filarial worms dr. rs 28 08-2017
TRANSCRIPT
FILARIAL WORMS
Dr. R.Someshwaran, MBBS, MD., Assistant Professor,
Department of Microbiology,
Karpagam Faculty of Medical Sciences and Research,
Othakalmandapam, Coimbatore-641032
Objectives of today’s class
• To enlist the human filarial worms (Nematodes)
• To understand and explain the morphology, life cycle, clinical presentation and pathogenesis of various filarial worms infecting humans
• To understand and explain the lab diagnosis, treatment and prevention of various filarial worms infecting humans
HELMINTHOLOGY
• Helminths are multicellular, bilaterally symmetrical animals
• Helminths – 2 Phylum
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Nemahelminthes
Nematodes
Platyhelminthes
Cestodes & Trematodes
Differences between Cestodes, Trematodes & Nematodes
CESTODES TREMATODES NEMATODES
Shape Tape like segmented
Leaf like unsegmented
Elongated,cylindrical, unsegmented
Sexes Sexes not separateMonoeciousHermaphrodite
Sexes not separateMonoecious except Schistosoma
Sexes are separateDiecious
Head end Suckers, often with hooks
Suckers, no hooks No suckers, no hooks, well developed
Alimentary canal
Absent Present,incomplete, no anus
Present, complete, anus present
Body cavity Absent Absent Present
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NEMATODES CLASSIFICATION(LOCATION OF ADULT IN BODY)
• INTESTINAL NEMATODES:a. Small intestine: Ascaris, Ancylostoma, Necator,
Strongyloides, Trichinella.b. Large intestine: Enterobius, Trichuris
• TISSUE NEMATODES (Somatic nematodes):a. Lymphatic: Wuchereria, Brugiab. Sub-cutaneous: Loa loa, Onchocerca, Dracunculusc. Mesentry: Mansonella spp.,d. Conjucntiva: Loa loae. Zoonotic filariasis: Dirofilaria spp.,
NEMATODES CLASSIFICATION(MODE OF INFECTION)
i. By ingestion:
a. Eggs: Ascaris, Enterobius, Trichuris
b. Larvae within intermediate host: Dracunculus
c. Encysted larvae in the muscle: Trichinella
ii. By Penetration of Skin: Ancylostoma, Necator, Strongyloides
iii. By blood sucking insects: Filariae
iv. By inhalation of dust containing eggs: Ascaris, Enterobius
NEMATODES CLASSIFICATION(BASED ON THEY LAY EGGS/LARVAE)
i. Oviparous: Egg laying nematodes
a. Unsegmented eggs: Ascaris, trichuris
b. Segmented eggs: Ancylostoma, Necator
c. Eggs containing larvae: Enterobius
ii. Viviparous: Producing larvae
Ex: Trichinella, Wuchereria, Brugia, Dracunculus
iii. Ovoviviparous: Laying eggs containing fully formed larvae which hatch out immediately: Strongyloides.
HUMAN FILARIAL WORMS
• Filarial worms belong to Superfamily: Filarioideae.
• Thread like worms transmitted by blood sucking insects (Arthropods)
• Vector borne disease / Zoonotic disease
• Infection by any filarial worm is called as ‘Filariasis’.
• Morphological forms: Adult worm & Microfilariae (embryo)
HUMAN FILARIAL WORMS
• Microfilaria (mf): Sheathed & Unsheathed/naked
• Sheathed mf: Retain their egg membrane
• Unsheathed mf: Ruptures out from the egg membranes
• 8 species of filarial worms infect humans
• Humans are the Definite hosts
Classification of Human filarial worms
A. Lymphatic filariasis:
a. Wuchereria bancrofti (Bancroftian filariasis)
b. Brugia malayi (Malayan filariasis)
c. Brugia timori
B. Subcutaneous filariasis:
a. Loa loa (Calabar swelling/Fugitive swelling)
b. Onchocerca volvulus (River blindness, dermatitis) &
c. Mansonella streptocerca (Skin diseases)
C. Serous cavity filariasis:
a. Mansonella ozzardi (Non-pathogenic) &
b. Mansonella perstans (Non-pathogenic)
Classification of Human filarial worms
D. Zoonotic filariasis:
a. Dirofilaria immitis
b. Dirofilaria repens
c. Brugia pahangi
d. Brugia beaveri
e. Brugia leporis
Filarial nematode
Habitat of Adults Habitat of Microfilaria
Vector Microfilaria periodicity
LYMPHATIC FILARIASISWuchereriabancrofti
Lymphatic tissue Blood Culex quinquefasciatus (W)Anopheles in rural AfricaAedes spp.,
Nocturnal (M)
Sub-periodic (R)
Brugia malayi Lymphatic tissue Blood Mansonia spp., AnophelesMansonia spp., Coquillettidia
Nocturnal (M)Sub-periodic (R)
Brugia timori Lymphatic tissue Blood Anopheles barbirostris Nocturnal
SUBCUTANEOUS FILARIASISLoa loa Subcutaneous
tissue, ConjunctivaBlood Chrysops (Deer fly) Diurnal
Onchocercavolvulus
Subcutaneous tissue
Skin and eye Simulium (Black fly) None
Mansonellastreptocerca
Subcutaneous tissue
Skin Culicoides (Midges) None
SEROUS CAVITY FILARIASISMansonellaperstans
Body cavities, Mesentry
Blood Culicoides (Midges) None
Mansonella ozzardi Body cavities Blood Culicoides (Midges)Simulium (Black fly)
None
Filarial nematode Characteristic feature of Microfilaria Epidemiology
LYMPHATIC FILARIASISWuchereria bancrofti Sheathed, Pointed tail tip free of nuclei South America,
Africa, Asia
Brugia malayi Sheathed, blunted tail tip with two terminal nuclei
Pacific Islands
Brugia timori Sheathed longer than Mf. malayi SE Asia, India, Indonesia
SUBCUTANEOUS FILARIASISLoa loa Sheathed, nuclei extending up to pointed tail tip West and Central
Africa
Onchocerca volvulus Unsheathed, blunt tail tip free of nuclei S. And C. America and Africa
Mansonellastreptocerca
Unsheathed, blunt tail tip with nuclei W. And C. Africa
SEROUS CAVITY FILARIASISMansonella perstans Unsheathed, pointed tail tip free of nuclei S. And C. America
Mansonella ozzardi Unsheathed, pointed tail tip with nuclei S. And C. America Carribean Islands
Head and Tail ends of Microfilariae
LYMPHATIC FILARIASIS
• Wuchereria bancrofti
• Brugia malayi
• Brugia timoria
Global Scenario
• Population at risk : 1.2 Billion
• No. of countries : > 80
• Mf carriers : 76 Million
• Diseased : 44 Million
• Hydrocele : 27 Million
• Lymphoedema : 16 Million
• TPE : 1 Million
National Scenario
• Total Population : 110 C
• Population at risk : 45.4 C (in 16 States & 5 UT’s)
• Total infected : 51.7 M(Wb - 99.4 % and Bm - 0.6 %)
• No. of diseased : 22.5 M
• Mf carriers : 29.2 M
• Hydrocele : 12.9 M
EPIDEMIOLOGY
Mode of Transmission & Incubation Period
• Lymphatic Filariasis is transmitted by the biteof Infected mosquito which harbours L3 larva.
• L1: 1-3 hours
• L2: 3-4 days
• L3: 5-6 days
• Pre-patent period: (L3 to Mf) Not known
• Clinical Incubation period: 8-16 months
Clinical Manifestations
• Manifestations are 2 types
1. Lymphatic Filariasis (Presence of Adult worms)
2. Occult Filariasis (Immuno hyper responsiveness)
Clinical Spectrum
None Asymptomatic
microfilaremiaFilarial
fever
Chronic
pathologyTPE
Stages in Lymphatic Filariasis
• There are 4 stages :
1. Asymptomatic amicrofilariaemic stage
2. Asymptomatic microfilariaemic stage
3. Stage of Acute manifestation
4. Stage of Obstructive (Chronic) lesions
Wuchereria bancrofti
Bancroftian Filariasis
Wuchereria bancrofti
Wuchereria bancrofti - Adult
LIFECYCLE OF W. bancrofti
Filarial fever
Complications
Lab diagnosis
Laboratory Diagnosis
1. Demonstration of microfilarae in the peripheral blood
a. Thick blood smear: 2-3 drops of free flowing blood by finger prick method, stained with JSB-II
b. Membrane filtration method: 1-2 ml intravenous blood filtered through 3µm pore size membrane filter
c. DEC provocative test (2mg/Kg): Afterconsuming DEC, mf enters into the peripheralblood in day time within 30 - 45 minutes.
2. Immuno Chromatographic Test (ICT): Antigendetection assay can be done by Card test andthrough ELISA. Circulating Filarial Antigendetection is regarded as “Gold Standard” fordiagnosing Wuchereria bancrofti infection.Specificity is near complete, sensitivity isgreater than all other parasite detection assays,will detect antigen in amicrofilaraemic as wellas with clinical manifestations likelymphoedema, elephantiasis.
3. Quantitative Blood Count (QBC):QBC will identify the microfilariae and will help instudying the morphology. Though quick it is notsensitive than blood smear examination.
4. Ultrasonography:Ultrasonography using a 7.5 MHz or 10 MHz probe canlocate and visualize the movements of living adultworms of W.b. in the scrotal lymphatics ofasymptomatic males with microfilaraemia. Theconstant thrashing movements described as “Filariadance sign” can be visualized.
5. Lymphoscintigraphy:The structure and function of the lymphatics of theinvolved limbs can be assessed by lymphoscintigraphyafter injecting radio-labelled albumin or dextran in theweb space of the toes. The structural changes can beimaged using a Gamma camera. Lymphatic dilation &obstruction can be directly demonstrated even in earlyclinically asymptomatic stage of the disease.
6. X-ray Diagnosis:X-ray are helpful in the diagnosis of Tropical pulmonaryeosinophilia.
Picture will show interstial thickening, diffused nodularmottling.
7. Haematology : Increase in eosinophil count
Peripheral smear showing Microfilaria
CLASSICAL FILARIASIS vs OCCULT FILARIASIS
CLASSICAL FILARIASIS OCCULT FILARIASIS
CAUSE Inflammatory changes to Devoloping worms and adult
Hypersensitivity reaction to Microfilaria antigen
PATHOLOGY Acute inflammation and epitheloid granuloma
Eosinophilic granuloma
ORGANS AFFECTED Lymph nodes & Lymphatic system
Lung, liver and spleen
MICROFILARIA Present in blood Present in affected tissues & absent in blood
THERAPEUTIC RESPONSE No response Responds to microfilaricidal agent
SEROLOGICAL TESTS Antobody not diagnostic IgE Ab Highly sensitive
DEC PROVOCATION TEST
• Diethyl carbamazine 2mg/kg Body weight
• 20-50 mins later – peripheral smear for microfilariae.
Post DEC Provocation test
Tropical Pulmonary Eosinophilia
Brugia malayi
Malayan Filariasis
LIFE CYCLE
Brugia malayi
Brugia malayi
Microfilaria of Wuchereria bancrofti& Brugia malayi
Features Wuchereria bancrofti Brugia malayi
Appearance Graceful sweeping curves Kinky with 2⁰ curves
Size 250-300 micrometres long 175 to 230 micrometres
Cephalic space Length to width ratio 1:1 Length to width ratio 2:1
Stylet at anterior end Single Double
Excretory pore Not prominent Prominent
Nuclei column Large coarse discrete nuclei Overlapping blurred nuclei
Tail Pointed & free of nuclei Pointed with 2 distinct nuclei
Sheath Faintly stained Well stained
Wuchereria bancrofti
Brugia timori
Lymphatic filariasis
Brugia timori
Loa loa
• African eye worm
• Calabar swelling
• Fugitive swelling
• Adult: 3-7cm long
• Treatment: Dec. Surgical removal
CALABAR SWELLING
Loa loa Subcutaneous nodules
LIFE CYCLE
Loa loa
Onchocerca volvulus
River blindness
Convoluted or Blinding filaria
50cm long adult worm
Onchocerca volvulus
Onchocerca volvulus
Mazzotti reaction
• DEC treatment causes intense reaction with rash, pruritus, facial edema, fever, hypotension, lymphadenopathy and occ. Eye damage.
• Drug of choice is Ivermectin
Life cycle
Mansonella streptocerca
• Subcutaneous filariasis
Life cycle
Mansonella ozzardi
Mansonella perstans
• Usually nonpathogenic
Mansonella perstans
Zoonotic filariasis
• Dirofilaria immitis – Dog heart worm
• Dirofilaria repens (dogs) – subcutaneous and conjunctival nodules in humans
• Dirofilaria conjunctivae (humans)
• Brugia pahangi- cats and dogs
Dirofilaria immitis
Dirofilaria immitis
Dirofilaria repens
Brugia pahangi
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