RIVER BLINDNESS
(An Overview)
CHINEDU UMEADI (Ph.D. Student)
Walden University
PUBH-8165-1
Instructor: Dr Stephen Arnold
Spring Quarter, 2011
-----------------------------------------------------------------Adult black fly feeding on skin. Retrieved from, http://www.canadatrip.co.uk
Adult man suffering with river blindness. Retrieved from, http://www.goldbamboo.com/pictures-t2344.html
Presentation Contents
Introduction
Black fly (Similium species)
Life cycle of Onchocerca volvulus
Eye lesion
Spread of river blindness
People at risk for river blindness
Epidemiology
Public health burden
Diagnosis
Prevention & Treatment
Questions and Discussions
Expected Learning Outcomes
Meaning of river blindness
Cause and pattern of spread of river blindness
Extent of the problem
Prevention and management of river blindness
Introduction
A parasitic disease
Caused by Onchocerca volvulus
Characterized by skin changes, subcutaneous nodules, ocular
lesions, lymphatic pathology and some systemic effects
Transmitted by blackflies of the Similium species
Almost exclusively a parasite that infects man
Picture of Onchocerca volvulus. Retrieved from, http://bio390parasitology.blogspot.com/2011/02/onchocerca-volvulus-another-price-of.html
World Health Organization. (2011). Prevention of blindness and visual impairment. Priority eye disease: Onchocerciasis (river blindness).
Retrieved July 19, 2011, from http://www.who.int/blindness/causes/priority/en/index3.htmt.
Black Fly (Similium species)
Different species of Similium
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Similium damnosum
Similium neavei
Similium ochraceum
Similium metallicum
Similium callidium
Similium species breed in fast-flowing streams and rivers
They only feed in the day and this corresponds to the time that the
microfilaria migrate to the skin
Adult black fly feeding on skin. Retrieved from, http://www.canadatrip.co.uk
Young girl playing near a fast flowing water. Retrieved from, http://img.ehowcdn.co.uk/article-page-main/ehow/images/a07/sa/tv/rid-bitingblack-flies-800x800.jpg&imgrefurl
Lucas, A., & Gills, H. (1990). A new short textbook of preventive medicine for the tropics. (3 rd ed.). Kent, UK: Edward Arnold.
Lifecycle of Onchocerca volvulus
Similium fly ingest microfilariae during feeds
Microfilariae undergoes development in the fly
Development in the fly takes about 15 days
Larval forms are transmitted to humans during
feeds
Lucas, A., & Gills, H. (1990). A new short textbook of preventive medicine for the tropics. (3rd ed.). Kent, UK:
Edward Arnold.
Lifecycle of Onchocerca volvulus Contd...
The larva migrates to the subcutaneous tissue of the new
host
They mature into adult worms over six to twelve months
Mature adult worms mate in the subcutaneous tissue
producing microfilaria
Microfilaria migrate to the skin where they are fed on by
the Similium flies
The cycle then starts again
Lucas, A., & Gills, H. (1990). A new short textbook of preventive medicine for the tropics. (3 rd ed.). Kent, UK: Edward Arnold.
Lifecycle of Onchocerca volvulus Contd...
Life Cycle of Onchocerca volvulus. Retrieved from, http://www.cdc.gov/parasites/onchocerciasis/biology.html
Eye lesions
Caused in humans by microfilariae which can be found in all internal
tissues of the eye except the lens
They cause the following types of lesions:
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Fluffy corneal opacities
Sclerosing keratitis
Anterior uveitis with or without secondary glaucoma
Choroidoido-retinitis
Optic neuritis and postneuritic optic atrophy
Endosybiont called Wolbachi pipientis are released when the worms
die
This triggers some immune response which can lead to blindness
Elderly man blinded by onchocerciasis. Retrieved from, http://apps.who.int/tdr/svc/diseases/onchocerciasis
Retina in Onchocerciasis. Retrieved from, http://www.sciencephoto.com/media/260256/enlarge
Lucas, A., & Gills, H. (1990). A new short textbook of preventive medicine for the tropics. (3rd
ed.). Kent, UK: Edward Arnold.
Spread of river blindness
Spreads from person to person by bite of
blackfly
Exposing the body increases the chance of
infection
The more the bites, the more the infection
Blindness occurs with longstanding and intense
infection
African fisherman. Retrieved from,
http://www.un.org/ecosocdev/geninfo/afrec/vol20no1/201-fishing-revolution.html
African men near a river. Retrieved from, http://www.superstock.co.uk/stock-photosimages/4022-20850
Holiday makers. Retrieved from, http://www.crete-connections.com/CreteAccommodation.htm
Centers for Disease Control and Prevention. (2011). Fact sheet for general public health:
River blindness (Onchocerciasis). Retrieved July 19, 2011, from
http://www.wellnessproposals.com/health-care/handouts/parasitic-zoonoticdiseases/onchocerciasis-factsheet.pdf
People at risk for river blindness
People living around fast flowing
streams
Adventure travellers
Missionaries
Peace Corp Volunteers
People exposed to blackfly bites for
long periods
Adventure traveller. Retrieved from, http://ericasavage.blogspot.com/2010_06_01_archive.html
People living near water fast flowing stream. Retrieved from
http://goafrica.about.com/od/africatraveltips/tp/bestwestafrica.htm
Volunteers teaching. Retrieved from, http://www.advance-africa.com/
Centers for Disease Control and Prevention. (2011). Fact sheet for general public health: River blindness
(Onchocerciasis). Retrieved July 19, 2011, from http://www.wellnessproposals.com/healthcare/handouts/parasitic-zoonotic-diseases/onchocerciasis-factsheet.pdf
Epidemiology
Some 37 million people are infected worldwide
Some 90 million people are at risk of infection based on their areas of
residence
About 270,000 people are blind as a result of the infection
About 500,000 people have visual impairment as a result of the infection
Nearly 99% of infected people live in Africa
Second leading infectious cause of blindness in the world
The remainder live in Yemen, and six countries in the Americas
Centers for Disease Control and Prevention. (2011). Fact sheet for general public health: River blindness (Onchocerciasis).
Retrieved July 19, 2011, from http://www.wellnessproposals.com/health-care/handouts/parasitic-zoonoticdiseases/onchocerciasis-factsheet.pdf
Public health burden of river blindness
Global burden of 987, 000 DALYS
Severe pruritis is responsible for 60% of the DALYS
About half of middle aged men in West Africa have been
blinded by the illness
Brings about economic loss
Annual economic losses were estimated in 1970s to be
US$ 30, 000,000
World Health Organization. (2011). Prevention of blindness and visual impairment. Retrieved from,
http://www.who.int/blindness/partnerships/onchocerciasis_disease_information/en/index.html
Diagnosis
Skin snip
Surgical removal and examination of
nodules
Slit-lamp examination of the anterior
part of the eye
Antibody tests
Demonstration of skin snip. Retrieved from
http://www.stanford.edu/class/humbio103/ParaSites2006/Onchocerciasis/Diagnosis.html
Laboratory scientist at work. Retrieved from, http://www.fmcowerri.com/departments-andunits/microbiology/
Centers for Disease Control and Prevention. (2011). Parasites – Onchocerciasis: Diagnosis.
Retrieved August 8, 2011, from http://www.cdc.gov/parasites/onchocerciasis/diagnosis.html
Prevention and treatment
No vaccines available
Personal protection measures against biting insects
Ivermectin is used to kill the larvae in the body (CDC, 2011)
Promising treatments such as doxycycline which will kill the adult
worms are being studied (CDC, 2011)
Mass distribution of Ivermectin to everyone living in areas where
Onchocerca volvulus is found has been shown to be effective (WHO,
2011)
World Health Organization. (2011). Onchocerciasis disease information: Prevention of Blindness and visual impairment.
Retrieved July 18, 2011
fromhttp://www.who.int/blindness/partnerships/onchocerciasis_disease_information/en/index.html
Centers for Disease Control and Prevention. (2011). Onchocerciasis: Prevention and Control. Retrieved July 19, 2011,
from http://www.cdc.gov/parasites/onchocerciasis/prevention.html
Treatment and Prevention Contd..
Covered up missionaries. Retrieved from, http://www.mafrome.org/ireland124.htm
Covered up peace volunteers. Retrieved from, http://ilint.illinois.edu/iir/online/illinois_in_the_world/
Ivermectin. Retrieved from, http://image.made-in-china.com/2f0j00fekTaSUcuozt/Ivermectin-Injection-1-50ml-100ml-Ivermectin-Drench-YN-002-.jpg
Patient attending her doctor. Retrieved from http://www.wellsphere.com/skin-health-article/will-the-last-medical-dermatologist-please-turn-off-the-lights-access-issues-for-dermatologypatients/724742
River blindness control programs
Onchocerciasis Control Program (OCP) – 1974
(Levine, 2007)
Onchocerciasis Elimination Program for the
Americas (OEPA) – 1992 (WHO, 2011)
African Program for Onchocerciasis Control
(APOC) – 1995 (Levine, 2007).
Levine, R. (2007). Controlling Onchocerciasis (River Blindness) in Sub-Saharan Africa. In Series Editor: Richard Riegelman. Case Studies in
Global Health: Millions saved, 49-56. Sudbury, Massachusetts: Jones and Bartlett.
World Health Organization. (2011). Prevention of blindness and visual impairment: Onchocerciasis elimination program for the Americas
(OEPA). Retrieved August 8, 2011, from http://www.who.int/blindness/partnerships/onchocerciasis_oepa/en/index.html
Key Learning goals
Understanding the cause and pattern of spread of
river blindness
Understanding the environmental components of
river blindness
Understanding the extent of the problem, and its
prevention and management
Understanding how prevention of spread of river
blindness can result in social change considering
the achievements of OCP, OEPA, and APOC
QUESTIONS
DISCUSSIONS
References
Centers for Disease Control and Prevention. (2011). Fact sheet for general public health: River blindness (Onchocerciasis).
Retrieved July 19, 2011, from http://www.wellnessproposals.com/health-care/handouts/parasitic-zoonoticdiseases/onchocerciasis-factsheet.pdf
Centers for Disease Control and Prevention. (2011). Onchocerciasis: Prevention and Control. Retrieved July 19, 2011,
from http://www.cdc.gov/parasites/onchocerciasis/prevention.html
Levine, R. (2007). Controlling Onchocerciasis (River Blindness) in Sub-Saharan Africa. In Series Editor: Richard Riegelman.
Case Studies in Global Health: Millions saved, 49-56. Sudbury, Massachusetts: Jones and Bartlett.
Lucas, A., & Gills, H. (1990). A new short textbook of preventive medicine for the tropics. (3rd ed.). Kent, UK: Edward
Arnold
World Health Organization. (2011). Onchocerciasis disease information: Prevention of Blindness and visual impairment.
Retrieved July 18, 2011
fromhttp://www.who.int/blindness/partnerships/onchocerciasis_disease_information/en/index.html
World Health Organization. (2011). Prevention of blindness and visual impairment. Priority eye disease: Onchocerciasis
(river blindness). Retrieved July 19, 2011, from http://www.who.int/blindness/causes/priority/en/index3.htmt
World Health Organization. (2011). Prevention of blindness and visual impairment: Onchocerciasis elimination program
for the Americas (OEPA). Retrieved August 8, 2011, from
http://www.who.int/blindness/partnerships/onchocerciasis_oepa/en/index.html
Further reading
Global network. Neglected tropical diseases. Onchocerciasis.
http://globalnetwork.org/about-ntds/factsheets/onchocerciasis
Helen Keller International. Onchocerciasis control. http://www.hki.org/preventingblindness/onchocerciasis-control/
TDR For research on disease of poverty. Onchocerciasis.
http://apps.who.int/tdr/svc/diseases/onchocerciasis
The Carter Center. Onchocerciasis elimination program of the Americas.
http://www.cartercenter.org/health/river_blindness/oepa.html
TropIKA.net. Tropical disease research to foster innovation and knowledge application.
Onchocerciasis. http://www.tropika.net/svc/home/onchocerciasis