1. Elephantiasis
Disease Picture: Filariasis occurs in almost every tropical country. This disease is manifested by gross and solid oedema of a limb–often of the legs or the scrotum. This, however, is the last stage of the disease. Earlier symptoms include lymphangitis and an allergic feverish reaction to the disease. There is also a form of filarial orchitis and hydrocele is a very common feature.Elephantiasis Cause. A small worm called Wuchereria bancrofti. It is a curious fact that often microfilariae (embrionic filariae) are found in the blood-stream in large numbers, only at night. Their presence in the vast majority cases is harmless. Only in a few does the adult worm block a part of the lymphatic system and cause elephantiasis.
Disease Source. Other persons infected with filariae. In some parts of the world as many as 60 per cent of people are infected.
Route. The mosquito bites an infected person, the microfilaria is drawn into the stomach of the mosquito as it feeds on the blood, develops in the mosquito and then escapes from it the next time it bites.
Susceptibles. All persons are susceptible, but the gross signs of the disease are not visible until at least 20 years of age.
Prevention. The prevention of elephantiasis consists in the control of mosquitoes (like prevention of malaria) and the early treatment of cases, especially schoolchildren.
Treatment. Diethylcarbamazine, Hetrazan, administered by a doctor.
2. Loa-Loa
There is another form of filariasis called loa-loa, caused by a worm known as Loa-loa. It has a tendency to migrate a good deal under the skin, usually causing no symptoms, but sometimes causing itching, and occasionally swellings. (Calabar Swellings) in various parts of the body. When, however, the parasite appears in the eye it causes considerable swelling though not very much permanent damage. It is transmitted from person to person by the mangrove fly. Treatment is with diethylcarbamazine.3. Onchocerciasis (River Blindness)
Disease Picture. Incubation period is 4-18 months. Onchocerciasis is another filarial disease. It occurs in Central America, in some parts of South America and in a belt in Africa from Ghana to the South Sudan, Ethiopia, Tanzania, and Uganda.The main sign of the disease is the appearance of nodules under the skin, which can occur all over the body. There is also a condition known as lizard skin which is caused by this disease.
This nodules do little harm, but when one of them occurs near the eye, the microfilariae can cause blindness. In the localities affected in some countries, as many as 10 percent of the total population are blind from the disease, but in most places the incidence of eye complications is about 1 per cent of the affected population. Besides blindness, this disease causes chronic itching of the skin.
Cause. A filarial worm called Onchocerca volvulus.
River Blindness Route
The filariae are transmitted from an infected person to a previously uninfected person by the bite of a fly of the genus Simulium. These flies breed in shallow fast-flowing streams, the larvae attaching themselves to stones or the backs of crabs. The flies bite those who live or work near the river. Hence the name river blindness.Susceptibles. All uninfected persons. Since the incubation period is about under 1 year of age.
Prevention. Affected villages may have to be evacuated, and the inhabitants live further away the river out of reach of the flies. The best method is to treat the infected stream water periodically using a very small concentration of DDT.
Treatment. Diethylcarbamazine in hospital.
