Filarial diseases cause chronic disease and disabilities in millions of people, leading to a lifetime of suffering and social stigmatization. Filariasis is a disease of the poor, and fosters poverty by decreased productivity, increased healthcare expenses and the abandonment of fertile land. In areas where two or more filarial diseases are endemic, people are frequently co-infected with more than one type of parasite.
Onchocerciasis affects the skin and eyes and is a major cause of blindness in African countries. The Onchocerca volvulus parasites are spread by infected female Simulium blackflies, which are abundant in riverside areas, giving the disease its common name of “river blindness”. The injected microfilariae take about a year to mature in fibrous nodules under the skin, and adults may live as long as 14 years. After mating, the mature female can produce up to 1000 microfilariae each day, which migrate through the skin and eyes. As they die, the large numbers of dead microfilariae produce severe itching and eye lesions. After many years, this may lead to disfiguring skin diseases and permanent blindness, and can shorten life expectancy by up to 15 years. In some West African communities about half of the men over 40 years of age have been blinded. As a consequence, people tend to avoid the fertile river lands for less productive areas resulting in a huge economic burden.
Human loaisis occurs in the rain forest and swamps of West and Central Africa, where Loa loa parasites are spread by infected Deer flies or Mango flies. Mature adults migrate through the subcutaneous tissues of the skin, and may cause red itchy swellings. Occasionally worms can be seen when they move about in the eye, which can be painful, but does not cause damage. In itself, loaisis is not particularly debilitating and is frequently untreated.
In each of these diseases, adult worms in the human host produce millions of juveniles which spread throughout the body via the blood and lymph systems. These microfilariae infect the insect host and pass through several stages of maturation before they can infect humans where they complete the maturation cycle and survive as adults for many years. The adult worms continue to produce new microfilariae in the body.
Filarial disease patients and doctors share their stories