1. Onchocerciasis (River Blindness)
Deepika Sundararaj
March 20, 2012

2. River blindness is caused by a nematode parasite: Onchocerca volvulus
Onchocerciasis is a parasitical disease caused by the filarial worm Onchocerca volvulus. Only when explorers entered these regions was the disease recognized for the first time. The diseased people were observed to experience blindness of unknown cause as well as scaly, itchy, nodular skin, which was known as kru kru or craw craw in West Africa. First visual identification of the worm was in 1874 by Dr. John O’Neill in Ghana.

3. It is predominately found in Africa, the Arabian Peninsula, and in Latin America.
Endemic in 36 countries across Africa, Latin America and Yemen, and these areas usually coincide with the path of rivers and streams. About 85.5 million people live in endemic areas and 50% of these reside in Nigeria. Currently affects over 18 million people, and 99% of all those live in Africa. The disease exists in isolated foci in Latin America (6 countries)

4. The parasites are transmitted by the black fly
Simulium: black fly or buffalo gnat
Found near rivers and streams because larval stages require fast-flowing and aerated water for development.
Species of fly depends on the area. Flies tend to bite the upper body in the Americas and lower body in Africa (different nodule distribution). Deforestation has changed the habitats of the flies.
Need hundreds of bites in order to develop onchocerciasis

5. Life cycle involves six main stages
A Simulium female black fly takes a blood meal on an infected human host, and ingests microfilaria.
The microfilaria enter the gut and thoracic flight muscles of the black fly, progressing into the first larval stage (J1.).
The larvae mature into the second larval stage (J2.), and move to the proboscis and into the saliva in its third larval stage (J3.). Maturation takes about 7 days.
The black fly takes another blood meal, passing the larvae into the next human host’s blood.
The larvae migrate to the subcutaneous tissue and undergo two more molts. They form nodules as they mature into adult worms over six to twelve months.
After maturing, adult male worms mate with female worms in the subcutaneous tissue to produce between 700 and 1,500 microfilaria per day.
The microfilaria migrate to the skin during the day, and the black flies only feed in the day, so the parasite is in a prime position for the female fly to ingest it. Black flies take blood meals to ingest these microfilaria to restart the cycle.

6. Symptoms are caused by the inflammatory response to dying microfilaria
The normal microfilariae lifespan is 1–2 years; however, their presence in the bloodstream causes little or no immune response until death or degradation of the microfilariae or adult worms.

7. Symptoms are caused by the inflammatory response to dying microfilaria
The normal microfilariae lifespan is 1–2 years; however, their presence in the bloodstream causes little or no immune response until death or degradation of the microfilariae or adult worms.

8. Symptoms are caused by the inflammatory response to dying microfilaria
The normal microfilariae lifespan is 1–2 years; however, their presence in the bloodstream causes little or no immune response until death or degradation of the microfilariae or adult worms.

9. Symptoms are caused by the inflammatory response to dying microfilaria
The normal microfilariae lifespan is 1–2 years; however, their presence in the bloodstream causes little or no immune response until death or degradation of the microfilariae or adult worms.

10. Only 5% of the cases experience ocular symptoms

11. At present, there aren’t any early diagnoses that are 100% reliable
Palpating
Skin snips
Mazzotti Test
DEC Patch Test
Slit Lamp Exam – ocular infection
Nodulectomy
ELISA
Alternative: Rapid-Format Antibody card tests
PCR – expensive, less invasive

12. Ivermectin has been the miracle drug since 1987
Provided free of charge by Merck & Co. since 1988
Ivermectin: selectively targets invertebrate nerve and muscle cells
Found in 1987 by Merck
Only kills microfilaria
Drug resistance
1-5% experience severe adverse side effects

13. New studies show many of the symptoms are caused by endosymbiont, Wolbachia
Mutualistic relationship with O. volvulus
Transmitted vertically like mitochondria
Linked to female fertility
Stimulate inflammatory response to microflaria
Release cytokines to recruit neutrophils
New evidence also indicates that doxycycline treatment for 6 weeks can make the female worms sterile for up to two years and thus unable to produce L1 microfilariae (Smith et al. 2006).
Tetracycline antibiotics for Wolbachia
Limits bacteria-induced immunopathology
Sterilization of female worms
Reduced Ivermectin side effects
Administrative difficulties

14. Public health initiatives were launched to stop the spread of Onchocerciasis
OCP was launched in 1975 and discontinued in 2002.

15. OEPA and APOC provide resources for local self-sustaining programs

17. Works Cited
Smith, D. S., D. Goverman, and J. Bass Onchocerciasis.
Andre, A. S., N. M. Blackwell, L. R. Hall, A. Hoerauf, N. W. Brattig, L. Volkmann, M. J. Taylor, L. Ford, A. G. Hise, J. H. Lass, E. Diaconu, amd E. Pearlman The role of endosymbiotic Wolbachia bacteria in the pathogenesis of river blindness. Science 295(5561):
Eezzuduemhoi, D., and D. Wilson Onchocerciasis.
Sinha,S., R. A. Schwartz, R. Kapila, and M. A. Forgione, Jr Onchocerciasis.
Strategic Direction for Research. Feb WHO: Tropical Disease Research. <
Onchocerciasis Disease Information WHO: Tropical Disease Research. <
"Distribution of Onchocerciasis " Map Mectizon Donation Program .
African Program for Onchocerciasis Control World Health Organization. <<
Onchocerciasis Elimination Program for the Americas World Health Organization. <<
Impact of long-term treatment of onchocerciasis with ivermectin in Kaduna State, Nigeria: first evidence in the operational area of the African Programme for Onchocerciasis Control, February Authored by: Afework H Tekle, Elizabeth Elhassan, Sunday Isiyaku, Uche V. Amazigo, Simon Bush, Mounkaila Noma, Simon Cousens, Adenike Abiose and Jan H. Remme
Onchocerciasis Treatment Figures WHO: Prevention of Blindness and Visual Impairment. <