Subcutaneous worm in humans

Introduction

There are several worm infections which can affect the subcutaneous tissues of the human. Some time these infections are difficult to eliminate.

1. Onchocerciasis

2. Loasis

3. Dirofilariasis

4. Dracanculosis

5. Gnathostomiasis

6. Mansonella streptocerca

7. Schistosomiasis

8. Brugia infection

9. Sparganosis

10. Coenurosis

Onchocerciasis

Onchocerciasis (“river blindness”) is caused by a filarial nematode (Onchocera volvulus) which infects an estimated 13 million individuals. The majority of individuals infected with O. volvulus live in the equatorial region of Africa extending from the Atlantic coast to the Red Sea.

Loasis

Loiasis is caused by Loa loa (the African eye worm), which is present in the rain forests of West and Central Africa. Adult parasites (females, 50 to 70 mm long and 0.5 mm wide; males, 25 to 35 mm long and 0.25 mm wide) live in subcutaneous tissues; microfilariae circulate in the blood with a diurnal periodicity that peaks between 12:00 noon and 2:00 P.M.

Dirofilariasis

This is a zoonotic filarial infection that affects primarily dogs, cats, and raccoons occasionally infect humans incidentally, as do Brugia and Onchocerca parasites that affect small mammals. Because humans are an abnormal host, the parasites never develop fully. The worm is known as Dirofilaria ripens.

Dracanculosis

Dracunculiasis, caused by Dracunculus medinensis, is a parasitic infection whose incidence has declined dramatically because of global eradication efforts. Current estimates suggest that there are 56,000 cases worldwide, the majority in Sudan. Humans acquire this infection when they ingest water containing infective larvae derived from Cyclops, a crustacean that is the intermediate host.

Gnathostomiasis

Infection of human tissues with larvae of Gnathostoma spinigerum can cause eosinophilic meningoencephalitis, migratory cutaneous swellings, or invasive masses of the eye and visceral organs.

Mansonella streptocerca

This filarial worm is found in West and Central Africa. It does not show any periodicity. Microfilariae are found in subcutaneous tissues and skin. The vector of this worm is a Culicoides (midges).

Schistosomiasis

Schistosomiasis is an important cause of parasitic myelitis in endemic areas. The myelitis is intensely inflammatory and granulomatous in nature, caused by a local response to tissue-digesting enzymes from the ova of the parasite.

Brugia infection

Zoonotic Brugia infection can produce isolated lymph node enlargement, Excisional biopsy is both diagnostic and curative; these infections usually do not respond to chemotherapy.

Sparganosis

Humans can be infected by the sparganum, or plerocercoid larva, of a diphyllobothrid tapeworm of the genus Spirometra. Infection can be acquired by the consumption of water containing infected Cyclops; by the ingestion of infected snakes, birds, or mammals; or by the application of infected flesh as poultices. The worm migrates slowly in tissues, and infection commonly presents as a subcutaneous swelling. Periorbital tissues can be involved, and ocular sparganosis may destroy the eye. Surgical excision is used to treat localized sparganosis.

COENUROSIS

This rare infection of humans by the larval stage (coenurus) of the dog tapeworm Taenia multiceps or T. serialis results in a space-occupying cystic lesion. As in Cysticercosis, involvement of the central nervous system and subcutaneous tissue is most common. Both definitive diagnosis and treatment require surgical excision of the lesion. Chemotherapeutic agents generally are not effective.