Big Head

Big head can be caused by the bacteria Clostridium novyi, Clostridium sordellii, or Clostridium chauvoei. Sheep that are head butting or fighting can cause bruising or laceration of the subcutaneous tissue. The bacteria thrives in this environment, and the animal’s face, head, and neck undergo edematous swelling.

Diagnosis is made from clinical signs and treatment includes antibiotics.

Black Disease

Black disease is caused by Clostridium novyi type B. Clostridium novyi is found in soil. Black disease is contracted when its spores are ingested, which commonly occurs while animals are grazing pastures. As the bacteria replicate, they release toxins that cause necrosis of the liver. The exotoxins produced enter the general circulation, where they cause damage to neurons, vascular endothelium, and other vital cells and tissues, leading to sudden death of the animal.

Clinical black disease consists almost entirely of animals found dead. If the animal is identified as being ill before death, it will be depressed, possibly show signs of respiratory distress, and anorexia. Temperature is elevated initially (104–106°F) but declines before death.

Diagnosis of clinical black disease often is made at necropsy. Upon necropsy, hemorrhage of subcutaneous blood vessels is seen, subendocardial and subepicardial hemorrhages are present, and the kidney and liver show signs of autolysis. Migrating flukes, if present, predispose the flock to black disease, and the liver will have channels and show signs of necrosis. Definitive diagnosis can be accomplished with a Gram stain and culture of the liver lesions at the margins of the liver.

Tetracyclines may prove effective if the animal is diagnosed before death, which is rare. Vaccines to prevent black disease are available. Control of liver fluke infestation is extremely important in the prevention of black disease.

Blackleg

See Chapter 13, Common Bovine Diseases.

Botulism

See Chapter 9, Common Equine Diseases.

Brucellosis

Brucellosis in sheep is caused by Brucella ovis. Brucellosis in goats is caused by Brucella melitensis. Brucella melitensis may cause abortion in sheep. Goats can become infected with B. abortus if they are in contact with infected cattle. All of these bacteria are gram-negative coccobacillus organisms. The disease is prevalent in the western portions of North America. It rarely causes abortion in sheep but does cause epididymitis in rams. In sheep the disease is spread from ram to ewe and from ewe to ram, but it cannot be spread from ewe to ewe. Rams can pass the organism in their semen. Goats often become infected once they consume contaminated feed or water. Goats shed the disease in their urine, feces, placenta, and milk.

One of the clinical signs that can be seen in sheep is abortion. If the ewe aborts, she will be free of the disease within a few months. If she does not abort, she will give birth to an infected lamb. The placenta is thickened and necrotic upon examination. Because ewes rarely abort, the major clinical sign is epididymitis in rams. Clinical signs of goats infected with brucellosis include abortion storms, lameness, mastitis, diarrhea, and depression.

Diagnosis is accomplished with the use of agglutination tests or complement fixation.

There is no treatment of brucellosis. Control of the disease usually is accomplished by herd slaughter. To prevent the spread of brucellosis, animals should be serologically tested before they are introduced to the flock. A vaccine is available for sheep, but its ability to prevent the disease is poor Vaccination of goats is not allowed in the United States. Brucella melitensis and B. abortus are considered zoonotic, and precaution should be used when handling potentially infected animals. Only pasteurized milk products should be consumed Brucella melitensis is the cause of Malta fever in humans.

Caseous Lymphadenitis

Caseous lymphadenitis is caused by the gram-positive rod Corynebacterium pseudotuberculosis. The bacterium infects both goats and sheep and is often found in manure and soil, on the skin, and in infected organs. The organism can gain access into the body through several different methods, including superficial wounds, ingestion, mucous membranes, and inhalation. Indirect infection can occur through contaminated equipment, including bedding, feeders, and clipper blades.

Clinical signs of infection often include dyspnea, tachypnea, cough, and weight loss.

Diagnosis involves culture of the bacteria from a transtracheal wash. Thoracic radiographs may reveal masses in the thoracic cavity. Hepatic abscesses may be found upon necropsy (Fig. 17-1). The disease often causes abscessation of the lymph nodes. Identification and removal of sick animals from the herd can help control outbreaks. Sanitation during management practices such as castration, tail docking, and parturition can also help prevent infection. Vaccination is controversial.

Chlamydophilosis

Chlamydophilosis is also known as enzootic abortion in ewes (EAE). EAE is caused by the bacterium Chlamydia psittaci. EAE is one of the most common causes of abortion in North America and is the number one cause of abortion in goats. The bacterium is spread by contact with uterine discharge, the fetus, and the placenta. Rams are another source of infection. Ewes infect rams, and the rams then spread the disease to other ewes in the flock. After aborting, the dam develops a good immune response, and elimination of Chlamydia from her uterus usually occurs within 3 months of the abortion, although persistent shedding can occur.

The most common clinical sign of EAE is abortion in the last 2 to 3 weeks of gestation. Lambs can be born weak or stillborn. Chlamydial infections also can produce pneumonia, keratoconjunctivitis, epididymitis, and polyarthritis.

Diagnosis is often achieved through the use of enzyme-linked immunosorbent assay (ELISA) tests, fluorescent antibody staining, and culture isolation.

Antibiotics can be used during the last few weeks of gestation as a form of treatment. Females that have aborted should be segregated from the herd, and any fetal tissue or placenta from the abortion should be burned or buried. Good feeding practices should be followed to help prevent contamination of the feed and water with C. psittaci. Vaccinations are available; however, they most likely will prevent only abortion and not the disease.

Clostridium Perfringens

Clostridium perfringens is a normal flora of the gastrointestinal (GI) system in sheep. The disease (enterotoxemia, overeating disease) can occur in peracute, acute, and chronic forms. All four types of C. perfringens can cause diarrhea in lambs.

Foot Rot

See Chapter 13, Common Bovine Diseases.

Joint Ill

Joint ill primarily occurs in kids. It is caused by several bacterial agents, but the majority are gram-positive agents. Some of the bacteria that cause joint ill include staphylococci, streptococci, Corynebacterium spp., Actinomyces, and coliform bacteria. The bacteria often gain entry to the body through breaks in the skin, the umbilical cord, or the GI or respiratory tract. Predisposing factors include overcrowding and unsanitary conditions.

Clinical signs include warm, painful, swollen joints, lameness, fever, umbilical cord abscessation, and leukocytosis with left shift.

Treatment can be successful if the disease is caught early. Antibiotics and joint flushing can be successful.

Leptospirosis

See Chapter 13, Common Bovine Diseases.

Listeriosis

Listeriosis is more prevalent in goats than in sheep or cattle. See Chapter 13, Common Bovine Diseases.

Malignant Edema

See Chapter 13, Common Bovine Diseases.

Paratuberculosis (Johne Disease)

See Chapter 13, Common Bovine Diseases, for discussion of paratuberculosis (Figs. 17-2 and 17-3).

Pinkeye

See Chapter 13, Common Bovine Diseases.

Tetanus

See Chapter 9, Common Equine Diseases (Fig. 17-4).

Transmissible Spongiform Encephalopathies

Transmissible spongiform encephalopathies (TSE) is also known as “scrapie.” Scrapie is thought to be caused by a prion. Sheep seem to be more or less sensitive to TSE depending on their genetics. Suffolk sheep are most commonly diagnosed. Sheep and goats are natural reservoirs for scrapie. Transmission of the disease is not fully understood. Sheep are suspected to become infected at birth and often begin displaying clinical signs around years of age. The infection is thought to be result from contact with infected animals or the environment.

Clinical signs include wool or hair loss, ataxia, weight loss, starring, aggressiveness, floppy ears, tremors, seizures, inability to swallow, and death. The disease is chronic and degenerative.

Diagnosis is accomplished by finding the scrapie prion protein with immunostaining of lymphoid tissue. There is no treatment of scrapie. The disease is considered fatal. The disease is reportable and often results in flock slaughter.

Prevention is being attempted through the Scrapie Flock Certification Program. The program requires flocks to be assessed for 5 years to determine that they do not contain any scrapie-infected sheep. This program has four levels of clearance. When the final level is attained, the producers are able to export and sell sheep both within the United States and internationally without restrictions.

Vibriosis

Vibriosis is caused by Campylobacter jejuni and Campylobacter fetus. The bacteria are gram-negative rods that live in the intestines of sheep, birds, and dogs. In North America, vibriosis is the number one cause of abortion in sheep. Infection occurs through ingestion of the organism by pregnant females.

Clinical signs include late term abortion, stillbirth, and weak limbs.

Diagnosis is made from culture of the bacteria.

Antibiotics can be helpful in the event of an outbreak; however, vaccination is the best prevention.