Onchocerca volvulus
(on-ko-sir-kah / vol-view-lus)
Microfilariae
Geographical Region
This parasite is found worldwide, although most of the cases that occur are from Africa, Latin America, Yemen and Saudi Arabia.
Transmission
It is transmitted through the bite of an infected female blackfly. When the fly bites, it releases the larval stage into the subcutaneous tissue, where the parasite grows into an adult worm.
Disease
Onchoncerciasis
or River Blindness
or River Blindness
- The adult worm can live in a human host for 14 years.
- They become encapsulated in fibrous tissue nodules.
- these measure a few millimeters to several centimeters in diameter.
- Symptoms begin 1-3 years after the initial infection.
- most common symptoms are rash and pruritis.
- other symptoms include:
- intense itching, swelling, pain
- hyper or hypopigmentation of the skin around the nodule
- The most serious complications occur when the microfilariae migrate to a create lesions in or around the eyes.
- this causes blindness in the eye
- mortality rate increase three to four told with blindness
Diagnostic
- Laboratory specimen
- skin snip
- look for microfilariae
- skin snip
- Testing
- tissue samples are placed in saline and teased to reveal microfilariae
- can also be cultured
- IgE levels can be tested
- will be elevated
- Adult forms may be surgically removed from nodules
Treatment
The best drug to treat this disease is Ivermectin. It is very effective in killing the microfilariae but does not kill the adult worm. If the eye is infected, prednisone is started several days before the Ivermectin treatment begins. They do this to minimize the inflammatory response to the dying microfilariae.