Uploaded byKamran Afzal, PhD.
Filariasis
The document discusses filarial nematodes which are roundworms that can cause filariasis in humans. It describes the main filarial species that infect humans including Wuchereria bancrofti, Brugia malayi, Brugia timori, Loa loa, Onchocerca volvulus, and others. It covers their life cycles, vectors, sites of infection in the body, symptoms, diagnosis, treatment and prevention. The distribution of different filarial species is worldwide for W. bancrofti and includes parts of Asia, Africa and the Pacific for others.
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Filariasis
- 1. Filarial Nematodes FilariasisDr Kamran Afzal Asst Prof Microbiology
- 2. Nematodes Nematodes Roundworms; appear round in cross section, they have body cavities, a straight alimentary canal and an anus Tissue Trichinella spiralis Dracunculus medinensis Toxocara canis Toxocara cati Intestinal Ascaris (roundworm) Trichuris (whipworm) Ancylostoma (hookworm) Necator (hookworm) Enterobius (pinworm or threadworm) Strongyloides Blood and tissue
- 3. Filarial nematodes (Bloodand tissue) Genus Wuchereria Species W. bancrofti Genus Brugia Species B. malayi Species B. timori Genus Loa Species L. loa Genus Mansonella Species M. ozzardi Genus Dipetelonema Species D. perstans Species D. streptocerca Genus Onchocerca Species O. volvulus
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- 5. Terms to Know…Filariasis: is a parasitic disease caused by roundworms Elephantiasis: is a disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs and genitals Lymph Edema: Is a condition of localized fluid retention caused by a compromised lymphatic system
- 6. Elephantiasis A debilitatingdisease Abnormal accumulation of watery fluid in the tissues causing severe swelling Skin usually develops a thickened, pebbly appearance and may become ulcerated and darkened
- 7. Epidemiology Source ofinfection: Humans harbor microfilariae in the blood stream Distribution: Filariasis of W. bancrofti is world-wide distribution, while filariasis of B. malayi is in Asia
- 8. Geographic Range Lymphaticfilariasis occurs in the tropics of India, Africa, Southern Asia, the Pacific, and Central and South America.
- 9. Morphology - AdultAdults 2-10 cm long 100 – 300 um in breadth Thread Like Small mouth No buccal cavity Cylindrical oesophagus Separate sexes Viviparous Need a second host for the development of larvae
- 10. Morphology - LarvaeImmature Larvae (Microfilariae) 50-300 um Sheath Arrangement of column of nuclei
- 11. Morphology - W. bancrofti W. bancrofti is sexually dimorphic The adult male worm is long and slender, between 4 to 5 cm in length, a tenth of a centimeter in diameter, and has a curved tail The female is 6 to 10 cm long, and three times larger in diameter than the male
- 12. Morphology - B. malayi Microfilariae are sheathed, and about 200 to 275 µm Not much is known about the adult worms, as they are not often recovered B. malayi microfilariae are slightly smaller than those of W. bancrofti One distinctive feature of B. malayi is that the microfilarial nuclei extend to the tip of the tail
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- 16. Life Cycle Biohelminth: Intermediate hosts (vector) are mosquitoes, bancroftian filaria is transmitted by Culex in which the larval development takes 10-14 days, the development of malayan filaria in Anopheles sinensis, requires 6-6.5 days Infective stage: Filariform larva (L3) Infective route: By skin (the wound bitten by mosquito)
- 17. Site of inhabitation: lymphatic tissue Life span: 4-10 years Microfilariae may survive 1-3 months Nocturnal periodicity : The microfilariae present in the peripheral blood during daytime is very low in density. The number of microfilariae gradually increases from evening to midnight
- 18. Periodicity Nocturnal W.bancrofti B. malayi B. timori Diurnal L. loa Subperiodic Some strains of W. bancrofti and B. malayi Aperiodic Mansonella
- 19. Intermediate Host W.bancrofti is transmitted by Culex, Aedes, and Anopheles species B. malayi is transmitted by Anopheles and Mansonia species Anopheles Aedes Culex Mansonia
- 20. Definitive Host Humansare the definitive host There are no known reservoirs for W. bancrofti B. malayi has been found in macaques, monkeys, cats and civet cats
- 21. Organ Distribution AdultsLymphatics W. bancrofti B. malayi B. timori L. loa Skin Onchocerca volvulus Deep tissues/serous cavities Mansonella ozardii Dipetalonema perstans
- 22. Pathogenesis: Acute stageMaturing larvae and adults provoke strong inflammatory reaction Acute symptoms are painful lymph node and lymph channel inflammation and swelling which is often accompanied by fever Acute reactions are more pronounced (e.g. formation of abscesses)
- 23. Pathogenesis: Chronic stageProgressive chronic disease can lead to wide spread fibrosis and damage of lymphatic vessels, which can result in rupture and discharge of lymph into the urinary system (chyluria) or the scrotum
- 24. Pathogenesis: Chronic stageIn men chronic infection often results in hydrocele, the swelling of the scrotum No effects on fertility, but wide spread sexual disability Profound effects on patients self esteem and family life
- 25. Pathogenesis: Chronic stageDead filaria are especially potent in triggering inflammation, and episodes of fever, pain and acute inflammation Secondary bacterial and fungal infections play an important role in acute episodes and chronic progression of the disease
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- 27. Clinical Presentation Acutephase Filarial fever Acute lymphangitis Acute lymphadenitis Chronic disease Hydrocoele Chyluria Lymphoedema Elephantiasis
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- 30. Clinical Features specificto Filarial type W. bancrofti 1. Asymptomatic 2. Inflammatory - lymphangitis - arms 25%, legs 11% Epididimitis, 42% ‘ Filarial fevers’, orchitis, filarial abscess 3. Obstructive - elephantiasis Chyluria Hydrocoele 4. Tropical pulmonary eosinophilia B. malayi Elephantiasis Scrotal involvement not present
- 31. Loasis (African eyeworm) Localized pain/ itching Calabar swellings Complications Emboli Endomyocardial fibrosis Renal disease
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- 33. Sheathed Microfilariae Tailnuclei Absent Present W. bancrofti B. Malayi L. loa
- 34. Unsheathed Microfilariae Tailnuclei Absent Present M. ozzardi O. volvulus M. perstans M. streptocera
- 35. Presumptive diagnosis: depends on the symptoms, signs and history of living in endemic areas Adults rarely found – on autopsy or a surgical operation Confirmative diagnosis: depends on the demonstration of microfilariae First choice method is thick and thin blood smears, taking blood at night from 9pm-2am Millipore membrane filtration is used for screening the patients or checking curative effect in the endemic areas with the low infective rate Diagnosis
- 36. Diagnosis Demonstration ofmicrofilariae in blood, or lymph (has to be done at midnight!) Antibody and antigen capture assays (dip stick format) Adult filariae can be detected in the scrotal lymph vessels of men with hydrocele by ultra sound
- 37. Diagnosis (other tests)PCR Histopathology Fine needle aspiration cytology Lymphoscintigraphy Ultrasonography
- 38. Prevention and TreatmentControl of Vector Abolishing breeding sites Larval and adult mosquito insecticides Avoiding mosquito bites Treating Microfilariae, not adult worms Chemotherapy Diethylcarbamazine DEC (6mg/KgBW) Ivermectin (400micrograms/KgBW) Other modalities Elastic stockings Surgery
- 39. Proboscis of a mosquito containing filariform larvae
- 40. Eight Species ofFilariae Parasitizing Humans _______________________________________________________________________ Species Site of inhabitation Vector Pathogenesis Distribution _______________________________________________________________________ W. bancrofti lymphatic tissues mosquito lymphatic damage worldwide _______________________________________________________________________ Brugia malayi lymphatic tissues mosquito lymphatic damage Asian _______________________________________________________________________ Brugia timor i lymphatic tissues mosquito lymphatic damage Island of timor ____________________________________________________________________ Onchocerca subcutaneous; eye black fly river blindness Africa volvulus _______________________________________________________________________ Loa loa subcutaneous deer fly skin swellings Africa _______________________________________________________________________ Dipetalonema subcutaneous midge indefinite Africa streptocerca _______________________________________________________________________ Dipetalonema thoracic and midge indefinite Middle and perstans abdominal cavities South America _______________________________________________________________________ Mansonella peritoneal cavity midge indefinite South America ozzardi