Merck Manual

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Professional Version

Handling Disease Outbreaks in Animals


Montserrat Torremorell

, DVM, PhD, Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota

Reviewed/Revised Feb 2021 | Modified Nov 2022

Feed and water consumption and production should be carefully monitored at all times, as well as the typical sounds and behaviors of individual animals. 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.

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. Yet, there comes a time when all producers must be apprised of a problem. Service workers visiting affected animals should wear protective footwear and clothing when they enter the facility, and no other farm should be visited without adequate decontamination.

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. Veterinarians should be aware of the owner’s economic plight and render advice and assistance as quickly as information is available or a judgment can be made.

In addition to causing serious economic and emotional loss, some diseases are hazardous for people. When zoonotic conditions are suspected or diagnosed, extra precautions must be taken to prevent 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.

Every effort should be taken to ensure appropriate nursing care, which plays a key role in improving the outcome of a disease outbreak. Therapeutic medication should be used only after the problem has been diagnosed and recommended/prescribed by the veterinarian. Therapy is not a sustainable method of disease control and should not be considered an ongoing part of any biosecurity program. The flock response to medication merely provides the time necessary to investigate, design, and implement further control measures to avert additional need for therapeutic medication. 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/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 may remain among apparently recovered animals.

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