RIVER BLINDNESS - ONCHOCERSIASIS -
TRANSPORTED BY BLACK FLY
- DISEASE ALSO IN ANIMALS -


With compliments
to Dr. Marta Botelho and
Dr. Pedro Faísca

NEW published
publication for medicine

A case of canine ocular onchocercosis in Portugal
Veterinary Ophthalmology (2010) 13, 2, 117–121:
included pictures

canine ocular onchocercosis in Portugal fulltext



BLACK FLY

NEW laboratorium photos Oct 08 by Dr. Pedro Faísca, dog Kinky
Lisbon Portugal



NEW pregnant female onchocerca volvulus

laboratorium photos Oct 08 by Dr. Pedro Faísca,
dog Kinky
Lisbon Portugal


O.volvulus:
females contain eggs and larvae in different stages of development.
Microfilariae measure between 200 x 6 and 300 x 8 µm
and survive for about 6 months in hosts tissues.
(Section of an adult containing microfilariae).


* . * . *


This blind eye has been taken out - the right eye still sees

MEDICATION used for Kinky 2008 with river blindness disease :

- Injection by veterinarian Ivermectine s.c.

NO metilprednisolon !!! NOT ORAL AND NOT IN THE EYE

- NOV 08: we start soon the heartworm treatment = 2 injections see heartworm and the premedication
- Nov 08: Flap of the eye, temporarily closed 10 days to heal itself better
sutured the 3rd membrane to the upper eyelid
and go on with the medicines for the eye

- IN THE EYE p/o veterinarian:

Nov 08: Flap of the eye, temporarily closed 10 days to heal itself better
and go on with the medicines for the eye

Not available yet in Portugal Nov08 Cicatrizante ocular con antibióticos & Visufenicol
So we use now in The algarve - Portugal
Visine drops
Vit A every 6 hrs quantity : a lot to fill the eye
Cloranfenicol every 8 hrs
one hour (or 2) between each, I give first Visine then Cloranfenicol then Vit A


Cicatrizante ocular con antibióticos 3x a day once
Visufenicol 3x a day once
Visine
every 2 hrs

- - - - -


- > Cicatrizante ocular con antibióticos
COMPOSICION: Cada 100 ml. contiene: L-Cistina 0.8 gr., L-Asparginina 0.22 gr., L-Glutamina 0.4 gr., Gentamicina S. 0.3 gr., Neomicina S. 0.5 gr., Lidocaína C. 0.005 gr., Vitamina A 90 u/c A.H. p 70000 u/g 0.64 gr., Vitamina D2 66 u/c Sol. 400000 u/g 0.082 gr. Excipientes Vaselinas oftálmicas purísimas de uso 
exclusivo, que a temperatura corporal se disuelve (no actúa como cuerpo extrano, formando una lente de protección sobre la capa acuosa de la córnea disponiendo un frente de ataque de sus componentes activos). c.s.p. 100 gr. 
INDICACIONES: Procesos infecciosos Oculares. Ulceras de Córnea. Queratitis. Heridas en General. Post-Operatorio
DOSIFICACION: 1 aplicación tres veces por día.

- > Visufenicol
COMPOSICION: Cada 100 ml. contiene: Cloranfenicol H.S. 1.304 gr., Nafazolina C. 0.065 gr., Lidocaína C. 0.0043 gr., Vitamina A Palmitato 0.0367 gr., Tween80 4.35 gr., Vaselina Sólida 41.30., Vaselina Líquida 52.94 gr.
INDICACIONES: Cunjuntivitis, Blefaritis, Queratitis, Epiescleritis, Iritis, Uveitis, Ulcera de Córnea, Tratamientos port-quirúrgicos.
DOSIFICACION: 1 aplicación 3 veces por día.

Visine drops, very often (about every 2 hrs)

- ORAL (=via mouth) p/o veterinarian:

- > NO metilprednisolon !!! NOT ORAL AND NOT IN THE EYE

(Kinky appeared resistent against Amoxicillina - Cefradur)
Ciprofloxacina 500mgr (2x a day 250mgr)
!!! Vibramicina 100 mgr (5 days 3x a day 200mgr then 2x a day 200mgr)
Chimar 2x a day 2 tablets

Ulsermin to protect the stomach
Painkiller!!!
Vitamin B complex is also advisable
Multi vitamins


Afterwards treatment needed for the Onchocerca parasite:
Either Injection Ivomec(includes Moxidectine) or heartgard tablet monthly


* . * . *

ARTICLE IN THE LANCET

* . * . *

Review several studies :
link
&
A. Hoerauf

Effects on ivermectin etc

Model-based analysis of trial data:
microfilaria and worm-productivity loss after diethylcarbamazine-albendazole or ivermectin-albendazole combination therapy against Wuchereria bancrofti.

* . * . *

!! plpnemweb.ucdavis.edu/NEMAPLEX/Taxadata/Ovolvulus.HTM !! :
Filarioidea Onchocercidae

Onchocerca volvulus has, for many years, been regarded as the causative agent of River Blindness.
Reports in 2002 indicate that the
bacterium Wolbachia, which is associated with the nematodes and which may be required for their growth and reproduction, has a major role in the pathology of the disease.
Wolbachia incites a severe inflammatory response, leading to blindness and serious skin disorders.

The immune response of the host is also involved in the disease. Mice lacking an immune cell receptor molecule called TLR4 showed fewer signs of eye inflammation when exposed to Wolbachia-laden worm extract (Hoerauf and Volkmann, 2002).

Management:
Surgical removal of nematode from eye; chemotherapy.
Pinpointing bacteria as the direct factor behind the virulence suggests new therapies for combating river blindness, especially since recent studies in infected humans have shown that the bacteria can be killed by the common antibiotic
doxycycline.


The battle against river blindness is taking place on two fronts at the moment:

* programs to control the spread of the black fly.
* distribution of an anti-worm medicine,
ivermectin.

Antibiotic treatment of Wolbachia may help reduce the severity of the symptoms of river blindness in already-infected individuals.

Targeting Wolbachia could prevent the spread of Onchocerca. Recent studies have shown that doxycycline treatments in infected humans kills Wolbachia and also sterilize the nematodes, breaking the life cycle. In contrast, ivermectin treatments only reduce numbers of microfilariae for a few months and repeated treatments are necessary.

* . * . *

commons.wikimedia.org/wiki/Image:Onchocerca_volvulus_LifeCycle.gif :


Geographic distribution of Onchocerciasis :

O.volvulus: geographic distribution.
onchocerciasis occurs especially in Tropical Africa,
between the 15° north and the 13° south (high endemicity in B.Faso and Ghana).
Foci are present in Southern Arabia, Yemen and in America
(Mexico, Guatemala, Colombia, Ecuador, Brazil, Venezuela).


www.cdfound.to.it/hTML/onc1.htm :



ONCHOCERCA VOLVULUS :



www.emedicine.com/med/topic1667.htm :

Causes

* Onchocerciasis is transmitted by the bite of black flies of the genus Simulium. Black flies breed in well-oxygenated water found in fast-moving streams and rivers. Females require a blood meal for ovulation, and they can transmit infective-stage larvae as well as receive microfilariae during the blood meal. The black fly tends to stay within 2 km of its breeding site.
* During the blood meal, the black fly can transmit infective-stage larvae to the host. Fly saliva acts as a chemoattractant for microfilariae in the surrounding subcutaneous tissues. Large quantities of microfilariae may be ingested during the blood meal. Microfilariae then migrate to the fly's flight muscles, where they emerge as infective-stage larvae after 6-18 days and travel to the proboscis.

Medical Care

* The current mainstay of treatment is ivermectin. Mass treatment campaigns are being run through the World Health Organization. Merck has made their drug (Mectizan) available without charge for use in the Onchocerciasis Control Programme (OCP). In 1997, more than 18 million people in endemic areas received treatment with ivermectin.
*
o Because ivermectin is a microfilaricide and does not kill adult worms, the treatment does not cure the disease. Rather, it significantly reduces microfilarial burden, which affects several facets of the disease. Ivermectin treatment decreases transmission and reduces the prevalence of onchodermatitis, sclerosing keratitis, and blindness.
o The optimal duration of treatment with ivermectin is not currently known. In hyperendemic areas, the drug should be administered every 6 or 12 months for the life span of the adult worm.

!!!
* Newer therapeutic strategies target bacteria of the Wolbachia species, known endosymbionts in O volvulus. Doxycycline 100 mg/d administered for 6-8 weeks has demonstrated efficacy in reducing microfilarial loads, sterilizing adult worms, and decreasing adult worm viability. However, the efficiency of using doxycycline in mass treatment campaigns has been questioned.

Surgical Care

Removal of all subcutaneous nodules can be curative; however, many nodules are difficult to find.

Background

Onchocerciasis is a chronic parasitic disease caused by the filarial nematode Onchocerca volvulus. Infection affects multiple organ systems, but the greatest morbidity is due to cutaneous and ophthalmologic complications. The disease is often called river blindness because infective microfilariae are acquired at the breeding site of the Simulium damnosum black fly vector.

Onchocerciasis occurs in 38 countries worldwide, including areas of Africa, South America, and the Middle East. More than 123 million people live in endemic areas, and an estimated 18 million people are currently infected. Of those infected, about 270,000 are blind, and an additional 500,000 have severe visual impairment.

In 1875, O'Neill first associated the microfilariae of O volvulus with an irritating papular dermatitis called craw-craw in Ghana. Eighteen years later, Leuckhart first described the adult worm of onchocerciasis in subcutaneous nodules. In 1917, Robles published findings on a new disease from Guatemala with associated subcutaneous nodules, anterior ocular lesions, dermatitis, and microfilariae. In Sierra Leone in 1923, Blacklock identified the black fly, Simulium damnosum, as the disease vector.
Pathophysiology

O volvulus has a 5-stage life cycle, and humans are the only definitive hosts. Simulium black flies are obligate intermediate hosts and release infective-stage larvae during a blood meal. In the human host, the larvae molt twice to become male and female adult worms. This process occurs in subcutaneous nodules known as onchocercomata, and a mature female can produce microfilariae after 6-12 months.

Female worm length ranges from 30-80 cm, and more than 1 worm may be coiled in a subcutaneous nodule. Male adult worms are usually 3-5 cm in length and migrate between various subcutaneous nodules to inseminate females. Over a life span of up to 14 years, the female worms produce 700-1900 microfilariae daily.

Microfilariae are usually 220-360 µm in length. When released from the female, microfilariae can migrate throughout the subcutaneous tissues and skin; they have a particular affinity for ocular tissues. When microfilariae are ingested in the blood meal of the black fly, they pass through 2 molts in a 2- to 3-week period to become infective-stage larvae.

Microfilariae live for 6-30 months; most die without completing their life cycle. Symptoms of onchocerciasis are caused by localized host inflammatory responses to the dead or dying microfilariae. In persons with heavy infection, as many as 100,000 microfilariae die each day. The predominant immune response is production of antibodies, but cellular responses, particularly those of eosinophils, are important.
Frequency
United States

Sporadic cases are observed in immigrants or travelers from endemic areas.
International

Onchocerciasis predominantly occurs in 30 countries of West and sub-Saharan Africa. In Africa, hyperendemic villages can have infection rates of 100%; 10% of the entire village may be blind, including up to 50% of those aged 40 years and older. Enlarging foci of infection are located in Central and South America, particularly in Guatemala, Ecuador, Mexico, Brazil, Venezuela, and Colombia. The Middle Eastern countries of Saudi Arabia and Yemen are also endemic for onchocerciasis.
Mortality/Morbidity

Onchocerciasis does not directly cause death, but social and economic consequences can be devastating.

* Onchodermatitis is the leading cause of morbidity in endemic areas. Disfigurement resulting from skin lesions and intense pruritus can cause devastating psychosocial consequences and isolation.
* Vision loss occurs in many areas of Africa and South America. Persons blinded by onchocerciasis have a life expectancy of 10 years after onset of blindness. Overall life expectancy of an infected individual in endemic areas is one-third that of an uninfected individual.
* In Africa, blindness is more commonly reported in the savanna and woodland areas, whereas depigmented skin disorders are more frequent in the forests.

Race

All persons in regions of endemicity, regardless of race, are at risk for infection.

Sex

Onchocerciasis is associated with no known sex predilection.

Age

* Greater morbidity with age is the result of cumulative exposure in endemic areas.
* Blindness tends to occur in adulthood after many years of infection.
* Transplacental infection can occur with microfilariae, but transmission of infective larvae from the black fly is required for the disease to progress.


CLINICAL
Section 3 of 11 Click here to go to the previous section in this topic Click here to go to the top of this page Click here to go to the next section in this topic

*
Authors and Editors
*
Introduction
*
Clinical
*
Differentials
*
Workup
*
Treatment
*
Medication
*
Follow-up
*
Acknowledgments
*
Multimedia
*
References


History

Onchocerciasis is a chronic infection with clinical manifestations that develop years after initial infection.

* The initial bite of the black fly tends to go unnoticed. A 1- to 2-year latent period is typical as the infective larvae migrate and develop into adult worms.
* Pruritus is the most common early symptom of infection. Itching and scratching ranges from mild to severe and from intermittent to unremitting. The term craw-craw is used in West Africa to describe chronic onchodermatitis and its associated scratch-induced excoriations, ulcerations, and secondary infection.
* Lymphadenopathy tends to occur in the inguinal and femoral regions.
* Subcutaneous nodules (onchocercomata) usually develop over bony prominences. African Simulium species tend to bite the ribs, hips, iliac crests and lower limbs, whereas South American Simulium species prefer the scalp and upper body.
* VisualVisual symptoms range from itching, redness, photophobia, and blurred vision in early disease to variable degrees of vision loss and frank blindness later on.
* Weight loss may also occur.

Physical

* Physical findings are diverse and range from early mild inflammatory lesions to chronic debilitating cutaneous and ophthalmic lesions.
* Onchodermatitis refers to the various cutaneous findings in infected individuals, and it has been classified into 6 diseases, as follows:
*
o Acute papular dermatitis involves numerous small pruritic papules that may progress to vesicles or pustules. Papules tend to develop on limbs, shoulders, face, and trunk.
o Chronic papular dermatitis is indicated by larger, pruritic, flat-topped papules distributed symmetrically over the buttocks, waist, and shoulders. Affected individuals may also demonstrate hyperpigmented papules and hyperkeratosis. Sowda is a localized form of chronic papular dermatitis that is usually confined to one extremity; characteristic findings also include hyperpigmented papules, regional lymphadenopathy, and edema.
* Lichenified dermatitis is an intensely pruritic dermatitis with excoriations and hyperpigmented and hyperkeratotic papules and plaques.
* Atrophy includes degeneration of elastic fibers and other structural elements of the skin due to chronic infection. The skin appears wrinkled and thin, and atrophic changes are most often noted over the buttocks and limbs.
* Depigmentation is a common finding in advanced onchocerciasis. The patchy lesions resemble vitiligo and are commonly found on the shins (also known as leopard skin).
* Lizard skin refers to the chronic ichthyoticlike changes that occur with longstanding infection.
* Soft tissue disease manifests as the following:
*
o Subcutaneous nodules (onchocercomata), which contain adult worms and are generally found over bony prominences.
o Lymphadenopathy: "Hanging groin" refers to inguinal lymphadenopathy accompanied by atrophy of the skin.
* Ocular findings
*
o Microfilariae enter the eye by direct invasion from the conjunctiva into the sclera or cornea. They may be identified in ocular tissues early in the disease.
o Ophthalmologic disease is caused by inflammatory responses to microfilariae as they migrate through the eye. The inflammatory reaction intensifies when microfilariae die. This intense host immune reaction can cause the following ocular findings, which are typically bilateral:
o
+ Punctate keratitis is the initial lesion and is caused by an immune response to dead microfilariae. It tends to resolve as inflammation wanes.
+ Sclerosing keratitis results from years of heavy prolonged infection; corneal opacities accumulate, causing irreversible visual impairment or blindness.
+ Anterior uveitis is caused by microfilariae invading the iris and ciliary body, which results in both granulomatous and nongranulomatous inflammation. This can lead to iris atrophy, inflammatory glaucoma, and cataracts.
+ Posterior segment lesions are also due to inflammatory responses to microfilarial death. This causes disturbances of the retinal pigment epithelium and can lead to chorioretinitis, chorioretinal atrophy, and subretinal fibrosis. Only 5% of patients have active retinitis.
+ Active optic neuritis may be due to infection or may develop after systemic treatment. Both optic neuritis and optic atrophy can cause blindness in up to 10% of some populations with onchocerciasis.

Causes

* Onchocerciasis is transmitted by the bite of black flies of the genus Simulium. Black flies breed in well-oxygenated water found in fast-moving streams and rivers. Females require a blood meal for ovulation, and they can transmit infective-stage larvae as well as receive microfilariae during the blood meal. The black fly tends to stay within 2 km of its breeding site.
* During the blood meal, the black fly can transmit infective-stage larvae to the host. Fly saliva acts as a chemoattractant for microfilariae in the surrounding subcutaneous tissues. Large quantities of microfilariae may be ingested during the blood meal. Microfilariae then migrate to the fly's flight muscles, where they emerge as infective-stage larvae after 6-18 days and travel to the proboscis.

Drug Category: Antiparasitics

Inhibit growth and proliferation of parasites.
Drug Name Ivermectin (Mectizan, Stromectol)
Description Selectively binds glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death. Half-life is 16 h. Metabolized in the liver. DOC for treating onchocerciasis.
Adult Dose 150 mcg/kg/d PO as single dose q6-12mo
Pediatric Dose <5 years: Not established
>5 years: Administer as in adults
Contraindications Documented hypersensitivity.
Interactions May interact with other ligand-gated chloride channels, such as those gated by GABA
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions Caution in pregnancy, breastfeeding women with infants <3 mo, and in elderly persons with serious medical problems; immunocompromised patients may require repeated courses of therapy; adverse effects typically occur within first 48 h after first dose and include edema, pruritus, arthralgias, and postural hypotension; may be associated with nausea, vomiting, mild CNS depression, and drowsiness; caution in regions where onchocerciasis and Loa Loa (another filarial disease) are both endemic; patients with high microfilarial loads of Loa Loa are susceptible to encephalopathy upon treatment with ivermectin

Drug Name Suramin (Metaret)
Description Only available macrofilaricidal agent. Extremely toxic; each dose requires several days of hospitalization. WHO only recommends use in selected individuals in nonendemic areas for curative treatment of severe hyperreactive onchodermatitis uncontrolled by repeated ivermectin treatment. Granted orphan drug status and available from the CDC under brand names Antrypol, Bayer 205, Belganyl, Fourneau 309, Germanin, Moranyl, and Naphuride.
Adult Dose <60 kg: Not established

Parenteral/IV:>60 kg: 0.2 g week 1; 0.4 g week 2; 0.6 g week 3; 0.8 g week 4; 1 g week 5 and 6; total dose 4 g
Pediatric Dose Not established
Contraindications Documented hypersensitivity
Interactions None reported
Pregnancy X - Contraindicated in pregnancy
Precautions Consult WHO prior to treatment; contraindicated in pregnant women with onchocerciasis, but may be used in African trypanosomiasis; may cause vision loss

Drug Name Diethylcarbamazine (Hetrazan)
Description Piperazine derivative microfilaricidal agent that can cause frequent unacceptable reactions ranging from urticaria and angioedema to death. Only used for Mazzotti test and not for treatment.
Adult Dose 6 mg PO once (Mazzotti test)
Pediatric Dose Not established
Contraindications Documented hypersensitivity
Interactions None reported
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions Contact a physician if itching and facial swelling (especially eyes), skin rash, fever, and painful or tender glands (armpits, groin, neck) occur; not known to cause birth defects, but do not treat during pregnancy; safety in breastfeeding unknown; prolonged use is associated with vision loss, night blindness, and tunnel vision


- - - - - - - -

From Wikipedia, the free encyclopedia


The life cycle of O. volvulus
(Illustration: Giovanni Maki)



Adult Black Fly (Simulium yahense) with
parasite (Onchocerca volvulus) emerging from
the insect's antenna. Magnified 100x.


Onchocerciasis
Classification and external resources


ICD-10 B73.
ICD-9 125.3
DiseasesDB 9218
eMedicine med/1667 oph/709
MeSH D009855
Onchocerca volvulus
O. volvulus, the causative agent of river blindness.
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Spirurida
Family: Onchocercidae
Genus: Onchocerca
Species: O. volvulus
Binomial name
Onchocerca volvulus
Bickel 1982

Onchocerciasis (pronounced /ˈɒnko
ʊsɝːˈsaɪəsɨs/ or /ˈɒnkoʊsɝːˈkaɪəsɨs/),[1] also known as river blindness, is the world's second leading infectious cause of blindness. It is caused by Onchocerca volvulus, a nematode that can live for up to fifteen years in the human body.[2] It is transmitted to people through the bite of a black fly. The worms spread throughout the body, and when they die, they cause intense itching and a strong immune system response that can destroy nearby tissue, such as the eye.[3]

The primary treatment is a drug, ivermectin. For best effect, entire communities are treated at the same time. A single dose may kill first-stage larvae (microfilariae) in infected people and prevent transmission for many months in the remaining population.[4]

About 18 million people are currently infected with this parasite; approximately 300,000 have been irreversibly blinded by it.[5]

* . * . *


In/Out Patient Meds:

* Ivermectin 150 mcg/kg PO once every 6-12 months

* . * . *

www.soton.ac.uk/~ceb/Diagnosis/Vol10.htm :

Microfilaria worms found in tissue and skin

The main species of microfilariae found in the skin and tissue are Onchocerca volvulus and Mansonella streptocerca. Microfilariae of Onchocerca volvulus and less often, Mansonella streptocerca migrate through the dermis causing itching and skin texture changes and occasionally arrive in the eye where they cause blindness. Detection of these microfilariae is from skin snips or nodule biopsies. When high numbers of microfilariae are present, they can occasionally be found in the blood and urine.


Onchocerca volvulus

Introduction

Onchocerca volvulus is mainly found in West Africa and Central and South America. Onchocerciasis, also known as river blindness, is a major public health problem, especially in West Africa, there an eradication program has been established. It is one of the world’s most distressing diseases of helminth origin, often resulting in blindness. Onchocerca volvulus is transmitted by the species Simulium or black fly whose breeding habitat is by fast flowing rivers or streams, therefore there is a patchy distribution of the disease as it is specified to where water courses are. The adult worms are found in nodules or onchodermata in superficial sites, but may invade other tissues.

It is estimated that there are 18 million cases worldwide with 17.5 million being found in Africa. Nigeria is the most infected region. The rate of morbidity is high in relation to those with an infection.

Life cycle


Figure 11. Diagram showing the life cycle of Onchocerca volvulus, a filarial nematode which causes onchocerciasis, or River blindness. It is known as river blindness due to the vector, Simulium damnosum, breeding in fast flowing rivers.

The life cycle is similar to W. bancrofti, except that the intermediate hosts are various species from the genus Simulium (Black flies), the most important species is Simulium damnosum. (Fig. 11)

The microfilariae are ingested by a Black fly during a blood meal, from where they are carried to the midgut where they penetrate the epithelium and migrate, via the haemocoele, to the indirect flight muscles. Here they undergo two moults, L1 – L3 and develop into infective L3 larvae which move to the mouth parts. Development is completed in 6 – 9 days.

When the infected fly takes another blood meal the infective larvae are once again transmitted into another host (definitive host). The microfilariae are released from the mouth parts and transmitted directly into the hosts bloodstream. Moulting takes place form L3 - L4 within 2 - 5 days and the larvae then migrate widely through the body under the skin and between muscles, ligaments and tendons. The final moult to L5 occurs at 1.5 – 2.5 months after transmission. Male worms are known to mature in about 4 months later. Female worms initiate the formation of the nodules and the males may join later. The sexually mature female worms release microfilariae which migrate out from the nodules into the skin and other tissues, most significantly into the eye.

Morphology

The whitish adult worm lies coiled within capsules in the fibrous tissue. The female can measure up to 50cm while the males are shorter measuring up to 5 cm. The microfilariae of O. volvulus are unsheathed and are usually found in the dermis. They measure between 221 - 287mm long. (Fig. 12 & Table 2)


Figure 12. Onchocerca volvulus microfilariae after being released by the adult female worm. They escape to the subcutaneous tissues and the eye and can be recovered with blood-free skin snips. (Wet mount preparation) (www.cdfound.to.it)


Clinical Disease

Clinical manifestations are due to microfilarie in the epidermis. (Table 4)

Light infections may be asymptomatic or cause pruritis. This leads to scratching which can result in infection. Lyphadenopathy may also be a feature of early infection. After months or years, onchodermatitis results in secondary stage of thickening due to intradermal oedema and pachydermis. There is a loss of elastic fibres resulting in hanging groin, hernias and elephantiasis of the scrotum. There is finally atrophy of the skin resulting in loss of elasticity. There is mottled depigmentation of the skin.



Ocular lesions are related to the intensity of the microfilariae in the skin. Ocular lesions include sclerosing keratitis, secondary glaucoma and cataract, coroidoretinitis and fluffy corneal opacities. The major complication of onchocerciasis is the development of lesions in the eye which may result in blindness or other distressing ocular diseases.



Laboratory diagnosis

1. Analysis of Skin Snips

Small amounts of skin are collected by using a needle to raise the skin and then to slice about 1 mg of skin to a depth of 0.5mm. Snips are collected from several sites, usually the shoulders or the buttocks and sometimes the chest and calves. The snips are placed immediately in 0.5ml normal saline in a microtitre plate and left for 4 hours to allow the microfilariae to migrate out of the tissues. After 4 hours, the wells are examined using an inversion microscope. The microfilariae should still be moving and can be identified from the table below. The microfilariae can also be collected by filtration or centrifugation and the deposit containing microfilariae can be stained with Giemsa at pH 6.8.



2. Analysis of Biopsies

Biopsies of tissue nodules can be dabbed on to a slide to produce impression smears and then stained with Giemsa stain at pH 6.8 for the presence of microfilariae.



Recent advances in diagnostic methods includes and ELISA-based antibody detection assay which utilises a cocktail of recombinant antigens. The advantages of using this test is that it is highly sensitive (almost 100% in onchocerciasis foci). It is also highly specific (100%), it also uses finger prick blood. Therefore, reducing the painful procedure of gaining a skin snip.



The disadvantages is that it requires advanced ELISA apparatus and reagents and cannot distinguish between past and present infections due to it detecting antibodies which stay present in the body for a long time after the infection. Another modern detection method is for Parasite DNA detection, which is based on the amplification of specific DNA sequences form microfilariae using molecular biology technology. The advantages of this technique is its exquisite sensitivity and detects active infections only. The disadvantages are that it requires specialised equipment and expensive reagents. Also it still require a skin snip but a urine assay is a possibility for the future.

Thick microfilaria. Does not have a sheath. Head often spatulate. Nuclei do not extend to tip of tail. Found only in skin.


* . * . *

With compliments to Dr. Marta Botelho and
Dr. Pedro Faísca