Scanning electron microscopy as a confirmatory tool for morphological identification of Dirofilaria (Nochtiella) repens

Document Type : Original Article

Authors

1 Department of Medical Parasitology, Faculty of Medicine,Alexandria University, Alexandria, Egypt

2 Maxillofacial and Plastic Surgery Department, Faculty of Dentistry

Abstract

Background: Dirofilaria repens (Railliet & Henry, 1911) is a filarial nematode that mainly affects canids.
It can also infect humans accidentally, causing subcutaneous or conjunctival lesions, especially in the Old-
World, including Egypt. Scanning electron microscopy (SEM) is very useful in diagnosis and identification
of different parasites including D. repens.
Objectives: The current work aimed to use SEM as a confirmatory tool for morphological identification
of D. repens.
Material and Methods: Morphological diagnosis of the excised nematodes was performed by studying
their naked eye and light microscopic appearance. This was then confirmed using scanning electron
microscopy (SEM).
Results: Three worms were identified; one was excised from a maxillofacial subcutaneous lesion and two
were excised from a bulbar conjunctival lesion. All worms were females. Scanning electron microscopic
examination showed external cuticular longitudinal ridges and circular striations on the worm surface
especially in the mid-body region; which are characteristic for D. repens. The anterior end of the worms
was wider than the posterior end that possessed a dimple-like anal orifice. The anterior end of the
subconjunctival worms was spoon-like, and wider than that of the subcutaneous worm. The dimple-like
anal orifice of the subconjunctival worm was more retracted than that of the subcutaneous worm.
Conclusion: SEM was used as a confirmatory tool for the diagnosis of two new human cases of dirofilariasis
diagnosed in Egypt.

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