A rare case of anterior chamber dirofilariasis.

We report a rare case of anterior chamber live dirofilariasis presenting as anterior uveitis. A 60-year-old man presented with dimness of vision in the right eye for 1 month. Vision recorded was 6/18 P, N 18 in the right eye. Slit lamp examination of the right eye revealed anterior uveitis with a moving nemathelminthes. The worm was removed live from the anterior chamber under local anesthesia with assisted methyl cellulose delivery and post-operatively, the worm was examined directly under light microscope. Morphometric measurement showed length of the worm was 6.061 mm. A thin, pale, slender worm was diagnosed as immature female Dirofilaria repens and was documented completely. Patient had made an excellent recovery of vision and intraocular inflammation after the surgical removal of the worm. Intraocular infection of dirofilaria is a rare presentation and successful surgical removal of the worm resulted in complete recovery of uveitis and visual status in the affected eye.

Introduction

Ophthalmic dirofilariasis is a rare entity caused by Dirofilaria, a dog tapeworm that is transmitted to human by mosquitoes.[12] Cases of zoonotic dirofilarial infection occurs widely throughout Africa, Europe, Middle Eastern, and Asian countries.[1234] Man is a dead end host for the parasite, and ophthalmic involvements include periorbital, subconjunctival, subtenon, and intraocular association.[123456789] The infestation of the worm, usually, associated with inflammation of varied nature.[12] Intraocular dirofilariasis in the form of anterior segment involvement is extremely rare phenomenon and was first reported from this region of north east India. Histopathological diagnosis and documentation of the dirofilaria in human is very challenging for the parasitologist and ocular pathologist.

Case Report

A 60-year-old man presented to a tertiary center of northeast India with dimness of vision in the right eye (OD) for 1 month. There was associated pain and redness of the OD. He had no history of ocular injury, allergy or recent onset of red eyes. He had earlier consulted a local ophthalmologist who had prescribed him antibiotic-steroid drops, ointment in the OD and oral steroid. Vision recorded in the OD was 6/18 P, N 18. Slit-lamp examination of the OD revealed mild circumcilliary congestion with anterior chamber flare and cells 2+. A small, thin, pale worm was seen in the anterior chamber, and it was changing its position in different illumination of the slit-lamp [Figure 1]. There was no hemorrhage or hypopyon noticed in the OD. Pupil in that eye was semi-dilated and posterior segment details could not be evaluated. Digitally, intraocular pressure was normal in the OD. Left eye was unremarkable except little corneal opacity. Fundus examination revealed no abnormality in both eyes. Complete blood counts including eosinophils count and hemoglobin were found to be normal. Peripheral blood smears done did not show any parasitic bodies.

Figure 1

Right eye of the patient with the worm in the anterior chamber. Anterior chamber reactions can be seen

Patient was taken to the operation theatre, and the worm was removed surgically after a written consent and the procedure was carried out under local anesthesia. A 2.75 mm, clear corneal incision was given in the 12 O’clock position. From 6 O’clock position, methyl cellulose was injected in the anterior chamber so that it pushed the worm out through the incision site, live. Postoperatively, intracameral vancomycin, and subconjunctival dexamethasone was injected. Corneal wound was closed with single, 10-0 suture. Patient was further prescribed local antibiotic-steroid drops along, and cycloplegic eye drops in the postoperative eye for 2 weeks. The live nematode was put in a normal saline and sent to the ocular pathology laboratory of the institute. The worm was inspected and later examined by ocular pathologist of the institute and subsequently seen by parasitologist of a local veterinary institute. The worm structure was directly visualized under microscope (Carl Zeiss, Axioskop 40) with camera attachment (Carl Zeiss Axio Cam MRc) and video documentation was taken under high power objective where all the internal structures of the transparent worm was visualized and compared with the wet mount preparation.

Description of the morphology of the worm

The worm was thin, slender, and pale whitish in color and was seen in hematoxylin-eosin stain [Figure 2]. The anterior end became gradually narrowed and ended with a slight concavity [Figure 3]. A number of rudimentary papillae could be noticed at the oral end. The posterior end was rounded. External surface morphology under light-microscopy revealed fine transverse cuticular striations at 1.96 μm distances. The length of the worm was 6.061 mm and maximum breadth at the middle-third was 0.2571 mm [Figure 4]. The position of nerve ring was at 0.179 mm distance from the anterior end. The length of esophagus was 0.380 mm. Uterus was long and coiled with indistinguishable masses inside. The position of vulva was at 0.385 mm from the anterior end. The anal opening was at 0.0789 mm distance from the posterior extremity [Figure 5]. The posterior end contained a number of small rudimentary papillae on the ventral surface [Figure 5]. The taxonomic identification of the worm was found to be consistent with immature female Dirofilaria repens.

Figure 2

A thin, slender, and pale Dirofilaria repens, length 6.061 mm and breadth, maximum 0.2571 mm (H and E, ×100)

Figure 3

The anterior end of the worm gradually narrowed and ended with a slight concavity (H and E, ×200)

Figure 4

The worm at the middle part. Internal structures could be visualized (H and E, ×200)

Figure 5

The anal opening of Dirofilaria repens was at 0.0789 mm distance from the posterior extremity (H and E, ×200)

First postoperative day, patient had minimal corneal edema with 1+ anterior chamber flare and cells in the affected eye. On the 6th postoperative day, patient had 6/6, N6 vision with normal anterior chamber reaction [Figure 6].

Figure 6

Eye, on the 6th postoperative day. Anterior chamber was relatively clear

Discussion

Dirofilariasis is zoonoses seen in a different region of the world.[123] The worm may lodge in many tissues of human bodies including eye and adnexa.[123456789] Dirofilariasis may have deep seated infection such as lungs where early and proper diagnosis can save a patient from major complications.[123] Dirofilariasis is a natural parasite of the carnivorous animal, particularly dogs, foxes, and cats.[1234]

Dirofilaria infection often reported in Europe, Mediterranean, and Asian countries.[1234] There were few reports of dirofilariasis from Indian subcontinent.[17] In India, Dirofilariasis were predominantly reported in published literature in southern Indian states particularly from Kerala.[17] A recent case report of an inhabitant of Kerala presented with subconjuctival dirofilaria infestation, who was working in Dubai, contracted the infection from his home visit in India.[1] The transmission to human is, usually, by bite of Culex and Aedes mosquitoes which are considered as vectors and often thought that parasitemia are due to accidental conduction.[17] Surgical removal of the worm is curative and relatively simple. Our patient had a live worm in the anterior chamber of the right eye with evidence of anterior uveitis. Removing of the worm live was a challenge and surgeon removed it without using the forceps so that its morphology and structure of the worm was preserved intact. After removal, the worm was visualized directly under an advanced light microscope in high power objective and video documentation of the procedure was taken. All the internal structures of the transparent worm could be seen and compared with the wet mount preparation in the later stage of pathological evaluation.

Identification of the worm was done using standard histopathological methods by in-house ocular pathologist and later confirmed by veterinary parasititologist. The immature female worm of D. repens had thick laminated cuticle, broad lateral cords, and female genital system. In certain advanced centers, direct polymerase chain reaction had aided in the identification of the DNA of D. repens.[12310]

Conclusion

We report the first, unique case of live anterior chamber dirofilariasis from the northeastern part of India. The macroscopic and microscopic characteristics of D. repens are important to establish the diagnosis and also to avoid unnecessary treatment by antihelminthic agents particularly in intraocular microfilaria involvement. Surgical removal of the parasite is always recommended.