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Printable Handouts
Navigable Slide Index
- Introduction
- Outline
- What is onchocerciasis?
- Onchocerciasis: The life cycle
- The simulium vector
- The parasite: nodules
- The parasite: microfilaria
- Onchocerciasis and the eye (1)
- Onchocerciasis and the eye (2)
- Punctate keratitis
- Microfilaria in the cornea
- Chronic uveitis
- Chronic anterior uveitis and secondary cataract (and glaucoma)
- Onchocerciasis and the eye (3)
- Retinal disease
- Effects of visual field loss
- Most common causes of blindness
- Onchocerciasis and the skin (1)
- Onchocerciasis and the skin (2)
- Onchocerciasis and the brain
- Onchocerciasis treatment/control mechanisms
- Destroying the adult filaria
- Use of a microfilaricide
- Eliminating the vector
- Treatment with Mectizan® (ivermectin MSD)
- Treatment
- Mass treatment with ivermectin
Topics Covered
- What is Onchocerciasis and its impact
- The Life cycle of the disease
- The vector
- The parasite
- The disease in the eye, skin, and brain
- Principles of treatment and breaking the transmission cycle including use of ivermectin
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Talk Citation
Hopkins, MBE, A. (2020, January 30). Onchocerciasis (River Blindness) 1: the parasite, vector, disease and treatment [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved October 12, 2024, from https://doi.org/10.69645/LBJW3821.Export Citation (RIS)
Publication History
Financial Disclosures
- Dr. Adrian Hopkins, MBE has not informed HSTalks of any commercial/financial relationship that it is appropriate to disclose.
Onchocerciasis (River Blindness) 1: the parasite, vector, disease and treatment
Published on January 30, 2020
34 min
HSTalks is pleased to grant unrestricted complimentary access to all lectures in the series Neglected Tropical Diseases. Persons not at a subscribing institution should sign up for a personal account.
Other Talks in the Series: Neglected Tropical Diseases
Transcript
Please wait while the transcript is being prepared...
0:00
Hello. My name is Adrian Hopkins.
We're going to look at onchocerciasis or river blindness.
My experience has been mostly in Africa where river blindness is a major disease.
But in the last few years,
I've been director of the Mectizan Donation Program which has been
the strategy we have used distributing mectizan to control the disease.
The first part of the talk is going to concentrate on the parasite,
the vector, the disease manifestations,
and the treatment; for the second part of the talk,
we'll concentrate on control and hopefully, the elimination of transmission.
0:37
This slide shows a picture of a lady who lives in South Sudan in
a community called Awadi.
In this community, there are around 5,000 people, but of that community,
800 are blind or severely visually impaired.
This disease is transmitted because people live near the river.
You can see from the photo just a small tributary of the River Nile,
which is where Awadi is situated.
We have to remember that small rivers like this are the source of
water for all of the daily living that people have to do,
washing, this is where children come and play,
sometimes that's the only source of water.
So, people can't get away from
this particular problem if they are just living geographically close to the river.
1:22
What is onchocerciasis?
Well, it's a parasitic disease which
is caused by a filaria,
which is like a long thin worm.
The filaria is called Onchocerca volvulus.
Volvulus implies what we will see shortly, with all the females that tend to stick together,
tied up in a knot,
which is where the word volvulus comes from,
and which is where the adults live in what we call nodules,
or sometimes you'll see them written as Onchus sarcoma.
The adult females produce many many larvae every single day,
thousands of larvae every day.
These are mobile and they move through the skin and some also get
into the eyes and some possibly get into some of the other tissues of the body,
around the brain and other parts of the body.
While the microfilariae or the larvae are alive,
they don't cause too many problems.
But after six months to a year,
if they haven't been swallowed by the vector,
which we'll come to in a minute,
they will start dying.
Every microfilaria that dies creates a little bit of inflammation around it as it dies;
it's not much of a problem if it's just one or two but if thousands are produced every day,
then thousands are going to be dying every day,
and this is what gives the major inflammatory changes that we see in the disease.
As I said, the filaria is transmitted by a small black fly,
it's one of the Simulium species.
The most common species is Simulium damnosum,
which some people can describe as the damn,
the black fly, which pretty much describes what it means when you get bitten by this fly.
The fly needs to have a blood meal to reproduce.
So, every time it lays a batch of eggs,
it has to have a blood meal before that.
The eggs are laid in fast-flowing water and they have
little strands that stick to the vegetation or sometimes to rocks.
They need well-oxygenated water.
Once they're stuck on vegetation or rocks,
the eggs develop into larvae and then into pupa as we'll see.
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