Infectious bovine keratoconjunctivitis (IBK), also known as pinkeye, New Forest eye or blight,Farming Small Areas, August/September, 2008, "Clearing up pinkeye" is a veterinary infection of cattle caused by '' Moraxella bovis'', a Gram-negative, β-haemolytic, aerobic, rod-shaped

bacterium Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the ...

. It is spread by direct contact or by

flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...

serving as

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

s. It is the most common ocular disease of

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

(mostly beef). IBK is similar to human pink eye and causes severe infection of the

conjunctiva In the anatomy of the eye, the conjunctiva (: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with gobl ...

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

corneal opacity Corneal opacification is a term used when the human cornea loses its transparency. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diamete ...

, and

ulceration An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected Organ (biology), organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caus ...

. This disease is highly contagious and occurs worldwide. Younger animals are more susceptible, but recovery with minimal damage is usual, if they are treated early.

Cause

'' Moraxella bovis'' is a

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

rod-shaped

aerobe An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. The ability to exhibit aerobic respiration may yield benefits to the aerobic organism, as aerobic respiration yields more energy than anaerobic ...

. This bacterium is an

obligate intracellular parasite Intracellular parasites are microparasites that are capable of growing and reproducing inside the cells of a host. They are also called intracellular pathogens. Types There are two main types of intracellular parasites: Facultative and Obligate ...

of the

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

s, and can usually be isolated from the

respiratory tract The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respirato ...

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

, and conjunctiva of healthy animals. Transmission of IBK is through direct contact with mucous membranes and their secretions and indirect contact where flies act as a mechanical vector.

Asymptomatic carrier An asymptomatic carrier is a person or other organism that has become infected with a pathogen, but shows no signs or symptoms. Although unaffected by the pathogen, carriers can transmit it to others or develop symptoms in later stages of the d ...

animals can also be source of infection.

Predisposing factors

Ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

(UV) radiation is implicated in cattle with no pigmentation around the eyelids and cattle with prominently placed eyes.

Exudate An exudate is a fluid released by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin language, Latin 'to (ooze out) sweat' (' 'out' and ' 'to sweat'). Medi ...

from the sun-burnt skin around the eyes can contain bacteria and attracts flies. UV light also directly damages the

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

epithelium Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

, leading to a breakdown in host

innate immunity The innate immune system or nonspecific immune system is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system). The innate immune system is an alternate defense strategy and is the dominant immune s ...

. Dust, dried-up plants, tall vegetation, and oversized or incorrectly placed ear tags may cause mechanical damage to the eye and facilitate bacterial colonization. The disease may be complicated by concurrent infection with viruses such as infectious bovine rhinotracheitis virus ( bovine herpesvirus 1) or

adenovirus Adenoviruses (members of the family ''Adenoviridae'') are medium-sized (90–100 nm), nonenveloped (without an outer lipid bilayer) viruses with an icosahedral nucleocapsid containing a double-stranded DNA genome. Their name derives from t ...

, bacteria such as '' Mycoplasma boviculi'' or ''

Listeria monocytogenes ''Listeria monocytogenes'' is the species of pathogenic bacteria that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the ho ...

'', or infestation by '' Thelazia'', a

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

Vitamin A deficiency Vitamin A deficiency (VAD) or hypovitaminosis A is a lack of vitamin A in blood and tissues. It is common in poorer countries, especially among children and women of reproductive age, but is rarely seen in more developed countries. Vitamin A pla ...

is also implicated. IBK is most prevalent in summer and early autumn. A recent Meat and Livestock Australia report "estimates that the disease costs Australian beef producers AU$23.5 million annually in lost production and treatment costs".

Clinical signs and diagnosis

The bacteria invade the lacrimal glands of the eye, causing

keratitis Keratitis is a condition in which the human eye, eye's cornea, the clear dome on the front surface of the eye, becomes inflammation, inflamed. The condition is often marked by moderate to intense pain and usually involves any of the following sy ...

uveitis Uveitis () is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. The uvea consists of the middle layer of pigmented vascular structures of the eye and ...

, and corneal ulceration. Cattle show signs of pain, increased lacrimation, excessive blinking, and

conjunctivitis Conjunctivitis, also known as pink eye or Madras eye, is inflammation of the conjunctiva, the thin, clear layer that covers the white surface of the eye and the inner eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness ...

. More severe cases may show systemic signs such as anorexia and weight loss. Chronic untreated cases can become blind. Diagnosis is usually based on the clinical signs, but the bacteria can be cultured from lacrimal swabs, or visualised on smears of lacrimal secretions.

Treatment and control

Shade,

insect repellent An insect repellent (also commonly called "bug spray" or "bug deterrent") is a substance applied to the skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellent ...

-impregnated ear tags, and lower stocking rates may help prevent IBK. Early identification of the disease also helps prevent spread throughout the herd. Treatment is with early systemic use of a long-acting

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

such as

tetracycline Tetracycline, sold under various brand names, is an antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. It is available in oral an ...

or florfenicol. Subconjunctival injections with procaine penicillin or other

s are also effective, providing a "bubble" of antibiotic which releases into the eye slowly over several days.

Anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation, fever or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs reduce pain by inhibiting mechan ...

therapy can help shorten recovery times, but topical

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are invo ...

s should be used with care if corneal ulcers are present. ''M. bovis'' uses several different

serotype A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or Cell (biology), cells are classified together based on their shared reactivity ...

d fimbriae as

virulence factor Virulence factors (preferably known as pathogenicity factors or effectors in botany) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following: * c ...

s, consequently pharmaceutical companies have exploited this to create vaccines. However, currently available

vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifi ...

s are not reliable.

Vaccination

A vaccine, known as "Piliguard", is available in Australia. The vaccine contains three strains of ''Morexella bovis'' (SAH38, FLA 64, EPP 63) pilli antigen. This stimulates antibody production against the bacterial pilli to prevent their attachment and invasion of the conjunctiva. The company claims the vaccine reduces the incidence and severity of the disease in an individual animal which directly reduces animal suffering and production loss on top of limiting the spread of disease through the herd. This, in turn, reduces the amount of antibioitics and fly repellent needed during high-risk seasons. The vaccine is marketed in multidose vials and has an adjuvant to create a long-term subcutaneous depot. This means no booster shot is necessary, but severe local reaction can be seen in people who accidentally inoculate themselves. Calves as young as one week old can be treated and no meat, milk, or export slaughter withdrawal is needed.

References

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External links

Infectious Bovine Keratoconjunctivitis at Wikivet
accessed 06/10/2011.
Animal Disease Diagnostic Laboratory
Bovine diseases