Loa loa,Onchocerca, Dirofilaria, Mansonella - gmch.gov.in lectures/Microbiology/25 Loa-Loa... · Onchocerca…

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<p>Loa loa,Onchocerca, Dirofilaria, Mansonella</p> <p>12.10.12</p> <p>Contd.</p> <p>Acanthocheilonemantinae</p> <p>Genus Species Habitat of adult worm</p> <p>Microfilaria </p> <p>Wuchereria W.bancrofti Lymphatic system</p> <p>Blood</p> <p>Brugia B.malayi Lymphatic system</p> <p>Blood</p> <p>Oncocerca O.volvulus Connective tissue</p> <p>Skin</p> <p>Dipetalonema</p> <p>Mansonella</p> <p>D.PerstansD.Streptocerca</p> <p>M.ozzardi</p> <p>Connective tissue</p> <p>Mesentery</p> <p>BloodSkin</p> <p>Blood</p> <p>Contd.</p> <p>Dirofilarinae</p> <p>Genus Species Habitat of adult worm</p> <p>Microfilaria </p> <p>Dirofilaria D. repensD. tenuis</p> <p>Connective tissues &amp; eyelid</p> <p>Dirofilaria D. immitis Heart of dog Blood</p> <p>Loa L.loa Connective tissue &amp; Conjunctiva</p> <p>Blood</p> <p>Differential characters of adult worms</p> <p>Superfamily FILARIOIDEA</p> <p> Cuticuta smooth Cuticula not smooth Head with Head without Provided with ProvidedCuticular Cuticular Appendages minute warts withAppendages W.bancrofti L.loa annular andD.Perstans B.malayi oblique</p> <p>thickningsO.volvulus</p> <p>Diffential characters of Microfilariae</p> <p>Microfilaria Found in blood Found in skinMf.bancrofti, Mf.malayi, Mf.loa, Mf.perstans Unsheathed and non-</p> <p>Mf.ozzardi periodicMf.volvulus,Mf.streptocerca </p> <p> Sheathed and Unsheathed and non-periodic Nuclei up to tail tip Tail tip Periodic Mf.perstans, Mf.ozzardi ( tail end crook like) free from Mf.bancrofti, Mf.malayi, Mf.streptocerca nuclei Mf.loa Volvulus</p> <p>Nucei upto tail tip Tail tip free Nuclei upto tail tip Free tail tipMf.malayi,Mf.loa Mf.bancrofti Mf.perstans Mf.ozzardi</p> <p>Contd. While examining a blood film the following microfilariae should be kept in </p> <p>mind-</p> <p>In Africa: Mf.bancrofti., Mf. Loa and Mf.perstans.</p> <p>In South America:Mf.bancrofti, Mf. Perstans and Mf.ozzardi.</p> <p>In India:Mf.bancrofti and Mf.malayi.</p> <p>Loa-loa Common name -The African eye worm</p> <p> Geographicaldistribution;</p> <p> CentralandWestAfrica</p> <p> Habitat: Adultwormsliveinthesubcutaneoustissuesofman ofteninthesubconjunctival tissueoftheeye.</p> <p>Contd.</p> <p> Morphology- Adult worm- Microscopically, the cuticula is found to have </p> <p>numerous rounded protuberances ( cuticular bosses) which vary in number and arrangement in the two sexes.</p> <p> Existsinthreeforms:Adult Microfilarial Larval Adultmale3034mmx0.4mm Adultfemale5077mmx0.5mm</p> <p>Contd. Embroys- They are found in the peripheral blood by daytime.</p> <p> Mf. Loa is enveloped in a sheath and measures 300m by 7m.</p> <p> The column of nuclei extends to the tail tip.</p> <p> Life cycle- The worm passes its life cycle in two hosts:Man</p> <p>Chrysops ( mango or deer flies) Larval development follows the same course as in other microfilariae.</p> <p> Loa-loa is maintained in nature by interhuman transmission.</p> <p>DaybitingChrysops flies</p> <p>Contd. The infection is transmitted by a day-biting female chrysops, C.silacea and </p> <p>C.dimidiata.</p> <p> Only females suck blood.</p> <p> Pathogenicity- The worm produces the disease in man called loisis.</p> <p> Man is infected by the bites of chrysops.</p> <p> The incubation period is 3 to 4 years.</p> <p> On entering the human host, the worm migrates rapidly to the various parts of the body through the subdermal connective tissues.</p> <p>Contd. The worm shows itself a special prediclection for creeping in and around </p> <p>the eyes.</p> <p> During migration, it causes oedema of subcutaneous tissues, known as Calabar swellings or fugitive swellings.</p> <p> They disappear in course of 2 to 3 days and are regarded as allergic reaction of tissues to filarial toxins.</p> <p> Microfilariae can seldom be found during the period of calabar swellings.</p> <p> The diagnosis is based on history of such fugitive swellings associated with intense eosinophilia ( 30-40%).</p> <p>Lab diagnosis Initial Diagnosis is based upon the history of fugitive swellings and intense </p> <p>eosinophilia (30-40%)</p> <p> Demonstration of the microfilariae in the peripheral blood during the day.</p> <p> Microfilariae are shed by the females on a random schedule.</p> <p> Therefore, multiple samples should be collected during daytime, preferably between 10 a.m. and 2 p.m.</p> <p> Demonstration of the sheathed microfilariae with nuclei extending to the tip of the tail is sufficient for the diagnosis.</p> <p> The infection can also be diagnosed by detection or removal of adults from the eye or Calabar swellings.</p> <p> Increased levels of anti- filarial antibodies.</p> <p>Treatment Treatment- Hetrazan is an effective remedy for loiasis, causing a quick </p> <p>disappearance of microfilariae from the peripheral blood and death of adult worms.</p> <p> Allergic reactions during the course of hetrazan therapy may occur.</p> <p> With large number of Mf. Loa ( in excess of about 30 per mm3 ) there is great risk of development of meningoencephalitis and nephrotic syndrome.</p> <p> These cases are treated with diethylcarbamazine.</p> <p> DOC is diethylcarbamazine.</p> <p>Contd. Prophylaxis- Loisis can be prevented by:</p> <p> Protection from Chrysops bites in endemic areas by application of repellents to exposed skin.</p> <p> Destructive campaigns against Chrysops.</p> <p> Detection and treatment of infected individuals with diethylcarbamazine.</p> <p>ONCHOCERCAVOLVULUS</p> <p>THECONVOLUTEDFILARIA</p> <p>Onchocerca volvulus Common name is convoluted filaria.</p> <p> The generic name Onchocerca means hooked tail.</p> <p> Geographical Distribution-In various parts of Africa and Central America also reported from south Arabia.</p> <p> Habitat-Adult worm in the subcutaneous connective tissues of man.</p> <p> Morphology- Adult worm-Microscopically the cuticula is seen to be raised in well </p> <p>marked annular and oblique thickenings.</p> <p>Contd. These are more prominent in females than in males.</p> <p> The male measures 3 cm in length by about 0.13 mm in breadth, it has a coiled tail.</p> <p> The female is very long, measuring up to 50 cm in length by 0.4 mm in its greatest diameter.</p> <p> The gravid females may live as long as 15 years.</p> <p>Contd Microfilariae: These are found in the skin.</p> <p> They are unsheathed and non-periodic.</p> <p> The column of nuclei does not extend to the tail tip.</p> <p> They measures 300m in length by 6 to 8 m in breadth.</p> <p>Mf of Onchocerca volvulus</p> <p>Themicrofilariaearesheathlesswithsharplypointed,curved</p> <p>tails.</p> <p>Life cycle O.volvulus completes its life cycle in two hosts.</p> <p> Man is the definitive host. </p> <p> Day biting female black fly of the genus Simulium is the intermediate host.</p> <p> Humans become infected by the bite of black fly, which possesses in its mouth parts the infective third stage larvae.</p> <p> The larvae enter the skin through the puntured wound and migrate to the subcutaneous tissue in which they moult twice and develop into male and female adult worms.</p> <p>Simulium flies breed in fast flowing rivers i.e well oxygenated water, because their larvae have an obligatory aquatic stage during which they require high oxygen tension (see picture below). </p> <p>'. ThusOnchocerciasisisoftenreferredtoas'riverblindness</p> <p>Contd. The adult worms live singly, in pairs, or in coiled entangled masses in the </p> <p>deep fascia or in the subcutaneous tissue.</p> <p> The females release actively motile, unsheathed microfilariae which migrate to the skin and eyes of infected subjects.</p> <p> They can survive in the body for 1-2 years.</p> <p> When a black fly again bites a diseased human at one of the infected sites, the microfilariae are taken up with the blood meal.</p> <p> They migrate from the gut of the vector into the thoracic muscles.</p> <p>Contd. They moult twice here and develop into infective larvae over a period of 6-</p> <p>8 days.</p> <p> These larvae then migrate to the mouth parts of the black fly where they may be transmitted to humans at the next blood meal.</p> <p> The cycle is thus repeated.</p> <p>Pathogenicity The infection is transmitted by the bite of an infected female Simulium.</p> <p> The infective larvae remain localised in the skin and grow into adult worms.</p> <p> The pathological changes in the skin and eyes result from a hypersensitivity reaction to the dead or dying microfilaria.</p> <p> The incubation period in man is about one year.</p> <p> O.volvulus causes the disease Onchocerciasis in man.</p> <p> The adult worms live in the subcutaneous connective tissues.</p> <p>Contd. They do not invade the muscle or viscera.</p> <p> The pathological lesions in Onchocerciasis may be divided into two groups as follows:</p> <p>1. Formation of subcutaneous fibrous nodules (Onchocercomas) caused by the adult worms.</p> <p>2. Ocular lesions caused by microfilariae</p> <p>3. Metabolites of adult worms may also be responsible for ocular lesions.</p> <p>Contd. The nodules are raised above the skin surface.</p> <p> They are painless and nonsuppurative.</p> <p> On section, they appear as a concentric mass of fibrous tissue with a honeycombed central area containing the adult worms of both sexes.</p> <p> Dead worms become calcified and initiate foreign body giant cell reaction.</p> <p> Actively motile microfilariae are found in subepithelial and deeper connective tissue in many areas of the body without any tissue reaction.</p> <p>Contd. Skin lesions such as dermatities associated with pruritus may be caused </p> <p>by a toxin from larva or adult worm.</p> <p> A high eosinophilia is observed in such cases.</p> <p> Other complications which may be observed are:1. Development of hydrocele or even lymph scrotum.2. Elephantiasis of scrotum and legs.3. Hanging groin (seen in Africa).The atrophied, inelastic skin of the </p> <p>groin hangs down in a fold containing enlarged, sclerosed femoral or inguinal lymph nodes.</p> <p> The skin shows lichenification and a mottled depigmentation(leopard skin).</p> <p>Contd. Ocular lesions-These are particularly seen in persons with nodules on head </p> <p>or face.</p> <p> They result from the presence of microfilaria which may be found moving about in the substantia propria of the cornea and also in the anterior chamber.</p> <p> They can lead ultimately blindness.</p> <p> Because of the association of the vector with rivers, the condition is known as river blindness.</p> <p>Clinicalfeaturesocular</p> <p> Ocularinvolvementprovidesthecommonnameassociatedwithonchocerciasis,riverblindness.Themicrofilariaemigratetothesurfaceofthecornea.</p> <p> Punctatekeratitis occursintheinfectedarea.Thisclearsupastheinflammationsubsides</p> <p> However,iftheinfectionischronic,sclerosingkeratitis canoccur,makingtheaffectedareabecomeopaque.</p> <p> Overtimetheentirecorneamaybecomeopaque,thusleadingtoblindness.</p> <p>Laboratory diagnosis The diagnosis of Onchocerciasis can be made by:</p> <p>1. Demonstration of adult worms-These can be demonstrated inside the excised nodules.</p> <p>2. Demonstration of microfilariae-These can be demonstrated in skin snips.</p> <p> Two to six skin snips are taken from iliac crests, buttocks, calves and shoulders.</p> <p> The skin is cleaned with spirit and allowed to dry before a piece of skin 2-3 mm in diameter and 0.5-1mm deep is taken.</p> <p> Biopsy specimens are placed in normal saline or distilled water on a slide or in the well of a microtitre plate for 30 minutes or longer.</p> <p>Contd. Then examined for microfilariae that migrate from the tissue.</p> <p> If no microfilariae are seen, the preparation should be left overnight and re-examined for the microfilariae.</p> <p> Live microfilariae can be seen moving vigorously in the medium by direct microscopy.</p> <p> In patients with ocular manifestations, small biopsied specimens of the corneal conjunctiva may yield the microfilariae.</p> <p> Live microfilariae may be demonstrated in the substantia propria of the cornea and in the anterior chamber of the eye by slit lamp examination.</p> <p>Contd. Rarely, the microfilariae may be found in the peripheral blood.</p> <p> A provocative test (Mazzotti test)-The appearance of a pruritic papular rash within 24 hours after an oral dose of 50 or 100 mg of diethylcarbamazine suggests the presence of cutaneous microfilaria.</p> <p> The reaction is caused by dead microfilaria of O.volvulus killed by the drug.</p> <p> Serological test-Cross reactivity of the antigens of O.volvulus with those of other nematodes, limit the usefulness of various serological tests.</p> <p> Recently, more specific enzyme immunoassays using recombinant O.volvulus antigens may help in diagnosing patients with suspected onchocerciasis.</p> <p>Contd. Polymerase chain reaction-Microfilarial antigens in skin samples may be </p> <p>detected by polymerase chain reaction.</p> <p> Treatment-Treatment consists of surgical removal of detectable nodules (nodulectomy).</p> <p> It is simple, easy to perform and produces immediate results.</p> <p> Suramin was the first successful drug for the treatment of Onchocerciasis.</p> <p> It has lethal effect on adult worms.</p> <p> It is too toxic and significant side effects occur in 10-30 % of the patients.</p> <p>Treatment contd. Diethylcarbamazine is an effective microfilaricidal drug and produces </p> <p>cutaneous and systemic side effects from death of the microfilariae.</p> <p> Ivermectin is as effective as diethylcarbamazine but has significantly fewer side effects.</p> <p> It does not kill adult worms but inhibits microfilarial release from female worms.</p> <p>Prophylaxis Onchocerciasis can be prevented by the application of insecticides to the </p> <p>streams where the vector Simulium is breeding.</p> <p> Mass chemotherapy as a control measure is not recommended because the available drugs produce severe side effects.</p> <p>Mansonella</p> <p>Mansonella streptocerca Mansonella streptocerca occurs in West and Central Africa.</p> <p> The adult worms live in the dermis, usually less than 1mm below the skin surface.</p> <p> The adult male measures 17-18 mm x 0.4 mm .</p> <p> The adult female measures 25-27mm x 0.6-0.8 mm.</p> <p> The microfilariae measure 180-240m x 5 m and are unsheathed.</p> <p> The tail end is bent in a crook like curve and the column of nuclei extends to the tail-tip.</p> <p>Contd. They are non-periodic.</p> <p> The microfilariae are fou...</p>


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