Pinkeye can cause significant economic loss for cattle producers
With summer fast approaching, cattlemen need to be diligent about monitoring their herds for pinkeye.
According to University of Nebraska Extension Veterinarian Richard Randle, pinkeye is an infectious disease that affects cattle worldwide and causes economic losses of $150 to $300 million each year. Most of the losses stem from reduced growth, decreased milk production, costs of treatment, reduced value of infected animals and death loss.
Mycobacterium bovis, which is the main cause of pinkeye, can be harbored in nasal or ocular secretions.
“Asymptomatic carrier animals can shed the organism,” Randle explained. “The infection can also be spread from animal to animal through direct contact, aerosols and vectors.”
Face flies can be a major problem in the spread pinkeye.
Unfortunately, face flies are difficult to control because they only feed off the ocular secretions for very short periods of time.
“The flies don’t stay on the cattle long enough to be able to control them,” Randle explained.
The first sign of the infection is tearing, followed by conjunctivitis. An animal can develop keratitis and corneal ulceration. The infection, which is quite painful to cattle, attaches to the cornea of the eye with pili and digests the eye surface with enzymes. It causes an ulceration of the cornea and the animal to lose its sight.
While the animal is infected, the eye becomes quite sensitive to ultraviolet light and environmental factors like dust, wind, weeds, pollens and sunlight. The cattle will become dirty-eyed and will squint.
“The white portion of the eye becomes inflamed and reddened. Organisms attach to the cornea and bring fluid into the cornea, as well as drawing white blood cells in to fight the infection,” Randle explained. “They can eat through the entire layer of the cornea if the infection progresses enough, but that only occurs in a small percentage of cattle. The vast majority of animals will recover their sight from this disease.”
Once the healing process starts, Randle said cells come in to heal the eye.
“The blood vessels infiltrate the cornea to clean up the debris,” Randle explained. “Any tissue that is damaged will develop a scar, which may reduce in size until it is the size of a pinpoint, depending upon how bad the infection was.”
Randle said although the eye can be cultured to diagnose pinkeye, it is very difficult to keep the culture alive until it arrives at the lab.
“It can be difficult to diagnose because other common isolates may be present,” he said. “There are also various strains of the organism that causes pinkeye.”
If a producer suspects an animal has pinkeye, the veterinarian recommends treatment for the animal and to segregate it to reduce the chance the infection will spread to other animals.
“It is also important to keep instruments and the hands clean, because they could serve as a vector to spread the infection,” he explained.
Pink eye susceptibility
Studies have shown that minerals and vitamins, like Vitamin A, are associated with skin health, Randle continued. If cattle are marginal or deficient, it could increase their susceptibility to pinkeye.
“It is important for producers to have a good, well-balanced vitamin and mineral program in place,” he stated.
The incidence of pinkeye varies from year to year, Randle concluded, but ranchers can control the incidence of the disease through good management.
“It is a difficult situation to deal with. I have been to ranches where there are two pastures of cattle with fence line contact. One pasture has 50 percent infected with pinkeye and the other pasture has zero,” he said.