Treatment: According to antimicrobial sensitivity studies, Mycobacterium bovis (M. bovis) is most often susceptible to oxytetracycline (LA-200TM IM or SQ, Bio-Mycin 200TM SQ, and AnchorOxy 200™ SQ), ceftiofur (Naxcel®,for use by or on the order of a licensed veterinarian), penicillin, and sulfonamides. Remember, these sensitivity patterns can and do change, making it necessary for your veterinarian to sample a representative number of infected cattle in your herd to determine proper drug usage. (Note: IM=intramuscular; SQ=subcutaneous).
Long-acting oxytetracycline has shown to be an effective treatment in calves when used early in the disease process. Long-acting oxytetracycline has been shown to clear M. bovis from the infected eye within 24 hours of the first injection, thereby eliminating the treated animal as a source of infection for other non-infected animals. Penicillin injected subconjunctivally (the thin membrane covering the white of the eye) has had similar healing rates as long-acting oxytetracycline injected intramuscularly but is more labor intensive. A combination of intramuscular long-acting oxytetracycline followed by feeding 2 grams/head/day of oxytetracycline in alfalfa pellets was reported to be effective in reducing the severity of a naturally occurring outbreak of pinkeye in 6-month-old Hereford calves. Also, calves receiving the oxytetracycline combination required fewer additional treatments than did calves treated with only subconjunctival procaine penicillin G. Other microbial products are used topically in the eye, but due to excessive tearing, their effectiveness is short lived and requires repeated treatments.
When severe corneal ulceration exists, protect the eye from UV light, flies, and other irritants through the use of eye patches, suturing the eyelids, or creating a third eyelid flap. Consult your veterinarian for assistance when considering these methods to enhance the healing process.
Follow all label instructions. Administer all intramuscular (IM) injectables in the neck and all subcutaneous (SQ) injectables in the neck or behind the shoulder. Do not administer over 10 ml in one injection site. Recheck all withdrawal times with your veterinarian. A veterinarian-client-patient relationship is necessary for the use of all prescription drugs and drugs used off-label (at dosages and for purposes other than defined on the label).
Pinkeye is a highly contagious infectious bacterial disease of the eye of cattle caused by Moraxella bovis (M. bovis). Costs resulting from decreased weight gain, milk production, and treatment were estimated to be $150 million in the United States alone, according to a 1993 study. Pinkeye (1.1% infection rate) was second to scours as the most prevalent condition affecting 1996-born unweaned calves over three weeks old, according to the National Animal Health Monitoring System of the USDA: APHIS: Veterinary Services. Pinkeye (1.3% infection rate) and foot rot (0.8% infection rate) were the two most prevalent conditions affecting all breeding beef females (replacement heifers and cows), according to the same 1997 report of 1996 conditions.
Cause: M. bovis is the primary infectious agent initiating pinkeye. Other microorganisms include chlamydia, mycoplasma, acholeplasma, or viruses such as the infectious bovine rhinotracheitis (IBR) virus and can either add to the severity of the disease process or may serve as predisposing factors permitting a secondary infection with M. bovis. Other factors instrumental in causing eye irritation, thereby allowing for invasion of M. bovis and subsequent disease, are excessive ultraviolet light (sunlight), the face fly (Musca autumnalis), plant material, and dust.
Ultraviolet (UV) light is especially a problem for cattle lacking pigmentation around the eye. Lack of pigmentation allows increased UV radiation to sensitize the eye resulting in inflammation and subsequent infection.
Face flies not only serve as irritants, as they feed on secretions from the eye, but they also serve as a means of transmitting M. bovis from infected to non-infected animals. Face flies can remain infected with M. bovis up to three days following feeding on infected material. Under experimental conditions, disease transmission is uncommon without the presence of face flies and is common with flies present.
Cool- and warm-season grasses, hybrid sudangrass, and other forage sorghums, weeds, and brush produce airborne irritants, pollen, and chaff, as well as serve as mechanical irritants. When animals consume the middle of round bales, leaving a hay shelf over their heads, the incidence of foreign body irritation is greatly increased. The same situation occurs when hay is fed in overhead feeders. This is especially true with wheat hay or hay containing cheatgrass.
Dust is more of a problem in confined feeding operations and is of minimal importance compared to UV radiation, flies, and plant material.
