Cow Tales: Winter pinkeye | TSLN.com

Cow Tales: Winter pinkeye

Kenny Barrett Jr., DVM, MS

For the January 22, 2011 edition of Tri-State Livestock News.

You will be hard pressed to find a fly in South Dakota this time of year. We have always been taught flies cause pinkeye. So where does winter pinkeye come from? Obviously there must be more to the story; and there is. Pinkeye is a multi-faceted disease that can leave producers scratching their heads looking rather pensive. Time of year, vaccination, forage maturity, cattle oilers, fly sprays, fly tags, fly predators, feeding practices and treatment choices are just a few of the considerations that need to be addressed.

Pinkeye is a lay term for infectious bovine keratoconjunctivitis. It is easy to see why people refer to the condition as pinkeye. By definition it is inflammation of the cornea of the eye caused by an infectious pathogen. The cornea is the clear portion of the eye that allows light into the eye and is surrounded by the whitish colored sclera. The cornea is made of a network of protein fibers perfectly oriented to allow light to pass through so it appears clear. The surface of the cornea is covered with a single layer of specialized epithelial cells. According to the definition, pinkeye is inflammation of that specialized layer of cells and often the protein fiber network that lies beneath – a corneal ulcer. Some of the light is reflected causing the cornea to look cloudy when the protein fiber orientation is disturbed by bacterial enzymes, inflammatory mediators and fluid.

Winter pinkeye is most often caused by management feeding decisions. Place a round bale in a pen and cattle will bore a hole to the center. The outer six- to eight-inches of the bale is susceptible to rain and rot, while the inside is relatively free from the effects of weather. But, boring holes can be devastating to eyes. Cattle abrade their corneas in their zest to reach the more nutritious center of the bale. Forage-related eye trauma also occurs in late summer as grasses grow taller and mature. The increased texture enhances the ability of the forage to cause eye trauma while cattle graze. The surface of the eye harbors potentially pathogenic or troublesome bacteria that aggravate feed-induced eye trauma. Management practices that minimize round bale feeders will help to minimize winter pinkeye. We recommend unrolling round bales or feeding ground hay.

Infectious causes of winter pinkeye include viruses and more often bacteria. The viruses are IBR or “red nose” and rarely a lesser-known virus called malignant catarrhal fever. With IBR, the symptoms ranging from pinkeye, respiratory issues and even abortion.

The most common pathogens associated with pinkeye are bacteria. The traditional bacteria are called moraxella bovis, although many other species can play a lesser role. This is the type of bacteria that is in commercial pinkeye vaccines. These bacteria have specialized protein structures called pili that adhere to the surface of the eye and start the disease process. Commercial vaccines are designed against these pili so the bacteria cannot attach themselves to the eye. The vaccines are pilus-specific, so bacteria with different pili are unaffected. The specificity of the vaccine for a limited number of pilus types means the vaccine has a narrow range of cross-protection. This partly explains the variable success of a vaccine in different herds, or a sudden increase in pinkeye incidence in a well-vaccinated herd. Furthermore, the disease process is enhanced by irritants like ultraviolet light, dust, forage, etc. The bacteria are spread from one animal to another by direct contact in tear and nasal secretions, flies and other inanimate objects.

More recently an additional type of bacteria has been recognized as a significant contributor to pinkeye. Moraxella bovoculi seems to be a stronger fighter, a pinkeye superpower that causes more severe disease and is less responsive to medical treatment. There have been many recent name changes, but producers tend to call it sheep pinkeye stemming from a former name, moraxella ovis. It has proven to be a significant contributor to winter pinkeye in many herds. This type of bacteria is not a component of any commercial vaccines and no cross-protection seems to exist from the moraxella bovis strains. But, the producer can work with their veterinarian to culture this aggressive pathogen and have an autogenous vaccine made for their herd.

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Treatment is centered around some sort of antibiotic. Drops or ointments can be applied to the surface of the eye. Topical antibiotics work well when administered three- to four-times a day for multiple days. The frequent administration is necessary because the tear film on the surface of the eye is shallow and can’t hold antibiotics for any measurable amount of time. The traditional veterinary approach was to inject a small amount of antibiotic in the subconjunctival space. Sometimes the injection was combined with a steroid to reduce inflammation. This practice is still debated amongst veterinarians. Some studies indicate a reduction in healing times and would suggest no effect. For sure this technique requires patience and adequate restraint. Newer treatment programs employ systemic antibiotics administered in the neck in compliance with Beef Quality Assurance guidelines. Additionally, it is always a good idea to cover the eye with a semi-permanent patch. The patch blocks the sun, relieving some pain; reduces transmission by flies and inanimate objects; and minimizes ongoing trauma by physical irritants.

Producers need to recognize the many aspects of pinkeye and especially the management considerations of winter pinkeye outbreaks. Efforts should be focused on reducing the effects of flies. Many products are available with varying success, including: oilers, sprays, pour-ons and fly tags. Steps should be taken to match application with peak fly season if possible. Minimize dusty environments and manage forage availability to decrease the likelihood of mature forage playing a role. If the disease seems to not fit any of the traditional causes, or they are refractory to treatment, then the eyes need to be cultured to rule out moraxella bovoculi. Treatment programs should be designed with the help of your local veterinarian. The animal welfare and economic implications of pinkeye are too important to ignore.

You will be hard pressed to find a fly in South Dakota this time of year. We have always been taught flies cause pinkeye. So where does winter pinkeye come from? Obviously there must be more to the story; and there is. Pinkeye is a multi-faceted disease that can leave producers scratching their heads looking rather pensive. Time of year, vaccination, forage maturity, cattle oilers, fly sprays, fly tags, fly predators, feeding practices and treatment choices are just a few of the considerations that need to be addressed.

Pinkeye is a lay term for infectious bovine keratoconjunctivitis. It is easy to see why people refer to the condition as pinkeye. By definition it is inflammation of the cornea of the eye caused by an infectious pathogen. The cornea is the clear portion of the eye that allows light into the eye and is surrounded by the whitish colored sclera. The cornea is made of a network of protein fibers perfectly oriented to allow light to pass through so it appears clear. The surface of the cornea is covered with a single layer of specialized epithelial cells. According to the definition, pinkeye is inflammation of that specialized layer of cells and often the protein fiber network that lies beneath – a corneal ulcer. Some of the light is reflected causing the cornea to look cloudy when the protein fiber orientation is disturbed by bacterial enzymes, inflammatory mediators and fluid.

Winter pinkeye is most often caused by management feeding decisions. Place a round bale in a pen and cattle will bore a hole to the center. The outer six- to eight-inches of the bale is susceptible to rain and rot, while the inside is relatively free from the effects of weather. But, boring holes can be devastating to eyes. Cattle abrade their corneas in their zest to reach the more nutritious center of the bale. Forage-related eye trauma also occurs in late summer as grasses grow taller and mature. The increased texture enhances the ability of the forage to cause eye trauma while cattle graze. The surface of the eye harbors potentially pathogenic or troublesome bacteria that aggravate feed-induced eye trauma. Management practices that minimize round bale feeders will help to minimize winter pinkeye. We recommend unrolling round bales or feeding ground hay.

Infectious causes of winter pinkeye include viruses and more often bacteria. The viruses are IBR or “red nose” and rarely a lesser-known virus called malignant catarrhal fever. With IBR, the symptoms ranging from pinkeye, respiratory issues and even abortion.

The most common pathogens associated with pinkeye are bacteria. The traditional bacteria are called moraxella bovis, although many other species can play a lesser role. This is the type of bacteria that is in commercial pinkeye vaccines. These bacteria have specialized protein structures called pili that adhere to the surface of the eye and start the disease process. Commercial vaccines are designed against these pili so the bacteria cannot attach themselves to the eye. The vaccines are pilus-specific, so bacteria with different pili are unaffected. The specificity of the vaccine for a limited number of pilus types means the vaccine has a narrow range of cross-protection. This partly explains the variable success of a vaccine in different herds, or a sudden increase in pinkeye incidence in a well-vaccinated herd. Furthermore, the disease process is enhanced by irritants like ultraviolet light, dust, forage, etc. The bacteria are spread from one animal to another by direct contact in tear and nasal secretions, flies and other inanimate objects.

More recently an additional type of bacteria has been recognized as a significant contributor to pinkeye. Moraxella bovoculi seems to be a stronger fighter, a pinkeye superpower that causes more severe disease and is less responsive to medical treatment. There have been many recent name changes, but producers tend to call it sheep pinkeye stemming from a former name, moraxella ovis. It has proven to be a significant contributor to winter pinkeye in many herds. This type of bacteria is not a component of any commercial vaccines and no cross-protection seems to exist from the moraxella bovis strains. But, the producer can work with their veterinarian to culture this aggressive pathogen and have an autogenous vaccine made for their herd.

Treatment is centered around some sort of antibiotic. Drops or ointments can be applied to the surface of the eye. Topical antibiotics work well when administered three- to four-times a day for multiple days. The frequent administration is necessary because the tear film on the surface of the eye is shallow and can’t hold antibiotics for any measurable amount of time. The traditional veterinary approach was to inject a small amount of antibiotic in the subconjunctival space. Sometimes the injection was combined with a steroid to reduce inflammation. This practice is still debated amongst veterinarians. Some studies indicate a reduction in healing times and would suggest no effect. For sure this technique requires patience and adequate restraint. Newer treatment programs employ systemic antibiotics administered in the neck in compliance with Beef Quality Assurance guidelines. Additionally, it is always a good idea to cover the eye with a semi-permanent patch. The patch blocks the sun, relieving some pain; reduces transmission by flies and inanimate objects; and minimizes ongoing trauma by physical irritants.

Producers need to recognize the many aspects of pinkeye and especially the management considerations of winter pinkeye outbreaks. Efforts should be focused on reducing the effects of flies. Many products are available with varying success, including: oilers, sprays, pour-ons and fly tags. Steps should be taken to match application with peak fly season if possible. Minimize dusty environments and manage forage availability to decrease the likelihood of mature forage playing a role. If the disease seems to not fit any of the traditional causes, or they are refractory to treatment, then the eyes need to be cultured to rule out moraxella bovoculi. Treatment programs should be designed with the help of your local veterinarian. The animal welfare and economic implications of pinkeye are too important to ignore.

kenny barrett jr. is a veterinarian at the belle fourche veterinary clinic in belle fourche, sd. check us out on facebook, “belle fourche vet clinic – cow/calf,” or drop us an e-mail at bfvc@live.com to suggest a topic for the next installment of cow tales.

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