Johne’s Disease

Johne’s disease is a chronic infection caused by the bacteria Mycobacterium avium subspecies paratuberculosis. Clinical signs include gradual weight loss despite a normal appetite, decreased milk production in cows, and manure that gradually becomes more fluid until it progresses into a severe diarrhea. Animals are typically infected with Mycobacterium avium subspecies paratuberculosis as calves, but do not show any clinical signs of Johne’s disease until after a prolonged incubation period (time from infection to clinical disease), often between 2 and 10 years. Such a long incubation period means that many infected animals show no outward clinical signs for many years, but during this time they are infecting new calves every year. No medical treatment exists for Johne’s disease. A killed vaccine for Johne’s disease is available in some states with prior approval by the State Veterinarian. However, the vaccine does have some limitations and side effects. Therefore, it is best to have new bulls tested for Johne’s disease. In addition to diagnostic tests, ask about the Johne’s disease status of a bull’s original herd to help avoid introducing the disease to your herd.

Anaplasmosis

Anaplasmosis is a disease characterized by progressive anemia and caused by the rickettsial organism Anaplasma marginale. Fever, anorexia, loss of body condition, decreased milk production, abortion, infertility, muscle weakness and depression are commonly seen with anaplasmosis. The disease is present in many parts of the U.S. and causes significant economic losses to the beef and dairy industries. In recent years, veterinarians in some parts of the U.S. are reporting an increase in the number of cases of anaplasmosis, perhaps as a result of increased cattle movement due to drought and other natural disasters. Anaplasma marginale is transmitted from a carrier to susceptible cattle by biting flies and ticks or via contaminated needles, tattoo instruments, dehorning and castration equipment, etc. Treatment of anaplasmosis is often too late once clinical signs are observed. However, animals that survive the initial infection will become lifelong, asymptomatic carriers. Therefore, all new bulls should be tested for anaplasmosis.

Bovine Viral Diarrhea Virus

Animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) are created when a fetus is exposed to the virus during the first half of pregnancy. During this time, the fetal immune system is not developed enough to respond to a BVDV infection. Instead, the immature fetal immune system recognizes the virus as normal and allows it to replicate freely. Most PI animals die by the time they are two years of age, but some will survive for several years and constantly shed BVDV throughout their life. PI animals will infect the rest of the herd causing fever, diarrhea, respiratory disease, reproductive problems, and much more depending on the age and immune status of each animal infected. Some PI calves are “poor-doers,” while others may look healthy and grow very well, making it impossible to consistently detect PI animals visually. Therefore, it is essential to test a new bull for BVDV-PI status before introducing him to the herd, unless he has previously tested negative by an appropriate BVDV-PI diagnostic test.

Bovine Leukemia

Bovine Leukemia, also known as bovine leukosis, lymphosarcoma or malignant lymphoma, is a viral disease of cattle caused by bovine leukemia virus (BLV). BLV is spread primarily through close physical contact and exchange of contaminated biological materials. The virus is present mostly in white blood cells (immune cells) called lymphocytes that can be found in blood, milk, and tumors. Transmission can occur through blood contaminated needles or equipment (dehorners, castration equipment, tattooing pliers, etc.), and can also occur through biting insects, in utero (4 to 8 percent of BLV cows give birth to calves infected with BLV), and possibly via colostrum or milk from an infected cow. However, infection by contaminated milk is thought to be rare, possibly due to the presence of maternal antibodies in the milk. Lymphosarcoma, the terminal stage of some BLV infections, only occurs in less than 2.5 percent of BLV-infected cattle, and infection with BLV typically occurs several years before the development of lymphosarcoma. All organ systems may be involved resulting in highly variable clinical signs. While most cattle infected with BLV do NOT exhibit clinical signs, BLV infections are lifelong so even asymptomatic animals can serve as viral reservoirs and expose uninfected animals.

Vaccination

Ensuring adequate vaccination of a new bull protects the health of the bull as well as the health of the rest of the herd. At a minimum, bulls should be vaccinated against IBR (infectious bovine rhinotracheitis), BVD (bovine viral diarrhea), PI3 (parainfluenza), BRSV (bovine respiratory syncytial virus), Leptospirosis 5-way, and Vibriosis (Campylobacter fetus). Six to eight weeks prior to the breeding season, bulls should be revaccinated so immunity is high during the breeding season. To ensure maximum product efficacy and safety, properly store and administer vaccines according to label directions, adhere to designated withdrawal times, and follow all other Beef Quality Assurance (BQA) guidelines found at www.bqa.org/ codeguidelines.aspx.