Editor’s note: The following are excerpts from the booklet “Prevention: Keeping Animals Safe and Healthy.”

External biosecurity – avoid bringing pathogens to your animals

Ways pathogens spread

In order to prevent the introduction of pathogens, one must understand how pathogens find their way onto livestock operations. The spread of pathogens is primarily caused by the movement of animals, people and contaminated equipment. Therefore, you can help prevent the spread of pathogens by controlling the movement of people and animals and avoiding contact with any potentially contaminated equipment or objects.

Controlling animal movement and contact

The easiest and most frequent way to transmit a pathogen is for an infected animal to come into contact with a healthy animal. Most disease is transmitted nose-to-nose or by other direct contact with sick animals. New additions to herds are a very common way to introduce pathogens. Stray pets that wander onto your farm or land can be another source of pathogen transmission. If a sick animal is allowed into a show or fair, it may infect other nearby animals. In addition to stray pets, wild animals, free-flying birds and insects can be responsible for the introduction of a pathogen.

People movement

People, vehicles, equipment and clothing in contact with an infected animal may be contaminated with pathogens. These contaminated articles (scientifically referred to as fomites) include equipment, machinery and other objects used for the transportation, care and management of livestock (i.e., halters, combs, brushes, water buckets, pitchforks, trucks, crates, boxes, etc.).

Does that mean that we cannot take an animal to a show? Can we even buy new animals? Yes, you can purchase animals and go to the fair, but you should isolate those animals when you return. The wisest decision is to choose shows and make livestock purchases from places where disease prevention is always given high priority.

Practical steps that improve isolation

Isolation (a form of quarantine) prevents contact between animals within a controlled environment. The idea behind isolation is to prevent contact between healthy animals and an animal that is or could be infected with a pathogen. Animals new to the herd or flock should be isolated away from the rest of the herd or flock for at least four weeks. Always isolate sick animals and only return them to their original group when they’ve fully recovered.

Livestock returning from fairs or shows should also be isolated, since they could have picked up a new pathogen at the show. After returning to the farm, isolate your show animals to avoid the possibility of infecting other animals on your farm. Ideally, this should be in a completely separate place to avoid close contact. At minimum it could be a separate pen in a different building or at least a separate corner of the barn. This may represent some extra work, but it can be very important.

Isolate all purchased animals for four weeks. If they are incubating a serious disease, the signs (i.e., diarrhea, hard breathing, etc.) of that disease will likely be observed in that four-week isolation period. This gives you some time to do follow-up testing or give booster vaccinations if needed.

Always purchase good, healthy animals. Do not buy sickly animals, even if they are being sold for a “cheap” price. Livestock at bargain prices can be expensive!

Since people can carry pathogens on their body or clothing, it is necessary to control the visitors that may come in contact with your livestock. Always make sure visitors wear clean boots and clothing. It is best if visitors come only when you are there to escort them around your farm. Locked gates and doors will keep people out when you’re not around. Signs and notices help to alert visitors of the potential risk that they may pose. Perimeter fences will keep people from accidentally wandering onto your property. Question visitors about the farms or animals they have visited or have been near recently, and ask if they have visited a foreign country within the past five days.

There are ways to help keep out wild animals, free-flying birds and insects. Although it is impossible to totally prevent all contact between wildlife and our livestock, we can make barnyards and surroundings unattractive to many of these species.

Cutting the grass and weeds around the outside of buildings will help prevent rodents from entering. Keep grain spills or other potential sources of food cleaned up and unavailable to wildlife. Clean up old board piles or woodpiles and inspect buildings for possible hiding or denning areas. Inspect the haymow or other protected areas for evidence of cats, raccoons or other animals likely using the hay or the straw for nesting areas.

Store feed where wild animals, including rodents and birds, cannot make contact with it. Dispose of all waste feed in a way that will not attract pests. Maintain barns and buildings in good repair, making it more difficult for animals or birds to gain access. Keep doors and windows shut when not needed for ventilation. Place screens or netting on the windows.

Location and construction of buildings

When planning the location of a barn or building used to house your livestock, isolation is key. The buildings or pens should be constructed to promote isolation from outside sources of disease. The facility should be a substantial distance from road traffic. It is important to consider possible exposure and the distance from other herds or populations of domestic or wild animals. It is especially crucial there is no nose-to-nose contact with other animals. There should not be any contact with drainage water or waste runoff from other animals.

Separation of species and ages

When planning the organization of either a large- or small-scale animal operation, the risk of disease can be greatly reduced whenever you keep different species and ages of the same species well separated. This is because pathogens producing little or no disease in one species can produce significant disease in another species. Mild infections in older animals can produce severe disease in young animals.

Disease susceptibility within the same species varies with age. Because they have acquired resistance, older animals may shed pathogens without getting sick themselves. These same pathogens can be serious to younger animals.

Various ways may be available to achieve species and age separation. They will be different depending on many factors such as the value of the animals, the economic and labor resources available to the herd owner and other factors such as farm size and marketing opportunities. They may include separate buildings, separate pens, different caretakers or, ideally, separate premises for different species and ages.

Internal biosecurity – avoid bringing your animals to pathogens

The farm environment can be a very comfortable place where pathogens can survive and multiply. Animal buildings, barns and pastures, as well as manure surfaces, are often damp environments favorable for a dangerous increase in pathogen populations. Depending on the number of animals, very large accumulations of manure may develop and become areas where pathogens can survive and multiply for many weeks or months.

Sanitation

How can you avoid bringing your animals to pathogens? The best way is to maintain a clean, dry and sanitary environment. Cleaning is very important in reducing pathogen levels. Cleanliness means freedom from dirt, filth and debris. Although buildings and equipment can appear clean when they are not visibly dirty, many microscopic contaminating pathogens can continue to be present. They remain and survive by clinging to surfaces and by hiding in tiny cracks and crevices. The use of a disinfectant kills these remaining pathogens.

Reducing the amount of pathogens around your animals will decrease the risk of disease. Disinfectants are chemical agents that kill pathogens on contact. However, it is important to clean before disinfecting so the pathogens become fully exposed to the disinfectant. Pre-cleaning is doubly important because a disinfectant can be used up or inactivated by dirt.

Disinfection and thorough, prompt drying are the last steps in the sanitation process. Without quick, thorough drying, any pathogens surviving the effects of the disinfectant can re-multiply to high numbers.

Hygienic manure management

Animal body wastes (feces, urine, etc.) ordinarily accumulate right in the environment (surroundings) where the animals spend most of their lives. This ordinarily unavoidable problem for animals is partially reduced when manure is managed in a way that at least lowers the level of exposure to potential pathogens. Accumulated manure must be managed to reduce its volume, its odor and to kill pathogens and weed seeds.

The essential parts of manure management include collection, transfer and storage. Spreading manure onto fields is the most common method of disposal. The sun will dry manure after it is spread onto fields which will kill many pathogens. A proper level of airflow over manure surfaces promotes drying and the decrease of many pathogen populations. In contrast, stagnant air contributes to the buildup of moisture and an increase in pathogen populations.

Chemical treatments can be beneficial in manure management. Raising the pH to at least 12 for 30 minutes will kill most of the microorganisms present. Lime is usually used to raise the pH. Treatments that produce anaerobic conditions (very low oxygen) are also used. Anaerobic lagoons take advantage of a natural process where manure is digested by beneficial anaerobic bacteria. In contrast, aerobic lagoons add oxygen to the manure. The addition of oxygen allows more common bacteria to survive and multiply and for the bacteria to break down the waste material. These bacteria convert the manure into carbon dioxide, water and more beneficial lagoon bacteria.

In animal pens or holding areas, we want the bedding and floor dry. Management of areas where water spillage or water accumulation is highest is very important. Good drainage and proper ventilation of buildings will help reduce the dangers of dampness. The frequent removal of wet bedding and a continuous, modest flow of air over manure surfaces will help to produce the drying needed to suppress bacteria.

Threats to animal health from the visible to the invisible

Animals may be injured or die from the attacks by something as large and dangerous as a coyote or wolf to something just as dangerous, but only as small, as a molecule. It ranges from dangers that are visible to the naked eye (predators), to some that are more easily seen with a hand lens (internal and external parasites), to some that can only be seen with a microscope (bacteria and viruses).

Predators

We know that disease-causing pathogens we cannot see threaten our livestock. In addition, there are also other threats that can be easily seen. Predators may easily be detected; however, many often appear at night or when people are not around. There are ways to help keep out predators that could potentially physically attack and harm your animals.

First, remove all easily accessible food supplies. This may be very difficult depending on the size of the farm and the amount of livestock feed on-hand. Keeping feed bins in good repair and sealed off will help prevent predators from entering areas where feed is stored. Keeping feed bins and feeding areas clean is very important. An accumulation of waste feed in and around feedbunks attracts animals.

Another suggestion is to modify habitat and reduce access. Clearing brush and keeping weeds away from barns and buildings will help deter animals just like it will help deter rodents. Finally, you can trap or control predators.

Barns and buildings should be kept in good repair. Predators often enter barns through open doors or cracks and holes that may exist. Closing doors and patching cracks and holes helps to reduce the problem. Wire mesh or screening on windows can also help.

External parasites

Small yet visible threats to livestock include external parasites such as ticks, flies, fleas, lice, mosquitoes, mites, grubs, etc. Parasites are a threat to livestock health just as microbial (invisible) pathogens are a threat. Parasites can transmit and spread microbial pathogens in addition to the harm and damage they naturally cause by irritating animals and sapping their energy.

The most common way to control external parasites is through the use of pesticides or insecticides. Pesticides kill and help control the parasite populations. Pesticides are applied as sprays, dips, pour-ons, dusts, injectables, pastes, boluses, etc. Ear tags impregnated with insecticide are commonly used in cattle.

Pesticides are very effective; however, pesticides alone will not control a threat such as flies. Keeping the environment clean and sanitary helps eliminate fly breeding areas. Manure management will help reduce fly breeding areas. Fly eggs and larvae in thinly spread manure are killed by drying and heat.

Internal parasites

Livestock can be attacked by a variety of large and small wormlike parasites such as roundworms and tapeworms. These internal parasites mainly invade the digestive passages while some also infest an animal’s breathing passages. Other parasites can go even deeper into the animal body reaching various vital organs and body tissues.

Most parasites enter an animal’s body when the animal eats the egg (ova) or an early life stage of the parasite. These ova or intermediate life stages come from the adult parasite reproducing and living inside an animal. They are typically passed by way of animal droppings onto the ground or into the bedding. As a result, an effective preventive strategy for many internal parasites rests on keeping animals from eating feed or licking surfaces contaminated by animal waste. It is a wise practice to keep animal yards, pens and buildings or other concentration points as clean from urine and accumulated fecal material as is practicable.

Various powerful chemicals are sometimes used to treat different types of infestation. Their improper or inappropriate use may produce more damage to your animals than would be done by the parasites alone. Consequently, it is best to seek guidance from your local veterinarian before you treat for worms. In the final analysis, prevention is often less expensive than treatment.

Bacteria and viruses

Bacteria and viruses are visible only when they are magnified hundreds to many thousands of times. They are not only able to attack the skin and digestive tract or respiratory linings of an animal’s body, but they are often able to devastate the entire body including such organs as the brain, heart, liver and spleen. Their extremely small size makes it possible for these pathogens to survive long periods of time outside an animal’s body. They can survive in fur and hair, in nasal and other discharges from a sick animal and in animal urine and fecal droppings.

Viruses survive, and bacteria can actually multiply, in animal bedding and manure. Many survive long periods of time in the tiny particles of dust or soil present in the farm environment. With many tiny, scattered hiding places they can easily be carried to a new farm or group of animals riding on a person’s clothing, on the surfaces of boxes, crates or equipment and on the wheels of cars and trucks.

Bacteria are single-celled microorganisms. They may live free in the environment or within a living cell. Viruses are tiny organisms that only grow inside the cells composing the animal’s body. All viruses rely on a live animal host to reproduce.

Although common viral or bacterial pathogens are unwelcome visitors or residents, certain ones can be especially troublesome. These special pathogens produce unusually high losses or unusual behavior such as extensive tenderfootedness, incoordination or slobbering. Milk production may cease or drop sharply. Your daily activities in caring for and feeding your animals put you in an excellent position where you could be among the first to spot the possible emergence of an especially unwelcome pathogen.

As previously emphasized, isolation, traffic control, hygiene and sanitation are the main ways to keep these essentially invisible pathogens from spreading and from reaching levels that can infect your animals.

Medications, antibiotics and vaccines are additional measures available to minimize the effects of bacterial or viral infections. Although powerful allies in an animal’s battle with one or more pathogens, they are really the second line of defense. The first line consists of all the steps you take to keep these microbes out or their numbers down to begin with.

Dangerous molecules

Prions

A prion is a very unusual infectious agent capable of causing an infection or disease. It is believed to be a self-reproducing protein structure similar to a virus. Prions cause prion diseases such as transmissible spongiform encephalopathies (TSEs). Unlike other infectious agents, prions produce no body-defending immune response.

Mold toxins

Mold growth takes place in feeds when they are damp. Mold does not always mean you cannot use the feed. Most molds are not toxic when fed to livestock; however, some are very toxic. The toxic byproducts produced by molds (fungi) are known as mycotoxins (mold toxins). Mold toxins are very diverse because they are produced by many different molds.

Fungi that have the ability to produce mycotoxins are very common in grain and other livestock feeds and in the facilities and equipment used for transportation and storage of feed. They can be very dangerous causing reduced growth rates, lowered immunities and increased susceptibility to various infectious diseases.

You should store and keep your animal feeds dry. You must realize that feeding any moldy feedstuffs is a risk to the health of your animal. There is less risk in feeding moldy feeds to fattening animals than for lactating or pregnant animals. The risk is also different among different species of animals.

Dryness is the simplest way to control the growth of mold. Take the following steps when evidence of mold growth (musty odor, visible mold) is suspected.

•Stop the moisture source. Fix the leak. Correct condensation problems in outside storage bins.

•Thoroughly dry or discard all porous items.

•Scrub mold off hard surfaces with detergent and water and thoroughly dry.

Bacterial toxins

Many bacterial pathogens have the ability to produce toxins which add to the disease they produce, thus making them a double threat to your animals. Some toxin-producing bacteria form their poisons outside the body (botulism), while others do so inside the body (tetanus, black leg and gangrene). These toxic bacteria can present a much greater risk than many ordinary bacteria. Vaccines are used to aid in their prevention, particularly where risks of exposure or infection are high.

Safeguarding animal health

The position of a herd is not unlike that of a populous city of which the public health largely depends on the functions of an intelligent health officer. The owner, above all, should function as a health officer to his or her herd. This element of animal management completes the picture of what it takes to keep animals safe and healthy.

Now, more than ever, the job of a health officer requires that they regularly apply the principles and strategies of animal disease prevention. They need to be alert to threats to the health of their own animals and to those belonging to others. They should be quick to recognize and properly respond to unusual diseases and to oversee and manage their own operations to prevent or minimize the effects of common diseases.

An alert, active disease prevention mindset provides many dividends. By protecting your own animals from pathogens, you are also helping to protect the animals of others.  PD

References omitted due to space but are available upon request.

—From Ohio State University College of Veterinary Medicine website

Bill Epperson
Associate Professor of Animal Science
To contact Bill, e-mail him at This e-mail address is being protected from spambots. You need JavaScript enabled to view it