Digestive Diseases

By William C. Rebhun.

Calf diarrhea is the number one cause of death losses in newborn calves. Calf diarrhea, or "calf scours" in layman's terminology, can be caused by several infectious agents.

The most common causative agent is Escherichia coli (E. coli), a bacteria which colonizes within the epithelium of the small intestine in calves and produces a secretory diarrhea. Although digestive tracts of all animals and man contain E. coli of various types, pathogenic E. colt in calves tend to be a specific subgroup called K-99 E. coli.

Signs of disease are specific in calves less than 2 weeks old and include diarrhea, usually a fever of 103 to 105 F, dehydration due to fluid loss in the form of diarrhea, depression, and decreased appetite. Because of the young age of these calves, dehydration, electrolyte (salt) losses, and acidosis may result in death in the most severe cases.

In addition, septicemia (blood poisoning) sometimes occurs due to spread of the organism from the intestine into the systemic circulation and subsequent infection of other major organs. Up to 100 percent of the newborn calves on a farm may develop calf diarrhea in severe outbreaks.

The disease can spread from calf to calf through fecal/ oral transmission. Once the organism is established on a farm, any manure that the calf is exposed to may contain the organism. Therefore, the calf can ingest the organism from the udder of its dam, feedstuffs, buckets with slight manure contamination, or from the floor, ground, or bedding.

Calves that have not been given colostrum with its protective antibodies within 12 hours of birth are definitely more at risk to the development of E. coli diarrhea. Calves older than 2 weeks may develop diarrhea, but it is seldom life-threatening since they are not as likely to suffer severe dehydration as newborn calves.

Calves do not transmit this disease to other species or humans since each species has specific E. coli subtypes which cause disease.

Treating, Prevention

Treatment consists of oral protectants, oral antibiotics such as neomycin, sulfa or tetracycline in some cases, oral supplementation with electrolytes (salt) and fluids, and decreasing the amount of milk fed for 1 to 4 feedings. Intravenous fluids and antibiotics may be necessary in severe cases where dehydration, acidosis, endotoxemia, or septicemia occur.

Prevention includes management changes to insure adequate colostral intake by the newborn calf, physical cleansing of the barn and maternity areas, and avoiding overcrowding.

Passive antibodies can be given for the newborn calf at birth by means of a new vaccine containing E. coli antibodies, or by adequate colostrum containing antibodies to E. coli created by vaccinating the dam with E. coli killed vaccines before calving. The vaccine should be discussed with a veterinarian familiar with these problems.

Other organisms such as Rota virus and Corona virus can cause similar diarrhea in calves less than 2 to 3 weeks old. These agents result in diarrhea and signs indistinguishable from mild to moderate E. coli diarrhea. Although the viruses can result in dehydration and occasional death, their major impact is to combine with pathogenic E. coli and result in severe diarrhea or death.

Vaccines are available against Rota and Corona viruses in calves. These vaccines are modified-live products that are given orally to the newborn calf at birth, or given to the dam before calving to cause antibodies to be present in her colostrum which the calf ingests.

When faced with neonatal diarrhea that results in calf mortality or severe illness in a number of calves, farmers should work in conjunction with their veterinarian to discover the cause. This is best done through bacterial and viral cultures of fecal material from affected calves.

Only through identifying an exact cause can management changes, medical therapy, and preventive vaccines be employed to solve the problem.

BVD Disease

Bovine Virus Diarrhea (BVD or BVD-Mucosal disease) is a contagious viral disease responsible for major losses in both beef and dairy cattle. The virus is spread through fecal contamination and secretions from infected to non-infected cattle.

Although most cows have subclinical disease or are immune from prior exposure, a percentage of unprotected calves or cows show clinical signs when exposed to this virus.

Signs may be mild, consisting of fever (103 to 108 F), salivation, falloff of appetite, mild oral lesions, and mild diarrhea. Or signs may be radical with severe diarrhea, fever, total loss of appetite, and erosions of mucous membranes in the oral cavity, nasal cavity, esophagus, rumen, intestine, and feet at the skin/claw junctures.

A wide variation in signs is possible with this disease. Laboratory work or autopsy of fatal cases often is necessary to confirm the disease. In general, affected animals have decreased numbers of white blood cells and reduced ability to fight off other infections (immunodeficiency) when affected with BVD.

Autopsy lesions include those mentioned earlier and destruction of lymphoid areas in the intestine. State diagnostic laboratories may culture the organisms from blood or tissues of affected animals.

Abortions may occur in cows that are affected in late pregnancy, and fetal anomalies can be present in calves from cows that were infected during the middle months of their pregnancy.

The causative virus is widespread in the United States and can cause disease in beef and dairy cattle of all ages. Its importance lies not only in death losses and abortions, but decreased production or growth in affected animals, and predisposition of affected animals to various secondary diseases.

Treatment is supportive primarily, with oral or intravenous fluids and electrolytes (salts), and antibiotics if secondary bacterial diseases occur. Blood transfusions to supply passive antibodies and white blood cells have appeared to help some severe clinical cases.

Control and prevention are now possible through vaccines. Although modified-live virus vaccines have long been available, they occasionally have been unprotective and in some instances have introduced the disease to a premise. New killed vaccines generally are indicated in herds or geographic areas that have a high incidence of BVD.