Blood And Tissue Nematodes PDF

Blood and Tissue nematodes Outline – General features – Classification – Geographical distribution Morphology, differential characteristics, life Cycles, Laboratory diagnosis, prevention and control of: Wuchereria bancrofti Brugia malayi/timori Loa loa Onchocerca vol...

Blood and Tissue nematodes Outline – General features – Classification – Geographical distribution Morphology, differential characteristics, life Cycles, Laboratory diagnosis, prevention and control of: Wuchereria bancrofti Brugia malayi/timori Loa loa Onchocerca volvulus Trichinella spiralis Dracunculus medinensis  Learning objective At the end of this unit the student will be able to: – Explain the general features of blood and tissue nematodes – Classify tissue nematodes – Explain the Geographical distribution, Morphology, differential characteristics, life Cycles, prevention and control methods of blood and tissue nematodes – Collect blood samples in appropriate timing  2.1.3 Blood and tissue nematodes 2.1.3.1. General features: Adults which live in the tissues of human (lymphatic system, subcutaneous tissues or muscle) Long thread - like worms Requires two host to complete their life cycle. Females are viviparous, larvae hatch in the uterus The female produce first stage larvae (L1) The immature L1 stage larva is called Microfilariae Small , slender, motile forms L1 require blood sucking insects (IH) to develop to infective form (L3) No reproduction in the vector, rather development 2.1.3.2. Classification: Tissue nematodes can be classified based on: – Habitat in the body – Clinical manifestation – Morphology  Three families/ groups 1. FAMILY FILARIDAE( Filarial worm) - Common/pathogenic filaria Wuchereria bancrofti Brugia malayi Brugia timori Loa loa Onchocerca ovolvulus – Less/non-pathogenic Filaria Mansonella perstance Mansonella streptocerca Mansonella ozardi 2. FAMILY TRICHINELOIDAE Trichinella sps 3. FAMILY DRACUNCULIDAE( guinea worm) Dracunculus medinensis Animal tissue nematode rarely infect human Dirofilaria sps Angiostrongylus cantonensis Gnathostoma spinigerem  2.1.3.3. FAMILY FILARIDAE ( Filarial worm) General features:  Filariae live as adults in various human tissues Agents of LF reside in lymphatic vessels and lymph nodes O. Volvulus, Loa loa, M. Ozzardi and M. Streptocerca in subcuraneous tissues M. Streptocerca besides reside in the dermis M. Perstans resides in body cavities and surrounding tissues 8  Cont ….  Three of these are responsible for most of the morbidity: W. bancrofti and B. malayi cause lymphatic filariasis, and O. volvulus causes onchocerciasis (river blindness). Animal reservoirs play9 no role of significance in Diagnosis based on Mf findings: Morphologic features: – Size – Presence or absence of “ sheath” – Appearance i.e. curvature, Kinks, coiling etc – Arrangement of the column of nuclei in the body – Presence of nuclei at the very tip of the tail  Factor to be considered when collecting blood – Collect blood at the correct time – Concentration technique recommended – In chronic infection Mf is rarely found in blood – In LF Mf are higher in capillary blood  FAMILY FILARIDAE( Filarial worm) Morphology Adult – The adults are long thread like worms. – Measure 2 cm – 120 cm (4 – 10 µ wide) – Live in body cavities, lymphatic, and subcutaneous tissues – Release embryos (microfilaria) which live in blood or dermis (skin) – all require an insect or crustaean vector as intermediate host  Microfilaria – The immature first stage larva of filarial worms – Are motile and live in blood or dermis – Measure, 150-350 µ long – Transparent and colorless with rounded or pointed tail in unstained smear – Internal structure can be visualized by the use of fixed stained preparation – Can be sheathed or unsheathed Periodicity:- Microfilaria of pathogenic filarial worms that found in the blood (m.f of filarial worms that causes lymphatic filariasis and Loasis) show periodicity Periodicity:- – Mf are found in the blood in greater number in a certain hours of a day or a night – Corresponds to peak biting times of their insect vector Nocturnal periodicity -mf is high in blood during night hrs Diurnal periodicity-mf is high in blood during day hrs Nocturnal or diurnal subperiodicity;- mf can found in blood 24 hrs with slight increase in number during day or night hrs Filarial worms Periodicity Main Vector Reservoir (Synonym) (IH) O. volvulus Non Black fly Human (River Periodic (Simulium) blindness) W. ancrofti Periodic (N) Culex, Human (LF) 22 – 04hr Anopheles (24hr) Sub Aedes Human Periodic 20 – 22 (21hr) 14 – 18 (16hr) B. Malayi (LF) Periodic (N) Anopheles Human 22 – 04hr (24hr) Sub Mansonia Human, Monkey, Cat Periodic – Zoonotic 20 – 22 (21hr) B. Timori (LF) Periodic (N) Anopheles Human 16 L. Loa (Eye Periodic (D) Deer fly Man, Monkeys  Flarial worm causes 3 main diseases – lymphatic filariasis (Elephantiasis) – Loasis – Onchocerciasis (river blindness) 2.1.3.4. Lymphatic Filariasis  Lymphatic Filariasis Disease caused by filarial worms living in the human lymphatic system Causative agents Wuchereria bancrofti Brugia malayi Burigia timori These worms lodge in the lymphatic system They live for four to six years, producing millions of minute larvae that circulate in the blood”  Lymphatic Filariasis Large numbers are present in the lymphatics of the: Lower extremities (inguinal and obturator groups), Upper extremities (axillary lymph nodes), and, Male genitalia (epididymis, spermatic cord, testicle) - particular for W. bancrofti  Social consequences It is one of the most debilitating and disfiguring diseases of the world 1. Disfigurement of the limbs and genitals leads to: – Stigma – Anxiety – Ostracization – Psychological trauma – Sexual disability  Social consequences….. 2. The disease impeds – Mobility – Travel – Educational opportiity – Employment opportunity – Marriage prospect  Epidemiology of Lymphatic Filariasis Endemic in 83 countries 1.2 billion at risk > 120 million people infected > 25 million men suffer from genital disease, > 15 million people suffer from lymphoedema or elephantiasis of the leg ~ 2/3 of infected people live in India and Africa Others live in parts of Asia, the Pacific, & in Central and South America. Distribution  Distributin Wuchereria bancrofti affects an estimated 119 million individuals and disfigures 40 million. Wide distribution (Africa, SE Asia, Indonesia, South Pacific Islands) Brugia malayi Limited distribution (China, India, SE Asia, Indonesia, Philippines) Brugia timori Leser sunda, island of Indonesia  Wuchereria bancrofti Disease: Bancroftian filariasis, Wuchereriasis, elephantiasis Distribution: tropical and subtropical countries Morphology: 1. Adult: – Thready – Cylinderical oesophagus – Creamy white in color – Male: About 4cm in lentth Curved posterior end 2 unequal spicules and has anal papillae 26  Wuchereria bancrofti Female: About 8 cm in length 2 sets of genitalia Vulva opens close to the posterior end Viviparous 2. Micrfilaria: – 250 x 8  – Body forms graceful curves – Body has a column of nuclei separated by free areas – Rounded anterior and tapered tail ends free of nuclei – Loose sheath (stretched vitelline membrane) closely fits the body but projects beyond the head and tail ends. 27  Wuchereria bancrofti 3. Infective larvae: 1500 – 2000 x 20 – Cylinderical oesophagus 28 W. Bancrofti & B. Malayi 29 Transmission and life cycle  Cont.... Requires two host Human-DH Mosquitoes-IH Transmission Bite female mosquitoes (Genera Culex, Aedes, Anopheles, Mansonia)  Infective larvae deposited onto human skin during the mosquito's blood meal Enter through the mosquito bite puncture wound or local abrasions. In humans: – Parasites passes to the lymphatic system – Undergo further molts – Become adult male and female worms  Adult female worms produce thousands of sheathed microfilariae per day Mf can be found in blood 9 months after infection (W.bancrofti) and 3 months (Burigia species) Normally found in peripheral circulation in evening.  Microfilariae ingested during blood meal from infected person Penetrate the mosquito stomach wall Enter the body cavity (hemocoel) Migrate to the insect's flight muscles for growth. After 2 molts, the L3 migrate through the head, Reach the proboscis of the mosquito.  Clinical manifestation. Depends on: – Site occupied by adult – Number of worms, – Length of infection and – Immune response of the host  Clinical manifestation. 1. Many infections are asymptomatic 2. Circulating Mf probably do not cause pathology 3. The main pathological lesions are: a) Inflammatory manifestations – due to toxic products of living or dead adult worms  Clinical manifestation. – There may be: Recurrent attacks of lymphangitis – Funiculits – Epididymitis – Orchitis, etc... Lymphadenitis Swelling and redness of affected parts Fever, chills, headache, vomiting and malais b) Obstructive manifestations – Fibrosis following the inflammatory process Coiled worms inside lymphatics. This may result in:  Dilatation  Rupture of distended lymphatics  In the urinary passage – chyluria  In the pleura – chylothorax  In the peritoneal cavity – chylous ascitis  In the testis – chylocoele  Elephantiasis:  Hard and thick, rough and fissured skin  Frequently legs & genitalia (scrotum, penis and vulva)  Less often arms and breasts.  Clinical...... 4. Tropical pulmonary eosinophilia Pulmonary symptoms: cough, dyspnoea, "asthmatic syndrome". Chest X-rays: patchy infiltrates Splenomegaly High ESR & marked eosinophilia No microfilariae in the peripheral blood. Serological tests strongly positive Responds very well to therapy with DEC 41  Diagnosis of W. bancrofti 1. BF (taken at night)  Thin and thick smears  Concentration methods Lyzed capillary blood technique Tube centrifugation lyzed blood technique Microhematocrite tube technique Membrane filtration technique Counting chamber technique  DEC provocation test 42  Diagnosis of W. bancrofti  Mf in:  Aspirates of hydrocele  Lymph gland fluid  Chylous urine 2. Intradermal test (antigen from Dirofilaria immitis) 3. Serological tests as IHA, IFA 4. Antigen detection: ICT filariasis test 43 45 46 Adult female worm of W. Adult male worm of W. bancrofti bancrofti 47  Differential diagnosis Podoconiosis (syn. lymphatic siderosilicosis or lymphoconiosis): – Very slow onset of oedema – Lymphoedema – Elephantiasis (mostly limited to below the knee) Caused by immune response to certain 48 minerals.  Treatment of W. bancrofti  Diethyl carbamazine (DEC)  General measures:  Rest, antibiotics, antihistamines, and bandaging  Surgical measures for elephantiasis 49  Prevention and control of W. bancrofti  Control of mosquitoes  Avoid mosquito bite  Treat patients  Health education  Global LF elimination program strategy:  Mass drug administration  Care for chronic cases 50 2.1.3.5. Loiasis  Loiasis Caused by filarial worms living in subcutaneous tissue Causative agents Loa loa (Eye worm) Distributed in Rain Forest areas of West Africa and equatorial Sudan.  Loa loa (Eye worm)  Habitat:  Adults live in:  Connective tissues under the skin  Mesentry  Parietal peritoneum  Subconjunctival tissue of the eye or thin skinned areas  Microfilaria in peripheral blood of man during day time  Infective larvae in the gut, mouth parts and muscles of chrysops 53  Loa loa (Eye worm)  Morphology  Adult – cylinderical and transparent  Microfilariae  Has several curves and kinks  Sheath which stains best with haematoxylin  Body nuclei are not distinct and more dense  Nuclei extend to the end of the tail which is rounded 54 55  Transmission Horse flies (Tabanidae) in genus Chrysops Day-feeding & forest-dwelling Also called the “deer fly” or mango fly. Life cycle  Life Cycle Adult worms continuously migrate through tissue at a rate of about 1 cm per minute. Found in back, chest, axilla, groin, penis, scalp and eyes.  Clinical manifastation Loiasis is often asymptomatic. Calabar swellings (episodic angioedema) – Itchy, red, and nonpitting swollen areas in the skin – 2-10 cm in diameter, Often painful/may be painless – In any portion of the skin/wrists & ankles most frequent  Clinical manifastation Adult worms also migrate in sub- conjunctival tissues. They can cause inflammation and irritation but not blindness  Laboratory diagnosis Mf in stained BF taken during the daytime Occasionally the Mf can be found in joint fluid Differentiation from mansonella required (hematoxylin staining) 61  Loa loa: Sheathed, Relatively dense nuclear column Tail tapers and is frequently coiled, and Nuclei extend to the end of the tail.  Mansonella perstans: Smaller than L. loa No sheath Blunt tail with nuclei extending to the end of the tail 63 Mf of Loa loa Mf of M. pestans 64 2.1.3.6. Onchocerciasis  Onchocerciasis Is a filarial disease caused by O. Volvulus 66  ONCHOCERCIASIS Commonly known as river blindness The world’s second leading infectious cause of blindness WHO estimates the global prevalence is 17.7 million, of whom about 270,000 are blind DISTRUBUTION MAP Foci are present in Southern Arabia, Tropical Africa Yemen and in S. & C. between the 15° America north and the 13° south  Occurs most widely along the courses of fast running rivers in the forests and Savannah areas of west and central Africa Also occurs in the Yemen, Arab Republic, Central and South America  Onchocerca volvulus Habitat: – Adult: Subcutaneous nodules and in the skin Adults can live ~ 8 – 10 years in nodules – Microfilariae: Skin, eye and other organs of the body – Infective larvae in: Gut, mouth parts70and muscles of black  Onchocerca volvulus Morphology Microfilariae: – 220 to 360 µm by 5 to 9 µm – No sheath – Head end is slightly enlarged – Anterior nuclei are positioned side by side – No nuclei in the end of the tail 71  Onchocerca volvulus Adult: – Females - 33 to 50 cm in length and 270 to 400 μm – Males - 19 to 42 mm by 130 to 210 μm. 72  Onchocerca volvulus Transmission: By the bite of infected vector (simulium species) 73  Life cycle During a blood meal, infected blackfly introduces L3 (infective stage) larvae onto the skin of the human L3 penetrate into the bite wound In subcutaneous tissues the larvae develop into adult filariae Adult commonly reside in nodules in 74  Life cycle The female worms produce Mf for ~ 9 years Mf have a life span ~ 2 years Mf found: – Typically in the skin and in the lymphatics of connective tissues – Occasionally in peripheral blood, urine and sputum 75  A black fly ingests the Mf during a blood meal Mf migrate from the blackfly's midgut through the hemocoel to the thoracic muscles Mf develop into L1 larvae and then to L3 L3 migrate to the blackfly's proboscis Infection occurs when the fly takes a 76 Life cycle of Onchocerca volvulus 77  Clinical feature Onchocerciasis Acute onchocerciasis: – Itchy (pruritic) – Erythematous – Papular rash with thickening of the skin 78  Clinical feature Chronic onchocerciasis: – Elephant or lizard skin Hanging groin – Leopard skin River blindness 79  Clinical feature Onchocercomata: – Upper part of the body (American onchocerchiasis) – Pelvic region (African form) Nodules surrounded by concentric bands of fibrous 80 tissue  Laboratory diagnosis Mf in skin snips Skin biopsy Skin Mf in urine, blood & most body fluids (in fragment heavy infection) – Wet mount preparation Staining 81 82  Mf must be differentiated from Mf of M. Streptocerca and M. Ozzardi. – Mf of O. Volvulus are longer and do not have nuclei to the end of the tail 83 84 85  Prevention and control Destruction of Simulium Avoiding Simulium bites Treatment of communities (~APOC) 86  Treatment Ivermectin: – Paralysis of worms – Reduces the microfilarial load Surgical Care: – Nodulectomy – Removes adult worms 87 2.1.3.7. Trichinellosis  Trichinella spiralis  A tissue nematode caused by Trichinella spiralis  Zoonotic disease  Disease in humans: Trichinosis, Trichiniasis, Trichinelliasis, Trichinellosis  Distribution: Temperate regions where pork is eaten 1. T. Spiralis spiralis – found in temperate regions 2. T. Spiralis nativa – found in the Arctic 3. T. Spiralis nelsoni – found in Africa and S. Europe 89  Trichinella spiralis  Habitat:  Adults in the small intestine of man and animals specially pigs and rats (reservoir hosts)  Larvae : encysted in muscles 90  Trichinella spiralis  Morphology; 1. Adults: Attenuated anterior end Cellular oesophagus Anus or cloaca terminal Male: 1.5 mm in length Posterior end curved ventrally 2 caudal papillae One set of genitalia 91  Morph....  Female: 3.5 mm in length  Posterior end bluntly rounded  One set of genitalia  Vulva opens at the junction of the anterior 5th with the rest of the body  Larviparous (viviparous) 92  Morph.... 2. Encycted larva: in cyst wall formed by tissue reaction  Larva (1mm) coiled inside the cyst (0.5 x 0.2 mm)  Larva grows from 0.1 to 1mm (~ 2 weeks to become infective)  Lies along the longitudinal axis of muscle fibres  Cyst usually become calcified 93  Transmission Eating flesh of infected pork (raw/undercooked) 94 Life cycle 95  Life cycle  The same host (animal/man) act as DH & IH  After fertilization, males die and are expelled.  Females penetrate deeply in the mucosa and lay  Female lays ~ 1500 larvae in its life span (~ 2 months) 96  Larvae to the circulation Passes through pulmonary filter Distributed all over the body (esp. diaphragm, tongue, eye, deltoid, pectoralis, intercostals, etc)  Larvae coil and encyst in the long axis of muscles  Pigs become infected by eating infected flesh from other pigs or ingestion 97 of infected dead  Life cycle  Larvae liberated from the cysts in small intestine and mature to adults  Larvae start to be deposited by the female 98  Pathogenicity  Intestinal invasion by adult worms  Abdominal pain, nausea, vomiting, diarrhoea and colic. 99  Migration of larvae 100  Encystment of larvae  Manifestations depend up on organs affected.  > 50 – 100 larvae/gm of muscle are symptomatic  < 10 larvae are often asymptomatic 101  Clinical signs & syptoms  The main findings are: o Oedema chiefly orbital o Muscle pain and tenderness o Headache, fever, rash, dyspnoea, general weakness o Death occurs in severe cases from exhaustion, heart failure (myocarditis), pneumonia, etc. 102 103  Laboratory diagnosis 1. Immunodiagnosis: a) Intradermal test (Bachman test) b) Serological tests: Bentonite flocculation (BF) Latex agglutination (LA) Counter – current electrophoresis (CEP) Complement fixation test (CFT) IFA and IHA 104  Diagnosis..... 2. Muscle biopsy: Direct examination After digestion in a pepsin hydrochloric acid medium 3. Eosinophilic leucocytosis in the acute stage 105  Encysted in Larvae, freed pressed muscle from their cysts tissue. 106 107 Adult worm from intestine wall  Prevention & control  Thorough cooking of pork  770c or freezing at – 150c for 20 days  – 180c for 24 hours  Proper breeding of pigs  Sterilizing garbage  Antirat campaign  Inspection of pork in slaughter houses  Trichinoscope. 108  Treatment  Non specific symptomatic treatment:  Sedatives  Cortisone and ACTH  Supportive treatment:  Rest, fluids, smooth diet and vitamins  Thiabendazole  Mebendazole 109 Dracontiasis 2.1.3.8. Dracunculus medinenis “Guinea worm, ”  Dracunculosis  Synonyms: Dracontiasis, Dracunculosis, Dracunculiasis  Causative agent  Scientific name: Dracunculus medinensis  Common name: Medina worm or Guinea worm 112  Epidemiology Most common in areas of limited water supply where individuals acquire water by physically entering water sources. – “Walk-in well” – Water holes in parts of Africa  Distribution of Dracunculus medinensis Global: Nile valley, India and areas where wells are used for water supply Ethiopia:  Dracunculosis  Habitat:  Adults in subcutaneous tissues of man/reservoir animals 115  Morphology I. Adult :thread like, I. Female: About 30 to cylinderical 100 cm in length oesophagus  Swollen anterior II. Male: About 3 cm in end length  Hooked posterior  Posterior end coiled end  2 unequal spicules  Inconspicuous vulva near anterior end 116  D. medinensis 2. Larva (or embryo):  600 x 20   Rhabditiform oesophagus  Anterior end rounded  Tapering and long tail (1/3 body) 117  Life Cycle of Dracunculus medinensis A blister is formed from the female worm's production of embryos released beneath the skin, and due to a burning pain that comes with this, the victims often immerses their legs in water for relief. With the sudden drop in temperature that follows, the blisters usually rupture, releasing the worms. These worms may release thousands of infective juveniles at this time, which enter the water. Before  The cephalic end of the fertilized female pressing on the skin, produces a papule that becomes a blister and then After ruptures forming an ulcer  Life Cycle of Dracunculus medinensis Infective larvae In water, larvae Must be eaten by Copepod (Crustacean), the IH,  Life Cycle of Dracunculus medinensis Once within the copepod, the infective juvenile larvae moves into the hemocoel where they develop into 3rd stage juveniles. These get consumed when humans drink  Life cycle of D. medinensis  Man is infected on drinking water containing cyclops  In the small intestine, the cyclops is digested , larvae liberated and penetrate through the duodenal wall and migrate to the subcutaneous tissues probably via lymphatics. At this point the females are fertilized by the males, and the males die. The females then migrate to the skin, reach sexual maturity, and produce juveniles.  They tend to go to parts most likely to come in contact with water122as the lower extremities  Life cycle of D. medinensis  Male dies after copulation  The cephalic end of the fertilized female pressing on the skin, produces a papule that becomes a blister and then ruptures forming an ulcer  When the ulcer contacts water, a loop of the uterus prolapses through a rupture in the anterior end of the worm and larvae are discharged. . They penetrate its intestine and settle in the body cavity to become infective in about 3 weeks 123 Copepod 124 Life Cycle of D. medinensis 125  Pathogencity of D. medinensis  Early manifestatiosn are produced when the female worm approaches the skin. It liberates a toxic substance that results in local erythema, tenderness and pain.  This is followed by formation of a blister that turns into a cesicle and ultimately ulcerates  There may be local or systemic symptoms as urticaria, pruritus, pain, dyspnoea, nausea and vomiting, which subside with rupture of the blister  The ulcer may be secondarily 126 infected producing Adult worm of D. medinensis 127 Adult worm of D. medinensis 128  D. medinensis Blister containing the Ruptured blister with worm filamentous worm A 129 B D. medinensis 130  D. medinensis Adult Dracunculus in foot 131  Diagnosis of D. medinensis  Laboratory tests to investigate dracunculiasis are limited because the larvae are normally washed into water  A diagnosis is usually made when the blister has ruptured and the anterior end of the female worm can be seen 132  Diagnosis of D. medinensis  If required, laboratory confirmation of the diagnosis can be made as follows: 1. Place a few drops of water on the ulcer to encourage discharge of the larvae 2. After a few minutes collect the water in a plastic bulb pipette or pasteur pipette 3. Transfer the water to a slide and examine microscopically using 10x objective – motile larvae will be observed 133 Adult D. medinensis 134  Prevention & Treatment People with an open Guinea worm wound should not enter ponds or wells used for drinking water. Water can be boiled, filtered through tightly woven nylon cloth, or treated with a larvae-killing chemical. No medication is available to end or prevent infection. – The only treatment is to remove the worm over many weeks by winding it around a small stick and pulling it out a tiny bit at a time. – Sometimes the worm can be pulled out completely within a few days, but the process usually takes weeks or months. – The worm can be surgically removed before the wound begins to swell.