F635
Pinkeye

Introduction: Pinkeye is a highly contagious infection of sheep and goats that affects the eye and surrounding structures. Pinkeye infections occur most commonly in the summer and fall when insects and sun exposure are at the highest levels. Pinkeye of cattle is caused by a different organism and will not affect sheep or goats. The organisms that cause pinkeye in sheep and goats will not affect cattle.

Causative Agents: This disease is caused by the organisms Mycoplasma and Chlamydia. This problem should not be confused with similar conditions caused by grass seeds or foreign bodies (sticks, plant material, etc.) that may also injure the eye. Environmental influences can increase the chances of developing the disease. Some of these influences are listed below:

  1. Exposure to excessive sunlight (ultraviolet light).
  2. Exposure to irritating flies.
  3. Certain plants (long stemmed, coarse feed or hay), weeds (cheat grass), and feeding conditions (overhead feeders and large round bales).
  4. Excessive wind, pollen, and dust.
  5. Other bacterial or viral infections.

* Each of the above conditions results in increased irritation to the eye and potential infections.

Clinical Signs: The infection begins when the invading organisms cause swelling and redness to the eyelid lining (conjunctiva) and surrounding tissues of one or both eyes. The eye is very sensitive to light and may have an excessive amount of tearing. These animals can have an increased temperature and often go off feed due to the pain associated with the infection. With time (2-6 days), the eye becomes cloudy and an ulcer may develop. If the infection is severe, the entire eye can become involved, sometimes resulting in rupture of the eye and/or blindness. Mild cases may only take 10-14 days to heal and return to almost normal. Severe cases may take 6 weeks to heal, but most animals recover completely. Some sheep and goats are resistant to reinfection for about a year.

Disease Transmission: Pinkeye is spread from animal to animal by direct contact with infectious material containing Mycoplasma and/or Chlamydia. This infectious material can be spread by flies, animal-to-animal contact, buckets, hands, and equipment. Studies show that when a sheep/goat has recovered, the organism may remain in the eye for up to approximately 200 days. Sheep and goats that carry the organism but have no sign of pinkeye are known as carriers. If these carriers come into contact with a clean flock/herd, they may cause an outbreak.

Treatment: Mildly affected sheep/goats recover without treatment. When a high percentage of the flock/herd is affected, penning and treatment of all animals may reduce the severity of the outbreak; however, penning should be avoided in most other situations because it may aid the spread of infection.

This disease is treated using many different antibiotics that are injected in the body or placed directly in the eye. Some of the products that are commonly used include tetracycline and tylosin. If a small group or an individual animal is affected, eye ointments containing tetracycline should be applied to the eye 2-4 times a day. If this is not possible in a large flock/herd or outbreak, intramuscular injections of tetracycline or tylosin can be given. Some studies also show that a non-irritating, intramammary mastitis treatment can be used and applied directly into the eye. Consult a local veterinarian for additional details.

Prevention: Disease prevention for pinkeye focuses on four major areas:

  1. Provide fly control when possible.
  2. Provide adequate protection from sunlight. Allow access to shade and protection from the sun.
  3. Maintain an environment free of irritation. This means keeping weeds, pollen, and dust to a minimum.
  4. Maintain optimal immune status for the flock/herd. All animals should receive adequate nutrition, be part of a flock/herd health program, and be managed in a way to prevent excessive stress due to environmental extremes, handling, and other diseases.

There are no vaccines available for this disease in sheep and goats. The vaccine commonly used for cattle is not effective for small ruminants and should NOT be used.