Handling Disease Outbreaks in Animals

Investigation of disease outbreaks can help strengthen biosecurity measures and prevent future disease. Feed and water consumption and production parameters, as well as the typical sounds and behaviors of individual animals, should be carefully monitored at all times.

Any deviation from normal indicates the possibility of infectious disease, and immediate action should be taken to prevent inadvertent spread of infection.

Initial steps include setting up a quarantine of the pen, building, farm unit area, or entire farm, depending on its design and programming; designating separate caretakers for affected animals; and checking and examining sick animals last.

There are recommended steps to investigate disease outbreaks. A key aspect is to confirm the existence of an outbreak and verify what is causing the outbreak.

A working case definition might be necessary for cases that require the identification of affected individuals or herds.

Often, simply knowing that an individual or a herd has tested positive for a given pathogen is sufficient to establish cause. Such assessments might require baseline knowledge of the health status of the population before disease occurs. If a disease-causing agent was already in the population, investigating an outbreak requires identification and characterization of the agent to determine whether the outbreak was caused by an existing agent or is a new introduction.

Investigating the source of an outbreak could require traveling to the outbreak location, conducting inspections, talking to multiple parties (including suppliers), understanding animal flow, collecting samples, and conducting source tracing upstream and downstream of the population being investigated.

Results of the investigation might require implementation of new control measures and communication of findings to multiple stakeholders.

Owners should seek professional diagnostic assistance, rather than trying to hide a disease because of possible public recrimination. Veterinarians and caretakers can and should help dispel this apprehension by maintaining high ethical standards and refraining from discussing one producer’s problems with others. Sometimes, however, all producers must be apprised of a problem.

Service workers visiting affected animals should wear personal protective equipment (PPE) such as dedicated footwear and clothing when they enter the facility, and no other farm should be visited without adequate decontamination or change of PPE.

It is important to reach a diagnosis as soon as possible. The nature of the disease will determine the course of action. Although it is not always possible to treat a disease or stop its deleterious effects, identifying primary and contributing diseases is important to plan effectively for the future.

In addition to causing serious economic and emotional loss, some diseases are hazardous to humans. When zoonotic conditions are suspected or diagnosed, extra precautions must be taken to prevent the infection of attending personnel.

Notifiable diseases require that appropriate government authorities be alerted and that all in-contact personnel be carefully tracked and assessed. In some regions, certain diseases must be reported immediately to the state animal disease control authorities so that proper investigation and action can be taken to protect the affected industry.

General guidelines to help control disease outbreaks are diagrammed in the guidelines image.

General guidelines to control disease outbreaks

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Every effort should be made to ensure appropriate nursing care, which plays a key role in improving the outcome of a disease outbreak.

Therapeutic medications should be used only after the problem has been diagnosed and should be recommended or prescribed by a veterinarian.

Therapy is not a sustainable method of disease control and should not be considered an ongoing part of any biosecurity program. The herd or flock response to medication merely provides the time necessary to investigate, design, and implement further control measures to avert additional need for therapeutic medications. No drugs should be given until a diagnosis is made and a veterinarian consulted.

Sick animals should not be moved or handled until they have recovered or stopped shedding the disease-causing agent, unless the move is to a more favorable environment as part of therapy. It is important to consider that some healthy carriers might remain among apparently recovered animals.

As part of handling a disease outbreak, interventions that require the removal of all animals, the temporary cessation of replacement animal introduction (herd closure), or mass vaccinations or partial depopulations might be needed. If a disease outbreak requires mass culling, steps must be taken to prevent disease spread resulting from the number of animals being disposed of and the complex logistics required in the disposal.

Disposal can take place on-site (eg, composting, burial), or carcasses can be moved to locations such as rendering plants. There might be local, state, or federal regulations that dictate how disposal should take place. Protection of workers from physical and emotional harm should be taken into consideration.