Molecular characterization of human Dirofilaria isolates from Kerala

Dirofilarial nodule as a differential diagnosis for subcutaneous lumps in children

PURPOSE

Subcutaneous nodules in children are commonly caused by pilomatrixoma, dermoid cysts, soft tissue tumors, etc. Parasitic infections are reported to cause subcutaneous nodules and are infrequently described, mostly in the adult literature. We aim to describe the clinicopathological features of subcutaneous lumps caused by dirofilarial infestation in children in an endemic country.

METHODS

A retrospective analysis was performed of all patients presenting with the above condition to Lady Ridgeway Hospital from 2018 to 2022 and their relevant details were captured in a proforma.

RESULTS

There were 55 patients with a male to female ratio of 2:1. The mean age at presentation was 50 months (7-156 months). The mean duration was 97 days (1-820 days). The common sites involved were scrotum (30.9%), back (14.5%), abdominal wall (102.7%) and face (10.9%). The majority had a painless nodule (70.9%), while ten (18.2%) had features of acute inflammation. Thirty (55.5%) had preoperative ultrasonography which showed features of parasitic nodules in 26 (47.3%). Parasite was demonstrated in histopathological analysis only in 30 patients (54.5%).

CONCLUSION

Dirofilarial nodule should be considered in the differential diagnosis of subcutaneous lumps in children, especially in the endemic areas.

Candidatus Dirofilaria Hongkongensis Infections in Humans During 2005 to 2020, in Kerala, India

We tried to determine the epidemiology and species of human dirofilariasis observed at two tertiary care hospitals in Kerala. We searched the hospital database to identify cases of dirofilariosis from January 2005 to March 2020. Along with human isolates, one dog Dirofilaria isolate was also subjected to PCR and sequencing of pan filarial primers cytochrome oxidase subunits 1 and 12S rDNA. We documented 78 cases of human dirofilariosis. The orbit, eyelid, and conjunctiva were the most commonly affected sites. Molecular characterization identified one dog and five human isolates as Candidatus Dirofilaria Hongkongensis. A rare case of subconjunctival infestation by B. malayi was also documented. Human dirofilariosis is a public health problem in the state of Kerala in India, and it is mostly caused by Candidatus Dirofilaria Hongkongensis. We propose that all diroifilaria isolates are subjected to sequencing for identification.

On the validity of "Candidatus Dirofilaria hongkongensis" and on the use of the provisional status Candidatus in zoological nomenclature

The fast development of molecular taxonomy is impacting our knowledge of the world parasite diversity at an unprecedented level. A number of operational taxonomic units have been uncovered and new species described. However, it is not always that new parasite species are being described in compliance with the International Code of Zoological Nomenclature. This is the case of “Candidatus Dirofilaria hongkongensis”, a nematode found in dogs, jackals and humans in Hong Kong and parts of India. This name has been proposed without a formal description and without the designation of a holotype, and therefore is an unavailable name. Finally, we argue that using the provisional status Candidatus in zoological nomenclature is inappropriate, considering this term is not considered in the International Code of Zoological Nomenclature.