Written by Nathan M. Slovis | DVM, DACVIM, CHT Hagyard Equine Medical Institute

At a training facility, you may have animals arriving that are traveling to shows locally as well as nationally. These clients’ animals may have been exposed unknowingly to infectious pathogens. The aim of a good biosecurity program is to prevent the dissemination of these pathogens. In order to prevent the dissemination of disease at your facility, you first must understand the pathology and disease course for the pathogen in question. Second, educate your barn staff about diseases and the importance of hygiene.

As veterinarians, we need to be able to optimize rapid containment for business continuity. Rapid containment will require criteria to identify a sick equid and the trigger points warranting the response for isolation. General recommendations to consider for designation as a response trigger for isolation include:

• Body temperature greater than 101.5ºF (38.6ºC)
• Ataxia or recumbency or other neurologic signs
• Passage of frequent loose feces
• Oral or coronary band vesicular or ulcerative lesions
• Nasal discharge, coughing, and/or lymphadenopathy
• Limb or ventral abdominal wall edema, especially if it occurs in multiple horses

Veterinarians will need to be prepared and have a plan in place should the need for testing become necessary. For example:

• Having the necessary supplies available to promptly implement containment protocols can limit the spread of disease
• Being prepared to perform exams and collect samples
• Communicating with the laboratory regarding protocols for the collection of appropriate samples and shipping prior to testing

The Equine Disease Communication Center’s website has recommendations for an Isolation Plan including forms on how to do an assessment and developing a detailed plan including supplies for setting up isolation. Implementation of biosecurity protocols will come at a cost, and decision-makers at all levels will require convincing of its importance.

To be successful, it will depend on getting buy-in from all those who have a role in caring for horses and in/on the facility. Education and incentivizing implementation of good biosecurity practices show your commitment to business continuity.

• Remember to lead by example
• Disinfect your hands between horses or use personal protective equipment (PPE) when necessary
• Disinfecting our equipment after use is just one example of how to reduce the risk of an outbreak

Disease spread can vary on the location, pathogen, horses’ housing, and people. This article will go over a variety of causes for dissemination of disease including how equipment can move pathogens if not cleaned between uses.

DISEASE PREVENTION

Disease prevention and control activities for infectious agents occur at four levels:

• Individual
• Institutional
• Community
• Global

The first level known as the individual is predominantly the domain of the primary provider. A variety of prevention strategies can be targeted to individuals through their primary provider. One example is the use of chemoprophylaxis in order to help prevent surgery site infections.

The second level is that of the institution which is the domain of the infection-control practitioner or the school health official. This level would include veterinary hospitals, pet boarding facilities, human health care facilities, nursing homes, other human residential facilities, and schools.

Programs to prevent the spread of fecal, respiratory, and blood-borne pathogens to healthcare workers or patients are examples of control strategies targeted at the institutional level. The third level is targeted to the community (in general) and is predominately the domain of public health agencies (local, state, and national levels). The removal of dead animal carcasses after a hurricane is an example of a control measure targeted at the community.

The fourth level is related to global strategies. For a number of important pathogens, it has become evident that global control strategies are critical to have an impact on disease occurrence within the U.S. An example of this is the global strategies for Bovine Spongiform Encephalopathy. Although some control measures are specific for each one of these levels, a substantial overlap can occur. For instance, immunization programs operate at all four levels.

The transmission of infectious agents requires three elements: a source (or reservoir) of the infectious agents, a susceptible host with a portal of entry receptive to the agent, and a mode of transmission for the agent.

Identification of areas or processes where transmission of pathogens is likely to occur (control points) and implementation of measures aimed at minimizing the possibility of such transmission, while allowing for reasonable flow and function within the veterinary hospital or animal facility, is an important component of biosecurity.

During the assessment and development of the prevention and control activities targeted to infectious diseases, the weakest link in the chain of infection (agent, transmission, host) needs to be considered for each specific pathogen.

In some situations, control of the agent in a specific reservoir may be the best way to reduce disease occurrence. The chlorination of water is an example of destroying an agent in its reservoir or eliminating a possible mode of transmission.

Strategies aimed at the level of transmission need to be tailored to the type of transmission involved. An example of a control activity targeted to airborne transmission is the isolation of the animal to a facility where there is no shared airspace or is located on premises where no other animals are currently housed.

The control of vector-borne transmission can be targeted toward destroying the vector and towards the use of repellents. In many instances, the best mechanism to prevent disease occurrence is through modification of the host, such as developing or boosting immunity through active or passive immunization. Other control activities targeted to the host may include improving the nutritional status of a neglected animal or providing chemoprophylaxis against a variety of agents.

Every effort should be made to minimize the contact between animals with a history or clinical signs suggestive of infectious contagious disease or those with a confirmed contagious disease and the remainder of the patients or animals at a boarding facility.

Before implementing disease prevention and control strategies, several issues need to be considered which include risk, feasibility, cost, and effectiveness. Risk can be defined by the potential for exposure.

Epidemiologic studies or analysis of surveillance data can serve to define animals at risk and can also quantify risk within different populations. Information that is needed for making the optimal decisions regarding the risk posed would include a history of the arriving animal, history regarding contact of the arriving animal with other animals having a contagious disease, pertinent laboratory testing performed prior to arrival, physical findings on initial examination of the new arrival and pertinent laboratory tests results if available at arrival or soon thereafter.

To help better understand the risks of the animal to disseminate a disease there is a need to know the past disease status and exposure status in order to best implement targeted control measures for contagious disease.

Admittance-based alert systems to notify infection control and clinical personnel about readmitted or transferred patients with a history of infection or colonization, and routine assessment of education and training among personnel, can improve infection prevention at the facility level.

One such mechanism would be self-certification by the owner or representative of the animal. The owner/authorized caretaker/transporter would sign a form and state the history of the animal in relation to exposure to a specific disorder. The reason for such self-certification is the inability to establish risk level without this type of information as those receiving the animal would have no mechanism to gather this information other than through self-certification for animals that have no overt signs of disease at the time of presentation to the facility yet the animal could have had exposure to contagious disease agent that would pose a substantial risk to other animals in the facility if not managed accordingly.

Risk adjustments require the collection of pertinent information (e.g., salmonella in hospitalized patients, surgery site infections, etc.) about the total population being monitored so that objective data can be used to help direct decisions being made regarding risk assessments. These risk adjustments are important because policies and procedures will need to be updated based on these findings.

In developing control programs, the feasibility of a strategy also needs to be assessed. Feasibility is dependent not only on sociodemographic factors but also on the operating needs of the facility. For instance, there may be equine facilities that buy and sell horses on a routine basis and will accept the risk of contagious disease outbreaks, such as Streptococcus equi, as the option to prevent exposure in newly arrived horses is not an option. Cost and the availability of resources also need to be considered when developing control strategies.

Implementing and maintaining even the most basic biosecurity program requires a trained and adequately staffed facility with appropriate supervision. Outbreak investigations have indicated an association between infections and understaffing; the association was consistently linked with poor adherence to hand hygiene. For example, the understaffing of human nurses can facilitate the spread of MRSA in intensive-care settings through relaxed attention to basic control measures.

Finally, control strategies need to be evaluated for their effectiveness. For example, the effectiveness of the control strategy is a critical issue in evaluating ways to curb salmonellosis in equine care facilities. Cost-effectiveness models are often used in making recommendations for population-based vaccine programs. Challenges to prevention include measurement of outcomes that may be complicated by diagnostic limitations, for example, diagnosis of ventilator-associated pneumonia in humans.

PREVENTION STRATEGIES

Prevention strategies for infectious diseases can be characterized by using the traditional concepts of primary, secondary, or tertiary prevention. Primary prevention will be defined as the prevention of infection by personal and community-wide efforts.

Secondary prevention includes measures available to individuals and the population for the detection of early infection and effective intervention. Tertiary prevention consists of measures available to reduce or eliminate the long-term impairment and disabilities caused by infectious diseases.

Primary Prevention
An example of primary prevention is immunoprophylaxis, which can be classified as active or passive.

Active immunoprophylaxis involves the administration of all or part of the microorganism (bacterin) or a product of the microorganism (toxoid) to alter the host by stimulating an immune response aimed at protecting against infection. Active administration is also used in post-exposure situations including immunization after exposure; for example, tetanus. Some of the vaccines may be given in conjunction with an antitoxin in the postexposure setting.

Passive immunization involves the administration of preformed antibodies, often to specific agents, after exposure. The most common forms of passive immunization may be hyperimmunized plasma for a foal with failure of passive transfer or botulism-hyperimmunized plasma.

A second type of primary prevention is antimicrobial prophylaxis often referred to as chemoprophylaxis. The use of effective chemoprophylaxis requires that the infectious agent be susceptible to the antimicrobial used. When used as a primary prevention the medication may be used before or after exposure in order to prevent infection.

Examples of chemoprophylaxis in the post-exposure setting include Rhodococcus equi( e.g. Azithromycin), Clostridium perfringens enterocolitis (e.g. Metronidazole), and Equine Herpes Type 1 Abortion or Neurological (e.g. Valacyclovir). Prophylaxis against surgical wound infections with broad-spectrum antimicrobial coverage before surgery is an example of chemoprophylaxis in a hospital setting.

In many situations, chemoprophylaxis is used because the likelihood of exposure to pathogenic organisms is present, even though proper documentation of exposure is not clear.

Secondary Prevention
Secondary prevention activities entail chemoprophylaxis and involve the identification of early or asymptomatic infection with subsequent treatment so that infections are eradicated, and the sequelae are prevented. Although most secondary prevention programs involve intervention at the individual level through the use of chemoprophylaxis, such programs often operate within the context of population-based or institutional-based screening efforts.

An example of secondary prevention would be the use of procaine penicillin or ceftiofur on horses that test positive for Streptococcus equi on a nasopharyngeal screening wash during a farm outbreak of the disease.

Factors To Consider When Selecting Hand Hygiene Products and Protocols
When evaluating hand hygiene products for potential use in health care facilities one must consider factors that can affect the overall efficacy of such products. Studies indicate that the frequency of handwashing or antiseptic washing by personnel is affected by the accessibility of hand hygiene facilities.

It is not uncommon to see some facilities have only one sink available in areas housing many patients or sinks located far away from the patient, which will discourage handwashing by personnel. In contrast, the availability of alcohol-based hand rubs does not require plumbing and can be made available adjacent to patient housing and at many locations in patient care areas.

Failure to perform appropriate hand hygiene is considered the leading cause of healthcare-associated infections and the spread of multi-resistant organisms and has been recognized as a substantial contributor to outbreaks.

Of nine hospital-based studies of the impact of hand hygiene on the risk of healthcare-associated infections, the majority demonstrated a temporal relationship between improved hand hygiene practices and reduced infection rates.

Isolation vs Quarantine
You have diagnosed an infectious agent on the property and now you must decide if isolation and quarantine are necessary. What are the differences between isolation and quarantine? What criteria do you use to determine isolation? Why should you quarantine? How long should you isolate? What horses should be quarantined?

Horses may be quarantined if they have had direct or indirect exposure to a sick horse. Indirect exposure would include stabling, personnel, and equipment. The duration of the quarantine depends on the mode of transmission, survivability, and incubation period. Some guidelines for an isolation/quarantine facility.

• The duration of quarantine should, at a minimum, be the incubation period and duration of transmission
• Horses should be moved to an isolation facility if they are sick with a known or presumptive infectious disease
• They would be moved to isolation as soon as they have the first clinical sign

This post was written by FVMA Communications Team.