FILARIASIS.ppt

FILARIASIS

ABA Bamikole M

OUTLINE

• INTRODUCTION• ARTHROPODS OF MEDICAL IMPORTANCE• CLASSIFICATION• EPIDEMIOLOGY• LIFE CYCLES & PATHOGENESIS• CLINICAL FEATURES• DIAGNOSIS• PREVENTION & TREATMENT• CONCLUSION

Introduction

• Parasitic disease caused by threadlike nematodes (roundworms).

• Belong to superfamily 'Filariae'.

• Disease is transmitted by arthropods mainly blackflies (simulium) and mosquitoes (plasmodium).

• They have an indirect life cycle.

Arthropods of medical importance

• Wuchereria bancrofti• Brugia malayi• Brugia timori• Loa loa• Onchocerca volvulus• Mansonella streptocerca• Mansonella perstans • Mansonella ozzardi

Classification

• Lymphatic filariasis:W.bancrofti and B malayi

• Subcuteneous filariasis:Loa loa and O. volvulus

• Serous cavity filariasis:M.perstans and M.ozzardi.

Life cycle

In general it is complicated and divided into 5 stages.

Male and female worms mate and the female worm produces thousands of microfilariae.

Microfilariae is taken up by vector during a blood meal.

Microfilariae moves and develops into infective larvae(3rd stage) in the thoracic wall of the vector.

Upon another blood meal the vector injects infective larvae into the dermis of the skin.

After about one year, the larvae molts through two more stages to adult worms.

Lymphatic filariasis

• Endemic in latin america,subsaharan africa and south-east Asia.

• W.bancrofti causes abt 90% of infections while B.malayi causes abt 10%.

• W.bancrofti affects only man while B.malayi affects both man and animal.

W.bancrofti

• Of two variants:

• 1. Nocturnaly periodic form:microfilariae appear in blood between 10p.m-2a.m.Culex mosquito is the vector.

• 2.Diurnally periodic form:microfilariae appear throughout the day.Anopheles mosquito is the vector.

• Adult worms only live in the human lymphatic system.

• Infects the lymphnodes and blocks flow of lymph throughout the body resulting in chronic oedema most often in the lower part of the body.

• Causes Elephantiasis.

B.malayi

• Also has two forms:

• 1.Nocturnally periodic forms:transmitted by night biting species of Mansonia moquitoes.

• 2.Diurnally subperiodic forms:transmitted by day biting species of Mansonia mosquitoes.

• Prevalent in India,New Guinea,Phillipines,and Japan.

• Also causes Elephantiasis.

Life Cycle

• Both have similar life cycles.• Female worms in the lymphatic channels

reproduce producing microfilariae which find their way into blood at various times of the day.

• Mosquito ingest the microfilariae when they bite.• Microfilariae within the mosquito then penetrates

the gutwall and move into the thoaracic muscles where they grow into INFECTIVE LARVA.

Life cycle contd

• After about 2 weeks,infective larva migrate to the mouth parts of the mosquito from where they are injected into the defitive host when the mosquito takes its next blood meal.

• Culex,Aedes,Anopheles and Mansonia serva as intermediate host for these two filarial worms.

Pathology

• Tissue damage occurs in two phases:Acute and Chronic.

• Acute phase:transient erythematous lesions occur especially in the perineal region but may also affect epitrochlear and axillary lymph nodes.

• In males,there is epididymo orchitis that may become complicated by scrotal gangrene and secondary bacterial infection.

• Chronic Phase:there is chronic lymphangitis.Damage to the lymphatics in the presence of the adult worms elicits granulomatous inflammation.

• These lesions heal by fibrosis and lead to lymphatic obstruction and the limbs that are drained by these lymphatics undergo lymphoedema.

• Pathogenic effects are due to adult worms

• Microfilariae do not produce any pathogenic effect, except in occult filariasis

• Adult worms cause lymphangitis by:– Mechanical irritation– Liberation of metabolites– Absorption of toxic products– Bacterial infection

Clinical features

• Clinical Features of Classical Filariasis:– Asymptomatic filariasis– Symptomatic

• Inflammatory phase• Obstructive phases

– Inflammatory phase:• Characterized by lymphangitis & lymphadenitis• Lasts few days & subsides spontaneously• Recurs at irregular intervals

– Obstructive Phase:• Varicose lymph nodes, lymph scrotum, hydrocele,

chyluria & elephantiasis• ,Take long time to develop .Other signs and

symptoms are:• Skin rashes• Arthritis• Urticarial papules• Hypopigmented papules

Wuchereria bancrofti

Brugia malayi

)

Onchocerca volvulus.

• Causes Onchocerchiasis.

• A.k.a river blindness and Robles disease.

• It is not the nematode but its endosymbiont, Wolbachia pipientis, that causes the severe inflammatory response that leaves many blind

• The parasite is transmitted to humans through the bite of a blackfly of the genus Simulium. .

• The larval nematodes spread throughout the body.

When the worms die their Wolbachia

symbionts are released, triggering a host

immune system response that causes

intense itching and can destroy nearby

ttissue, such as the eye.

Epidermiology

• Over 85 million people live in endemic areas and half of these reside in Nigeria, with approximately 270,000 cases of blindness related to the infection.

Onchocerciasis is endemic in 36 countries. Due

to the vector’s breeding habitat, the disease is

more severe along the major rivers in the

northern and central areas of the continent, and

severity declines in villages farther from rivers

Causative organism

Onchocerca volvulus,Blackflies of the genus Simulium are the

only vectors of O volvulus. At least 15 different species of blackfly

simuliids can transmit onchocerciasis; (eg, Simulium damnosum in Africa).

Their eggs require fast-running rivers for breeding grounds. As a result, the numbers of flies produced fluctuate with the season.

Life cycle

During a blood meal, an infected blackfly introduces 3rd-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound.

• In subcutaneous tissues the larvae develop into adult filariae, which commonly reside in nodules in subcutaneous CT.

• Adults can live in the nodules for approximately 15 years.In the subcutaneous nodules, the female worms are capable of producing about 1000 microfilariae daily for approximately 9 years. The microfilariae have a life span that may reach 2 years.

A blackfly ingests the microfilariae during a blood meal.

After ingestion, the microfilariae migrate from the blackfly's midgut through the hemocoel to the thoracic muscles.

There the microfilariae develop into 1st-stage larvae -> 3rd stage infective larva (6-10days).

The 3rd-stage infective larvae migrate to the blackfly's proboscis

and can infect another human when the fly takes a blood meal

Pathogenesis

• Microfilariae and adult worms of O. volvulus contribute to the pathogenesis of onchocerciasis, both through consequences of host immune response.

• Adult worms are the least pathogenic, usually causing no symptoms at all and at worst, stimulate the development of noticeable subcutaneous nodules called onchocercomas.

• These nodules are usually situated over bony prominences.(pelvic area, chest, spine, and knees,on the head and neck)

• The presence of nodules doesn’t cause

pain or ill health to patients but does cause

some disfigurement to the body.

• The impairment of vision is the most

terrible complications of onchocerciasis

• . Eye impairment takes years to develop,

which is why affected individuals are those

over 40 years old

Signs and symptoms

o Microfilariae elicit the ONCHOCERCIASIS SYNDROME that

includes blindness, lymphadenitis, and dermatitis. The dermatitis is the result of inflammation due to the

release of Wolbachia bacteria from dead juveniles.

The first symptoms of dermatitis are itching, bacterial

infection, and abnormal pigmentation but later

on followed by the thickening, loss of

pigmentation.

Skin changes

Leopard skin ;A term referring to the spotted depigmentation

of the skin that may occur with onchocerciasis.

Elephant skin ;A term used to describe the thickening of human

skin that may be associated with onchocerciasis.

Lizard skin ;A term used to describe the thickened, wrinkled

skin changes that may result with onchocerciasis.

Ocular involvement provides the common name associated with onchocerciasis, river blindness and may involve any part of the eye from conjunctiva and cornea and posterior segment, including the retina and optic nerve.

The microfilariae migrate to the surface of the cornea causing Punctate keratitis. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area opaque. Over time, the entire cornea may become opaque, thus leading to blindness.

Simulium damnosum

WOLBACHIA PIPIENTIS

Loa loa

• Causes Loiasis.

• A.k.a Calabar swelling,fugitive swelling and African eye worm.

• Vector is Chrysops spp

• The worm migrates throughout the subcuteneous tissues of humans,occasionally passing into subconjuctival tissues of the eye where it can be easily observed.

• It does not normally affect the eye but can be painful when moving through the eyeball and nose bridge.

• it can cause red itchy swellings below the skin called calabar swellings

• Loiasis is coendermic with Onchocerciasis in areas of western and central Africa.

Clinical features

• Asymptomatic microfilaremia

• Lymphoedema

• Angiooedema(calabar swelling)

• Pruritus

• Urticaria

• Eosinophilia

• Abscesses

• Malaise

LIfe Cycle

• Similar to others above.but has Chrysops spp as its vector/intermediate hosts.

• Vector has both diurnal and nocturnal species.

• C.silacea and C.dimidiata are the commonest species involved.

Pathology

• Presence of worms elicits Type I hypersensitivity reactions.

• Occasionally worms are entrapped and secondary suppurative inflammation occurs.

• When worms traverse the subconjuctival tissues,it may cause.excessive lacrimation,itchiness,and secondary bacterial conjuctivitis.

Loa loa

D.streptocerca

• Causes Streptocerciasis.

• Seen in Tropical Africa

• Vector is Culicoides grabami.

• Adult worms inhabit the subcuteneous tissues of the chest and shoulder area.

• Infection is asymptomatic but may cause dermatitis and pruritus.

D. petalonema perstans

• Causes Perstans filariasis.

• Seen in tropical Africa and South America.

• Transmitted by Culicoides austeni.

• Adults inhabit pleural,peritoneal and pericardial cavities.

• Infection has been associated with skin lesions,Calabar swelling.

Mansonella Ozzardi

• Causes Ozzardi filariasis.

• Found in South America

• Infection is associated with inguinal lymphadenopathy,lymphoedema,coldness of legs,itchy skin nodules and joint pain.

• Vector is biting midge-Culicoides spp

Organism Adult worm Microfilariae

Major vector

Clinical signs Distribution

Wuchereria bancrofti

Lymphatics Blood Culex spp

FeverLymphangitisElephantiasis

Tropics

Brugia malayi/timori

Lymphatics Blood Mansonia spp

FeverLymphangitisElephantiasis

East and South East asia,South India .

Loa loa Subcutaneous

Blood Chrysops spp

Calabar swellings Urticaria

West and Central Africa

Onchocerca Subcutaneous

Skin, Eye

Simulium spp

Subcutaneous nodulesEye disease

Africa,South America

Mansonella perstans

Retroperitoneal

Blood Culicoides spp

Allergic eosinophilia

Sub saharan africa,south america

Diagnosis

• Based on morphological appearance of microfilariae in blood,and sometimes in other body fluids.

• History of travel to endemic areas.

• Biopsy

Prevention and treatment

• Albendazole

• Diethylcarbamazine(DEC)

• Ivermectin

• Control vectors-(physical and chemical methods).

• Awareness

CONCLUSION

• Filarial diseases are a relatively common disease in Africa and Nigeria especially in the Northern part of country and all hand must be on deck to further reduce the incidence of the disease.

• The knowledge of the clinical features, life cycles,pathogenesis and various preventive measures for Filariasis will go a long way in steming the tide further.

THANKS FOR LISTENING. GRACIAS