Mycoplasma conjunctivae infection

Pictures

Picture	Title	Caption	Copyright
Title Symptoms - sheep Caption Eye of sheep infected with infectious keratoconjunctivitis showing redness of the conjunctival mucosa, neovascularization and pannus. Copyright John B. Bashiruddin	Symptoms - sheep	Eye of sheep infected with infectious keratoconjunctivitis showing redness of the conjunctival mucosa, neovascularization and pannus.	John B. Bashiruddin
Title Symptoms - Alpine ibex Caption Eye of an Alpine ibex (Capra I. Ibex) affected with infectious keratoconjunctivitis showing conjunctival hyperaemia, perilimbic neovascularization and mucous secretions. Copyright John B. Bashiruddin	Symptoms - Alpine ibex	Eye of an Alpine ibex (Capra I. Ibex) affected with infectious keratoconjunctivitis showing conjunctival hyperaemia, perilimbic neovascularization and mucous secretions.	John B. Bashiruddin
Title Symptoms - Alpine ibex Caption Eye of an Alpine ibex (Capra i. Ibex) affected with infectious keratoconjunctivitis showing corneal oedema. Copyright John B. Bashiruddin	Symptoms - Alpine ibex	Eye of an Alpine ibex (Capra i. Ibex) affected with infectious keratoconjunctivitis showing corneal oedema.	John B. Bashiruddin
Title Symptoms - Alpine chamois Caption Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis showing corneal opacity caused by cellular infiltration in response to damaged corneal epithelium Copyright John B. Bashiruddin	Symptoms - Alpine chamois	Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis showing corneal opacity caused by cellular infiltration in response to damaged corneal epithelium	John B. Bashiruddin
Title Symptoms - Alpine chamois Caption Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis showing corneal scar after perforation. Corneal ulceration occurs in severe cases and may lead to anterior synechia and melanin deposits forming staphyloma. Copyright John B. Bashiruddin	Symptoms - Alpine chamois	Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis showing corneal scar after perforation. Corneal ulceration occurs in severe cases and may lead to anterior synechia and melanin deposits forming staphyloma.	John B. Bashiruddin
Title Adult|Symptoms - Alpine chamois Caption Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis with a muscadid fly, Hydrotaea irritans on the affected cornea.|Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis with Hydrotaea irritans on the affected cornea. Copyright John B. Bashiruddin	Adult|Symptoms - Alpine chamois	Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis with a muscadid fly, Hydrotaea irritans on the affected cornea.|Eye of an Alpine chamois (Rupicapra r. rupicapra) affected with infectious keratoconjunctivitis with Hydrotaea irritans on the affected cornea.	John B. Bashiruddin

Identity

Preferred Scientific Name

• Mycoplasma conjunctivae infection

International Common Names

• English: conjunctivitis in sheep and goats; contagious conjunctivo-keratitis; contagious ophthalmia; contagious ovine ophthalmia; epidemic caprine keratoconjunctivitis; infectious caprine keratoconjunctivitis; infectious keratoconjunctivitis; infectious ovine keratoconjunctivitis; keratoconjunctivitis; kerato-conjunctivitis; mycoplasma conjunctivae keratoconjunctivitis in sheep and goats; ovine infectious keratoconjunctivitis; ovine keratoconjunctivitis; pink eye; pink-eye; pinkeye of sheep and goats
• French: kératoconjonctivite

English acronym

• ICK
• IKC
• IOK

Pathogen/s

Overview

Introduction

Mycoplasma conjunctivae (Mconj) is the cause of infectious keratoconjunctivitis (IKC), or pink-eye, in domestic and wild ovine and caprine species (Jones et al, 1976; Giacometti et al, 1998), although M. arginini and Acholeplasma oculi have also been isolated from sheep with ocular infections (Leach, 1970; Arbuckle and Bonson, 1980). M. agalactiae, the classical cause of contagious agalactia, and some members of the M. mycoides cluster may also cause keratoconjunctivitis (Bergonier et al., 1997). Bacterial causes of the disease include Chlamydia and Rickettsia (Egwu, 1991). IKC is a localized inflammatory condition of the conjunctiva and cornea in domestic and wild small ruminants. In the early stages, the disease may present as a unilateral or bilateral conjunctivitis with hyperaemia of the vessels but untreated cases may progress to mucopurulent keratitis and corneal ulceration resulting in opaque or perforated corneas and transient blindness. IKC with M. conjunctivae may be exacerbated by exposure to sunlight. In Scotland it occurs most frequently in the autumn: black face and Cheviot ewes are equally susceptible (Hosie, 1989). M. conjunctivae may be isolated with some difficulty in most mycoplasma media; it ferments glucose but does not use arginine or urea (Jones et al., 1976). Topical or parenteral administration of tetracyclines has been recommended for treatment (Hosie, 1989) although a report by Waseem Shahzad et al. (2013) indicated topical treatment with a sterile solution of gentamycin at 100mg/ml was suitable in Pakistan.

History

Mycoplasmas from sheep and goats with naturally occurring IKC were characterised biochemically and serologically from samples obtained from two farms in Maryland, USA, in the late 1960s and found to be a different species. They were not related to any known mycoplasmas isolated from sheep and goats with IKC but were similar to some conjunctival strains from Australia and Canada and named M. conjunctivae (Surman, 1968; McCauley et al., 1971; Barile et al., 1972;). IKC progresses slowly and it was not considered economically important at the time. Although a causal relationship between M. conjunctivae and IKC was not firmly established, the disease was subsequently reproduced experimentally (Jones et al., 1976; Trotter et al., 1977; ter Laak et al., 1988; Dagwall, 1993). Further isolations from sheep and Swiss chamois and ibex revealed that the disease was more severe in wild animals in which it caused total blindness (Nicolet and Freundt, 1975; Mayer et al., 1996). The M. conjunctivae genome is 846,214 bases, it has a G+C content of 29% with an estimated 734 genes (Calderon-Copete et al., 2009).

Host Animals

Hosts/Species Affected

Experimentally, M. conjunctivae has been shown to infect sheep (Jones et al., 1976; van Halderen et al., 1994), goats (Trotter et al., 1977), Alpine ibex, (Capra ibex) (Giacometti et al., 1998) and European mouflon (Terrier, 1998). Sheep strains were infectious for ibex (Giacometti et al., 1998). M. conjunctivae has been isolated from cases of IKC in Alpine chamois (Rupicapra rupicapra) (Nicolet and Freundt, 1975; Degiorgis et al., 2000a), Pyrenean chamois (Rupricapra p. pyrenaica) (Arnal et al., 2013), mouflon (Terrier, 1998), and Himalayan thar (Hemitragus jemlahicus) (Belloy et al., 2001).

Systems Affected

Distribution

IKC caused by M. conjunctivae is probably present worldwide (Jones, 1991), but the prevalence is not well known anywhere.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Pathology

In acute cases of M. conjunctivae infection, the conjunctiva and cornea are infiltrated with large numbers of neutrophils and small numbers of plasma cells and lymphocytes. In one study the neutrophil count rose on the 1st day after inoculation, peaked 8 days afterwards, and decreased subsequently from day 13 to 25 when it was negligible (Dagnall, 1993). Cells scraped from the conjunctival fornix and stained by Giemsa show large numbers of uni-, bi- or tripolar bodies about 250-1100 µm in diameter closely associated with epithelial cells. Specific immufluorescence staining of such cells shows that these bodies are aggregations of M. conjunctivae.

In alpine ibex, the course of infection and pathogenesis (both clinically and histologically) seems to be more severe than in sheep. Mucopurulent and purulent discharges develop more rapidly and mononuclear infiltrates in conjunctival and limbic areas is more progressed. Vascularisation, ulceration and serious disruption of ocular structures are also more apparent (Mayer et al., 1997).

Diagnosis

Clinical Diagnosis

Clinical diagnosis is made after the elimination of the existence of foreign bodies and entropions. The differential diagnoses include pine or cobalt deficiency, pasteurellosis, bluetongue and IKC caused by other mycoplasmas or Chlamydia spp.

Laboratory Diagnosis

Growth, Isolation and Biochemical Identification

Laboratory diagnosis is the only means of confirming the cause of IKC. Isolation of M. conjunctivae is more successful in the early stage of the disease because heavy bacterial contamination is usually found in chronic cases (Nicolet and Freundt, 1975). Although isolation is difficult and cumbersome, a variety of liquid and solid culture media such as Eaton’s (Nicholas and Baker, 1998), enriched PPLO broth (Difco, USA) (Giacometti et al., 1998), and commercially available mycoplasma media from Mycoplasma Experience (Reigate, UK) support its growth.

The type strain of M. conjunctivae is inhibited by digitonin, requires serum or cholesterol for growth, ferments glucose, does not hydrolyse arginine or urea, does not have phosphatase activity, reduces tetrazolium aerobically and anaerobically, does not digest serum, and does not produce film and spots (Barile et al., 1972). However, Dutch, Swiss and British strains of M. conjunctivae produce film and spots and reduce tetrazolium aerobically to a variable extent (ter Laak et al., 1988).

Growth Inhibition test

The growth inhibition (GI) test, where specific hyperimmune serum directly inhibits mycoplasma growth on solid media, and epifluorescence tests are probably the most popular test for the identification of M. conjunctivae (Bradbury, 1998; Poveda and Nicholas, 1998).

Serological tests

A direct fluorescent antibody test performed on fixed conjunctival scrapings has shown some success (Welchman, 1998).

Cross reactions with other mycoplasmas in particular M. ovipneumoniae have been seen in Western blots in sera from wild and domestic Caprinae (Grattarola et al., 1999; Degiorgis et al., 2000a). An indirect ELISA made with Tween-20 extracted antigens was developed that showed useful specificity and was used for the assessment of the prevalence of M. conjunctivae in domestic sheep (Belloy et al., 2001).

Molecular Diagnosis

A polymerase chain reaction (PCR) test based on the 16S rRNA genes has been used for the detection of M. conjunctivae from goats, sheep, ibex and chamois (Giacometti et al., 1999). This PCR with purified sample DNA and primers McoR1 and McoF1 was adequate for detection and rapid identification (Bashiruddin, 1998; Baker et al., 2001), however a nested PCR is probably necessary to achieve equivalent sensitivity to cultural methods (Giacometti et al., 1999). A PCR method using the 16S rDNA gene followed by the use of denaturing gradient gel electrophoresis has been able to detect and identify the majority of Mycoplasma species including M. conjunctivae (McAuliffe et al., 2005). Additionally a TaqMan rt-PCR based on the lppS gene is also used (Vilei et al., 2007).

List of Symptoms/Signs

Disease Course

Four clinical stages of disease are recognised in ovine and caprine IKC (and apply for both bacterial and mycoplasmal causes of ocular infections) (Egwu, 1991).

Stage 1: Hyperaemia of the palperbral and the bulbar conjunctival vessels, serous lachrymation, increased blinking and blepharospasm. The corneoscleral junction may show congestion prior to vascular migration (pannus) into the cornea. Most cases do not progress beyond this stage, but regress spontaneously.

Stage 2: Continuation of stage 1, characterised by corneal inflammation with blood vessels and pannus spreading from the corneoscleral margin. Early keratitis causes great irritation and, consequently, the blepahospasm and lachrymation are more obvious. Again spontaneous regression may occur.

Stage 3: Progress from stage 2, to a mucopurulent keratitis with extension of migrating blood vessels and a more purulent lachrymal discharge. Sometimes shallow corneal ulceration is apparent, which affects vision. These cases are very obvious and usually receive treatment.

Stage 4: A corneal ulcer develops and vision is lost. Pus may be present in the anterior chamber of the eye (hypopyon). These cases are slow to resolve, even with treatment. Corneal scarring may persist permanently following resolution. Lymphoid follicle hyperplasia causes the conjunctiva and third eyelid to appear granular and nodular.

Frequently, the disease is less severe in lambs and most cases do not progress through all stages described. Corneal ulceration also is rare in lambs. Relapses in treated and naturally recovering animals commonly occur in keratoconjunctivitis associated with mycoplasmas.

Epidemiology

The main reservoirs of M. conjunctivae are populations of domestic sheep. In an infected sheep the organisms can persist for up to 23 weeks, even after clinical recovery (Janovsky et al., 2001). Therefore, domesticated sheep in which the agent is self-maintained, are sometimes considered as reservoirs also for wild animals (Giacometti et al., 2002; Belloy et al., 2003; Egwu et al., 1989). Transmission from animal to animal is presumed to be by physical contact. One study recorded few contacts between wild and domestic animals in the Swiss Alps, and in this case the observation of Muscidid flies from the genera Hydrotaea, Musca, Morellia and Polietes frequenting infected eyes led to the suggestion of a possible role of these flies as vectors of M. conjunctivae (Giacometti et al., 2002). Another study observed that short-distance encounters between free-ranging individuals of different domestic and wild Caprinae species, are not uncommon events in the Alps (Degiorgis, 1998). In a study of wild Caprinae with and without clinical signs of infectious keratoconjunctivitis Mavrot et al. (2012) concluded that the mycoplasma load was significantly lower in eyes from healthy carriers; therefore the presence and severity of signs are related to the quantity of M. conjunctivae in the eyes.

Impact: Economic

The economic evaluation of IKC is difficult because of the variability of the clinical manifestations. At tupping time the occurrence of IKC was reported to reduce twining and induce toxaemia in affected ewes and temporarily reduce growth in lambs (Axelsen, 1961). Blindness, either unilateral or bilateral, leading to the accidental suffocation with placenta, or trampling of lambs, starvation, weight-loss, death or drowning of adult animals are among the losses ascribed to M. conjunctivae infection. The cost of treatment is probably the most significant economic loss (König, 1983; Hosie, 1988). M. conjunctivae-causing IKC has most severe consequences from blindness for wild chamois and ibex; a welfare concern for conservationists.

Disease Treatment

The use of corticosteroids is contra-indicated in keratitis especially where ulceration is present because it often antagonises rather than complements ocular defence mechanisms. Ophthalmic preparation of 350 mg of chlortetracycline twice a day for 3 days may eliminate M. conjunctivae. A single intramuscular dose of long-acting oxytetracycline may be used to supplement topical therapy or given on its own (König, 1983; Hosie and Greig, 1989).

References

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Vilei EM; Bonvin-Klotz L; Zimmermann L; Ryser-Degiorgis MP; Giacometti M; Frey J, 2007. Validation and diagnostic efficacy of a TaqMan real-time PCR for the detection of Mycoplasma conjunctivae in the eyes of infected Caprinae. Journal of Microbiological Methods, 70(2):384-386. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T30-4NTB92T-5&_user=10&_coverDate=08%2F31%2F2007&_rdoc=22&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%234932%232007%23999299997%23662442%23FLA%23display%23Volume)&_cdi=4932&_sort=d&_docanchor=&view=c&_ct=22&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5bdf4ba9e8f764a77f58c958cb10c0ca

Waseem Shahzad; Rashid Munir; Rana MY; Rashid Ahmad; Khan MS; Ghulam Akbar; Mohammad Ijaz; Fayyaz Mehmood, 2013. Prevalence, molecular diagnosis and treatment of Mycoplasma conjunctivae isolated from infectious keratoconjunctivitis affected Lohi sheep maintained at Livestock Experiment Station, Bahadurnagar, Okara, Pakistan. Tropical Animal Health and Production, 45(3):737-742. http://rd.springer.com/journal/11250

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Distribution Maps