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Year : 2021  |  Volume : 14  |  Issue : 1  |  Page : 80-83  

A rare case of subcutaneous dirofilariasis from a tertiary care hospital in Western Maharashtra

Dr. D. Y. Patil Medical College Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, Maharashtra, India

Date of Submission31-Jul-2020
Date of Decision15-Sep-2020
Date of Acceptance25-Sep-2020
Date of Web Publication22-Jan-2021

Correspondence Address:
Shahzad Mirza
Dr. D. Y. Patil Medical College Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune - 411 018, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mjdrdypu.mjdrdypu_432_20

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Dirofilaria are tissue nematodes which can cause zoonotic diseases and have been reported from all over the world. They are transmitted by zooanthropophilic arthropods. The genus causes subcutaneous ocular, pulmonary, and lesions in other subcutaneous tissues. The most commonly implicated species are Dirofilaria immitis and Dirofilaria repens. Confirmation of the diagnosis of dirofilariasis is mainly dependent upon microbiological identification of the parasite by macroscopical and microscopical analysis and histology. Documented reports from India are mainly from South India and of ocular presentations by D. immitis. Hence, this case of subcutaneous dirofilariasis is being presented. The present case was a 65-year-old female who presented with a swelling over the left lower side of the neck for 1 month. The patient underwent surgery for the mass and the lesion was excised. The mass was sent for microbiological identification. The parasite showed a cuticle, which had longitudinal as well as transverse striations. The parasite also had a body cavity, which had internal organs and structures. The worm was identified as Dirofilaria spp. based on morphological features, both microscopic and macroscopic. It is likely to be D. repens due to the presentation as a subcutaneous nodule with which it is more associated.

Keywords: Dirofilaria, filaroids, subcutaneous swelling, tissue nematode

How to cite this article:
Gandham NR, Mirza S, Das NK, Misra RN. A rare case of subcutaneous dirofilariasis from a tertiary care hospital in Western Maharashtra. Med J DY Patil Vidyapeeth 2021;14:80-3

How to cite this URL:
Gandham NR, Mirza S, Das NK, Misra RN. A rare case of subcutaneous dirofilariasis from a tertiary care hospital in Western Maharashtra. Med J DY Patil Vidyapeeth [serial online] 2021 [cited 2021 Mar 7];14:80-3. Available from: https://www.mjdrdypv.org/text.asp?2021/14/1/80/307684

  Introduction Top

Parasitic infections manifest clinically in variable ways. Mostly, they have a chronic onset. Nematode infections may be intestinal or somatic. Genus Dirofilaria are tissue/somatic nematodes. They generally cause infections in animals such as cats, dogs, and some other wild animals.[1] They may cause zoonotic infections in humans and are considered as emerging zoonotic infections transmitted by zooanthropophilic arthropods. They have been reported from all over the world.[2] Humans could be just paratenic hosts as they are not natural hosts. The infection in humans is a dead-end infection. The genus Dirofilaria includes Dirofilaria immitis, Dirofilaria repens, Dirofilaria tenuis, and Dirofilaria ursi to name a few.[3] The most common Dirofilaria spp. causing infections in humans are D. repens and D. immitis. In the animal host (definitive host), the parasite is present in the form of unsheathed microfilariae, which is transmitted to other animals or humans by mosquitoes (Culex, Aedes, or Anopheles) bites, which also serve as an intermediate host.[4] The parasite causes subcutaneous, ocular, and lesions in other subcutaneous tissues from where the adult worms can be recovered and identified usually post excision.[5] The symptoms of dirofilariasis depend upon the site of the infection. It may vary from local sensation, redness in eyes, proptosis, diplopia, etc., The diagnosis is mainly dependent upon histological identification of the parasite by macroscopical and microscopical analysis. The treatment is mainly by surgical excision of the parasite.

Dirofilarial infections have been widely reported from European countries. In Asia, Sri Lanka seems to be the most affected country with an infection rate of almost 60% in dog population [Table 1].[6] In India, it has mostly been documented in South India with Kerala reporting most cases. Reports are also available from Karnataka and very few from Maharashtra [Table 1].[5] In India, the documented cases are mainly ocular infections.[9] Hence, we present this case of subcutaneous dirofilariasis from western Maharashtra.
Table 1: Related publications in dirofilariasis

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  Case Report Top

A 65-year-old female presented with a swelling over the left upper side of the chest of at least 1-month duration. The patient accidentally discovered this mass about a month back. She gave no history of trauma, fever, weight loss, similar swelling anywhere else in the body, loose stools, or constipation. Her general systemic examination was within normal limits. The mass was initially smaller a month back, but had gradually increased to its present size. Local examination showed the mass to be of 2 cm × 2 cm, and 2 cm above and lateral from the head of the left clavicle. The mass was tender, immobile, nonfluctuant with no local rise of temperature. The mass was solitary, over the clavicle, with well-defined margins, did not adhere to the underlying tissue, did not move with deglutition, and the skin over it was normal.

The patient gave no significant medical or surgical past history or any history of allergies.


An ultrasonography of the neck region was performed. The right side revealed nothing unusual. The left base of the neck above and lateral to the head of the clavicle revealed a hypoechoic lesion of size 10.8 mm × 0.5 mm, seen in the supraclavicular region in the subcutaneous plane on the left side of the neck. Further, the lesion showed linear structures with hyperechoic walls and central hyperechoic line which appeared to be coiled, suggestive of a worm with cavity. Chest X-ray was normal. Her hematological investigations were normal with normal eosinophil count.

The patient underwent surgery for the mass and the lesion was excised.

Microbiological diagnosis

The gross specimen was received in the department of microbiology in normal saline. Macroscopic examination-It was a grayish white dense mass with a thread-like structure, whitish in color, opaque, about 8 cm in length, cylindrical with tapering anterior and posterior ends [Figure 1].
Figure 1: Macroscopic view of Dirofilaria worm

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Microscopic examination- Under the microscope, the adult parasite showed a cuticle, which had longitudinal as well as transverse striations [Figure 2]. The parasite also had a body cavity, which had internal body structures. The head was bilaterally symmetrical.
Figure 2: Microscopical view of Dirofilaria transverse striations with prominent longitudinal ridges

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With this, it was identified as adult worm of Dirofilaria spp. based on microscopic and macroscopic morphological features. It was not possible to differentiate it as male or female. Based on its subcutaneous presentation and documented reports of the geographical region, it is most likely that this is D. repens.

The patient was started on tablet albendazole on discharge and was asked to come for follow-up visit.

  Discussion Top

The Phylum Nematoda has two classes Adenophorea and Secernentea. The superfamily Filarioidea to which the genus Dirofilaria belongs is from Class Sercentea. The other genera in Filarioidea are Brugia, Mansonella, Onchocerca, and Wuchereria. Genus Dirofilaria belongs to the family Onchocercidae of the order Spirurida.[1] Further, the genus Dirofilaria has two subgenera Dirofilaria and Nochitella. D. repens is a species type of Nochitella which has longitudinal circular ridges and is usually found in subcutaneous tissue.[6] In humans, mostly two types of diseases, pulmonary dirofilariasis, primarily caused by D. immitis, and subcutaneous dirofilariasis, caused by D. repens, are seen.[10] Dirofilariasis is an emerging zoonotic infection and can cause accidental infection in humans. The infection is acquired by mosquito bite. Culex, Aedes, and Anopheles spp. all can be the vectors. The unsheathed microfilarias are taken up from the blood of the animal host. The microfilaria develops in the malpighian tubules of mosquitoes and the larvae migrate to the proboscis. The Dirofilaria spp. have poor vertebrate host specificity, in regard to the mammalian spp. it infects. They are best adapted to wild and domestic dogs and less for cats and humans. The vectors are mosquitoes of various species, and mainly of the Culicidae family.[11] Subcutaneous nodules occur usually on exposed areas such as the face, neck, and limbs. In the present case, it was on the neck.

The prevalence of this disease is increasing in many parts of the world and has a notably higher female predilection between the 4th and 5th decades of age.[10] The present case was also a female 65-year-old. Endemicity, close contact with reservoir animals like stray cats and dogs, environmental changes like deforestation, etc., which changes are the risk factors which causes dirofilariasis.[12] The patient is a resident of Maharashtra and has visited the Konkan region. There are a few case reports of dirofilariasis from Maharashtra [Table 1].[8] Mostly, the commonest clinical feature of subcutaneous dirofilariasis is a painless subcutaneous nodule. However, in this case, it was a subcutaneous nodule which was tender.[10] Most hematological investigations in parasitic infections have a peripheral eosinophilia. However, in case of subcutaneous dirofilariasis, Eosinophilia or raised immunoglobulin E is rarely observed. The present case too was characterized by normal eosinophil count (2%). Therefore, high clinical suspicion is required for pre excision diagnosis.

Precise identification of Dirofilaria species can be achieved with DNA analysis by polymerase chain reaction (PCR), but it requires a large number of specific probes, so it greatly limits its usefulness for clinical diagnosis.[2]

Microscopy and PCR can be used for the diagnosis of the disease. Microscopy is cheap and reliable but less sensitive and reliable to differentiate between different species. PCR is sensitive and specific but not widely available. For such rare cases, it is practically difficult to have PCR primers in nonendemic areas, so heavy reliance on microscopy is there [Table 1].[12]

Furthermore, determining the exact species and gender based on microscopy has its limitations. Probable speciation can be done on the basis of site, symptoms, history, geographical location macroscopic, and microscopic appearance.[13] Most of the case reports in India of dirofilariasis come from Southern India. The present case was a former resident of South India and had spent a considerable amount of time in the Konkan region of Maharashtra.

This case is significant because of its occurrence in Western Maharashtra and its presentation as a subcutaneous nodule with normal eosinophilic count. The most likely parasite being D repens given the complete work up done with available resources and limitations

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

  Conclusion Top

The lessons learnt from this particular case is that dirofilariasis is an emerging zoonotic disease and its differential diagnosis should be kept in mind while dealing with subcutaneous nodules on exposed areas in a patient from warm regions with higher prevalence of mosquitoes. A high index of suspicion is required for clinical diagnosis. Microbiological diagnosis is the key in the absence of positive hematological findings. An up to date data on the reports of recent infections will go a long way in planning of vector controls and treatment aspects of this disease. Even after treatment, the patient should be followed up for recurrence of nodules from other sites.


We would like to thank the Department of General Surgery, Dr. D Y Patil Medical College and Hospital, Pimpri, Pune, Maharashtra, for the samples and providing with necessary information.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Gibson DI. Nature and classification of parasitic helminthes. In: Cox FE, Wakelin D, Gillespie SH, Despommier DD, editors. Topley and Wilson's Microbiology and Microbial Infections. 10th ed. London: Hodder Arnold; 2005. p. 573-99.  Back to cited text no. 1
Khurana S, Singh G, Bhatti HS, Malla N. Human subcutaneous dirofilariasis in India: A report of three cases with brief review of literature. Indian J Med Microbiol 2010;28:394-6.  Back to cited text no. 2
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Gunathilaka N, Siriwardana S, Wijesooriya L, Gunaratne G, Perera N. Subcutaneous dirofilariasis caused by Dirofilaria (Nochtiella) repens in Sri Lanka: A potential risk of transmitting human dirofilariasis. Sage Open Med Case Rep 2017;5:1-4  Back to cited text no. 3
Chatterjee KD. Phylum nemathelminthes: Class nematod. In Chattrejee KD, editor. Parasitology (Protozoology and Helminthology). 13th ed. Kolkata: CBS Publishers and Distributors Pvt. Ltd.; 2011. p. 199-258.  Back to cited text no. 4
Agrawal S, Agrawal R, Shastri J. Ocular dirofilariasis: A rare case from Mumbai, India. J Clin Diagn Res 2017;11:DD09-10.  Back to cited text no. 5
Dissanaike AS, Abeyewickreme W, Wijesundera MD, Weerasooriya MV, Ismail MM. Human dirofilariasis caused by Dirofilaria (Nochtiella) repens in Sri Lanka. Parassitologia 1997;39:375-82.  Back to cited text no. 6
Kini RG, Leena JB, Shetty P, Lyngdoh RH, Sumanth D, George L. Human dirofilariasis: An emerging zoonosis in India. J Parasit Dis 2015;39:349-54.  Back to cited text no. 7
Kombade SP, Mantri RS, Ambhore NA, Karyakarte RP. Subcutaneous human Dirofilariasis in Vidarbha. Indian J Pathol Microbiol 2015;58:387-8.  Back to cited text no. 8
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Yaranal PJ, Priyadarshini MM, Purushotham B. Human subcutaneous dirofilariasis of forearm an unusual presentation. Indian J Dermatol 2015;60:103.  Back to cited text no. 9
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Jayasinghe RD, Gunawardane SR, Sitheeque MA, Wickramasinghe S. A case report on oral subcutaneous dirofilariasis. Case Rep Infect Dis 2015;2015:648278.  Back to cited text no. 10
Simon F, Siles-Lucas M, Morchon R, Gonzalez-Miguel J, Mellado I, Carreton E, et al. Human and animal dirofilariasis: The emergence of a zoonotic mosaic. Clin Microbiol Rev 2012;25:507-44.  Back to cited text no. 11
Kamyingkird K, Junsiri W, Witsanuwat C, Kengradomkij C, Saengow S, Sangchoto K, et al. Prevalence and risk factors associated with Dirofilaria immitis infection in dogs and cats in Songkhla and Satun Provinces, Thailand. Agric Nat Resour 2017;51:299-302.  Back to cited text no. 12
Joseph K, Vinayakumar AR, Criton S, Vishnu MS, Pariyaram SE. Periorbital mass with cellulitis caused by dirofilaria. Indian J Med Microbial 2011;29:431-3.  Back to cited text no. 13


  [Figure 1], [Figure 2]

  [Table 1]


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