There's a simple and easy way to prevent most infectious diseases from entering a herd: keep the herd closed to any new additions, any transport vehicles, all wildlife, and every other avenue a disease pathogen could take.
Since such isolation is impractical, though, the most effective way to limit the introduction of infectious diseases is to understand the potential pathways of introduction — the biosecurity critical control points — and how you can most effectively provide safeguards (Table 1). Biosecurity here is defined as infectious disease control programs that prevent or limit introduction of new diseases to an operation, as well as prevent or limit the spread of diseases within an operation.
Moreover, the Bovine Alliance on Management and Nutrition (BAMN) suggests developing an effective biosecurity plan revolves around individual producers' risk tolerance. How much risk are you willing to assume, relative to the chances a particular disease will occur in your herd, and the expected production and economic consequences of such an occurrence?
BAMN is a team producer education effort by the American Association of Bovine Practitioners, the American Dairy Science Association, the American Feed Industry Association and USDA.
To begin evaluating disease risk in order to develop an effective biosecurity program, BAMN suggests:
Develop a written risk assessment of your operation, facility and management practices. With the help of your veterinarian, identify the level of any infectious diseases already existing in your operation.
Identify and prioritize in writing the diseases targeted for control through your biosecurity program.
Assess the diseases not present on your operation and prioritize those you wish to continue to exclude. Walk through your facilities with your veterinarian to determine the risk level for disease transmission or movement, and write down a prioritized list of biosecurity obejectives.
Develop with your veterinarian a written biosecurity plan to meet your needs. Work with all your operation's personnel and advisors to implement the plan. Review and update the written plan annually.
“Movement of pathogens among groups of animals is similar to introduction of pathogens from outside the farm,” say BAMN biosecurity recommendations. “Ideally, each production class (calves, growing heifers, bred heifers, lactating cows, dry cows, etc.) should be thought of as individual management units. Direct or indirect contact among groups should be minimized or timed to have the least risk of clinical disease.”
With that in mind, effective risk management techniques include buying animals, semen and embryos from reputable sources that can document their own operations' infectious disease control programs. BAMN also suggests testing potential additions for diseases you want to keep out of your herd.
|Exposure Area||Examples||Control points|
|New additions||Cattle, semen and embryos Many infectious disease agents can be introduced to the herd by new additions. Organisms like Neospora and bovine viral diarrhea (BVD) can be introduced with apparently healthy animals. In addition, diseases with prolonged incubation times, such as Johne's disease, can be introduced with apparently healthy animals. Semen and embryos are often overlooked as a source for infectious disease agents. The artificial insemination industry does extensive work to assure semen brought into the herd is free of infectious disease agents. However, diseases like trichomonosis, BVD and bovine leukosis can be introduced with semen from sources with less stringent testing requirements. Recipients can pass BVD and Johne's to calves, too.||•Physically inspect all animals. |
•Test for diseases of concern.
•Culture milk from individuals for contagious organisms.
•Vaccinate twice, well before the stress of transport.
•Quarantine for 3 weeks before mixing with the herd.
•Buy semen, embryos or bulls from suppliers with control programs for infectious disease.
|Feeds and water|| Concentrates (corn, barley, cottonseed, canola, soybeans, etc.) Salmonella, a cause of diarrhea, has been shown to occur in some feed sources. |
Forages (corn, silage, alfalfa, oat hay, etc.) Salmonella has been shown to occur on forages irrigated with contaminated water sources, such as lagoon water. Improper harvest or storage can lead to clostridial infections.
Water (wells, ground water, lakes, streams, etc.) Contaminated water sources could result in the introduction of E. coli, Salmonella, Cryptosporidium, etc., to the herd.
|•Test water for bacterial, chemical or nutrient contamination. |
•Ask feed suppliers about quality assurance program, storage and delivery of their products.
•Prevent fecal and urine contamination of feed and water.
|Animal contacts||Fence-line |
Shared maternity/hospital pens
|•Minimize animal contact between groups. |
•Treat returning animals as new additions.
•Minimize contact with non-resident animals (fenceline contact with neighboring cattle).
| Wildlife contacts and vectors |
(organisms that can transfer infectious organisms from one individual to another)
| Rodents, birds, deer, coyotes, etc. |
Birds and wildlife can introduce Salmonella; deer and elk can harbor brucellosis, TB or anaplasmosis depending on region; coyotes can carry Salmonella and leptospirosis.
Insects: They transfer infectious agents such as Bluetongue and anaplasmosis.
Rodents: Feces from rodents can be a source of Salmonella or E. coli
|•Where possible, exclude wildlife from the premises. |
•Control pest (rodent and bird) populations and access to feedstuffs.
•Control populations of insects, birds and rodents in contact with cattle.
|Health management practices|| Animal management procedures |
Some infectious disease agents can be transmitted with small amounts of blood that might be transferred animal to animal during routine procedures. Infections with bovine leukemia virus and anaplasmosis are examples of diseases in which this method of transmission is important. Procedures like dehorning, implanting or repeated use of the same needle while vaccinating can result in small amounts of blood being transferred between animals. Though these organisms are unlikely to survive for prolonged periods on equipment, transmission can occur if cattle were processed within a short period with the same equipment.
|•Use disposable equipment (AI sleeves and needles) once, then discard. |
•Disinfect reusable equipment (tattooers, gouges, hoof tools, implant guns) between every animal.
| Fomites |
(objects that mechanically transfer infectious organisms from one individual to another)
| Transport vehicles |
Diseases transmitted by feces are a common problem in transport vehicles. In most cases, agents associated with respiratory disease (primarily viruses) would be too fragile to withstand prolonged periods in transport vehicles in the absence of the original infected and shedding animal. If the transport vehicle contains animals from another source, then this would be similar to other animal-to-animal spread such as can occur via fenceline contact or at sales and fairs.
Rendering vehicles are a concern because the animals may have died from a transmissible disease. Organisms can be transmitted to livestock or feedstuffs coming in contact with leakage from contaminated vehicles.
In some cases, poor hygiene habits of workers can result in infections of livestock with organisms such as Taenia saginata, a tapeworm that causes cysticerosis in beef cattle. Manure on visitors' boots is also a potential infection source, as is unwashed clothing of employees who own livestock.
|•Wash cattle trucks between uses. |
•Haul dead animals away from facilities for disposal.
•Restrict people access to animal facilities, order work routines from younger to older animals, provide boot and hand washing facilities, and remove heavy manure deposits from clothing before moving between groups.
•Remove manure from equipment (cattle carts, feed equipment, etc.) between uses. Do not use feed equipment for manure handling.
|Source: Bovine Alliance of Management and Nutrition: An Introduction to Infectious Disease Control on Farms|