Helminthic Dermatosis Roundworm

CUTANEOUS LARVA MIGRANS. (Fig 35-7). This is a disease caused by hookworms, usually parasites of dogs and cats. The ova are excreted through the feces, and they remain viable in sandy, moist ground. The larva then penetrate the skin of bathers or people who walk on the contaminated ground. Usually the "culprits" are Ancylostoma duodenal, Necator americanus, and other hookworms. Clinically, the parasite causes a serpentine, erythematous, papular, pruritic skin eruption. The parasite is usually ahead of the tract. Vesicles, excoriation, and crusts are present. Treatment includes topical thiabendazole and albendazole 200 mg by mouth twice daily for three days.

Gnathostomiasis Parasite
Figure 35-7. Larva migrans.

LARVA CURRENS. As opposed to cutaneous larva migrans, in which lesions move over a period of days, the cutaneous form of strongyloidiasis moves over a period of hours, which is the reason for the "currens" denomination. It is more common in immunosuppressed patients in whom multiple tracts can be seen. At the present time, ivermectin is the treatment of choice, 200 micrograms per kilogram, and in immunosuppressed patients it can actually be life-saving.

GNATHOSTOMIASIS. This condition was first diagnosed in South America in Ecuador in 1979 and extensively studied by Oyague. It is caused by Gnathostoma spinigerum. Clinically, it produces a nodular migratory eosinophilic panniculitis. This parasite normally inhabits the stomach of domestic animals such as dogs and cats. The eggs are excreted in the stools of these animals. They then reach the rivers and hatch in the water and are ingested by organisms of a Cyclops species, developing into the second larval stage. This is later ingested by fish, forming a third larval stage in their muscular tissue which in turn is eaten by a definitive host. Humans, who are not the definitive hosts, could develop the characteristic panniculitis of this disease from eating raw fish such as in cebiche or sushi. The parasite migrates through the tissues, most commonly to the skin, but it may go to any of the internal organs. Clinically, after a variable incubation period of 4 weeks to 3 years, patients develop the classic symptom of pruritic edematous migrating cutaneous plaque, which on biopsy occasionally shows the parasite. More commonly, only a very intense eosinophilia through the dermis and subcutaneous tissue occurs. Treatment alternatives include albendazole 200 mg twice daily for 5 days or ivermectin 200 micrograms per kilogram in a single dose.

FILARIASIS. Filariasis is a systemic infection due to one of several different species of nematode, all transmitted by mosquito bites, with hematogenous (rather that cutaneous as in onchocerciasis) spreading of microfilaria. The symptoms are related to chronic inflammation of the lymphatic system. They commonly occur in tropical areas of the world. Loa loa infections are reported in West Africa. Wuchereria bancrofti and Brugia malayi are more common in Asia and tropical Africa. The symptoms are related to the stage of disease. During the hematogenous spread, microfilariae are abundant in blood, producing temporary migratory swelling in extremities that is self-limited and recurrent. Acute lymphangitis and lymphadenitis may affect the groin and axillae. Genital involvement includes acute orchitis, epididymitis, and funiculitis, which are very painful. They can also be recurrent and evolve into fibrosis. Urticaria may be part of the clinical presentation. Late changes are due to obstruction of lymphatics, giving origin to different forms of elephantiasis affecting the extremities and scrotum with massive edema. Diagnosis is reached by the presence of microfilaria in blood smears and by serological testing. Treatment is based on the use of diethylcarbamazine. Recent reports on the use of ivermectin seem very promising.

ONCHOCERCIASIS. Onchocerciasis is a chronic infestation of the skin by Onchocerca volvulus. This is a microfilarial nematode whose natural hosts are humans and fleas from the genus Simulium. The disease was first described in Africa and later in Central America. Recently, the reports extend the disease to the northern countries of South America. The transmission occurs when flies become infected by biting sick people. After a short period of maturation, the microfilariae move to the buccal apparatus of the insect and enter the skin of a noninfected human with the next blood meal. The infective forms become adults in 6 to 8 months inside cutaneous nodules, where they begin producing microfilariae. From there on the infection propagates to all the tegumentary system. Cutaneous involvement includes the characteristic nodules containing adult forms. They tend to locate in the scalp in Central American patients and on extensor surfaces in African patients. Other clinical presentations include facial erythema, facial livedoid discoloration, and prurigo-like eruption on buttocks and extremities. Later signs are extensive lichenification, dyschromia, elephantiasis of extremities and scrotum, and the so-called hanging groin. Ocular involvement is related to the direct invasion of eye structures by the microfilariae, resulting in complete and permanent loss of vision; this is the reason the disease was called river blindness. Diagnosis is easy to confirm either by direct scraping or by histologic analysis of skin lesions in which the adult form and microfilaria are identified. This disease is particularly worthy of mention because we can now count on a specific treatment which consists of the oral administration of ivermectin. It is extremely effective even as a single-dose therapy.

How To Deal With Rosacea and Eczema

How To Deal With Rosacea and Eczema

Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.

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