Ocular dirofilariasis: Still in the dark in western India?

SI Sahdev¹, SP Sureka¹, PA Sathe², R Agashe¹,  
¹ Department of Ophthalmology, Seth G S Medical College and KEM Hospital, Mumbai, India
² Department of Pathology, Seth G S Medical College and KEM Hospital, Mumbai, India

Correspondence Address:
S P Sureka
Department of Ophthalmology, Seth G S Medical College and KEM Hospital, Mumbai
India

Full Text

Sir,

A three-year-old male child from Mumbai, India presented with a mass on the right upper lid 3×3×2 cm since two months with redness and pain. The mass was tender, firm and non-reducible. Computed tomography (CT) scan revealed diffuse inflammatory swelling of the lid [Figure 1]. Rest of the eye examination was normal. On exploration, two, pink, firm, well-circumscribed masses were dissected [Figure 2]. Microscopy revealed fibrocollagenous tissue with lymphoid follicles and adult filarial nematode worms, at least one of which was a non-gravid female. The filaria was identified as Dirofilaria repens, as indicated by the noticeable cuticular ridges [Figure 3]. Eosinophil count was normal and peripheral smear did not reveal any microfilariae. The patient was asymptomatic on follow-up after five months. {Figure 1}{Figure 2}{Figure 3}

Dirofilariasis in humans occurs due to Dirofilaria repens [1] which is encountered in subcutaneous tissues of dogs. The intermediate host, mosquitoes, take up microfilariae while feeding on an infected host and the infective third-stage larva develops, which is transmitted to the definitive vertebrate host such as dogs, cats or humans, the dead end host. [2]

D. repens causes transitory inflammatory swellings which have a predilection for upper body sites (76%) over the lower body (24%). Of these, orbital lesions account for 31% cases. [3]

Human ocular dirofilaria infections were initially reported from Kerala, south India [4] and then from other areas in India. [1] As per Megat Abd Rani et al., the distribution of human cases of subcutaneous dirofilariasis seems to mirror the distribution of canine cases. [5] The prevalence of D. repens in canines in Kerala [2] and Karnataka [6] in southern India was 7% and 21% respectively. A number of human cases of dirofilariasis due to D. repens have been reported from this region. [2] Veterinarians in India believe that D. repens is confined to southern India. Culex, Aedes, Amrigeres and Anopheles mosquitoes, suitable vectors for this parasite, are present all over India. A study that detected microfilariae in canines in Mumbai by blood smear microscopy and Polymerase Chain Reaction (PCR), revealed that the prevalence of D. repens in canines was 8% and 16.7% respectively. [6] In spite of D. repens being present in canines in Mumbai area, [6] there is no similar reporting of cases of dirofilariasis from Mumbai and from western India.

This is probably the first reported case of subcutaneous ocular dirofilariasis from Mumbai, India. This could be due to the lack of cases, the lack of identification of D. repens on histopathology, lack of description of imaging features of orbital dirofilariasis or lack of reporting in indexed medical literature. This case emphasizes that surgeons and ophthalmologists need to be more alert and include D. repens in the differential diagnosis in case of subcutaneous swellings especially in the endemic areas. Pathologists and radiologists must be aware of and identify this agent. Physicians and ophthalmologists need increased awareness about the existence of a range of zoonotic helminthes other than those natural parasites of humans that might be expected to be found in patients' eyes. [7] There is a need for exploration of a possible reservoir of D. repens in western India, which is hitherto unexplored and unknown.

 Acknowledgment

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