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Filariasis introduction overview
Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. These are spread by blood-feeding black flies and mosquitoes. This disease belongs to the group of diseases called helminthiases.
Reports of the disease have been documented in ancient Greek literature, and its symptoms were first recorded in the 16th century, during early explorations of Goa, Asia, and Africa.
Lymphatic filariasis is caused by the worms Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms occupy the lymphatic system, including the lymph nodes; in chronic cases, these worms lead to the syndrome of elephantiasis. Subcutaneous filariasis is caused by Loa loa (the eye worm), Mansonella streptocerca, and Onchocerca volvulus. These worms occupy the subcutaneous layer of the skin. Serous cavity filariasis is caused by the worms Mansonella perstans and Mansonella ozzardi, which occupy the serous cavity of the abdomen.
According to the World Health Organization (WHO), as of 2006, there has been an estimated 1.3 billion people in more than 80 countries at risk of contracting lymphatic filariasis. At present, there are over 120 million infected individuals,. Affected people mostly live in India, Africa, South Asia, the Pacific, and South, and Central America.
Lymphatic Filariasis is considered the highest among the world’s diseases that cause severe disability and disfiguration. It mostly strikes poor portions of the population in areas where there are great numbers of breeding sites for mosquitoes that carry the disease.
Mosquitoes are infected with microfilariae by ingesting blood when biting an infected host. Microfilariae mature into infective larvae within the mosquito. When infected mosquitoes bite people, mature parasite larvae are deposited on the skin from where they can enter the body. The larvae then migrate to the lymphatic vessels where they develop into adult worms, thus continuing a cycle of transmission.
The most spectacular symptom of lymphatic filariasis is elephantiasis – edema with thickening of the skin and underlying tissues. Elephantiasis affects mainly the lower extremities, Wuchereria bancrofti can affect the legs, arms, vulva, breasts, and scrotum (causing hydrocele formation) Onchocerca volvulus manifests itself in the eyes, causing “river blindness” (onchocerciasis), one of the leading causes of blindness in the world.
In the past, it was very difficult to diagnose filariasis because the parasitic worms could only be detected by looking at blood samples through a microscope.
These parasites are also nocturnal, which meant that they only showed up in the blood shortly before or after midnight. Just recently, a simple and very sensitive ICT “card test” was developed that could identify parasite antigens from infection, in just a few drops of blood. This could now be achieved at any time during the day without the need for a laboratory.
Filariasis is usually diagnosed by identifying microfilariae on Giemsa stained, thin, and thick blood film smears, using the “gold standard” known as the finger prick test.
The recommended treatment for people outside the United States is albendazole combined with ivermectin. Side effects of the drugs include nausea, vomiting, and headaches. All of these treatments are microfilaricides; they have no effect on adult worms. In a study from India, it was shown that a formulation of albendazole had better anti-filarial efficacy than albendazole itself. In 2003, the common antibiotic doxycycline was suggested for treating elephantiasis.
Currently, there is no vaccine for Filariasis. As of the present, scientists are still working to find a preventive inoculation for the disease. The World Health Organization also continues its drive to stop the infection from spreading and to ease the symptoms of those already infected. Even global healthcare corporations like SmithKline Beecham, and Merck and Co., Inc. have joined the fight against lymphatic filariasis through the donation of medicines and supporting the elimination of the disease.