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Pink eye

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Source: msdvetmanual.com

Overview

  • Infectious keratoconjunctivitis of cattle, sheep, and goats is a common ocular condition characterized by blepharospasm, conjunctivitis, lacrimation, and varying degrees of corneal opacity and ulceration. In severe cases, ocular rupture leading to blindness can result.
  • Moraxella bovis has long been considered to be the etiologic agent of IBK, other species of Moraxella, such as M bovoculi, M ovis, various Mycoplasma species (M bovis and M bovoculi), and infection with bovine herpesvirus type 1 and infectious bovine rhinotracheitis (IBR) virus may also play a role in disease.
  • Contagious ophthalmia (infectious keratoconjunctivitis or pink eye) is a contagious bacterial infection of sheep, goats and cattle. Clinical signs include inflamed conjunctivae, ocular discharge, corneal opacity and impaired vision, with corneal ulceration and perforation occurring in severe cases (Motha, et al., 2003). Bacteria commonly associated with this condition include Mycoplasma conjunctivae, Chlamydia pecorumand Moraxella(Branhamella)ovis. However, Colesiota(Rickettsia) conjunctivaand Listeria monocytogenescan also be involved (Abbott, 2018). M. conjunctivaehas been identified as the major cause of contagious ophthalmia in sheep

Diagnosis and differentials

  • Agents associated with naturally occurring conjunctivitis or keratoconjunctivitis in sheep and goats include:
    • Chlamydia pecorum
    • Mycoplasma spp (notably M conjunctivae)
    • Moraxella ovis
    • Colesiota conjunctivae
    • Listeria monocytogenes
    • Acholeplasma oculi
    • Thelazia spp

Treatment and control

  • Moraxella spp are susceptible to many antibiotics. Because antibiotic susceptibility may vary in different geographic locations, susceptibility testing of isolated organisms is advised. In the USA, long-acting oxytetracycline (two injections of 20 mg/kg, IM or SC, at a 48- to 72-hour interval) and tulathromycin (2.5 mg/kg, SC, given once) are approved for IBK treatment in cattle. Other effective (but not FDA-approved) antibiotics include ceftiofur crystalline free acid (6.6 mg/kg, SC, at the base of the ear) and florfenicol (20 mg/kg, IM, two doses at a 2-day interval). According to current federal regulations in the USA, use of ceftiofur in cattle must follow approved bottle directions, including dose, route, and frequency.

References

  • Read Full Article and Cases with Images
    • CONTAGIOUS OPHTHALMIA ASSOCIATED WITH MYCOPLASMA CONJUNCTIVAE IN SHEEP
    • Laura Kerrison, Veterinary Student, University of Sydney, Bruce Watt, Central Tablelands Local Land Services, Bathurst and Mark Hazelton, Ania Deutscher and Mark Westman, Elizabeth Macarthur Agricultural Institute, Menangle
      • Posted Flock & Herd November 2020
    • INTRODUCTION
      • Contagious ophthalmia (infectious keratoconjunctivitis or &squo;pink eye&squo;) is a contagious bacterial infection of sheep, goats and cattle. Clinical signs include inflamed conjunctivae, ocular discharge, corneal opacity and impaired vision, with corneal ulceration and perforation occurring in severe cases (Motha, et al., 2003). Bacteria commonly associated with this condition include Mycoplasma conjunctivae, Chlamydia pecorumand Moraxella(Branhamella)ovis. However, Colesiota(Rickettsia) conjunctivaand Listeria monocytogenescan also be involved (Abbott, 2018). M. conjunctivaehas been identified as the major cause of contagious ophthalmia in sheep (Naglić, et al., 2000); however, other mycoplasma spp. can be involved, for example Mycoplasma arginini has been isolated (Surman, 1973). Moraxella ovis may be present in infections with contagious ophthalmia, but can also be found as part of the normal conjunctival flora of healthy sheep (Bankemper, et al., 1990 and Dagnall, 1994) and, therefore, may be the primary pathogen or an opportunist infection.
      • This report details four cases of contagious ophthalmia in lambs and ewes where M. conjunctivae was detected via PCR, with and without concurrent isolation of Moraxella ovis. This finding supports the view that an antibiotic that is effective against Mycoplasma spp. (such as oxytetracycline) is the preferred option in severe cases of contagious ophthalmia.
    • HISTORY AND CLINICAL FINDINGS
      • Four cases of contagious ophthalmia were investigated in the Central Tablelands, NSW, from March to June 2020.
      • Case 1. In March 2020, ocular disease was noted amongst a total of 2450 Merino, Merino x West Suffolk and Merino Dorset lambs running in several mobs. Approximately 75% of the lambs were affected; however, few had notable visual deficits. The eyes of three lambs were examined, all presenting bilateral or unilateral serous ocular discharge, cloudy oedematous corneas (Figure 1) and peripheral neovascularisation. One had a shallow corneal ulcer (Figure 2).
      • Case 2. In March 2020, 30 of 300 Merino lambs were noticed to be affected with ophthalmic disease. Some lambs had been treated with topical cloxacillin as benzathine salt (278mg OU; Opticlox, Norbrook) with no noticeable improvement. Six were completely blind. Three lambs and one ewe were examined. The lambs had cloudy, oedematous corneas, red conjunctivae and serous ocular discharge (Figure 3). The ewe had bilateral stromal abscesses, extensive neovascularisation and corneal opacity (Figure 4).
      • Case 3. In March 2020, a mob of 515 composite ewe lambs, mustered for investigation of ewe infertility, were noted to be affected with mild contagious ophthalmia. From a selection of ten ewes examined closely, four were affected. The affected lambs had serous ocular discharge and some also presented with red conjunctiva and a cloudy cornea.
      • Case 4. In June 2020, 20 Merino ewe hoggets from a mob of 200 presented with blindness and a high stepping gait. Four were examined, all with bilateral cloudy corneas, superficial corneal erosions, marked neovascularisation and serous ocular discharge.
      • Image of cloudy sheep eye
      • Figure 1: An affected lamb from Case 1 with a serous ocular discharge and corneal oedema
      • Image of cloudy sheep eye
      • Figure 2:* An affected lamb from Case 1 *with diffuse corneal oedema, peripheral neovascularisation and a large corneal ulcer of the left eye
      • Image of inflamed sheep eye
      • Figure 3: A ewe hogget from Case 2 with conjunctivitis, mild diffuse corneal oedema and serous ocular discharge
      • Image of inflamed sheep eye
      • Figure 4: An affected ewe from Case 2 with marked neovascularisation, conjunctivitis, a stromal abscess and a seropurulent ocular discharge
    • LABORATORY FINDINGS
      • Dry eye swabs were collected for all cases and submitted to the EMAI for bacteriology diagnostics. Mycoplasma spp. and Chlamydia spp. PCRs were performed for all cases. Three cases had aerobic culture (sheep blood agar plate incubated at 37°C with 5% CO2, and MacConkey agar plate incubated at 37°C) performed on all swabs, set up the day after the swabs were collected. One case (Case 3) did not have any culture performed.
      • Table 1 displays all laboratory results for Cases 1 to 4. Moraxella ovis was cultured in Cases 1 and 4. Mycoplasma spp. were detected via PCR from all cases. Employment of a real-time Mycoplasma spp. PCR for Cases 2-4 revealed that the relative amount of the target sequence was high (cycle threshold [Ct] values between 21-29).
      • The Mycoplasma sp. detected in all cases was determined to be M. conjunctivae by amplification and sequencing part of the 16S rRNA gene using in-house Mycoplasma-specific primers. Chlamydia spp. were not detected via PCR (individual or pooled) from any of the cases.
      • Table 1 Summary of laboratory results
      • CaseLamb or EweAerobic cultureMycoplasma spp. PCR1Chlamydia spp. PCR1
      • 11Sparse mixed growthD3 (3 swabs pooled) M. conjunctivaeND (3 swabs pooled)
      • 2Sparse mixed growth
      • 3Sparse mixed growth including Moraxella ovis2
      • 21Profuse mixed growthD3 M. conjunctivaeND
      • 2Moderate mixed growthD3 M. conjunctivaeND
      • 3Sparse mixed growthD3 M. conjunctivaeND
      • 4No growthD3 M. conjunctivaeND
      • 31Not performedD3 (5 swabs pooled) M. conjunctivaeND (5 swabs pooled)
      • 2Not performed
      • 3Not performed
      • 4Not performed
      • 5Not performed
      • 41Sparse mixed growth including Moraxella sp.4D3 M. conjunctivaeND (3 swabs pooled)
      • 2Moderate mixed growth including Moraxella sp.4D3 M. conjunctivae
      • 3Sparse pure growth of Moraxella ovis2D5
        • D=detected, ND = not detected
        • Species determined via amplification and sequencing of the 16S-23S intergenic spacer region.
        • Species determined via amplification and sequencing part of the 16S rRNA gene using in-house Mycoplasma-specific primers.
        • DNA amplicon not sent for sequencing.
        • Unable to determine the species due to a mixed sequence result from sequencing part of the 16S rRNA gene using in-house Mycoplasma-specific primers.
    • DISCUSSION
      • M. conjunctivae was detected by PCR from eye swabs from all four cases. M. conjunctivae is a common isolate associated with contagious ophthalmia (Abbott, 2018). Chlamydiaspp. were not detected via PCR in any of the four cases.
      • The concurrent isolation of Moraxella ovisin Cases 1 and 4 may be due to its presence as part of normal conjunctival flora, or as a consequence of colonisation following infection with M. conjunctivae (Bankemper, et al., 1990 and Dagnall, 1994). There are some reports that suggest concurrent infection with Moraxella ovisand M. conjunctivaemay be associated with more severe clinical signs; however, severity may depend on the pathogenicity of the strain of Moraxella ovis(Dagnall, 1994).
      • In this case series, most lambs were not treated; however, severe cases such as shown in Figure 3 were treated with injectible long-acting tetracyclines. In our experience, severe cases respond to oxytetracyclines rather than antimicrobials that target cell wall synthesis (as expected given Mycoplasmas lack a cell wall).
      • Almost all of the affected sheep resolved within two weeks, which is consistent with the observations of Abbott, 2018. However, in our experience, severe cases may be refractory to treatment with permanent eye damage. This finding has been observed by others (Motha, et al., 2003 and Naglić, et al., 2000). Repeated yarding may exacerbate clinical signs due to increased stress and dust and increased transmission to naïve animals (Abbott, 2018). Animals with severely compromised vision may benefit from being separated to an area with adequate shade and easy access to food and water.
      • Flies and dust are believed to play a role in the transmission of infection (Toop, 1964, Abbott, 2018). However, on the Central Tablelands this disease often occurs in the colder seasons without predisposing factors such as flies, dust or other causes of eye damage such as grass seeds. While these mostly mild, but occasionally severe, cases all involved young sheep, contagious ophthalmia also occurs sporadically in flocks of mature ewes without obvious predisposing factors. Disease prevalence may be affected by host susceptibility and virulence of the organisms involved (Bankemper, et al., 1990). Recovery from contagious ophthalmia results in short-term immunity for approximately one year before the sheep become susceptible if re-exposed to the organisms (Toop, 1964).
    • ACKNOWLEDGEMENTS
      • We thank NSW DPI Veterinary Bacteriology and Molecular Biology Diagnostic teams for performing the bacterial cultures and molecular testing.
    • REFERENCES
      • Toop C. Contagious ophthalmia (pinkeye) of sheep. Journal of the Department of Agriculture, Western Australia, Series 4 1964;5:955-957
      • Motha M, Frey J, Hansen M, Jamaludin R, Tham K. Detection of Mycoplasma conjunctivae in sheep affected with conjunctivitis and infectious keratoconjunctivitis. New Zealand veterinary journal 2003;51:186-190
      • Abbott K. The Practice of Sheep Veterinary Medicine. 1st edn. University of Adelaide Press, Adelaide, 2018
      • Barile MF, Del Giudice RA, Tully JG. Isolation and Characterization of Mycoplasma conjunctivae sp. n. from Sheep and Goats with Keratoconjunctivitis. Infection and Immunity 1972;5:70
      • Naglić T, Šeol B, Hajsig D et al. Epidemiological and microbiological study of an outbreak of infectious keratoconjunctivitis in sheep. Veterinary Record 2000;147:72-75
      • Surman P. Mycoplasma aetiology of keratoconjunctivitis (&quo;pink-eye&quo;) in domestic ruminants. Australian Journal of Experimental Biology & Medical Science 1973;51
      • Bankemper KW, Lindley DM, Nusbaum KE, Mysinger RH. Keratoconjunctivitis associated with Neisseria ovis infection in a herd of goats. Journal of Veterinary Diagnostic Investigation 1990;2:76-78
      • Dagnall G. The role of Branhamella ovis, Mycoplasma conjunctivae and Chlamydia psittaci in conjunctivitis of sheep. British Veterinary Journal 1994;150:65-71

Links to this note

Important topicsPink eye - Snow blindness - Infectious KeratoconjunctivitisUAE Vet Examcontagious ophthalmia ASSOCIATED WITH MYCOPLASMA CONJUNCTIVAE IN SHEEP - Pink Eye - Snow blindness - Infectious Keratoconjunctivitis

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