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Year : 2011  |  Volume : 54  |  Issue : 1  |  Page : 214-215
Fungal keratitis associated with mite embedded in cornea


Iladevi Cataract and IOL Research Centre, Gurukul Road, Memnagar, Ahmedabad - 380 052, Gujarat, India

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Date of Web Publication7-Mar-2011
 

How to cite this article:
Parmar TJ, Gajjar DU, Pal AK, Ghodadra BK. Fungal keratitis associated with mite embedded in cornea. Indian J Pathol Microbiol 2011;54:214-5

How to cite this URL:
Parmar TJ, Gajjar DU, Pal AK, Ghodadra BK. Fungal keratitis associated with mite embedded in cornea. Indian J Pathol Microbiol [serial online] 2011 [cited 2018 Dec 11];54:214-5. Available from: http://www.ijpmonline.org/text.asp?2011/54/1/214/77415


Herein we describe the presence of tarsonemid mite in the eye of a patient with keratitis. This case illustrates the importance of scanning the slide under a fluorescent microscope using calcofluor white stain in addition to the routine laboratory protocol.

A 59-year-old male highway contractor presented with ocular discomfort, foreign body sensation, photophobia, redness, and occasional pain in the right eye for a week. On slit lamp examination of the eye, a foreign body with oval pigmented keratitis was detected at the 7.00 O'clock position, two mm from the limbus into the cornea [Figure 1]a. This foreign body was observed to be a dry, raised, brown-pigmented lesion with a deep surrounding zone of corneal infiltration. The eyelid showed no evidence of edema or blepharitis.
Figure 1: Clinical and microscopic photographs of the keratitis case. (a) Peripheral corneal ulcer and surrounding infiltration at the 7.00 O'clock position 2 mm away from the limbus. (b) A wet mount of scraped material in 10% KOH revealed hyaline, septate, branched fungal hyphae when examined under a light microscope (unstained, 400). (c) A wet mount of scraped material in 10% KOH revealed the presence of a mite when examined under a fluorescent microscope (unstained, 400). (d) The presence of fungal hyphae and mite both seen together in the scraped material (unstained, 400). The bar represents a scale of 50 μm

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The corneal infected area was scraped for microscopic examination. A 10% potassium hydroxide (KOH) wet mount showed fungal filaments [Figure 1]b. After following our usual laboratory protocols, the slide was examined under a fluorescent microscope. A microscopic insect (200 μ m) with four pairs of legs and no apparent wings was observed entangled in the fungus [Figure 1]c. The fungal hyphae and the mite both appeared in the same field in the scraped material [Figure 1]d when observed once more under the light microscope. Entomologists further observed the slide and identified the mite as belonging to a sub-cohort of Heterostigmae (family Tarsonemid). This identification was made on the basis of the size of the insect and the morphology of its microscopic features like setae, genital structures, and spines.

After observing the corneal scraped culture on potato dextrose agar for 4 days, the fungus was identified as Aspergillus fumigatus. Visual acuity improved from 6/24 to 6/12 following a treatment regime that included antibiotics (moxifloxacin), application of antifungal eye drops every 2 h, application of atropine eye ointment twice a day, and daily administration of oral antifungal (150 mg fluconazole) for 3 weeks. Anti-mite treatment was not started as only one mite was found in the scraped material and fungal hyphae were predominantly found in the scraped material. When a foreign body is lodged on the cornea, there is an acute inflammatory response in the form of exudation of plasma and fibrin. This normally dislodges the foreign body. The composition of the foreign body determines the extent of the inflammatory response. For example, bee or wasp stings usually produce acute reactions due to toxic agents contained in their venom. In the present case, the inflammatory response was insufficient and the mite got embedded in the eye. Mites are known to bite humans and cause irritation, itchy papules, and rashes. However, to the best of our knowledge, there are no reports on the immune response of the cornea to a tarsonemid mite. Hence it would be difficult to predict the outcome if a surgeon misses the presence of a mite in the eye.

The present case reports the presence of microscopically visible mite in the cornea along with infection by A.fumigatus. Previous reports of insect foreign bodies on the cornea were mostly based on clinical suspicion, patients' history, and memory. Corneal injuries have been reported to be associated with various insects and spiders. [1] Mite is a term commonly used to refer to a group of insect-like organisms, some of which bite or cause irritation. Mites and/or mite eggs have been found in human urine, stool, and sputum but the clinical and medical significance of these studies have not been well established. [2],[3],[4] Little is known about the medical and clinical significance of tarsonemid mites. Tarsonemid mites have been found in the sputum and have been associated with house dust allergy. [4]

It has been reported that most species of the Tarsonemid family feed on the mycelia of fungal and algal bodies. [5] This group of insects was shown to play a central role in the dispersal of fungal spores. [6] Although we did not find any association between tarsonemid mites and Aspergillus spp. in the literature, the possibility of this mite being a vector of A. fumigatus cannot be excluded. Therefore, any one of the following options is a possibility: (1) the mite was the carrier of Aspergillus; (2) the mite entered the cornea along with dust particles containing Aspergillus spores; (3) Aspergillus spores entered the cornea after the mite had traumatized it.

Further we illustrate the importance of carrying out an examination under a fluorescent microscope using the calcofluor white stain. This stain has the advantage of being highly sensitive in its ability to detect not only fungal hyphae and Acanthamoeba cysts but also chitin containing insects (mite in the present case). [7] We recommend meticulous examination and laboratory investigation as mandatory procedures to rule out unusual causes like insect parts or fungi. Mite in the eye might be serious!


   Acknowledgments Top


The authors thank Dr. Meenakshi Bharti, Department of Zoology, Punjabi University Patiala, Punjab, India, Dr. Lars Lundqvist, Lund University, Sweden, Prof TCN Trust, Calicut, India and Mr. Santhosh Shreevihar, Research Fellow, Systematic Entomology Laboratory, Department of Zoology, University of Calicut, Kerala, India for their help in identification of the mite.

 
   References Top

1.Gilboa M, Gdal-On M, Zonis S. Bee and wasp stings of the eye. Retained intralenticular wasp sting: A case report. Br J Ophthalmol 1977;61:662-4.  Back to cited text no. 1
    
2.Dini LA, Frean JA. Clinical significance of mites in urine. J Clin Microbiol 2005;43:6200-1.  Back to cited text no. 2
    
3.Werneck JS, Carniato T, Gabriel A Jr, Tufik S, Andrade SS. Mites in clinical stool specimens: Potential misidentification as helminth eggs. Trans R Soc Trop Med Hyg 2007;101:1154-6.   Back to cited text no. 3
    
4.Ryu JS, Ree HI, Min DY, Ahn MH. A human case of house dust mite Tarsonemus floricolus collected from sputum. Korean J Parasitol 2003;41:171-3.  Back to cited text no. 4
    
5.Idph.state.il.us[Internet]. Illinois: Illinois Department of Public Health; Prevention and Control: Mites affecting Humans [Last updated on 2010 Jul 12]. Available from: http://www.idph.state.il.us/envhealth/pcmites.htm)[Last cited on 2010 Jul 16].  Back to cited text no. 5
    
6.Roets F, Wingfield MJ, Crous PW, Dreyer LL. Discovery of fungus-mite mutualism in a unique niche. Environ Entomol 2007;36:1226-37.  Back to cited text no. 6
    
7.Chander J, Chakrabarti A, Sharma A, Saini JS, Panigarhi D. Evaluation of Calcofluor staining in the diagnosis of fungal corneal ulcer. Mycoses 1993;36:243-5.  Back to cited text no. 7
    

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Correspondence Address:
Devarshi U Gajjar
Iladevi Cataract and IOL Research Centre, Gurukul Road, Memnagar, Ahmedabad - 380 052, Gujarat
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.77415

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