• Onchocerciasis also known as ‘’river blindness’’ and ‘’Robles disease.’’ • It is a parasitic disease caused by infection by Onchocerca volvulus, a nematode (roundworm). • It is the world's second-leading infectious cause of blindness. • The parasite is transmitted to humans through the bite of a black fly of the genus Simulium. • The larval nematodes spread throughout the body Figure 1 Onchocerciasis CAUSES The disease is caused by filaria of O Volvulus. Figure 2 O Volvulus. LIFE CYCLE OF O. VOLVULUS 1. A Simulium female black fly takes a blood meal on an infected human host, and ingests microfilaria 2. microfilaria enter the gut and thoracic flight muscles of the black fly 3. progressing into the first larval stage. 4. The larvae mature into the second larval stage 5. move to the proboscis and into the saliva in its third larval stage 6. Maturation takes about 7 days. 7. After maturing, adult male worms mate with female worms in the subcutaneous tissue to produce Simulium female black fly takes a blood meal on an infected human host, and ingests between 700 and 1,500 microfilaria per day. 8. the black flies only feed in the day Figure 3 LIFE CYCLE OF O. VOLVULUS SIGNS AND SYMPTOMS Skin involvement • Typically consists of intense itching, swelling, and inflammation. • Skin atrophy - loss of elasticity, the skin resembles tissue paper 'lizard skin' appearance. • Depigmentation • Nodules under the skin form around the adult worms. Ocular involvement • may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve • cornea: Punctate keratitis • can lead to visual impairment and permanent blindness Figure 4 'lizard skin' Onchocerciasis – the disease and its impact  Onchocercal skin disease also has an important socio-cultural impact. People with the disease often have low self esteem, experience social isolation, and worry that they will never marry. Children are distracted in school due to constant itching.  Blindness is caused when microfilariae migrate to the eye and die, causing an inflammatory response. Over time the affected area becomes opaque, leading to impaired vision and eventually blindness. TREATMENT • infected people can be treated with two doses of ivermectin, • six months apart, repeated every three years • Ivermectin treatment is particularly effective because it only needs to be taken once or twice a year PREVENTION Primary prevention: • Vector control- applications of environmentally safe insecticides to the black flies breeding areas during rainy seasons. • Mass treatment with Ivermectin. • Various control programs aim to stop Onchocerciasis from being a public health problem • larvicide spraying of fast-flowing rivers to control black fly populations • The disease can be controlled by actions at the primary level with the village health worker administering the drug according to t

1. Optometry and Orthoptics
Maryam Fida
Other name lifecycle
effects prevention Onchocerciasis

2. Onchocerciasis
 Onchocerciasis also known as ‘’river
blindness’’ and ‘’Robles disease.’’
 It is a parasitic disease caused by
infection by Onchocerca volvulus, a
nematode (roundworm).
 It is the world's second-leading
infectious cause of blindness.
 The parasite is transmitted to
humans through the bite of a black
fly of the genus Simulium.
 The larval nematodes spread
throughout the body
Figure 1 Onchocerciasis
CAUSES
The disease is caused by filaria of O
Volvulus.
Figure 2 O Volvulus.
LIFE CYCLEOF O. VOLVULUS
1. A Simulium female black fly takes a blood meal on an infected human host, and ingests
microfilaria
2. microfilaria enter the gut and thoracic flight muscles of the black fly
3. progressing into the first larval stage.
4. The larvae mature into the second larval stage
5. move to the proboscis and into the saliva in its third larval stage
6. Maturation takes about 7 days.
7. After maturing, adult male worms mate with female worms in the subcutaneous tissue
to produce Simulium female black fly takes a blood meal on an infected human host,
and ingests between 700 and 1,500 microfilaria per day.
8. the black flies only feed in the day

3. Figure 3 LIFE CYCLE OF O. VOLVULUS
SIGNS AND SYMPTOMS
Skin involvement
 Typically consists of intense itching, swelling, and inflammation.
 Skin atrophy - loss of elasticity, the skin resembles tissue paper 'lizard skin' appearance.
 Depigmentation
 Nodulesunderthe skinformaroundthe adultworms.
Ocular involvement
 may involve any part of the eye from conjunctiva and cornea to uvea and posterior
segment, including the retina and optic nerve
 cornea: Punctate keratitis
 can leadto visual impairmentandpermanentblindness
Figure 4 'lizard skin'

4. Onchocerciasis –the disease andits impact
 Onchocercal skin disease also has an important socio-cultural impact. People with the
disease often have low self esteem, experience social isolation, and worry that they will
never marry. Children are distracted in school due to constant itching.
 Blindness is caused when microfilariae migrate to the eye and die, causing an
inflammatory response. Over time the affected area becomes opaque, leading to
impaired vision and eventually blindness.
TREATMENT
 infected people can be treated with two doses of ivermectin,
 six months apart, repeated every three years
 Ivermectin treatment is particularly effective because it only needs to be taken once or
twice a year
PREVENTION
Primary prevention:
 Vector control- applications of environmentally safe insecticides to the black flies
breeding areas during rainy seasons.
 Mass treatment with Ivermectin.
 Various control programs aim to stop Onchocerciasis from being a public health
problem
 larvicide spraying of fast-flowing rivers to control black fly populations
 The disease can be controlled by actions at the primary level with the village health
worker administering the drug according to the weight and maintaining a record.
Secondary and tertiary level Prevention: action includes training, supervision and
management of complicated cases.