Biological risk management (BRM) is important because of the interaction of people with animals, the animal health and economic consequences of allowing disease entry and spread, the rise in emerging and re-emerging infectious diseases, increasing globalization, and the role of the veterinarian in BRM, says Danelle Bickett-Weddle, DVM, MPH, PhD, Dipl. ACVPM Center for Food Security and Public Health, Iowa State University.

There are five main routes of disease transmission: aerosol, direct contact, fomite, oral and vector, Bickett-Weddle explained at the 2010 Western Veterinary Conference. Diseases can be spread to humans (zoonotic) by those same five routes. By implementing prevention practices for each route of disease transmission, veterinarians and animal owners can reduce their risk of common, everyday diseases entering their clinics and farms, as well as foreign animal or emerging diseases. Another advantage of this approach is that control measures for one route of transmission can minimize the risk and impact of a number of diseases.

Route Definitions

Aerosol: Pathogenic agents contained in aerosol droplets are passed from one animal to another, or between animals and humans. Most pathogenic agents do not survive for extended periods of time within the aerosol droplets and close proximity of infected and susceptible animals is required for transmission

Direct contact: A susceptible animal becomes exposed through physical contact when the agent from an infected animal or the environment enters open wounds, mucous membranes, or the skin through blood, saliva, nose-to-nose, rubbing, or biting another animal. Some disease agents can spread between animals of different species, as well as to humans.

  • Subtype: Reproductive—Diseases spread through venereal contact (from animal-toanimal through coitus) and in-utero (from dam to offspring during gestation).

Oral: Consumption of pathogenic agents in contaminated feed, water or licking/chewing on contaminated environmental objects. Feed and water contaminated with feces or urine are frequently the cause of oral transmission of disease agents. Contaminated environmental objects could include equipment, feed bunks, water troughs, fencing, salt and mineral blocks, and other items an animal may lick or chew.

Fomite: A contaminated inanimate object transmits a disease agent from one susceptible animal to another. It involves a secondary route of transmission (direct contact or oral) for the pathogen to enter the host. Examples include contaminated shovels, clothing, bowls/buckets, brushes, tack, and clippers.

  • Subtype: Traffic—Vehicle, trailer, or human causes the spread of a pathogenic agent through contaminated tires, wheel wells, undercarriage, clothing, or shoes/boots by spreading organic material to another location.

Vector-borne: An insect acquires a pathogen from one animal and transmits it to another either mechanically or biologically. Mechanical transmission: disease agent does not replicate or develop in/on the vector; it is simply transported by the vector from one animal to another (e.g., flies). Biological transmission: vector takes up the agent, usually through a blood meal from an infected animal, replicates and/or develops it, and then regurgitates the pathogen onto or injects it into a susceptible animal. Fleas, ticks, and mosquitoes are common biological vectors of disease.

Zoonotic: Diseases transmitted between animals and humans. Human exposure occurs through one of the previously listed five main routes of transmission (aerosol, direct contact, fomite, oral, and vector-borne).It is a separate route of transmission due to its importance.

For more information and detailed resources for infection control and BRM for livestock, companion animals and veterinarians, click here.