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Onchocerciasis “River Blindness”

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Presentation on theme: "Onchocerciasis “River Blindness”"— Presentation transcript:

1 Onchocerciasis “River Blindness”

2 Onchocerciasis “River Blindness” Second leading infectious cause of blindness in the world

3 Onchocerciasis “River Blindness” Second leading infectious cause of blindness in the world Also causes skin lesions and skin nodules and intense itching

4 More than 30 million people worldwide are infected with Onchocerciasis

5 Transmission is concentrated in central Africa and Latin America Over 90% of all cases occur in Africa

6 Infection caused by the parasitic worm Onchocerca volvulus Microfilariae of O. volvulus from a skin nodule of a patient from Zambia Adult worms

7 Infection spreads from person to person by the bite of an infected Simulium blackfly WHO/TDR/Stammers

8

9 1. Infected blackfly introduces third stage larvae onto the skin of the host, then they penetrate the skin Human Stages

10 1. Infected blackfly introduces third stage larvae onto the skin of the host, then they penetrate the skin 2. Larvae develop into adults in subcutaneous tissue Human Stages

11 3. Adults produce microfilariae Human Stages

12 3. Adults produce microfilariae 4. A blackfly ingests microfilariae during blood meal Human Stages

13 5. After ingestion, microfilariae migrate to the thoracic muscles of the blackfly Blackfly Stages

14 5. After ingestion, microfilariae migrate to the thoracic muscles of the blackfly 6. There they develop into stage 1 larvae, and then stage 3 larvae Blackfly Stages

15 5. After ingestion, microfilariae migrate to the thoracic muscles of the blackfly 6. There they develop into stage 1 larvae, and then stage 3 larvae 7. 3 rd stage larvae can infect another human when the blackfly takes a blood meal Blackfly Stages

16 But…how does this cause blindness and other symptoms?

17 As mentioned earlier, adult worms produce microfilariae in the human stages 3. Adults produce microfilariae– up to 1000 per day!

18 Microfilariae induce intense inflammatory responses, especially upon their death

19 Microfilariae induce intense inflammatory responses, especially upon their death Some microfilariae will migrate throughout the upper layers of the skin, causing large nodules to form under skin…

20 …and skin rashes and lesions, known as “leopard skin”

21 Others migrate to the surface of the cornea, causing sclerosing Keratitis to occur

22 Others migrate to the surface of the cornea, causing sclerosing Keratitis to occur The infected area becomes increasingly opaque with more microfilariae

23 Ivermectin is the drug of choice for Onchocerciasis Paralyzes and kills microfilariae of O. volvulus

24 Ivermectin is the drug of choice for Onchocerciasis Paralyzes and kills microfilariae of O. volvulus Doesn’t kill adult females, but prevents them from producing any offspring

25 Ivermectin is the drug of choice for Onchocerciasis Paralyzes and kills microfilariae of O. volvulus Doesn’t kill adult females, but prevents them from producing any offspring – Thus, prevents transmission

26 Studies in hyperendemic foci have shown the effectiveness of Ivermectin

27 Has anyone done anything about this?

28 Onchocerciasis Control Programme (OCP) was launched in 1974 Launched by WHO

29 Goals of OCP 1.Control blackfly populations 2.Use Ivermectin to treat infected people

30 Controlling blackfly populations involved interrupting transmission by eliminating the blackfly vector

31 Helicopters are used to spray insecticides on rivers and fast moving waters (Simulium breeding sites) Controlling blackfly populations involved interrupting transmission by eliminating the blackfly vector

32 OCP was a huge success and ended in 2002 African Programme for Onchocerciasis Control (1995) Onchocerciasis Elimination Programme for the Americas (1992 )

33 References Diawara L, Traoré MO, Badji A, Bissan Y, Doumbia K, et al. (2009) Feasibility of Onchocerciasis Elimination with Ivermectin Treatment in Endemic Foci in Africa: First Evidence from Studies in Mali and Senegal. PLoS Negl Trop Dis 3(7): e497. doi: /journal.pntd "DPDx - Filariasis." DPDx – Filariasis. Web. 05 Nov "Onchocerciasis (River Blindness)." Stanford.edu. Web. 05 Nov "Priority Eye Diseases." WHO. Web. 05 Nov


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