Common sense biosecurity steps help keep organic livestock healthy
By Jen Burton, DVM, and Guy Jodarski, DVM
The recent outbreak of highly pathogenic avian influenza (HPAI) affected conventional confinement poultry farms to a much greater degree than organic operations. Because organic methods leverage synergies between soil management, forage quality, nutrition and animal health, organically managed animals are primed to resist invasion by disease-causing pathogens—but that doesn’t mean we can be complacent in the face of serious illnesses like HPAI. As veterinarians serving organic livestock farmers, we have experienced severe disease outbreaks on several farms. Poultry, dairy and beef cattle, small ruminants, and swine can and have become ill on farms under organic management. The origin of these events often traces back to a breach in biosecurity practices.
Prevention of infectious disease is a matter of keeping the host’s immune system ahead of environmental challenges. Organic methods do a great deal to provide advantage to the host. To get the most out of organic management efforts, though, livestock farmers should examine current practices regarding biosecurity and consider the risks inherent in the way they manage their operations. Many procedures and practices for preventing the introduction and spread of disease to groups of animals are inexpensive and follow a common sense approach. Biosecurity is not something to dread, nor does it have to be complex or difficult to implement. It involves attention to detail and due diligence at all times but, once one gets in the habit of exercising good biosecurity, the effort involved is not taxing.
As with any management strategy, biosecurity actions make sense when the benefits outweigh the costs. Sensible biosecurity addresses legitimate risk. Two questions should come to mind when assessing risk: how likely is the undesirable outcome, and how bad would it be if it happened? We tend to put our efforts into preventing diseases that are both very common and very bad. Frequently underestimated, however, are those diseases that are either widespread or potentially ruinous, but not both. This includes moderate diseases, common enough that one may begin to accept their negative impacts as normal or expected, even though significant losses accumulate over time. It also includes diseases that are devastating, but so rare they “probably won’t happen to me.” Sadly, management changes may come too late to prevent disaster once a devastating disease is recognized in your region. It is in these two areas—common-moderate and rare-ruinous disease—that we see the most room for significant improvement.
If you are monitoring animal health and productivity, you are more likely to notice changes that could be related to these types of disease. Thoughtful management at key points in the movement of animals and people can greatly reduce your losses and risks, and prevent you from becoming a risk to others.
Movement of Animals
In order to choose biosecurity practices that will provide the most benefit, it’s important to have a basic understanding of common diseases for the type of livestock you have, to know whether your current farm is free of the disease-causing agent or not, and to have some idea about the likelihood of exposure from neighboring farms, farm traffic, or wildlife. Exposure of the flock or herd to new, potentially disease-carrying animals increases disease risk.
Testing animals for disease before purchase and movement to your farm is a good practice and is required to move animals across state borders. An accredited veterinarian must inspect the animals, do the required testing and complete an interstate health certificate prior to sending animals to an out-of-state destination. The requirements for testing vary with species and differ depending of the state of origin and ultimate destination for the animals. A local veterinarian can assist you with completing this process.
Even when testing is not required, it can be extremely useful. For example, cows carrying the mastitis-causing bacteria Staphylococcus aureus may not show any signs of disease. However, the bacteria can be transferred to other cows by equipment at milking time. Cows that develop Staph aureus infections can be difficult to cure, eventually leading to significant losses. Testing milking cows for Staph aureus infection before buying them is a good practice if you are unsure whether the herd of origin or individual cows may be carrying this infection.
We often talk about having a “closed herd” to minimize exposure to disease-causing organisms —bacteria, viruses or parasites—being carried by infected animals. A truly “closed” herd raises all of its own replacement animals, never takes animals to shows or fairs and uses male breeding animals raised on the farm or artificial insemination for breeding. Farmers often overlook the purchase of breeding males as a potential carrier of disease. Dairy farmers, for example, frequently say they keep a closed herd and forget the fact that they purchase bulls for breeding. There’s nothing wrong with bringing in new animals to provide genetic diversity or improvement; it’s the way new additions are brought into the operation that’s important.
The introduction of new animals to a farm should include a period of isolation from the herd or flock during which the newly acquired animals are observed for disease problems. Ideally these animals would be kept in facilities away from the main herd for a period of three to four weeks. This quarantine period allows time to make sure the new animals are healthy, and provides the opportunity to complete testing for specific disease and/or vaccination if these procedures weren’t done prior to moving the animals.
An alternative approach to quarantine is to practice “all in, all out” management. Egg farmers often do this with laying hens—culling the entire flock of birds in a building after they reach an age when production has declined. Facilities are cleaned out, disinfected, allowed to remain empty for a period of time and then restocked for the next production cycle. This periodic emptying, cleaning and disinfection of a building breaks the chain of infection from disease-causing germs. The principle can be applied on a smaller scale on other livestock farms. We have seen dairy farms that provide individual pens for calving inside during winter. Each cow and newborn calf are provided with a pen that’s been completely cleaned out and disinfected prior to the cow giving birth. This breaks the cycle of exposure to bacteria like E. coli and viruses such as coronavirus that cause calf scours.
Limiting contact with other animals is an important strategy to consider if wildlife in your region carry infectious organisms that are likely to affect your livestock. As organic farmers, we consider the complex interactions between species in an ecosystem to be important. We value diversity and “being in touch” with soil, plants and animals, working to promote harmony and synergy between all members of an ecological community. Keeping animals confined (as in the case of HPAI “bird flu”) goes against our nature as it probably well should. If wildlife disease in your area becomes a significant concern for your animals, you may be able to reduce risks to an acceptable level by removing clutter and cleaning up feed storage areas to minimize rodents, managing outdoor access areas and planning grazing rotations with consideration for wildlife migration patterns and life cycles.
Vaccination is another important biosecurity practice. It does more than just protect the animal receiving the injection. By reducing the number of pathogens that animal sheds into the environment, vaccination helps prevent disease in other herd members and reduces the odds that people or animals will spread the pathogen to other areas. For example, bovine virus diarrhea (BVD) is very common in cattle, and is easily transferred by infected animals or people who move between farms after working with or being near cattle. Regular vaccination for BVD can be an important tool in a biosecurity program that considers neighbors as well as one’s own farm.
Movement of People
People who work in agriculture transport pathogens on their boots and outerwear, on vehicle tires or in footwells, in their hair and even in their nostrils. Whether you’re moving between farms, or between the sick pen and the rest of the herd on your own farm, the following guidelines can minimize the risk that you will help pathogens do their dirty work:
- Visit the cleanest sites first and dirty sites last whenever possible.
- Carry clean coveralls and disinfected or disposable boots.
- Wear a light nylon shell alone or over a regular coat if needed.
- Remove and bag dirty boots and outerwear (inside out) before entering your vehicle.
If you suspect contact with a pathogen that could cause serious harm, the safest course of action is to launder all outerwear, shower, and minimize farm contact for a day or two. While this is seldom considered practical, it’s good to be aware of the “gold standard” course of action, so that any deviation from that best practice can be done thoughtfully.
Neighbors and visitors can do their part by using common parking areas, away from farm-related traffic, and by staying out of animal areas unless there is a need to enter those areas. Some callers may wish to act appropriately, but lack knowledge about biosecurity or about specific pathogens present in your area. A biosecurity sign with simple instructions to clean boots and avoid animal areas can provide guidance for those individuals and help prevent trouble.
Disinfect Boots, Vehicles and Equipment
Disinfectants should be chosen for effectiveness against the target organisms in the environment in which they’re used. Other considerations include safety, convenience, environmental impact, and cost. In many cases, basic cleaning removes most of the infectious agents present, and disinfection simply finishes the job—so it’s important to clean regularly with soap or detergent, in addition to using the right disinfectant. (See the chart on page 14 for help choosing a disinfectant.)
Oils and organic materials such as dirt, feed or manure can extend a pathogen’s lifespan from hours or days to months or even years. Such substances provide a safe haven for bacteria and viruses, protecting them from chemicals, sunlight, and dessication. Organic material can also deactivate many disinfectants. It is critical to remove grease and organic material before applying most disinfectants! At the same time, some disinfectants are inactivated by detergents or other chemicals, so it’s also important to rinse away other cleansers before disinfecting.
When mixed at an appropriate concentration—about 1 cup of 5.25% commercial bleach per gallon of water—bleach is one of the most practical and efficacious disinfectants for footwear. Its broad-spectrum effectiveness is not reduced by temperature, humidity, or hard water. Bleach is quickly rendered ineffective by evaporation or contamination with organic matter, so it should be mixed just before use, and boots should be cleaned before it is applied.
While the bleach solution described above is appropriate for disinfecting boots, its short effective lifespan and deactivation by organic matter makes it a mediocre choice for use in a boot bath. Phenolic compounds tend to be preferred because they remain a bit more robust as the bath inevitably becomes contaminated with dirt and manure. Even so, boots should be cleansed of organic matter prior to entering the bath, and the solution must be changed every 1 to 3 days to remain effective. While a boot bath can be a useful part of good farm biosecurity, it should not be the primary method for addressing dirty boots.
For passenger vehicles, tires are a primary biosecurity concern. A pressure washer may be needed to remove gross dirt and manure from treads. The entire vehicle should be washed with detergent before disinfectant is applied. Environmental impact of runoff is a significant factor when cleaning vehicles, and iodophores (iodine-based products) tend to be used for this application. When washing and disinfecting a vehicle, be sure to include the undercarriage.
While the products suggested are accepted in organic production for the general uses described here, it is recommended that you check with your certifier before using any product in a new way.
Best Management Practice: Adaptation
One aspect of organic farming that’s important to remember is each region, farm and year are unique—we shouldn’t expect to have protocols, practices or a strict set of rules that apply in all situations. This reality gives some farmers much discomfort as they search or long for “best management practices” that can be blindly followed. Instead, good organic farmers stay in touch with changing situations and adapt their efforts to balance what they are experiencing, with basic principles as their guide. Each of us must strike a balance between the extremes of livestock totally confined, isolated or controlled and being totally open, allowing unlimited access to the animals and free flow of all types of pathogens.
As we watch for changes in animal health and productivity that could help shape bio-security practices, we have many tools at our disposal to help reduce the risk of disease transmission by either limiting exposure to pathogens or building resistance in our animals through genetics, nutrition, vaccination and stress reduction.
Dr. Jen Burton and Dr. Guy Jodarski are veterinarians with Organic Valley/CROPP Cooperative.
From the July | August 2015 Issue