Pinkeye prevention and treatment options available
According to University of Nebraska Extension Veterinarian Richard Randle, pinkeye is an economically important infectious disease that may result in losses of up to $300 million per year for producers worldwide.
Transmitted by a bacterium, Mycobacterium bovis, there are measures that producers can take to protect against pinkeye, as well as treatment options if the disease is contractd by cattle.
Pinkeye vaccines can be utilized that will reduce the incidence and severity of the infection but will not reduce the incidence of pinkeye to zero.
“The M. bovis vaccines are directed against the pili to prevent attachment and the production of enzymes,” Randle explained. “It can reduce the incidence and severity of the disease, but there have been a wide variety of responses to these vaccines.”
If pregnant cows are vaccinated, they can pass on colostral immunity to their calves for six months, Randle said.
When cattle are vaccinated, antibodies develop in the blood and travel to the cornea of the eye to build up immunity against the disease.
“The vaccine works, but it takes 21 to 42 days to develop immunity,” Randle explained.
“There are also different strains of the disease, so the vaccine you use may not be labeled for the particular strain you have,” he added.
However, if pinkeye is a problem, producers can have the organism for a specific ranch cultured and then have a vaccine manufactured.
“The vaccine would be site specific and could only be used on that site,” he said.
Randle recommended producers give the vaccine a month to six weeks ahead of the peak season for pinkeye.
“If you vaccinate at branding, it is questionable how much value you will get out of the vaccine when you take into account when peak fly season starts,” he said.
Many treatments currently available need to be applied two to three times a day, which is not very economical in a cattle operation, Randle explained. Topical treatments like ophthalmic ointments or powders need frequent application two to three times a day for several days. Examples would be gentamicin, triple antibiotic, tetracycline and nitrofurazone.
Producers can also give subconjunctival injections by injecting an antibiotic like penicillin, ampicillin, amoxicillin or tetracycline beneath the conjunctiva.
“The antibiotic leaks out of the injection site to bathe the ocular surface,” Randle said. “The effects last approximately eight hours, but the injections need to be given two to three times daily for several days. Single injections have not proven to alter the course of pinkeye.”
A more economical solution may be giving an intramuscular or subcutaneous injection of oxytetracycline at 10 milligrams per pound, which maintains therapeutic levels up to 72 hours, Randle said.
“It will also reduce the rate of shedding in acute cases,” he added. “Two injections given 48 to 72 hours apart is recommended.”
In addition, producers need to protect the infected eyes of cattle from ultraviolet light by covering them with eye patches or third eyelid flaps.
Atropine can also be used to reduce spasms and eye pain, and corticosteroids can be used to reduce scarring. Randle cautioned that atropine can dilate the iris, so producers need to cover the infected eye with a patch to protect it from light.