10/4/2004 4:24:33 AM
Cattle in all beef herds are subjected to some of the common diseases of cattle. Included are diseases that may interfere with pregnancy, cause abortion and cause intestinal infection and systemic illnesses in newborn calves. Older calves, yearlings and mature cattle may develop warts, get foot rot, cancer, chronic diarrhea and wasting, respiratory diseases, mastitis, lumpy jaw, and eye and brain infections, to name a few conditions.
In addition to diseases already present in the herd, infection may be introduced by purchased herd replacements, by show cattle returning to the herd and across fences from the herd next door. Skunks may infect cattle with leptospirosis and rabies.
The economic impact of some infectious diseases is subtle and often not realized. Vaccines are available that can induce some degree of protection against several of the major diseases of cattle. Pastured cattle whose diet does not contain adequate levels of biologically available copper, zinc and selenium may not have optimum disease resistance. Secondary copper deficiency is a significant problem in cattle pastured on soils high in organic matter (peat) in coastal parishes.
This article lists and briefly reviews major infectious diseases of beef cattle in Louisiana.
Diseases Causing Acute, Often Fatal, Disease Outbreaks
This disease is an important cause of mortality in Louisiana cattle. Severe anemia occurs. Horseflies are known transmitters of infection from cow to cow. Incubation period is one to three months. Other biting flies, mosquitoes, ticks, needles and surgical instruments may also transmit infected red blood cells from a carrier or from an acute case to susceptible cattle. A vaccine developed at LSU is available through veterinarians. Annual vaccination of herd bulls is recommended. Problem herds may benefit from vaccination of cows as well. Herd treatments with tetracycline can stop an outbreak, once a diagnosis has been confirmed.
Called charbon by French-speaking Louisianans; spores of the anthrax bacillus probably still remain in the soil where outbreaks of this disease have occurred in the past. Known as anthrax endemic areas, these include the river parishes south of Baton Rouge where a major outbreak occurred in 1971 and west into St. Martin Parish where confirmed cases were reported in 1971. The coastal parishes and pastures along the Red, Cane and Ouachita rivers have experienced anthrax. Cases were confirmed in St. Landry Parish near Morrow, where charbon occurred in 1975 and 1977. An effective vaccine is available. Antibiotics will interfere with vaccine.
Bacillary Hemoglobinuria (Red Water)
An infrequently diagnosed disease caused by toxins liberated by the bacterium Clostridium hemolytica. Red water is often associated with liver damage induced by the liver fluke (Fasciola hepatica), a parasite common to cattle pastured on wetlands. Affected cattle are anemic, jaundiced, have dark red urine (port wine) and die soon after illness becomes apparent. Vaccine is available. To maintain good protection, frequent boosters (two to four times per year) may be necessary.
An acute, fatal disease of cattle generally four months to two years of age, but the age range is six weeks to several years. The large, bacterial rods of Clostridium chauovei from feces and contaminated soil enter the calf, perhaps through oral lesions, and localize in muscle tissue. The organisms multiply, producing toxins that kill muscle, causing a quickly fatal toxemia. Affected muscle contains small gas bubbles, hemorrhages and is black. An inexpensive vaccine is available. Multiple antigen vaccines are available that include several diseases caused by related Clostridium sp. bacteria.
A disease of calves from several days old up to perhaps age one month. The cause is toxin produced by Clostridium perfringens type C growing in the small intestine. An occasional cause of death in calves, enterotoxemia tends to occur in calves that have an abundant supply of milk. Cows immunized before calving can provide protective antibodies to their calves though colostrum.
A lethal disease of nursing calves infected with one of several types leptospira bacteria. Skunks, cattle and other animals may shed the organism in their urine. Calves are exposed when they drink contaminated water. Affected calves become anemic, jaundiced, have dark red urine (port wine) and, at necropsy, have hemoglobin-stained kidneys (blue-black or gun metal colored).
Immunization and frequent boosters to cows stimulate production of antibodies that will be present in colostrum and may protect calves for up to four months.
A common, acute, often fatal bronchopneumonia caused by lung infection with Mannheimia hemolytica, a gram negative bacterial rod. This is a major disease of cattle, young or old, at pasture, in stocker cattle programs and in the feedlot. In cow herds, pasteurellosis commonly occurs within a few days or weeks after introducing new cattle into the herd. Illness and mortality may strike the new animals and/or the home herd. Modern vaccines given before exposure may reduce the economic impact of the disease to some degree. Variation in virulence and antigenic makeup of strains of the organism, the resistance of the animal including the effects of deficiencies of zinc and copper, as well as physical stress, timing of vaccination before stress and other factors influence severity of pasteurellosis. Pasteurella multocida also causes bovine pneumonia.
Diseases Causing High Mortality, Affecting Individual Cattle
Brain infections such as listeriosis caused by Listeria monocytogenes and sporadic bovine encephalitis caused by Chlamydia sp. are occasionally seen in Louisiana cattle. Fatal nervous system virus infections like rabies from skunk bite and pseudorabies from feral swine are not common diagnoses. The North American form of malignant catarrhal fever is rarely seen, usually in cattle in close contact with sheep.
Economically Important Infectious Diseases
Actinobacillosis (Wooden Tongue)
The classical disease is “wooden tongue,” which is actually a hard, swollen tongue. Wooden tongue can be treated successfully. Another form of actinobacillosis is formation of multiple abscesses in the throat region. Abscesses vary from golf ball to grapefruit in size and require draining and often leave lumps of scar tissue. Abscesses may affect 30 percent or more of a group of cattle. Wooden tongue is seen statewide, but the multiple abscess problems tend to occur more often in south Louisiana, particularly in coastal parishes.
Actinomycosis (Lumpy Jaw)
This is a slowly developing infection of the jaw (mandible or maxilla) that may impair eating or breathing. A draining sore develops. Treatment is less effective than for wooden tongue.
Infectious Keratoconjunctivitis (Pink Eye)
Pink eye is an economically important disease that may infect 30 percent to 50 percent or more animals in a herd of cattle. Severity varies from mild to severe. Mild cases resolve in one to three weeks. Damage to the cornea in severe cases results in permanent scaring and loss of sight. The bacterium Moraxella bovis is the primary infectious agent. Affected cattle must be penned and treated individually. Vaccines are of variable benefit because a number of strains of Moraxella bovis exist.
Interdigital Necrobacillosis (Foot Rot)
The most important cause of lameness in beef cattle, foot rot can be a nagging problem in some herds. Environmental factors such as muddy fields, plant stubble and rough dry ground may lead to bruising and abrasion of skin between the claws, which allows certain bacteria to invade. Prompt treatment at first sign of lameness with injectable antibiotics cures most cases.
Chronic Diseases of Significant Economic Importance
Leukosis is a virus disease of cattle often referred to as bovine lymphosarcoma because of the lymphoid tumors produced in some infected cattle. Infected cattle respond to the virus with increased levels of lymphocytes but less than 10 percent of these cows eventually develop tumors. There is a BLV serum test. Tumors develop in the heart, abomasum (fourth or true stomach) and various lymph glands. The uterus and spinal cord may be involved as well. Depending on location of tumors, cattle may drop dead, have unexplained weight loss, anemia with a black stool or develop rear limb paralysis. Presence of bovine leucosis at slaughter is cause for carcass condemnation.
Paratuberculosis (Johne’s Disease)
Pronounced yo-knee’s, this is a chronic, contagious disease caused by Mycobacterium avian var. paratuberculosis. It is a complex disease in which infection generally occurs in the first few weeks of life but diarrhea does not develop until after two years of age. Many infected cattle shed the organism in their feces but never develop the diarrhea and chronic wasting disease. The herd infection rate in Louisiana beef herds is probably less than 10 percent. There is no treatment or vaccine. Immediate slaughter of clinical cases is recommended.
Diseases Affecting Breeding Efficiency
Brucellosis (Bang’s disease)
Bovine brucellosis (Brucella bovis) is a bacterial infection transmitted through oral exposure to uterine discharges from infected cows at time of calving or abortion. This previously common disease has been eliminated from the state through the cooperation of the cattle industry and state-federal animal health officials. Immunization of female cattle was an important facet in effort. Research at the LSU Veterinary Science Department helped establish the safety and efficacy of the vaccine now in use. Continue vaccinating heifers at 4-11 months.
This important venereal disease causes embryo loss and two to three months of infertility, after which immunity develops and pregnancy can be maintained. Vaccination of heifers and cows can provide substantial protection. Give booster annually within 30 days of breeding for best results.
This venereal disease is caused by the protozoan Tritrichomonas fetus. The calving interval is greatly extended in recently infected herds. Bulls remain infected for life. No approved drugs are available for treatment. Cows recover if allowed to have three estrus cycles of sexual rest. This is a difficult disease to manage, but fortunately it does not appear to be common.
Serum tests of Louisiana cows indicate many have experienced bluetongue virus infection, which is transmitted by “no-seeums”or biting gnats (Culicoides sp). Most infections are inapparent and few cattle exhibit clinical signs. Signs include oral ulcerations, a cooked appearance to the dental pad, lameness and inflamed skin of the muzzle, teats, vulva and conjunctiva. The closely related epizootic hemorrhagic disease virus of deer (EHD) may cause similar lesions. Bluetongue virus may cause an occasional abortion or birth of blind calves with virtually no cerebral tissue (hydranencephaly).
Bovine Virus Diarrhea (BVD)
This common virus infection is maintained in cattle herds by persistently infected (PI) cattle that constantly shed virus in feces, saliva, etc. Elimination of PI cattle from the herd is recommended. PI cattle can be detected by histochemistry of small pieces of skin "ear notch." A fetus may become a PI if it survives BVD virus infection acquired before 120 days of gestation. BVD virus may also cause fetal loss and abortion. Other developmental defects may include calves born with incoordination, cataracts, skin defects and other anomalies. An occasional clinical case of BVD, marked by diarrhea and oral erosions, is seen in yearlings. A fatal termination of PI cattle called mucosal disease is marked by diarrhea, oral ulceration and emaciation. Vaccines are available. Heifers should be immunized at 6 to10 months of age and given boosters annually.
Infectious Bovine Rhinotracheitis (IBR)
IBR is a herpes virus infection of cattle. IBR was first recognized as a respiratory infection in feedlot cattle. It can be an important cause of abortion from field virus infection. A modified-live vaccine not cleared for use in pregnant cattle can induce abortion in susceptible cows. A related IBR herpes virus can cause inflammation of the prepuce of bulls and vagina of heifers and cows. Heifers should be vaccinated at 6 to 10 months of age and given annual boosters.
In addition to affecting nursing calves, as described above, leptospira are an important cause of abortion. Immunization begins with heifer calves and boosters are recommended at 6- to 12-month intervals.
Abortion caused by the protozoan Neospora caninum. In a previously uninfected herd, ingestion of canine (dogs, coyote) feces containing the infective coccidian organism is the means of exposure for the pregnant bovine. Infection can be maintained in the herd by being transfered vertically cow to calf, one generation to the next. Some abortions may occur.
Chlamydia, bacilli, streptococci, aspergillus and other fungi may cause abortion.
Diseases of Young Calves
Infectious agents known to cause illness in young calves are probably present in most beef herds. E. coli and salmonella bacteria, corona and rota viruses, bovine respiratory syncytial virus and other pathogens may cause disease when calves are born weak, do not receive adequate antibody protection from colostrum and are exposed to wet, crowded conditions. Calves deficient in copper, zinc or selenium have lowered resistance to disease.
Vaccination Recommendations for Cow-calf Herds
1. Brucellosis -- Heifers at 4-11 months of age, one time only.
2. “Lepto” -- Calves, two doses 4 weeks apart, booster at 6 months to 12-month intervals.
3. “Blackleg” -- All calves at 4-8 months of age with multiple clostridial disease products. Annual booster.
4. “Vibrio” -- Heifers and cows before breeding.
5. IBR-BVD -- Heifers at 4-8 months of age. Annual boosters.
Anthrax (only e in anthrax areas), Anaplasmosis (Bulls especially, Pasteurella, Pinkeye (ask your veterinarian).
*For blackleg, use multiple clostridium vaccine. If vaccinated early, give booster at weaning.
**Note: Combination vaccines: Lepto, Vibrio, IBR and BVD are commonly used.