|Year : 2022 | Volume
| Issue : 2 | Page : 356-358
Ocular dirofilariasis - A zoonosis with rapidly changing epidemiology
Vikas Sharma1, Ankuj Tinna2, Ishan Aggarwal3, Atul K Singh1, Ritesh Waghray4, Arpit Srivastava5
1 Department of Eye, AFCME, New Delhi, India
2 Department of Eye, INHS Asvini, Mumbai, Maharashtra, India
3 Department of Eye, MH Danapur, Bihar, India
4 Department of Eye, 5AFH, Jorhat, Assam, India
5 Department of Eye, MH Chenni, Chennai, Tamil Nadu, India
|Date of Submission||25-Oct-2021|
|Date of Acceptance||31-Jan-2022|
|Date of Web Publication||13-Apr-2022|
Department of Eye, AFCME, Subroto Park, Dhaula Kuan, Delhi - 110 010
Source of Support: None, Conflict of Interest: None
Human dirofilariasis is a rare but known zoonotic infection with a worldwide geographical distribution. Ocular dirofilariasis is rare but more and more cases are being reported from all over India. Despite the southern states being endemic for this disease, cases are being reported from different Indian states due to better transport facilities, better infrastructure, and increased awareness among healthcare workers regarding this zoonosis. We present a series of three cases that focuses on the epidemiology of the disease and compares cases reported from various states, which indicates a northward shift of the disease to non-endemic states.
Keywords: Dirofilaria repens, epidemiology, ocular dirofilariasis, zoonosis
|How to cite this article:|
Sharma V, Tinna A, Aggarwal I, Singh AK, Waghray R, Srivastava A. Ocular dirofilariasis - A zoonosis with rapidly changing epidemiology. Indian J Ophthalmol Case Rep 2022;2:356-8
|How to cite this URL:|
Sharma V, Tinna A, Aggarwal I, Singh AK, Waghray R, Srivastava A. Ocular dirofilariasis - A zoonosis with rapidly changing epidemiology. Indian J Ophthalmol Case Rep [serial online] 2022 [cited 2022 May 24];2:356-8. Available from: https://www.ijoreports.in/text.asp?2022/2/2/356/342963
Zoonosis is a disease or infection that can be transmitted naturally from vertebrate animals to humans and vice versa. Dirofilaria are parasitic roundworms that are transmitted by mosquito bites. Dogs and cats are the definitive hosts. Human beings are accidental dead-end hosts, in which Dirofilaria larvae can develop into adult worms but remain sexually immature and no microfilariae are produced.
Southern Indian states are the hub for this zoonosis and so far, very few cases have been reported from north India. We came across three such cases from Delhi in which patients presented with different chief complaints and without any travel history to endemic states in the past. We tried to find the reasons behind this changing trend in the epidemiology of ocular dirofilariasis.
| Case Series|| |
A 25-year-old female patient, presented with redness and foreign body sensation in her left eye. Her vision in both eyes was 6/6 unaided. Slit-lamp examination revealed cystic swelling of inferior forniceal conjunctiva with a moving thread-like worm underneath in the left eye. Right eye examination was within normal limits. A live worm was retrieved by making a small opening in the conjunctiva. The worm was sent for direct microscopic examination [[Figure 1]a–inferior forniceal subconjunctival worm].
|Figure 1: (a) Inferior forniceal subconjunctival worm. (b) Subcutaneous worm. (c) Superotemporal bulbar subconjunctival worm. (d) Direct microscopic examination of the subconjunctival worm from case 1|
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A 48-year-old female patient reported a firm swelling in her left upper eyelid. Slit-lamp examination revealed a small streak-like firm swelling under the skin of the upper lid of the left eye, which changed shape on applying pressure, suggestive of a moving subcutaneous organism. An incision was made in the line of lid crease and a living worm was carefully removed. The organism was sent for microbiologic examination [[Figure 1]b–subcutaneous worm].
A 52-year-old male patient reported pain and irritation in his right eye. Slit-lamp examination revealed subconjunctival swelling in superotemporal bulbar conjunctiva with a moving thread-like structure. An opening was made in the conjunctiva, the worm was removed in toto with the help of a blunt forceps and was sent for examination [[Figure 1]c–superotemporal bulbar subconjunctival worm].
Post-procedure, all patients were given topical antibiotics and anti-inflammatory eye drops. During follow-up visits, eyes were quiet and patients were comfortable. Microbiologic examination revealed a live unsheathed worm measuring 15 to 18 cm in length with a blunt head and a tapering tail. The worm showed distinct longitudinal ridges with multi-layered cuticle, which forms the basis of identification along with its size and internal morphologic features such as esophagus tube and vulval opening. Based on the morphological features, all three worms were identified as Dirofilaria repens [[Figure 1]d–direct microscopy examination of the subconjunctival worm from case 1].
| Discussion|| |
Dirofilariasis, a zoonotic infection, is caused by parasites of the genus Dirofilaria belonging to the family Onchocercidae. The infection is prevalent in canines and wild animals, which are the principal reservoir hosts. Humans are infected accidentally by the bite of mosquitoes. Human infection is caused most commonly by three species, D. immitis, D. repens, and D. tenuis. Of these, D. repens is the species responsible for ocular as well as subcutaneous dirofilariasis.,
Ocular dirofilarial worm is most commonly reported in subconjunctival tissue although cases have been reported from the anterior chamber, retina, and vitreous also. Diagnosis of dirofilariasis is established by the identification of cuticular ridges by histopathologic and microscopic examination of the worm. Molecular identification can also be used for species differentiation using mitochondrial gene amplification by polymerase chain reaction.
Treatment involves complete excision of the subcutaneous nodule and careful traction of the complete worm from the subconjunctival space. Anti-filarial medication (ivermectin or diethylcarbamazine) is considered if the diagnosis is suspected before surgery.
Geographically, Sri Lanka is one of the most affected countries, Kerala is the focus of dirophilariasis in India due to in close proximity to Sri Lanka, its warm and humid climate, which is conducive for breeding mosquitos, and a high prevalence of dirofilariasis in dogs and cats in Kerala.
This case series, from a tertiary care center in New Delhi, do not just add to the existing database of patients with ocular dirofilariasis but also raises an alarm to further investigate this recent increase in the number of dirofilariasis cases in North India. We did literature research of ocular dirofilarial cases reported from 2011 to 2021 in India [Table 1]. A total of 36 cases of ocular dirofilariasis were reported from 2011 to 2021 [Figure 2]. As per our observation, very few cases of ocular dirofilariasis were reported in the last few years, and the diagnosis could be attributable to the reduced outpatient load due to the COVID-19 pandemic situation in India. Also, only one case was reported in 2021, which was made through a telemedicine consultation.
|Figure 2: Number of reported cases of ocular dirofilariasis over the last decade|
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|Table 1: Documented case reports from various states in India over the last decade|
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According to cases reported from various states, it is evident that more and more cases are being reported from non-endemic northern Indian states [Figure 3]. Reasons behind this shift could be due to increased migration to the Delhi NCR region for education and employment, improved infrastructure, better travel facilities, and mixed food culture. Warm, humid climate, and industrialization have given a conducive atmosphere for the breeding of mosquitoes that are the vectors of Dirofilaria, which in turn could be a causative factor in the shift of epidemiology. A few studies also indicated that there is a northward migration of the disease that potentiates our findings.
|Figure 3: Statewise comparison of total reported cases between 2011 to 2015 and 2016 to 2021|
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| Conclusion|| |
Dirofilariasis is a well-known zoonosis that rarely involves ocular tissues. With the increased incidence of ocular cases, there is an increased awareness among ophthalmologists. We suggest that ocular dirofilariasis is no more a rare disease entity and is rapidly changing its epidemiology. It is no more confined to the south Indian states with a gradual shift of the disease to pan India. Clinical suspicion for ill-defined subconjunctival/subcutaneous mass in ocular tissue should always have ocular dirofilariasis as a differential diagnosis.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]