means (e.g., web cameras, closed-circuit video) facilitates the ability to deliver excellent patient care while minimizing risks associated with direct contact.These units must be strictly managed with specific predetermined protocols in order to reliably manage the risk of transmission. Isolation protocols should be comprehensive and clearly documented in writing. Proper training of all staff, particularly lay staff that may have no background in infectious diseases and infection control, is critical. Standardized protocols for management of isolation units in human health care settings have been published by the CDC.74 However, similar standardized guidelines have not been established for veterinary medicine, and protocols used at veterinary facilities are highly variable because they are tailored to specific operations and different facility and logistic resources. It is logical for veterinary facilities to consider guidelines that have been developed at other veterinary facilities and in human health care settings when developing their own isolation protocols.
In some situations, housing of potentially infectious animals in an isolation unit is not possible because of patient care issues or limitations in isolation space. As a result, consideration needs to be given to management of higher risk patients within the general hospital environment. This can be done in a few different ways, including grouping those with general risk and applying intermediate isolation techniques to cases that are considered at higher risk of being infectious but not deemed candidates for housing in an isolation unit. In-hospital isolation protocols allow for an increased level of protection but are not a replacement for a proper isolation unit and should not be used solely for clinician convenience. Protocols should be developed regarding the handling of animals, the stall, and the area around the stall. Animals that are isolated in the hospital should not leave stalls unless they are being moved for required procedures. If movement is necessary, feet should be cleaned and disinfected using appropriately diluted chlorhexidine solutions. The potential for environmental contamination can be reduced by having a person follow the animal with a bucket to collect any feces that may be passed during transit. Traffic areas should be promptly cleaned and disinfected. Protective barrier clothing such as full waterproof coveralls or full-length waterproof gown, gloves, and dedicated footwear or boot covers should be worn for any contact with the patient or its environment. The area around the stall entrance should be considered potentially contaminated and disinfected routinely (at least three to four times per day). Disinfectant footbaths or footmats used at stall doors can reduce bacterial contamination of footwear.66-68 Attention should be paid to the pattern of water drainage from the stall and in the area. If water runs from the stall to the breezeway or runs down the breezeway past the stall, then housing potentially or known infectious animals in the stall may be inappropriate. Animals should not be allowed contact with neighboring animals. Barriers may be required if solid walls are not present on all sides. Specific protocols should be developed for cleaning in-hospital isolation stalls. These stalls should be cleaned last, personnel cleaning the stalls must wear protective gear, and items used to clean the stalls must be disinfected immediately after use.
Isolation guidelines for human medicine target the prevention of five different types of transmission: contact transmission, droplet transmission, airborne transmission, common vehicle 56 58 72 74 (fomite) transmission, and vector-borne transmission.56,
• Contact transmission is typically the most important mode of transmission and involves transmission of infectious agents to patients by caregivers or directly between patients. In large animal medicine, this could include situations such as transfer of MRSA from a colonized person to an animal under his or her care, transmission of S. equi between horses by personnel, or direct transmission of viral respiratory pathogens between horses in adjacent stalls that can have nose-to-nose contact.
• Droplet transmission involves transmission of infectious agents in relatively large fluid droplets generated by coughing, snorting, or vocalizing. These large droplets do not remain suspended in the air for long periods, nor are they transmitted long distances; therefore special air handling is not required. An example of this is transmission of bacterial agents from a coughing horse to another horse stabled in relative proximity. An extrapolation to veterinary context might also include transmission of surface contaminants during environmental cleaning processes with water under high pressure.
• Airborne transmission involves agents that can be transmitted effectively in small particles (5 μm or smaller) that can remain suspended in air and travel greater distances. Special air handling is required to control this route of transmission. Equine influenza can be spread through a barn via the airborne route over extended distances.
• Common vehicle or fomite transmission involves infection caused by contact with contaminated items such as feed bins, muzzles, twitches, thermometers, and other medical equipment.
• Vector-borne transmission involves vectors such as mosquitoes, flies, and rodents. This may be of particular concern in some areas with reportable vector-borne diseases such as equine infectious anemia.