|Year : 2017 | Volume
| Issue : 2 | Page : 136-138
A case of pediatric ocular dirofilariasis
Cornea and Cataract Services, Malabar Eye Hospital, Kannur, Kerala, India
|Date of Web Publication||10-Aug-2017|
K M Seema
Malabar Eye Hospital, Thavakkara, Kannur - 670 002,
Source of Support: None, Conflict of Interest: None
A 4 year old boy presented with an inflammed subconjunctival swelling in the right eye which was responsive to topical steroids but recurred on discontinuing steroids. Parasitic granuloma was suspected and an excision biopsy performed which revealed a dirofilarial worm inside the granuloma. This case report is being presented to emphasise the presence of this rare zoonosis in our state.
Keywords: Dirofilariasis, parasitic granuloma, zoonosis
|How to cite this article:|
Seema K M. A case of pediatric ocular dirofilariasis. Kerala J Ophthalmol 2017;29:136-8
| Introduction|| |
Dirofilariasis is a helminthic infection caused by a parasite of domestic and wild animals that can infect humans accidentally. Ocular dirofilariasis has been observed in the eyelid, periorbital region, subconjunctival tissues, and rarely in the vitreous. Dirofilariasis is occasionally reported from different parts of India. We report a case of ocular dirofilariasis which presented as a subconjunctival mass mimicking nodular scleritis in a 4-year-old boy. The parasite was identified as Dirofilaria repens. The purpose of this case summary is to emphasize the presence of this emerging zoonosis though rare in our state and also to review the literature.
| Case Report|| |
A 4-year-old school going boy from a middle-class family presented to us with redness, watering, and a painful swelling on the temporal side of the right eye (RE) of 1 month duration. He had consulted at different places and was treated with topical steroids and nonsteroidal anti-inflammatory drugs. According to the child's mother, the swelling would resolve partially with topical steroids but would recur immediately on stopping steroids. There was no history of any immunological disorders or travel outside from hometown in the past 1 year.
On examination, child was orthophoric and extraocular movements were full. Visual acuity and intraocular pressure were normal. There was a subconjunctival cystic, congested swelling on the temporal side of the bulbar conjunctiva of the RE [Figure 1]. Surrounding episcleral vessels were congested. The swelling was nontender and mobile over the sclera. Examination of the rest of the anterior segment was normal. Examination of the vitreous and retina was also normal. A provisional diagnosis of parasitic granuloma with a differential diagnosis of episcleritis and foreign body granuloma was entertained. Investigations showed Hb 11.7 g%, total count 10,400 with a differential count of P63%, L30%, E07%, M0, B0, and erythrocyte sedimentation rate 25 MM/1st h. Antiretroviral antibody screening, hepatitis B surface antigen and mantoux test were negative. Peripheral smear showed microcystic hypochromic anemia with mild eosinophilia and thrombocytosis which was in favor of an allergic/parasitic etiology.
Since the child had already been given multiple trials of topical steroids outside, we decided to proceed with an excision biopsy of the swelling under general anaesthesia. The cyst was excised in toto and measured 2 cm × 1.6 cm, surface of the cyst had a polycystic appearance and it appeared to be filled with serous fluid. On incising the cyst, a slender pearly white-elongated worm, 6 cm in length emerged along with serous fluid [Figure 2]. Both the cyst and the worm were sent for histopathological examination. The conjunctival defect was closed and healed well subsequently [Figure 3].
Histopathological examination of the cyst showed benign squamous epithelium, subepithelial loose connective tissue admixed with benign adipose tissue, and capillaries and showed a tiny cavity (worm space), surrounded histiocytes with surrounding chronic inflammatory infiltrate with good numbers of eosinophils. Sections of the worm showed cross sections of the dirofilarial worm. The genus Dirofilaria was identified by its thick, multilayered cuticle with ridging and striations and prominent lateral cord. On the basis of cuticular and internal morphological features, the worm was identified as D. repens.
| Discussion|| |
Dirofilariasis is an emerging zoonosis in India. The first two cases of human ocular dirofilariasis in India were reported from Kerala in 1976 (Joseph et al.) and in 1978 (George and Kurian). Dirofilariasis is a helminthic infection caused by parasites of the Dirofilaria genus, family onchocercidae, which is included in the class of nematodes. It is a common zoonotic disease affecting mostly dogs, other canines, foxes, and cats. It is transmitted to humans through arthropods, and mosquitoes are the vectors. Humans are the final host of Dirofilaria.
Dirofilaria is a parasite that can be detected in various ocular and periocular tissues. Once it enters the blood circulation, the adult female helminths produce microfilariae that typically are found in peripheral blood. A mosquito takes a blood meal of the infected host and ingests microfilariae. Once in the vector's midgut, the microfilariae reach the infectious stage in about 2 weeks. The larvae are injected into human tissues through the mosquito proboscis, and usually, they do not survive crossing the tissues. The larvae that manage to survive evolve into adult helminths.
In the eye, Dirofilaria can be found subconjunctivally or in Tenon's layer,, periorbital tissues (lids, orbit), and intraocularly (anterior chamber, vitreous ). The parasite migrates as microfilaria into the vitreous and anterior chamber through the blood stream of the eye and into the lids and orbit through the subconjunctival and subcutaneous tissues and develops into an adult helminth. Intravitreal dirofilariasis should be distinguished from diffuse unilateral subacute neuroretinitis (DUSN). DUSN is a blinding form of uveitis caused by ocular nematode infestation infiltrating the subretinal space. Several nematodes have been proposed as the etiologic agent of DUSN, but no conclusive evidence has been provided for a specific nematode.
The only treatment for ocular dirofilariasis is removal of the parasite. Subconjunctival Dirofilaria is removed through an incision in the conjunctiva. The parasite must be removed in toto. Parasite remnants can cause severe allergic reaction. In our case, subconjunctival Dirofilaria was excised in toto, sacrificing a small portion of the conjunctiva. The conjunctival defect was closed and additionally covered with a small piece of amniotic membrane to facilitate epithelialization. Additional antihelminthic treatment was not required in our case. Antihelminthic drugs are not indicated since Dirofilaria is reproductively inactive and has a single location. After removal of the parasite, eosinophilia returned to normal level in about 2-month time. Peripheral blood eosinophilia and/or presence of eosinophils in affected tissues suggest an allergic reaction caused by the inflammatory response induced by the nematode.
| Conclusion|| |
Human ocular dirofilariasis is not widely recognized in India though several cases have been reported in the past few years. Increasing number of such cases in India suggest more attention toward this emerging zoonosis. Removal of the entire parasite is the only appropriate treatment.
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[Figure 1], [Figure 2], [Figure 3]