e learning sensori

7/28/2019 E Learning Sensori

1/15


2/15

amastigote form. Once internalized in a phagosome the macrophage lysosome fuses with

the phagosome to from a phagolysosome containing the parasite.

How does the parasite survive this hostile environment?

Unlike other intracellular protozoans, which either inhibit lysosomal fusion with thephagosome (Toxoplasma gondii), or escape the parasitophorous vacuole (T. cruzi),

Leishmania sp depend on their defense mechanisms to survive.

Within the parasitophorous vacuole the parasite has to resist host defense mechanisms

such as products of the respiratory burst and the release of powerful lytic enzymes

SURVIVAL IN THE MACROPHAGE PHAGOLYSOSOME

Respiratory burst products:

H2O2, superoxide

hydroxyl radicals

Defense strategies:

a)Detoxification with antioxidant enzymes: Trypanothione peroxidase is a unique

antioxidant enzyme which can detoxifies hydrogen peroxide.

Superoxide dismutase - removes the reactive superoxide molecule.

b) Down-regulation - Lipophosphoglycans on the surface of the promastigote interferewith signal transduction pathways, specifically inhibits protein kinase C, which triggerthe respiratory burst in response to the parasite.

Hydrolytic enzymes:

a)Leishmania possess surface glycoproteins that are refractory to host lysosomal

enzymes and may also destroy them.

Once the protozoan has entered the vacuole it transforms into the amastigote form andundergoes binary fission. Eventually this leads to lysis of the macrophage releasing the

amastigotes which immediately infect a new population of macrophages.

When seen in a stained blood smear the amastigotes within the macrophages are referredto as LD bodies (Leishman-Donovan bodies). Named after Leishman who in 1900

discoveredL. donovani in smears taken from the spleen of a soldier who died of a fever

in India. Locally the fever was known as Dum-Dum or Kala-azar. Leishman's

observations were published in 1903, the same year that Charles Donovan found the sameparasite in the spleen.


3/15

Insect Vector

Phlebotomus sp. Only the female insects of this genus are blood feeders, the male flies

feed on plant nectar.

When the insect vector a phlebotomine sandfly takes a blood meal they become infectedby taking up the infected macrophage.

Amastigotes released from the macrophages in the midgut of the sandfly transform into

promastigote forms, 10-20 m in length. Repeated division by the flagellatedtrophozoites eventually results in blockage of the gut which results in the movement of

the promastigotes forward into the pharynx and buccal cavity. During this period there is

attachment of the promastigotes to the epithelial lining of the sandfly, usually via the

flagella. This attachment is likely to be through specific lectin like receptors on thesandfly epithelium attaching to a lipophosphoglycan secreted by the parasite. It is thought

that the type of nutrition may therefore effect the distribution of attached and free

promastigotes in the sandfly gut.

In addition to being used for attachment, the flagella has also been observed to penetrate

the epithelial cells allowing for leakage of cell sap which may be an important source of

nutrients for the promastigotes.

It has been generally supposed that the numbers of promastigotes in the sandfly becomesso large that they eventually block they proboscis. The fly would then have to regurgitate

in order to free the blockage allowing it to take a blood meal, and in doing so, infect thehost. However, recent studies offer an alternative infection process.

Promastigotes release chitinolytic enzymes which are inhibited by haemoglobin. Whenthe sandfly is between blood meals and feeding on plant juices these enzymes become

activated. It is proposed that the enzymes damage the fly's cardiac valve, which normally

prevents back flow of the blood meal. When the fly takes a blood meal the damaged


4/15

cardiac valve allows flow in both directions thus allowing some promastigotes to escape

back into the hosts skin.

It has also been suggested that secretion of the chitinases by the promastigotes trappedtogether with the blood meal, within the peritrophic membrane of the sandfly, allow it to

escape through the peritrophic membrane and continue their development. If release ofthis chitinase were inhibited the leishmania would be excreted with the residual blood

meal.

Leishmaniasis

There are a large number of species and subspecies ofLeishmania and they have beengrouped according to their development within the sandfly vector. The names given to

the groupings refer to the promastigote development in the digestive tract relative to the

position of the pylorus, the valve dividing the stomach from the ileum.

Hypopylaria - develop in the ileum and rectal areas of the sandfly Peripylaria - development occurs both in the anterior ileum and in the stomach

and pharynx.

Suprapylaria - development in the stomach and pharynx.

Those species infecting humans are principally found in the suprapylaria group with afew in the peripylaria group.

There are 5 principal species ofLeishmania causing three main forms of the disease in

humans.

Dermal cutaneous leishmaniasis -L. tropica, L. major Visceral leishmaniasis -L. donovani (L. chagasi)

Mucocutaneous leishmaniasis -L. braziliensis, L. mexicana

L. tropica and L. major

These two species have very similar life cycles and result in similar clinical symptoms ofdisease but have different geographical distributions.

Major complex- North Africa, Middle East, West India, Sudan

Tropica complex - Ethiopia, India, European Mediterranean region, Middle East, Kenya,North Africa

Dermal leishmaniasis, also known as tropical sore, is transmitted by the sandfly genusPhlebotomus. The infection site is usually localized to the site in which the sandfly bite

occurs. The amastigotes multiply in the reticuloendothelial system of the skin. The

incubation period spans from a period of day up to several months. A symptom of thedeveloping infection is the appearance on the surface of the skin of a small red papule,


5/15

the result of the development of a thin crust on the skin at the bite site which hides the

developing ulcer underneath. However, several sites of infection which are close together

may coalesce to form a large sore on the skin. If kept clean the sores will healspontaneously within 2 months to 1 year. However, these sores often are the sites of

secondary infections and can result in permanent disfiguration. Examples of secondary

infections are a spirochete infections which causes a condition known as Yaws and adisease condition known as myiasis where the ulcers become infected with fly maggots.

Once the infection has been cleared the host is immune to reinfection. In some regions,

natives inoculate their children in a site normally not visible to protect the child from

getting disfiguring scars latter in life.

The distribution pattern and location of these two species ofLeishmania is largely

dependent on the habitat of the vector species and the reservoir host. L. tropica is largely

confined to densely populated areas with transmission primarily occurring between the

sandfly and man with the dog being a possible reservoir host.

L. majorby comparison. is found in sparsely inhabited regions with the parasite mainly

cycling through gerbils and other small rodents. Man is the incidental host.

These are classic examples of a zoonosis.

Diagnosis

The principal method of diagnosis of the disease is by the identification of amastigotes inthe macrophages in the tissues in scrapings from infected areas.

Treatment

If possible natural healing of the infection is best as the only effective drug treatment is

with the use of antimonial drugs which have sever toxic side effects. Drugs such as

Pentostam and Glucantime are often used although recently, aminosidine has been foundto be more effective for cutaneous leishmaniasis and better tolerated. Vaccination would

be the method of choice and currently there are a number of vaccine trials being carried

out both in South America and the Middle East with mixed success. Current vaccinecandidates consist of whole killed promastigotes together administered together with

BCG (as an adjuvant) against cutaneous Leishmaniasis. New phase III clinical trials are

underway in India on a new oral treatment for kala-azar. The drug is called miltefosine

and would appear to be less toxic and highly effective. (see report from WHO TDRnews) Another strategy currently being investigated is to activate macrophages to kill the

leishmania parasite by the induction of nitric oxide production. This is being acheived by

using a drug previoulsy used to cure genital warts which are caused by humanpapillomaviruses. (see ref)

Other approaches are the control of the sandfly vector or in the case ofL. major, rodent

control. Both of these are difficult.
http://martin.parasitology.mcgill.ca/JIMSPAGE/BIOL/miltefosine.htmhttp://martin.parasitology.mcgill.ca/JIMSPAGE/BIOL/miltefosine.htmhttp://martin.parasitology.mcgill.ca/JIMSPAGE/biol/buates_s.htmhttp://martin.parasitology.mcgill.ca/JIMSPAGE/BIOL/miltefosine.htmhttp://martin.parasitology.mcgill.ca/JIMSPAGE/BIOL/miltefosine.htmhttp://martin.parasitology.mcgill.ca/JIMSPAGE/biol/buates_s.htm


6/15

L. donovanigroup

Known as visceral leishmaniasis, or Kala-azar, this disease has a new and old world form

It is located in South America, particularly Brazil, and in the old world is found in

Mediterranean Europe, North Africa, East Africa, India and China.

The amastigote forms, measuring 2-3 m, are found within the reticulo-endothelial cells

of the viscera, ie the spleen, lymph nodes, liver and intestine. Largely transmitted by

Phlebotomus, in South America transmission is by the genusLutzomyia (L. chagasi).

The incubation time of the disease can be as short as 10 days or take up to a year, but theNormal period is from 2 to 4 months. The symptoms are a slow developing low grade

fever which accompanies a general malaise. There is a progressive wasting of the patient

with anaemia. Other classic symptoms as the disease progresses is the protrusion of the

abdomen, brought about by the enlargement of the liver and spleen. If untreated death

will occur within 2-3 years of contracting the infection.

In more acute forms of the disease it can run its course within 6- 12 months. Clinical

signs include edema, particularly of the face, bleeding mucus membranes, breathingdifficulties and diarrhea.

A small proportion of patients can recover spontaneously and have a condition known as

post-Kala-azar dermal Leishmanoid in which the face is badly disfigured. This condition

is rare in the Mediterranean and Latin America but can occur in 5-10% of cases in India.

Diagnosis

Positive diagnosis can be obtained when L-D bodies are detected, but often this requires

the use of invasive methods requiring spleen biopsy.

Immunodiagnosis is also possible using ELISA or IFA methods. However there are a

number of problems, for instance, there is cross reactivity with T. cruzi antibodies. Inaddition it is not easy to differentiate between patent and past infections.

There is also a problem with symptomatic or clinical diagnosis because many of the

symptoms of the disease are similar to those produced by typhoid, malaria, syphilis,

tuberculosis and relapsing fever.

Treatment

The only treatment is with antimonial compounds. This should be supplemented with a

good protein and vitamin diet for best chance of recovery. If treatment is incomplete

relapses can occur. Therefore treatment regimes are usually long and arduous.

L. Braziliensis - Mucocutaneous leishmaniasis


7/15

Found in south and central America is transmitted be Lutzomyia sp. The life cycle is

similar to other species with the primary lesion in the skin at the site of the sandfly bite.

However, the infection secondarily involves the mucosal system of the nasal and buccalcavity. The resulting ulcerations can cause sever disfigurations of the lips, nose and vocal

chords. Death often results from secondary infections.

Diagnosis and treatment

Diagnosis is often difficult because L-D bodies not seen in routine preparations. It usuallyrequires the culture of infected tissue to obtain a positive diagnosis. Treatment is similar

to other forms but disease can lie dormant erupting many years later in mucocutaneous

sites.

L. Mexicana

This largely causes a cutaneous form of the disease but can also on rare occasions have

mucocutaneous involvement. Heals spontaneously within a few months except for somestrange reason if the infection is in the ear. In this case it can cause disfiguration and the

infection can last up to 40 years. It is found in North and Central America, Mexico andTexas, and is transmitted by Lutzomyia sp. The main reservoir hosts are small rodents.

Diagnosis and treatment are similar to that used for other species of leishmania.


8/15

Loa loa filariasis

Loa loa filariasis

Classification & external resources

Loa loa microfilaria. Source: Arcari et al.

Loa loa filariasis (also loiasis andAfrican eyeworm) is a skin and eye disease caused by

the nematodeworm, loa loa filaria. Humans contract this disease through the bite of ahorsefly, also known as mango fly. The deer fly is also a vector of Loa loa. The disease

can cause red itchy swellings below the skin called "Calabar swellings". The disease is

treated with the drug diethylcarbamazine (DEC).

Human loiasis geographical distribution is restricted to the rain forest and swamp forestareas ofWest Africa, being especially common in Cameroon and on the Ogowe River.

Humans are the only known natural reservoir. It is estimated that 2-13 million humans

are infected with the Loa loa larvae.
http://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Wormhttp://en.wikipedia.org/wiki/Wormhttp://en.wikipedia.org/wiki/Loa_loa_filariahttp://en.wikipedia.org/wiki/Horseflyhttp://en.wikipedia.org/wiki/Deer_flyhttp://en.wikipedia.org/wiki/Calabar_swellingshttp://en.wikipedia.org/wiki/Diethylcarbamazinehttp://en.wikipedia.org/wiki/Rain_foresthttp://en.wikipedia.org/wiki/Swamphttp://en.wikipedia.org/wiki/West_Africahttp://en.wikipedia.org/wiki/Cameroonhttp://en.wikipedia.org/wiki/Ogowe_Riverhttp://en.wikipedia.org/wiki/Natural_reservoirhttp://en.wikipedia.org/wiki/Natural_reservoirhttp://en.wikipedia.org/wiki/Image:Loa_loa_larva.jpghttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Wormhttp://en.wikipedia.org/wiki/Loa_loa_filariahttp://en.wikipedia.org/wiki/Horseflyhttp://en.wikipedia.org/wiki/Deer_flyhttp://en.wikipedia.org/wiki/Calabar_swellingshttp://en.wikipedia.org/wiki/Diethylcarbamazinehttp://en.wikipedia.org/wiki/Rain_foresthttp://en.wikipedia.org/wiki/Swamphttp://en.wikipedia.org/wiki/West_Africahttp://en.wikipedia.org/wiki/Cameroonhttp://en.wikipedia.org/wiki/Ogowe_Riverhttp://en.wikipedia.org/wiki/Natural_reservoir


9/15

Life cycle

Loa loa life cycle. Source: CDC

Thevectorfor Loa loa filariasis are flies from two hematophagous species of the genusChrysops, C. silacea and C. dimidiata. During a blood meal, an infected fly (genus

Chrysops, day-biting flies) introduces third-stage filarial larvae onto the skin of thehuman host, where they penetrate into the bite wound. The larvae develop into adults that

commonly reside in subcutaneous tissue. The female worms measure 40 to 70 mm in

length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35

to 0.43 mm in diameter. Adults produce microfilariae measuring 250 to 300 m by 6 to 8m, which are sheathed and have diurnal periodicity. Microfilariae have been recovered

from spinal fluids,urine, and sputum. During the day they are found in peripheral blood,

but during the noncirculation phase, they are found in the lungs. The fly ingestsmicrofilariae during a blood meal. After ingestion, the microfilariae lose their sheaths and

migrate from the fly's midgut through the hemocoel to the thoracic muscles of the

arthropod. There the microfilariae develop into first-stage larvae and subsequently intothird-stage infective larvae. The third-stage infective larvae migrate to the fly's proboscis

and can infect another human when the fly takes a blood meal.
http://en.wikipedia.org/wiki/Vector_(biology)http://en.wikipedia.org/wiki/Vector_(biology)http://en.wikipedia.org/wiki/Hematophagyhttp://en.wikipedia.org/wiki/Chrysopshttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Host_(biology)http://en.wikipedia.org/wiki/Subcutaneous_tissuehttp://en.wikipedia.org/wiki/Cerebrospinal_fluidhttp://en.wikipedia.org/wiki/Cerebrospinal_fluidhttp://en.wikipedia.org/wiki/Urinehttp://en.wikipedia.org/wiki/Sputumhttp://en.wikipedia.org/wiki/Lungshttp://en.wikipedia.org/wiki/Open_circulatory_systemhttp://en.wikipedia.org/wiki/Arthropodhttp://en.wikipedia.org/wiki/Proboscishttp://en.wikipedia.org/wiki/Image:L_loa_LifeCycle.gifhttp://en.wikipedia.org/wiki/Vector_(biology)http://en.wikipedia.org/wiki/Hematophagyhttp://en.wikipedia.org/wiki/Chrysopshttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Skinhttp://en.wikipedia.org/wiki/Host_(biology)http://en.wikipedia.org/wiki/Subcutaneous_tissuehttp://en.wikipedia.org/wiki/Cerebrospinal_fluidhttp://en.wikipedia.org/wiki/Urinehttp://en.wikipedia.org/wiki/Sputumhttp://en.wikipedia.org/wiki/Lungshttp://en.wikipedia.org/wiki/Open_circulatory_systemhttp://en.wikipedia.org/wiki/Arthropodhttp://en.wikipedia.org/wiki/Proboscis


10/15

Clinical features

Lymphaticfilariasissuch as loiasis most often consists ofasymptomatic microfilaremia.

Some patients develop lymphatic dysfunction causing lymphedema. Episodicangioedema (Calabar swellings) in the arms and legs, caused by immune reactions are

common. When chronic, they can form cyst-like enlargements of the connective tissuearound the sheaths ofmuscletendons, becoming verypainfulwhen moved. The swellingsmay last for 1-3 days, and may be accompanied by localized urticaria (skin eruptions)

andpruritus (itching). Subconjunctival migration of an adult worm to the eyes can also

occur frequently, in this is the reason Loa loa is also called the "African eye worm." The

passage over the eyeball can be sensed, but it usually takes less than 15 min. Genderincidence of eyeworms have approximately the same frequency, but it tends to increase

with age. Eosinophilia is often prominent in filarial infections. Dead worms may cause

chronic abscesses, which may lead to the formation of granulomatous reactions andfibrosis.

Laboratory diagnosis

Identification of microfilariae by microscopic examination is the most practical

diagnostic procedure. Examination of blood samples will allow identification ofmicrofilariae of Loa loa. It is important to time the blood collection with the known

periodicity of the microfilariae. The blood sample can be a thick smear, stained with

Giemsa orhematoxylin and eosin (see staining (biology)). For increased sensitivity,

concentration techniques can be used. These include centrifugation of the blood samplelyzed in 2% formalin (Knott's technique), orfiltration through aNucleopore membrane.

Antigen detection using an immunoassay for circulating filarial antigens constitutes a

useful diagnostic approach, because microfilaremia can be low and variable.Identification of adult worms is possible from tissue samples collected during

subcutaneous biopsiesor worm removal from the eye. Antibody detection is of limited

value. Substantial antigenic cross reactivity exists between filaria and other helminths,

and a positive serologic test does not distinguish between past and current infection.

Source

Loa Loa. Center for Disease Control and Prevention (CDC). US Government

public domain text and images.

External links

Loa Loa: a cutaneous filarial parasite of humans. The Filarial Genome Network

A to Z Guide to Parasitology. Volume 10. The Blood Nematodes. By: M. Arcari,

A. Baxendine and C. E. Bennett. University of Southampton, UK.

Filariasis. eMedicine.
http://en.wikipedia.org/wiki/Lymphatic_systemhttp://en.wikipedia.org/wiki/Filariasishttp://en.wikipedia.org/wiki/Filariasishttp://en.wikipedia.org/wiki/Asymptomatichttp://en.wikipedia.org/wiki/Asymptomatichttp://en.wikipedia.org/wiki/Lymphedemahttp://en.wikipedia.org/wiki/Angioedemahttp://en.wikipedia.org/wiki/Connective_tissuehttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Tendonhttp://en.wikipedia.org/wiki/Pain_and_nociceptionhttp://en.wikipedia.org/wiki/Pain_and_nociceptionhttp://en.wikipedia.org/wiki/Urticariahttp://en.wikipedia.org/wiki/Urticariahttp://en.wikipedia.org/wiki/Itchhttp://en.wikipedia.org/wiki/Itchhttp://en.wikipedia.org/wiki/Eosinophiliahttp://en.wikipedia.org/wiki/Eosinophiliahttp://en.wikipedia.org/wiki/Eosinophiliahttp://en.wikipedia.org/wiki/Abscesshttp://en.wikipedia.org/wiki/Granulomatosishttp://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/wiki/Microscopehttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Giemsahttp://en.wikipedia.org/wiki/Hematoxylinhttp://en.wikipedia.org/wiki/Hematoxylinhttp://en.wikipedia.org/wiki/Eosinhttp://en.wikipedia.org/wiki/Staining_(biology)http://en.wikipedia.org/wiki/Sensitivityhttp://en.wikipedia.org/wiki/Sensitivityhttp://en.wikipedia.org/wiki/Centrifugationhttp://en.wikipedia.org/wiki/Formalinhttp://en.wikipedia.org/w/index.php?title=Knott%27s_technique&action=edithttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/w/index.php?title=Nucleopore&action=edithttp://en.wikipedia.org/wiki/Antigenhttp://en.wikipedia.org/wiki/Immunoassayhttp://en.wikipedia.org/wiki/Biopsyhttp://en.wikipedia.org/wiki/Biopsyhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/Antibodyhttp://en.wikipedia.org/wiki/Helminthhttp://www.dpd.cdc.gov/dpdx/HTML/Filariasis.asp?body=Frames/A-F/Filariasis/body_Filariasis_l_loa.htmhttp://www.dpd.cdc.gov/dpdx/HTML/Filariasis.asp?body=Frames/A-F/Filariasis/body_Filariasis_l_loa.htmhttp://maven.smith.edu/~sawlab/fgn/pnb/loaloa.htmlhttp://www.soton.ac.uk/~ceb/Diagnosis/Vol10.htmhttp://www.soton.ac.uk/~ceb/Diagnosis/Vol10.htmhttp://www.soton.ac.uk/~ceb/Diagnosis/Vol10.htmhttp://www.emedicine.com/med/topic794.htmhttp://en.wikipedia.org/wiki/Lymphatic_systemhttp://en.wikipedia.org/wiki/Filariasishttp://en.wikipedia.org/wiki/Asymptomatichttp://en.wikipedia.org/wiki/Lymphedemahttp://en.wikipedia.org/wiki/Angioedemahttp://en.wikipedia.org/wiki/Connective_tissuehttp://en.wikipedia.org/wiki/Musclehttp://en.wikipedia.org/wiki/Tendonhttp://en.wikipedia.org/wiki/Pain_and_nociceptionhttp://en.wikipedia.org/wiki/Urticariahttp://en.wikipedia.org/wiki/Itchhttp://en.wikipedia.org/wiki/Eosinophiliahttp://en.wikipedia.org/wiki/Abscesshttp://en.wikipedia.org/wiki/Granulomatosishttp://en.wikipedia.org/wiki/Fibrosishttp://en.wikipedia.org/wiki/Microscopehttp://en.wikipedia.org/wiki/Diagnosishttp://en.wikipedia.org/wiki/Giemsahttp://en.wikipedia.org/wiki/Hematoxylinhttp://en.wikipedia.org/wiki/Eosinhttp://en.wikipedia.org/wiki/Staining_(biology)http://en.wikipedia.org/wiki/Sensitivityhttp://en.wikipedia.org/wiki/Centrifugationhttp://en.wikipedia.org/wiki/Formalinhttp://en.wikipedia.org/w/index.php?title=Knott%27s_technique&action=edithttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/w/index.php?title=Nucleopore&action=edithttp://en.wikipedia.org/wiki/Antigenhttp://en.wikipedia.org/wiki/Immunoassayhttp://en.wikipedia.org/wiki/Biopsyhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/Antibodyhttp://en.wikipedia.org/wiki/Helminthhttp://www.dpd.cdc.gov/dpdx/HTML/Filariasis.asp?body=Frames/A-F/Filariasis/body_Filariasis_l_loa.htmhttp://maven.smith.edu/~sawlab/fgn/pnb/loaloa.htmlhttp://www.soton.ac.uk/~ceb/Diagnosis/Vol10.htmhttp://www.emedicine.com/med/topic794.htm


11/15

Onchocerciasis

Onchocerca volvulus

O. vovulus, the causative agent of river

blindness.

Scientific classification

Kingdom: Animalia

Phylum: Nematoda

Class: Secernentea

Order: Spirurida

Family: Filariidae

Genus: Onchocerca

Species: O. volvulus

Binomial name

Onchocerca volvulusBickel 1982

Onchocerciasis (pronounced [n.k.s ka .ss]) or river blindness is the world's

second leading infectious cause ofblindness. It is caused by Onchocerca volvulus, a

Parasitic wormthat can live for up to fourteen years in the human body.
http://en.wikipedia.org/wiki/Scientific_classificationhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Nematodahttp://en.wikipedia.org/wiki/Secernenteahttp://en.wikipedia.org/w/index.php?title=Spirurida&action=edithttp://en.wikipedia.org/w/index.php?title=Filariidae&action=edithttp://en.wikipedia.org/wiki/Binomial_nomenclaturehttp://en.wikipedia.org/wiki/Infectioushttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Parasitic_wormhttp://en.wikipedia.org/wiki/Parasitic_wormhttp://en.wikipedia.org/wiki/Image:Onchocerca_volvulus_01.jpghttp://en.wikipedia.org/wiki/Scientific_classificationhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Nematodahttp://en.wikipedia.org/wiki/Secernenteahttp://en.wikipedia.org/w/index.php?title=Spirurida&action=edithttp://en.wikipedia.org/w/index.php?title=Filariidae&action=edithttp://en.wikipedia.org/wiki/Binomial_nomenclaturehttp://en.wikipedia.org/wiki/Infectioushttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Parasitic_worm


12/15

Life cycle

The life cycle ofO. volvulus (Illustration: Giovanni Maki)

The life cycle ofO. volvulus begins when a parasitised female Black fly of the genus

Simulium takes ablood meal. Saliva containing stage three O. volvuluslarvae passes intothe blood of the host. From here the larvae migrate to the subcutaneous tissue where they

form nodules and then mature into adult worms over a period of six to twelve months.

After maturation, the smaller adult males migrate from nodules to subcutaneous tissuewhere they mate with the larger adult females, producing between 1000 and 3000 eggs

per day. The normal adult worm lifespan is up to 15 years. The eggs mature internally to

form stage one microfilariae, which are released from the female's body one at a time andremain in the subcutaneous tissue.

These stage one microfilariae are taken up by black flies upon a blood meal, in which

they mature over the course of one to three weeks to stage three larvae, thereby

completing the life cycle. Humans are the only definitive host for O. Volvulus. Thenormal microfilariae lifespan is 1-2 years.
http://en.wikipedia.org/wiki/Black_flyhttp://en.wikipedia.org/w/index.php?title=Simulium&action=edithttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Salivahttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Subcutaneoushttp://en.wikipedia.org/wiki/Monthhttp://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/w/index.php?title=Microfilariae&action=edithttp://en.wikipedia.org/wiki/Image:Life_Cycle_of_Onchocerca_volvulus_PLoS_Medicine.jpghttp://en.wikipedia.org/wiki/Image:Life_Cycle_of_Onchocerca_volvulus_PLoS_Medicine.jpghttp://en.wikipedia.org/wiki/Black_flyhttp://en.wikipedia.org/w/index.php?title=Simulium&action=edithttp://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Salivahttp://en.wikipedia.org/wiki/Larvahttp://en.wikipedia.org/wiki/Subcutaneoushttp://en.wikipedia.org/wiki/Monthhttp://en.wikipedia.org/wiki/Egg_(biology)http://en.wikipedia.org/w/index.php?title=Microfilariae&action=edit


13/15

Causes of morbidity

Adult worms remain in subcutaneous nodules, limiting access to the host's immune

system. Microfilariae, in contrast, are able to induce intense inflammatory responses,especially upon their death. Dying microfilariae have been recently discovered to release

Wolbachia-derived antigens, triggering innate immune responses and producing theinflammation and its associated morbidity. Wolbachia species have been found to beendosymbionts of O. Volvulus adults and microfilariae and are thought to be the driving

force behind most of O. Volvulus morbidity. Severity of illness is directly proportional to

the number of microfilariae and the power of the resultant inflammatory response.

Skin involvement typically consists of intense itching, swelling, and inflammation. Agrading system has developed to categorize the degree of skin involvement: Acute

papular dermatitis - scattered pruritic papules; Chronic papular dermatitis - larger

papules, resulting in hyperpigmentation; Lichenified dermatitis - hyperpigmentedpapules

and plaques, with edema, lymphadenopathy, pruritus and common secondary bacterial

infections; Skin atrophy - loss of elasticity, skin resembles tissue paper, 'lizard skin'appearance; Depigmentation - 'leopard skin' appearance, usually on anterior lower leg.

Ocular involvement provides the common name associated with onchocerciasis, riverblindness. The surface of the cornea is another area to which the microfilariae migrate,

where they are also attacked by the immune system. In the area that is damaged, punctate

keratitis occurs, which clears up as the inflammation subsides. However, if the infection

is chronic, sclerosing keratitis can occur, making the affected area become opaque. Overtime the entire cornea may become opaque, thus leading to blindness.

Treatment and control

The treatment for onchocerciasis is ivermectin (Mectizan); infected people can be treated

once every twelve months. The drug paralyses the microfilariae and prevents them fromcausing itching. In addition, while the drug does not kill the adult worm, it does prevent

them from producing additional offspring. The drug therefore prevents both morbidity

and transmission.

Since 1988, ivermectin has been provided free of charge by Merck & Co. through theMectizan Donation Program (MDP). The MDP works together with ministries of health

and non-governmental development organisations such as the World Health Organization

to provide free Mectizan to those who need it in endemic areas.

There are various control programs that aim to stop onchocerciasis from being a publichealth problem. The first was the Onchocerciasis Control Programme (OCP), which was

launched in 1974 and at its peak covered 30 million people in eleven countries. Through

the use oflarvicide spraying of fast flowing rivers to control black fly populations and,from 1988 onwards, the use of ivermectin to treat infected people, the OCP eliminated

onchocerciasis as a public health problem. The OCP, a joint effort of the World Health

Organisation, the World Bank, the United Nations Development Programme and the UN
http://en.wikipedia.org/wiki/Wolbachiahttp://en.wikipedia.org/wiki/Wolbachiahttp://en.wikipedia.org/wiki/Endosymbiontshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/w/index.php?title=Plaque_(dermatology)&action=edithttp://en.wikipedia.org/wiki/Edemahttp://en.wikipedia.org/wiki/Edemahttp://en.wikipedia.org/wiki/Lymphadenopathyhttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Keratitishttp://en.wikipedia.org/wiki/Opaquehttp://en.wikipedia.org/wiki/Ivermectinhttp://en.wikipedia.org/wiki/1988http://en.wikipedia.org/wiki/1988http://en.wikipedia.org/wiki/Merck_&_Co.http://en.wikipedia.org/w/index.php?title=Mectizan_Donation_Program&action=edithttp://en.wikipedia.org/wiki/World_Health_Organizationhttp://en.wikipedia.org/wiki/Endemic_(epidemiology)http://en.wikipedia.org/w/index.php?title=Onchocerciasis_Control_Programme&action=edithttp://en.wikipedia.org/wiki/1974http://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/1988http://en.wikipedia.org/wiki/World_Bankhttp://en.wikipedia.org/wiki/World_Bankhttp://en.wikipedia.org/wiki/United_Nations_Development_Programmehttp://en.wikipedia.org/wiki/Wolbachiahttp://en.wikipedia.org/wiki/Wolbachiahttp://en.wikipedia.org/wiki/Endosymbiontshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/wiki/Dermatitishttp://en.wikipedia.org/wiki/Papuleshttp://en.wikipedia.org/w/index.php?title=Plaque_(dermatology)&action=edithttp://en.wikipedia.org/wiki/Edemahttp://en.wikipedia.org/wiki/Lymphadenopathyhttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Keratitishttp://en.wikipedia.org/wiki/Opaquehttp://en.wikipedia.org/wiki/Ivermectinhttp://en.wikipedia.org/wiki/1988http://en.wikipedia.org/wiki/Merck_&_Co.http://en.wikipedia.org/w/index.php?title=Mectizan_Donation_Program&action=edithttp://en.wikipedia.org/wiki/World_Health_Organizationhttp://en.wikipedia.org/wiki/Endemic_(epidemiology)http://en.wikipedia.org/w/index.php?title=Onchocerciasis_Control_Programme&action=edithttp://en.wikipedia.org/wiki/1974http://en.wikipedia.org/wiki/Larvicidehttp://en.wikipedia.org/wiki/1988http://en.wikipedia.org/wiki/World_Bankhttp://en.wikipedia.org/wiki/United_Nations_Development_Programme


14/15

Food and Agriculture Organization, was considered to be a success and came to an end in

2002. Continued monitoring ensures that onchocerciasis cannot reinvade the area of the

OCP.

In 1992 the Onchocerciasis Elimination Programme for the Americas(OEPA) was

launched. The OEPA also relies on ivermectin.

In 1995 the African Programme for Onchocerciasis Control (APOC) began covering

another nineteen countries and mainly relying upon the use of ivermectin. Its goal is toset up a community-directed supply of ivermectin for those who are infected. In these

ways, transmission has declined.

External links

Mectizan Donation Program

Merck & Co., Inc

River Blindness Documentary "37 Million and Counting" by Aaron Edell

http://www.sightsavers.org/Who%20We%20Are/Interactive/Videos/World4572.html

http://www.cbm.org/en/general/CBM_EV_EN_general_article_17601.html

Pathology of the eye(primarily H00-H59)

Eyelid, lacrimal system

and orbit

Stye - Chalazion - Blepharitis - Entropion - Ectropion -

Lagophthalmos - Blepharochalasis - Ptosis - Xanthelasma -Trichiasis - Dacryoadenitis - Epiphora - Exophthalmos -

Enophthalmos

Conjunctiva Conjunctivitis - Pterygium - Subconjunctival hemorrhage

Sclera and cornea

Scleritis - Keratitis - Corneal ulcer- Snow blindness -Thygeson's superficial punctate keratopathy -Fuchs' dystrophy -

Keratoconus - Keratoconjunctivitis sicca - Arc eye -

Keratoconjunctivitis - Corneal neovascularization- Kayser-Fleischer ring - Arcus senilis

Iris and ciliary bodyIritis - Uveitis - Iridocyclitis - Hyphema - Persistent pupillary

membrane

Lens Cataract - Aphakia

Choroid and retina

Retinal detachment - Retinoschisis - Hypertensive retinopathy -

Diabetic retinopathy - Retinopathy - Retinopathy of prematurity- Macular degeneration - Retinitis pigmentosa - Macular edema

Ocular muscles,

binocular movement,

accommodationand

refraction

Strabismus - Ophthalmoparesis - Progressive external

ophthalmoplegia - Esotropia - Exotropia - Refractive error-

Hyperopia - Myopia - Astigmatism - Anisometropia -Presbyopia - Fourth nerve palsy - Sixth nerve palsy - Kearns-

Sayre syndrome - Esophoria - Exophoria - Duane syndrome -

Convergence insufficiency - Internuclear ophthalmoplegia -
http://en.wikipedia.org/wiki/Food_and_Agriculture_Organizationhttp://en.wikipedia.org/wiki/Food_and_Agriculture_Organizationhttp://en.wikipedia.org/wiki/2002http://en.wikipedia.org/wiki/1992http://en.wikipedia.org/w/index.php?title=Onchocerciasis_Elimination_Programme_for_the_Americas&action=edithttp://en.wikipedia.org/w/index.php?title=Onchocerciasis_Elimination_Programme_for_the_Americas&action=edithttp://en.wikipedia.org/wiki/1995http://en.wikipedia.org/wiki/1995http://en.wikipedia.org/w/index.php?title=African_Programme_for_Onchocerciasis_Control&action=edithttp://en.wikipedia.org/w/index.php?title=African_Programme_for_Onchocerciasis_Control&action=edithttp://www.mectizan.org/http://www.mectizan.com/http://www.37millionandcounting.com/http://www.sightsavers.org/Who%20We%20Are/Interactive/Videos/World4572.htmlhttp://www.sightsavers.org/Who%20We%20Are/Interactive/Videos/World4572.htmlhttp://www.cbm.org/en/general/CBM_EV_EN_general_article_17601.htmlhttp://en.wikipedia.org/wiki/Pathologyhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/ICD-10_Chapter_VII:_Diseases_of_the_eye,_adnexa;_Chapter_VIII:_ear,_and_mastoid_process#H00-H59_-_Diseases_of_the_eye_and_adnexahttp://en.wikipedia.org/wiki/Eyelidhttp://en.wikipedia.org/wiki/Lacrimal_systemhttp://en.wikipedia.org/wiki/Orbit_(anatomy)http://en.wikipedia.org/wiki/Styehttp://en.wikipedia.org/wiki/Chalazionhttp://en.wikipedia.org/wiki/Blepharitishttp://en.wikipedia.org/wiki/Entropionhttp://en.wikipedia.org/wiki/Ectropionhttp://en.wikipedia.org/wiki/Lagophthalmoshttp://en.wikipedia.org/wiki/Blepharochalasishttp://en.wikipedia.org/wiki/Ptosis_(eyelid)http://en.wikipedia.org/wiki/Xanthelasmahttp://en.wikipedia.org/wiki/Trichiasishttp://en.wikipedia.org/wiki/Dacryoadenitishttp://en.wikipedia.org/wiki/Epiphora_(medical)http://en.wikipedia.org/wiki/Exophthalmoshttp://en.wikipedia.org/wiki/Enophthalmoshttp://en.wikipedia.org/wiki/Conjunctivahttp://en.wikipedia.org/wiki/Conjunctivitishttp://en.wikipedia.org/wiki/Pterygiumhttp://en.wikipedia.org/wiki/Subconjunctival_hemorrhagehttp://en.wikipedia.org/wiki/Sclerahttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Scleritishttp://en.wikipedia.org/wiki/Keratitishttp://en.wikipedia.org/wiki/Corneal_ulcerhttp://en.wikipedia.org/wiki/Snow_blindnesshttp://en.wikipedia.org/wiki/Thygeson's_superficial_punctate_keratopathyhttp://en.wikipedia.org/wiki/Fuchs'_dystrophyhttp://en.wikipedia.org/wiki/Fuchs'_dystrophyhttp://en.wikipedia.org/wiki/Keratoconushttp://en.wikipedia.org/wiki/Keratoconjunctivitis_siccahttp://en.wikipedia.org/wiki/Arc_eyehttp://en.wikipedia.org/wiki/Keratoconjunctivitishttp://en.wikipedia.org/wiki/Corneal_neovascularizationhttp://en.wikipedia.org/wiki/Corneal_neovascularizationhttp://en.wikipedia.org/wiki/Kayser-Fleischer_ringhttp://en.wikipedia.org/wiki/Kayser-Fleischer_ringhttp://en.wikipedia.org/wiki/Arcus_senilishttp://en.wikipedia.org/wiki/Iris_(anatomy)http://en.wikipedia.org/wiki/Ciliary_bodyhttp://en.wikipedia.org/wiki/Iritishttp://en.wikipedia.org/wiki/Uveitishttp://en.wikipedia.org/wiki/Iridocyclitishttp://en.wikipedia.org/wiki/Hyphemahttp://en.wikipedia.org/wiki/Persistent_pupillary_membranehttp://en.wikipedia.org/wiki/Persistent_pupillary_membranehttp://en.wikipedia.org/wiki/Lens_(anatomy)http://en.wikipedia.org/wiki/Cataracthttp://en.wikipedia.org/wiki/Aphakiahttp://en.wikipedia.org/wiki/Choroidhttp://en.wikipedia.org/wiki/Retinahttp://en.wikipedia.org/wiki/Retinal_detachmenthttp://en.wikipedia.org/wiki/Retinoschisishttp://en.wikipedia.org/wiki/Hypertensive_retinopathyhttp://en.wikipedia.org/wiki/Diabetic_retinopathyhttp://en.wikipedia.org/wiki/Retinopathyhttp://en.wikipedia.org/wiki/Retinopathy_of_prematurityhttp://en.wikipedia.org/wiki/Macular_degenerationhttp://en.wikipedia.org/wiki/Retinitis_pigmentosahttp://en.wikipedia.org/wiki/Macular_edemahttp://en.wikipedia.org/wiki/Ocular_muscleshttp://en.wikipedia.org/wiki/Binocularhttp://en.wikipedia.org/wiki/Accommodation_(eye)http://en.wikipedia.org/wiki/Accommodation_(eye)http://en.wikipedia.org/wiki/Refractionhttp://en.wikipedia.org/wiki/Strabismushttp://en.wikipedia.org/wiki/Ophthalmoparesishttp://en.wikipedia.org/wiki/Progressive_external_ophthalmoplegiahttp://en.wikipedia.org/wiki/Progressive_external_ophthalmoplegiahttp://en.wikipedia.org/wiki/Esotropiahttp://en.wikipedia.org/wiki/Exotropiahttp://en.wikipedia.org/wiki/Refractive_errorhttp://en.wikipedia.org/wiki/Hyperopiahttp://en.wikipedia.org/wiki/Myopiahttp://en.wikipedia.org/wiki/Astigmatism_(eye)http://en.wikipedia.org/wiki/Anisometropiahttp://en.wikipedia.org/wiki/Presbyopiahttp://en.wikipedia.org/wiki/Fourth_nerve_palsyhttp://en.wikipedia.org/wiki/Sixth_nerve_palsyhttp://en.wikipedia.org/wiki/Kearns-Sayre_syndromehttp://en.wikipedia.org/wiki/Kearns-Sayre_syndromehttp://en.wikipedia.org/wiki/Esophoriahttp://en.wikipedia.org/wiki/Exophoriahttp://en.wikipedia.org/wiki/Duane_syndromehttp://en.wikipedia.org/wiki/Convergence_insufficiencyhttp://en.wikipedia.org/wiki/Internuclear_ophthalmoplegiahttp://en.wikipedia.org/wiki/Food_and_Agriculture_Organizationhttp://en.wikipedia.org/wiki/2002http://en.wikipedia.org/wiki/1992http://en.wikipedia.org/w/index.php?title=Onchocerciasis_Elimination_Programme_for_the_Americas&action=edithttp://en.wikipedia.org/wiki/1995http://en.wikipedia.org/w/index.php?title=African_Programme_for_Onchocerciasis_Control&action=edithttp://www.mectizan.org/http://www.mectizan.com/http://www.37millionandcounting.com/http://www.sightsavers.org/Who%20We%20Are/Interactive/Videos/World4572.htmlhttp://www.sightsavers.org/Who%20We%20Are/Interactive/Videos/World4572.htmlhttp://www.cbm.org/en/general/CBM_EV_EN_general_article_17601.htmlhttp://en.wikipedia.org/wiki/Pathologyhttp://en.wikipedia.org/wiki/Eyehttp://en.wikipedia.org/wiki/ICD-10_Chapter_VII:_Diseases_of_the_eye,_adnexa;_Chapter_VIII:_ear,_and_mastoid_process#H00-H59_-_Diseases_of_the_eye_and_adnexahttp://en.wikipedia.org/wiki/Eyelidhttp://en.wikipedia.org/wiki/Lacrimal_systemhttp://en.wikipedia.org/wiki/Orbit_(anatomy)http://en.wikipedia.org/wiki/Styehttp://en.wikipedia.org/wiki/Chalazionhttp://en.wikipedia.org/wiki/Blepharitishttp://en.wikipedia.org/wiki/Entropionhttp://en.wikipedia.org/wiki/Ectropionhttp://en.wikipedia.org/wiki/Lagophthalmoshttp://en.wikipedia.org/wiki/Blepharochalasishttp://en.wikipedia.org/wiki/Ptosis_(eyelid)http://en.wikipedia.org/wiki/Xanthelasmahttp://en.wikipedia.org/wiki/Trichiasishttp://en.wikipedia.org/wiki/Dacryoadenitishttp://en.wikipedia.org/wiki/Epiphora_(medical)http://en.wikipedia.org/wiki/Exophthalmoshttp://en.wikipedia.org/wiki/Enophthalmoshttp://en.wikipedia.org/wiki/Conjunctivahttp://en.wikipedia.org/wiki/Conjunctivitishttp://en.wikipedia.org/wiki/Pterygiumhttp://en.wikipedia.org/wiki/Subconjunctival_hemorrhagehttp://en.wikipedia.org/wiki/Sclerahttp://en.wikipedia.org/wiki/Corneahttp://en.wikipedia.org/wiki/Scleritishttp://en.wikipedia.org/wiki/Keratitishttp://en.wikipedia.org/wiki/Corneal_ulcerhttp://en.wikipedia.org/wiki/Snow_blindnesshttp://en.wikipedia.org/wiki/Thygeson's_superficial_punctate_keratopathyhttp://en.wikipedia.org/wiki/Fuchs'_dystrophyhttp://en.wikipedia.org/wiki/Keratoconushttp://en.wikipedia.org/wiki/Keratoconjunctivitis_siccahttp://en.wikipedia.org/wiki/Arc_eyehttp://en.wikipedia.org/wiki/Keratoconjunctivitishttp://en.wikipedia.org/wiki/Corneal_neovascularizationhttp://en.wikipedia.org/wiki/Kayser-Fleischer_ringhttp://en.wikipedia.org/wiki/Kayser-Fleischer_ringhttp://en.wikipedia.org/wiki/Arcus_senilishttp://en.wikipedia.org/wiki/Iris_(anatomy)http://en.wikipedia.org/wiki/Ciliary_bodyhttp://en.wikipedia.org/wiki/Iritishttp://en.wikipedia.org/wiki/Uveitishttp://en.wikipedia.org/wiki/Iridocyclitishttp://en.wikipedia.org/wiki/Hyphemahttp://en.wikipedia.org/wiki/Persistent_pupillary_membranehttp://en.wikipedia.org/wiki/Persistent_pupillary_membranehttp://en.wikipedia.org/wiki/Lens_(anatomy)http://en.wikipedia.org/wiki/Cataracthttp://en.wikipedia.org/wiki/Aphakiahttp://en.wikipedia.org/wiki/Choroidhttp://en.wikipedia.org/wiki/Retinahttp://en.wikipedia.org/wiki/Retinal_detachmenthttp://en.wikipedia.org/wiki/Retinoschisishttp://en.wikipedia.org/wiki/Hypertensive_retinopathyhttp://en.wikipedia.org/wiki/Diabetic_retinopathyhttp://en.wikipedia.org/wiki/Retinopathyhttp://en.wikipedia.org/wiki/Retinopathy_of_prematurityhttp://en.wikipedia.org/wiki/Macular_degenerationhttp://en.wikipedia.org/wiki/Retinitis_pigmentosahttp://en.wikipedia.org/wiki/Macular_edemahttp://en.wikipedia.org/wiki/Ocular_muscleshttp://en.wikipedia.org/wiki/Binocularhttp://en.wikipedia.org/wiki/Accommodation_(eye)http://en.wikipedia.org/wiki/Refractionhttp://en.wikipedia.org/wiki/Strabismushttp://en.wikipedia.org/wiki/Ophthalmoparesishttp://en.wikipedia.org/wiki/Progressive_external_ophthalmoplegiahttp://en.wikipedia.org/wiki/Progressive_external_ophthalmoplegiahttp://en.wikipedia.org/wiki/Esotropiahttp://en.wikipedia.org/wiki/Exotropiahttp://en.wikipedia.org/wiki/Refractive_errorhttp://en.wikipedia.org/wiki/Hyperopiahttp://en.wikipedia.org/wiki/Myopiahttp://en.wikipedia.org/wiki/Astigmatism_(eye)http://en.wikipedia.org/wiki/Anisometropiahttp://en.wikipedia.org/wiki/Presbyopiahttp://en.wikipedia.org/wiki/Fourth_nerve_palsyhttp://en.wikipedia.org/wiki/Sixth_nerve_palsyhttp://en.wikipedia.org/wiki/Kearns-Sayre_syndromehttp://en.wikipedia.org/wiki/Kearns-Sayre_syndromehttp://en.wikipedia.org/wiki/Esophoriahttp://en.wikipedia.org/wiki/Exophoriahttp://en.wikipedia.org/wiki/Duane_syndromehttp://en.wikipedia.org/wiki/Convergence_insufficiencyhttp://en.wikipedia.org/wiki/Internuclear_ophthalmoplegia


15/15

Aniseikonia

Visual disturbances

and blindness

Amblyopia - Leber's congenital amaurosis - Subjective

(Asthenopia, Hemeralopia, Photophobia, Scintillating scotoma)- Diplopia - Scotoma - Anopsia (Binasal hemianopsia,

Bitemporal hemianopsia, Homonymous hemianopsia,

Quadrantanopia) - Color blindness (Achromatopsia) -Nyctalopia - Blindness/Low vision

Commonly associated

infectious diseasesTrachoma Onchocerciasis

Other

Glaucoma - Floater- Leber's hereditary optic neuropathy - Redeye - Argyll Robertson pupil - Keratomycosis - Xerophthalmia -

Aniridia
http://en.wikipedia.org/wiki/Aniseikoniahttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Amblyopiahttp://en.wikipedia.org/wiki/Leber's_congenital_amaurosishttp://en.wikipedia.org/wiki/Asthenopiahttp://en.wikipedia.org/wiki/Hemeralopiahttp://en.wikipedia.org/wiki/Photophobiahttp://en.wikipedia.org/wiki/Scintillating_scotomahttp://en.wikipedia.org/wiki/Diplopiahttp://en.wikipedia.org/wiki/Scotomahttp://en.wikipedia.org/wiki/Anopsiahttp://en.wikipedia.org/wiki/Binasal_hemianopsiahttp://en.wikipedia.org/wiki/Bitemporal_hemianopsiahttp://en.wikipedia.org/wiki/Homonymous_hemianopsiahttp://en.wikipedia.org/wiki/Quadrantanopiahttp://en.wikipedia.org/wiki/Color_blindnesshttp://en.wikipedia.org/wiki/Achromatopsiahttp://en.wikipedia.org/wiki/Nyctalopiahttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Low_visionhttp://en.wikipedia.org/wiki/Infectioushttp://en.wikipedia.org/wiki/Trachomahttp://en.wikipedia.org/wiki/Glaucomahttp://en.wikipedia.org/wiki/Floaterhttp://en.wikipedia.org/wiki/Leber's_hereditary_optic_neuropathyhttp://en.wikipedia.org/wiki/Red_eye_(medicine)http://en.wikipedia.org/wiki/Red_eye_(medicine)http://en.wikipedia.org/wiki/Argyll_Robertson_pupilhttp://en.wikipedia.org/wiki/Fungal_keratitishttp://en.wikipedia.org/wiki/Xerophthalmiahttp://en.wikipedia.org/wiki/Aniridiahttp://en.wikipedia.org/wiki/Aniseikoniahttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Amblyopiahttp://en.wikipedia.org/wiki/Leber's_congenital_amaurosishttp://en.wikipedia.org/wiki/Asthenopiahttp://en.wikipedia.org/wiki/Hemeralopiahttp://en.wikipedia.org/wiki/Photophobiahttp://en.wikipedia.org/wiki/Scintillating_scotomahttp://en.wikipedia.org/wiki/Diplopiahttp://en.wikipedia.org/wiki/Scotomahttp://en.wikipedia.org/wiki/Anopsiahttp://en.wikipedia.org/wiki/Binasal_hemianopsiahttp://en.wikipedia.org/wiki/Bitemporal_hemianopsiahttp://en.wikipedia.org/wiki/Homonymous_hemianopsiahttp://en.wikipedia.org/wiki/Quadrantanopiahttp://en.wikipedia.org/wiki/Color_blindnesshttp://en.wikipedia.org/wiki/Achromatopsiahttp://en.wikipedia.org/wiki/Nyctalopiahttp://en.wikipedia.org/wiki/Blindnesshttp://en.wikipedia.org/wiki/Low_visionhttp://en.wikipedia.org/wiki/Infectioushttp://en.wikipedia.org/wiki/Trachomahttp://en.wikipedia.org/wiki/Glaucomahttp://en.wikipedia.org/wiki/Floaterhttp://en.wikipedia.org/wiki/Leber's_hereditary_optic_neuropathyhttp://en.wikipedia.org/wiki/Red_eye_(medicine)http://en.wikipedia.org/wiki/Red_eye_(medicine)http://en.wikipedia.org/wiki/Argyll_Robertson_pupilhttp://en.wikipedia.org/wiki/Fungal_keratitishttp://en.wikipedia.org/wiki/Xerophthalmiahttp://en.wikipedia.org/wiki/Aniridia

e learning sensori

Documents