Year : 2010 | Volume
: 53 | Issue : 1 | Page : 157--159
Reema Nath1, Rajen Gogoi2, Narayan Bordoloi3, Tapan Gogoi2,
1 Department of Microbiology, Assam Medical College, Dibrugarh, India
2 Department of Ophthalmology, Assam Medical College, Dibrugarh, India
3 Chandraprava Eye Hospital, Jorhat, Assam, India
Department of Microbiology, Assam Medical College, Dibrugarh, Assam
Dirofilaria is a parasite of domestic and wild animals that can infect humans accidentally. It is being reported in increasing numbers from Mediterranean countries like Italy. In India this infection is occasionally being reported. We report three cases of ocular dirofilariasis from the state of Assam presenting as periorbital and subconjunctival cysts. The parasites were identified as Dirofilaria repens. The purpose of this article is to take note of this emerging zoonosis in Assam; also to review literature in the cases reported.
|How to cite this article:|
Nath R, Gogoi R, Bordoloi N, Gogoi T. Ocular dirofilariasis.Indian J Pathol Microbiol 2010;53:157-159
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Nath R, Gogoi R, Bordoloi N, Gogoi T. Ocular dirofilariasis. Indian J Pathol Microbiol [serial online] 2010 [cited 2020 Jul 3 ];53:157-159
Available from: http://www.ijpmonline.org/text.asp?2010/53/1/157/59213
Dirofilaria is a genus of the family Onchocercidae of the super family Filaroidea, order Spirurida in the subphylum Nematoda. It is being reported in increasing numbers from Mediterranean countries like Italy , while in India it is occasionally being reported. ,,, The life cycle of the worm depends on two hosts, a vertebrate species as a definitive host and an arthropod as an intermediate host, which also acts as a vector. The infective third stage larvae of the filarial worm migrate actively through the mouth part, leave the intermediate host and enter the channel produced by the blood sucking arthropods to enter the blood vessel or tissue of the vertebrate.  Human dirofilariasis is not widely recognized in India though a number of cases are reported from South India. , Different species of dirofilaria can be found in man causing different clinical signs and symptoms; ocular dirofilariasis is one of them. Six out of 40 species of Dirofilaria are known to cause diseases in human; they are D. immitis, D. repens, D. striata, D. tenuis, D. ursi and D. spectans. Species causing infection in man varies according to different geographical locations. Human dirofilariasis caused by Dirofilaria repens have been reported to occur widely throughout Asia minor, Central Asia, Southern and Eastern Eourope and Sri Lanka.  Human infection with Dirofilaria repens, though not widely recognized in India, is a common zoonotic infection in Sri Lanka. 
Here, we report three cases of D. repens infection from Tinsukia and Dibrugarh districts of Assam, two of them presenting as peri orbital cysts in upper and lower eyelids and another presenting as sub conjunctival cyst. The purpose of this article is to take note of human dirofilariasis as an emerging zoonosis in Assam as many cases remain unreported. These cases were diagnosed within a period of three months.
A 23-year-old lady reported to a private eye clinic in Assam with a cyst of 1x1 cm in diameter in the left upper eyelid of one month duration. The cyst was slightly movable on palpation, round, non tender, and gradually increasing in size. There was no history of travel to other places in the last two years. Rest of the ocular examination was within normal limits and visual acuity was 6/6 in both the eyes. A surgical procedure was undertaken to remove the pre-septal cyst and during the procedure a live worm, 12 cm in length came out of the cyst along with some fluid.
A 70-year-old male presented with pain and swelling of the right eye of one week duration to a private eye hospital. On examination, a tender subconjunctival cystic swelling of 1x1 cm was detected under the bulbar conjunctiva on the temporal side of the right eye with congestion and chemosis. Visual acuity was 6/9 in both the eyes and other ocular examination findings did not reveal any abnormality. The cyst on removal showed the presence of a live, white, 13 cm long worm.
A 30 year old male presented with swelling and tenderness of the left lower lid of one week duration. On examination, a cystic swelling of 1x1.5 cm was detected in the lower lid with congestion and chemosis. Visual acuity was 6/6 in both the eyes and rest of the ocular examination did not reveal any abnormality. No history of travel to other endemic places could be elicited. Excision of the pre-septal cyst was done which revealed a live, white worm of 12cm in length. In all the three cases there was no history of travel in the last two years to places where this worm is known to be endemic in human. The worm was properly preserved and sent to the department of microbiology for identification.
The worms were fixed in formalin and cleared in glycerine for proper viewing of the structures. The worms were white, elongated, 0.5mm thick and 12--13cm in length [Figure 1]. The diameter was almost same al throughout the length of the worm, except at the two ends where it was comparatively thin. The cuticle was multilayered with distinct longitudinal ridging [Figure 2] and [Figure 3]. At the lateral cord, a thickening of the innermost layer formed an inwardly directed ridge on either side of the body. The spaces between the ridges were equal to the length of the ridges themselves. The muscle cells were well developed specially at the level of the lateral cords [Figure 4]. The genus Dirofilaria was identified by its thick, multilayered cuticle with ridging and striations, large muscle cells, prominent lateral cord. The paired uteri and the intestinal tube were seen . Based on size, cuticular and internal morphologic features the worms were identified as adult females of Dirofilaria (Nochtiella) repens.
The genus Dirofilaria is a nematode of domestic and wild animals , . It has two subgenera: Dirofilaria with D. immitis as the type species and Nochtiella with D. repens as the type species. The mosquito vectors are Culex and Anopheles  found in India and many parts of the world. Of the different dirofilarial worms of medical relevance, D. repens is the most frequent and most widely distributed in the world with endemic foci in Southern and Eastern Europe, Asia minor, Central Asia and Sri Lanka.  Italy is one of the most affected countries. The most affected areas are head, orbit, thoracic wall and the upper limbs. The most common presentations are subcutaneous and submucous lesions. Some cases are reported with internal localizations. Most of these internal dirofilariasis cases presented with pulmonary lesions. Human ocular dirofilarial infections were reported from Kerala in 1976 and 1978.  Subsequently, several other cases were reported from India; which were mostly ocular dirofilariasis. Subconjunctival dirofilariasis due to D. repens were reported from several parts of India. Subcutaneous dirofilariasis is also reported from India.  Human dirofilariasis, due to D. repens, is important as regards not only the number of subjects affected in different parts of the world but also the variety of different organs affected.  Clinical presentations vary from tumor like lesions to cystic lesions.
The identification of the worm is done by studying the fully matured worm. D. immitis causes microfilaremia in human and may require use of anthelmentic drugs. Surgical removal of the worm is one modality of treatment in D. repens infecion.
Human cases of dirofilariasis in Assam are probably under-reported because the parasite isolated remains undiagnosed and unreported. In countries like Italy, human dirofilariasis cases are increasingly being reported and it is regarded as an emerging zoonosis.
Our first case presented as a cystic, slightly movable lesion which adds to the diverse clinical presentations that Dirofilaria repens can lead to. As the patients had no travel history to other endemic areas, it can be assumed that human dirofilariasis is not uncommon in many parts of India including Assam. Recovery from the infection is sometimes spontaneous while some cases remain undiagnosed. Clinicians should be alerted regarding the possibility of this zoonotic infection in cases of localized nodules in any part of the body.
Authors are grateful to the parasitologists of DPDx team, Center for Disease Control, Atlanta, Georgia, USA, for help in initial identification of the worm.
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