Biosecurity in the dairy

Three strategies exist to control unwanted disease in a livestock operation: 1) prevent the douintroduction of infected cattle, 2) raise the overall level of resistance and specific resistance to infectious disease, and 3) minimize herd exposure to infectious disease. In addition, if unwanted disease exists in the herd, then a plan to eliminate the disease should be implemented. Maintenance of closed herds, testing procedures, vaccination schedules, sanitation, and good husbandry practices are integral parts of biosecurity procedures. The procedures in place should produce a benefit in terms of both economics and public perception that the quality and safety of our food supply is of the utmost importance to livestock producers. Livestock units exist for the purpose of purproducing a nutritious food product, which is comaccomplished through the use of forages and cereal grains. This system benefits the producer enterby adding value to renewable resources. Society addibenefits through the availability of a wholesome, safe, food supply in addition to the creation of new wealth within our economic system. The time has come for the food production industry, especially the dairy and beef sectors, to recognize the benefits of biosecurity procedures. Those of us involved in the food production particubusiness must always keep in mind the importance of maintaining healthy animals and a healthy food supply.; Dairy Day, 1997, Kansas State University, Manhattan, KS, 1997;


Introduction
Three strategies exist to control unwanted In the dairy industry, measurements of the disease in a livestock operation: 1) prevent the cost of disease are quite sensitive.Each douintroduction of infected cattle, 2) raise the bling of the somatic cell count above 50,000 is overall level of resistance and specific resistance estimated to cost as much as 400 lb per lactation to infectious disease, and 3) minimize herd in mature cows.Any clinical disease or even exposure to infectious disease.In addition, if subclinical disease will result in a cost to the unwanted disease exists in the herd, then a plan operation.In addition, some disease incidents to eliminate the disease should be implemented.
may pose a risk to herdmates as well as a Maintenance of closed herds, testing procedures, zoonotic risk to producers and a foodborne risk vaccination schedules, sanitation, and good to the public.husbandry practices are integral parts of biosecurity procedures.The procedures in place Three strategies can prevent disease from should produce a benefit in terms of both entering or occurring in a livestock production economics and public perception that the quality unit.The first is preventing the introduction of and safety of our food supply is of the utmost infected cattle.This approach begins by ensuring importance to livestock producers.
that cattle are purchased from uninfected herds Livestock units exist for the purpose of an effective vaccination program.Never purproducing a nutritious food product, which is chase cattle from unknown sources or from comaccomplished through the use of forages and mingled sources.Purchased cattle should be cereal grains.This system benefits the producer isolated and monitored for 30 days before enterby adding value to renewable resources.Society ing the herd.If necessary, test new herd addibenefits through the availability of a wholesome, tions for infectious disease, such as brucellosis, safe, food supply in addition to the creation of Johne's, BVD, and bovine leukosis, before new wealth within our economic system.The introduction to the herd.Recipients used for time has come for the food production industry, embryo transfer also can be sources of disease especially the dairy and beef sectors, to recog-and should be tested as necessary.If young nize the benefits of biosecurity procedures.
calves are purchased, they should be from a Those of us involved in the food production reputable source and tested as necessary, particubusiness must always keep in mind the impor-larly for persistent infection with BVD viruses.tance of maintaining healthy animals and a Purchased animals should be transported in clean healthy food supply.and disinfected trailers or trucks.
(Key Words: Biosecurity, Disease, Manage-The second is raising the overall level of ment.)resistance and specific resistance to infectious or herds with known health status, which implies disease.Reducing environmental stress can increase the overall level of resistance.Provide clean dry bedding and comfortable housing to all animals and use shades during the summer and virus (BVDV) has at least two genotypes, type 1 windbreaks during the winter.Reduce nutri-and type 2, and two biotypes, cytopathic and tional stress through proper transition diets and noncytopathic.Both type 1 and type 2 genotypes balanced lactation rations.Colostral management have cytopathic and noncytopathic biotypes as is the most important factor for increasing the members, and both type 1 and type 2 genotypes overall resistance in newborn calves.
have many different strains, some of which are The third is minimizing herd exposure to genotype has caused many of the most severe infectious disease.Limit exposure of the dairy cases of BVD.facilities to outside people.Require your veterinarian and other professionals to use sanitary Clinical Syndromes practices (e.g., sanitize equipment, use clean boots and coveralls).Reduce manure contamina-Most BVDV infections are subclinical, but tion of feed bunks, water sources, feed, and the clinical disease syndromes can be grouped feeding equipment.Utilize cattle loading facili-into three categories: acute BVD, in utero ties away from the main animal facilities to infections, and diseases in persistently infected minimize exposure to buyers and transportation (PI) animals.equipment.Raise calves in individual hutches that are disinfected between uses.Sick animals Acute BVD can vary greatly in presentation should be isolated in most instances, particularly from fever, depression, and runny nose and eyes in unusual cases or when the response to treat-to diarrhea to respiratory disease and can end in ment is unfavorable.Animals that die should be complete recovery or death depending on several necropsied, either to identify the cause of death factors.These include the immune status of the or to confirm the diagnosis.Necropsied animals animal, strain with which they are infected, and must be disposed of properly, either via the age of the animal.BVDV has a profound renderer or burning and burying.
immunosuppressive effect on infected cattle.
Elimination of disease when present in a respiratory and intestinal pathogens.BVDV is herd is almost always more expensive and diffi-also an important component of bovine respiratocult than prevention.For some diseases such as ry disease complex (BRDC).leptospirosis, eliminating or effectively keeping animals from exposure may be impossible.
In utero infections with BVDV can result in Other diseases require a long-term and disci-abortion; PI animals; congenital defects; or plined plan for reduction and elimination.For normal, immune-tolerant calves, depending on some diseases, elimination may involve total the stage of gestation and the cow's immune depopulation.Elimination of certain diseases status when she is infected with the virus.The requires active monitoring and action plans to noncytopathic biotype is responsible for all in handle each case as it occurs.
utero infections.If a cow is infected with The following sections provide short fetus will most likely die, and the cow may description of diseases of importance to dairy reabsorb the fetus, abort, or give birth to a mumherds and suggestions for prevention, treatment, mified fetus.The abortions are usually sporadic and elimination.and at a low rate, usually only 2-7% in an out-Bovine Virus Diarrhea tween 60 and 120 days of gestation, the calf may Bovine virus diarrhea (BVD) is one of the BVDV and shed large quantities of virus in all most significant viral infections of cattle.BVD secretions throughout their entire lives.The was first recognized as a disease syndrome in immune system in calves less than 120 days of 1946, and today 70-90% of the world's cattle gestation is not capable of responding properly population is seropositive for BVD.The BVD to BVDV, so the virus simply multiplies in the more deadly than others.Recently, the type 2 Infected cattle are more susceptible to many BVDV in the first trimester of pregnancy, the break.If the cow is infected with BVDV bebe PI.These animals are lifelong carriers of calf.When the immune system becomes compe-Transmission tent, the virus is recognized as "self", and the calf is "immune tolerant" to that strain of BVDV BVDV rapidly loses infectivity outside the for life; that is, it never develops an immune host and is very susceptible to detergents, light, response to that strain.Infection with BVDV temperature changes, and other environmental between 100 and 180 days in gestation can result conditions.It is mainly transmitted by close in congenital defects such as cerebellar contact with PI or acutely infected cattle via the hypoplasia, hydrocephaly, cataracts, and other oral or nasal routes.Acutely infected animals similar defects.Infection of the dam in the last shed the virus only for a short time (about 2 wk), trimester of gestation, when the calf's immune whereas PI animals shed constantly in all bodily system is functional, will yield a normal, immu-secretions for life.Acutely infected bulls shed nized calf.
virus in their semen for at least 2 wk, and PI Persistently infected animals can result from semen is another potential source of infection in utero infection as described above or by being during natural mating.Reputable A.I. studs will born to a PI dam.The prevalence of these ani-check their bulls and semen for BVDV.Sheep, mals in cattle herds is low (.5-3%), but their goats, and pigs can become infected from close potential to shed large quantities of virus and contact with cattle, and sheep can transmit the infect other animals in the herd is tremendous.
virus to cattle in close contact.Needles, rectal Persistently infected cows always give birth to sleeves, water troughs, feed bunks, nose tongs, infected calves, and seronegative cows (cows and other equipment can aid the spread of virus.that have not mounted an immune response to Experiments have shown that biting insects also BVDV) are much more likely to give birth to spread the virus.infected calves.However, some seropositive cows can give birth to infected calves, if their Diagnosis circulating antibodies do not cross-react with the virus to which they are exposed.Persistently Diagnosis of BVD is accomplished by infected calves are often "poor doers" and are observation of clinical signs, serology, virus more susceptible to other calfhood diseases isolation, fluorescent antibody, or polymerase because of the immunosuppressive effects of chain reaction (PCR) tests.The virus can be BVDV.Sometimes, however, infected calves isolated from nasal swabs, serum, or tissue may look perfectly normal and healthy.Persis-depending on the disease syndrome present.tently infected calves reportedly have death rates Diagnosis of BVD-MD is very important, beof 50% in the first 12 months of life.Some of cause if BVD-MD animals are found, the herd these probably die from other calfhood diseases should be screened for more persistently infected as well, but many die from BVD-mucosal dis-animals.ease (BVD-MD).BVD-MD occurs when PI animals that harbor noncytopathic BVDV are ex-Prevention posed to a cytopathic variant probably through mutation of the noncytopathic strain to a Adding PI animals to a herd should be cytopathic strain.BVD-MD is characterized by avoided, because that is the most common way profuse diarrhea with severe erosions and ulcers to introduce BVDV into a herd.Replacement on all mucosal surfaces.It occurs most often in animals should be purchased from herds with cattle 6 to 24 months of age and is nearly 100% accurate records of disease and vaccination.All fatal.
new animals, or at least any small group of new bulls shed virus constantly in their semen.Thus, animals, such as bulls, should be isolated and tested for BVDV before entering the herd.
Semen should be from tested bulls only.If embryo transfer work is performed, all recipients should be isolated, tested for acute or persis-before weaning or vaccinate with MLV before tently BVDV infection, and vaccinated against weaning.BVDV.
Vaccination programs are essential to decrease losses to BVD.The goal of any vaccina-If a diagnosis of BVD is made in a herd and tion program is to prevent fetal infection and significant losses are occurring, control measures increase colostral immunity.This may not al-may need to be taken to decrease future ecoways work, depending on the strain of vaccine nomic losses.Vaccination will slow the spread and the field strain, but it is the best weapon we through the herd but will not prevent PI animals have.Vaccination does not clear persistent from shedding virus.They must be removed infections from a herd, but the virus doesn't from the herd.Several procedures have been spread as quickly through a vaccinated herd.
outlined to screen the herd for PI animals.One Two types of vaccine available include the serum from every animal in the herd and anamodified live and inactivated (killed) forms.
lyze it with the microplate virus isolation test, Much controversy exists over which is better.
and then remove all animals that test positive.

Modified live vaccines (MLVs) offer more
This test is very sensitive and specific for cross-protection against different strains, and the BVDV.Another option is to perform serology on immunity conferred by them is longer lasting and every animal in the herd and cull those animals stronger.Modified live vaccines should be used with very low or absent titers.This can be with caution, however, because they can cause performed only in herds that are vaccinated or immunosuppression or fetal infection or revert to have active BVDV circulating and is not as virulence.Inactivated vaccines are not sensitive for detecting PI animals as the immunosuppressive, do not infect fetuses, and microplate test.Some researchers recommend have minimal risk.However, the immune re-testing only the calves with microplate virus sponse they generate is weaker, of shorter dura-isolation and then testing only the dams of the tion, and may not cross-protect as well as MLVs.
calves that test positive.A common theme in Cattle receiving inactivated vaccine also must these procedures is that all calves born for the have a booster 3 to 4 wk after the first vaccina-next 9 months also must be tested to ensure that tion.Neither MLVs nor inactivated vaccines no new PI animals are born into the herd.With give lifelong protection, and yearly boosters are any screening procedure, biosecurity measures as required with both.outlined in the "Prevention" section must be No one vaccination program works for all mals.situations.Producers should consult their veterinarian for a program tailored for their herd.Here Neosporosis are a few options.
For replacement heifers (separated from that originally was found in dogs but later found pregnant cows), use an MLV at 6 months of age to be a major cause of abortion in cattle, sheep, and again 60 days before breeding or use an goats, and horses.The complete life cycle is not inactivated vaccine 5 wk before breeding and known, which makes formulation of control again 2 wk before breeding.
programs difficult.We assume that some defini-For cows, use inactivated vaccine 2 wk most cows are infected congenitally, which is before breeding or use MLV before breeding.
the only known natural route of infection.Either of these options can be used with either Abortion is the only clinical sign in Neospora option for heifers.
infected cows, and multiple abortions can occur Vaccinate calves with a different strain of months of gestation but can occur any time inactivated vaccine than used for cows 3 to 4 wk between 3-8 months of gestation.Calves in- Infected calves shed billions of infective If abortions from neosporosis are high in some as well, but far fewer than calves.Transnumber, control measures may need to be taken.mission from calf to calf or calf to human is Many control programs exist.One possible first primarily by the fecal-oral route, although it can step is to screen 35-50 cows, depending on herd be transmitted by the aerosol route as well.The size, with serology (ELISA or IFA) to find the most common place for calves to become inprevalence of Neospora in the herd.If the preva-fected is in the calf-rearing area.Control of lence is low, the entire herd can be screened, and "Crypto" focuses mainly on management.The the seropositive animals culled.If the prevalence organism is hardy and has been shown to survive is too high to cull out the seropositives, one from 2 to 6 months at 4EC (40E).The organism possibility is to test all dams and daughters of is resistant to most disinfectants, but bleach at cows that have aborted and cull the sero-half strength is effective, as is formalin (formalpositives.Also, testing replacement animals and dehyde).Formalin is very toxic and should be permitting only seronegative replacements to used only under strict supervision.Putting calves enter the herd will reduce congenital infections.
in hutches or on a clean pasture with low stock-If embryo transfer is done, use only seronegative ing density will reduce the level of exposure to recipients, and don't purchase a heifer whose C. parvum, and thereby reduce losses from recipient was seropositive.
be detected to help point out cattle at higher risk "Crypto", is a protozoan parasite closely related oocysts in their feces, and adult cattle can shed If calves become ill with "Crypto" diarrhea, from decreased milk production and increased the only treatment is supportive care, especially susceptibility to other diseases such as mastitis electrolyte and fluid therapy.The use of can be major.Johne's disease is a reportable anticoccidial drugs has been suggested for treat-disease in Kansas.
Recently, M. paratument and prevention but has not proven to be berculosis has been associated with Crohn's effective.
disease in people, but scientific evidence is not Salmonella Infections the disease at this point.
Many species of the bacterium Salmonella Most cattle with Johne's disease were inaffect cattle.They can cause sporadic abortions fected as young calves, which are most susceptiand, more commonly, neonatal diarrhea, espe-ble.Calves have no clinical signs, and, therefore, cially in dairy calves.They are not common this stage of the disease has been called the causes of diarrhea in beef calves.Humans can "silent" stage.After an incubation period of 2-10 be infected with Salmonella by drinking unpas-years, infected adult cows can be more prone to teurized milk or handling infected placentas and mastitis or infertility.These animals can be fetuses.Most cattle become infected by inges-shedding the organism in their feces at undetecttion of contaminated feed, water, or milk.
able levels, which can contaminate the environ-Salmonella can be shed by asymptomatic carrier ment.Within a few weeks, clinical signs such as cows and calves, and it can survive in a damp gradual weight loss with a normal appetite, environment for months.Rodents can also be a diarrhea, and decreased milk production can source of the bacterium.
appear.In advanced cases, animals are very Good hygiene is essential to halt the contin-can have intermandibular edema, or "bottle jaw", ued spread of Salmonella.The calving area and death follows shortly.For every such case of should be clean, and hutches should be used.
advanced Johne's disease on a farm, 15 or 25 The hutches should be cleaned and disinfected other animals likely are infected.after each group of calves, and the feeding utensils should be cleaned between feedings.A The major route of infection of calves is rodent control program should be instituted.All ingestion of colostrum and/or milk contaminated replacements should be tested to be sure they are with fecal material.Calves also can be infected not carriers, and aborting animals should be in utero, especially if their dam is clinically ill.isolated.Vaccinating cows with two doses of a Such infection is unlikely in early, subclinically killed bacterin may help control Salmonella in infected dams.Infected cows can shed the organcalves less than 3 weeks of age, but vaccination ism directly in colostrum or milk as well, which of the calves is usually not protective.Good hy-is another potential source of infection for giene, not vaccination, should be the main focus calves.Adults can be infected from contamifor controlling Salmonella diarrhea.nated feed, but they are less susceptible than Johne's Disease likely will be culled before they shed the organ-Johne's disease, also known as paratuber-semen, in uterine fluids, by rectal examinations, culosis, is caused by Mycobacterium paratu-and by wildlife, but these are not likely sources berculosis, a slow growing bacterium that can of infection.Embryo transfer and artificial survive in the environment for approximately 1 insemination are not likely sources of infection year.It is best known in the dairy industry, because of frequent testing.However, all emwhere it costs U.S. dairy producers an estimated bryo transfer recipient cows should be tested, $1.5 billion annually, but cases in beef herds, because fetal infection can occur transespecially seedstock operations, can be devastat-placentally. ing as well.In addition to death loss, premature culling, and decreased weight at slaughter, losses available to prove or disprove its involvement in weak, have profuse, "pipestream" diarrhea, and calves, and because of the long incubation time, ism.The organism also can be transmitted by

Prevention
probe test, which is fast but expensive and less Because of the nature of the disease, preven-Rectal scrapings or histopathology of tissues are tion is much more economical than control once both sensitive in detecting clinically ill animals.it has entered the herd.Herds are infected The newest test method, which tests for cellular primarily by purchasing infected animals.These immunity, is not proven yet, but has a promising animals may show no clinical signs for many future.The Johnin Test, which has been used in years and may even test negative on serologic the past, is no longer recommended.and fecal culture tests.The sensitivity of tests for Johne's disease is only about 50%, which means Control 50% of animals with the disease will not test positive.Therefore, it is best to maintain a Control and/or eradication of Johne's disease closed herd or purchase replacements from herds on a farm that has had confirmed cases of the that are certified to test negative.If this is not disease is a long, difficult process and should be possible, prepurchase testing of the seller's undertaken only if management changes can be entire herd should be done.

Hairy Heel Warts
Environmental mastitis is caused by Papillomatous digital dermatitis, also known pathogens present in feces, bedding, or other as hairy heel warts, is a contagious infection of places in the cow's environment.They are the skin, usually on the back of the foot between impossible to eliminate, so steps to prevent the bulbs of the heel, most often on the rear feet.environmental mastitis include decreasing expo-It is primarily a disease of housed dairy cattle sure of teat ends to pathogens and increasing the and rarely occurs in pasture cattle.Unlike true resistance of cows to intramammary infections.
bovine warts, which are caused by a virus, heel Conditions that increase exposure to environ-warts are most likely caused by spirochetes, mental pathogens include overcrowding; ele-which are spiral-shaped bacteria.Early heel vated temperature and humidity in barns; poor warts can be flat and circular and later become ventilation; accumulation of manure, urine, and raised masses and develop hair-like projections.water; poor stall design; access to ponds or They bleed easily if traumatized and can cause muddy lots; and dirty maternity stalls or calving severe pain and lameness, resulting in economic areas.To increase the resistance of cows to losses from decreased milk production, intramammary infections with environmental decreased reproductive efficiency, and cost of pathogens, they should be fed a well-balanced treatment.Only about 50% of cows with heel diet that is sufficient in vitamin E and selenium.warts are actually lame, which makes control The J-5 bacterin-toxoid has proven effective in difficult.decreasing incidence and severity of these infections as well.
Introduction of the bacteria into a clean herd Contagious mastitis is transmitted from cow closed herd, but isolation of replacement animals to cow via infected milk at milking time through for at least 1 month and checking all their feet the milker's hands, milking units, common very closely before introducing them into the sponges and towels, and other items used during herd are good practices.Also, hoof trimmers, milking.Most Strep.agalactiae and some S.
veterinarians, and any other visitors should clean aureus infections respond to most commercial and disinfect their boots and equipment before intramammary antibiotic products in both the working on the herd.lactating and dry periods.Chronic S. aureus and Strep.agalactiae infections may not respond to Once introduced, the warts spread quickly antibiotic therapy, and chronically infected cows through the herd, and eradication is difficult or should be identified, segregated, and milked last impossible because of the subclinical cases and at every milking.They should be culled when lack of immune clearance.Lactating heifers and enter the milking herd.New animals should be gious mastitis are returned.
may be difficult to prevent in anything but a young cows may show more lameness than older effective method of whole-herd treatment is by cows, but this pattern does not always hold true.
topical spray of antibiotics, such as tetracycline, Treatment of heel warts is by extra-label only if properly prepared and maintained, which drug use, so your veterinarian must be consulted can be very expensive.Whole-herd treatment is for a treatment protocol.Whole-herd treatment not a cure and will have to be repeated on a reguis necessary to control heel warts, because of the lar basis to limit the incidence of this disease in high incidence of subclinical cases that can the herd.perpetuate the problem in the herd and the propensity of the warts to recur.The most cost-after washing the feet.Foot baths are effective unable to rise, uncoordinated, or normal.MostNeospora is a major cause of abortions in cases of neosporosis have been associated with cattle.Prevention and control are complicated dairy cattle, but congenital infections and abor-by the unknown life cycle of the parasite.Diagtions also have been documented in beef cattle.nosis is difficult in live cows, but antibodies can Diagnosis of neosporosis is difficult in live of aborting.Testing all new animals before they cattle but can be accomplished in aborted fetuses enter the herd and protecting feed and water by a combination of immunohistochemistry on from contamination by other animals are keys to the tissues and serology from the dam.
If none or very few instituted.No "cookbook" method of control test positive, chances are very good the animals works for every farm, but a summary of key purchased are not infected.At the minimum, points follows.Control programs have two replacements should be purchased from reputa-fundamental objectives.The first is to prevent ble herds with no clinical history of Johne's.All highly susceptible newborn calves and young new animals should be isolated and tested before animals from ingesting manure, colostrum, and they enter the herd.The risk of bringing in milk from infected cows.To accomplish this, paratuberculosis in an animal from a sale barn remove the calves early; put them in hutches; has been estimated at 10% per animal.Another and feed them only uninfected colostrum, milk, preventative measure that should be practiced on or milk replacer.Improving hygiene to reduce all farms is proper cleaning of calving areas and exposure of calves to M. paratuberculosis also calf hutches.reduces exposure to Salmonella, E. coli, Crypto, killed vaccine is available for use by daily feed costs exceed income from milk proaccredited veterinarians, usually under the duction.Prevention and control or eradication of supervision of the state veterinarian, and its S. aureus and Strep.agalactiae infections can be usage varies from state to state.It does not accomplished by good milking practices, espeprevent infection, but it does delay the onset of cially proper udder preparation using single-use clinical signs.However, it interferes with diag-towels and post-milking teat dips.Also, purnostic tests for Johne's disease and is not recom-chase animals from herds with low somatic cell mended.counts and test individual animals before they Escherichia coli and Klebsiella pneumo-ments, because yeast are resistant to antibiotics.nia.Mastitis also can be caused by other organisms such as Nocardia sp. and yeast. A