Filarial worm( 丝虫 )

1. Filarial worm(丝虫)

2. General Introduction Wuchereria bancrofti Brugia malayi Brugia timori Onchocerca volvulus (river blindness - black fly) Loa loa (eye worm - deer fly) Dipetalonema streptocerca Dipetalonema perstans Mansonella ozzardi William C. Campbell Satoshi Omura 2015 Nobel Prize in physiology and Medicine Avermectin

3. General Introduction • Roundworm • Adult filaria live in body cavities, lymphatics, and subcutaneous tissues • Embryos (microfilaria) live in blood or dermis • All require an insect vector

4. Wuchereria bancrofti(班氏吴策线虫) & Brugia malayi (马来布鲁线虫)

5. Morphology • ADULTS: 2 mm – 120 mm (4 – 10µm wide) • W. B. Female ~105mm; Male ~42mm • B. M. Female ~58.5mm; Male ~23mm

6. Morphology • Microfilaria: • 150-350 µm long head tail

7. Morphological differences between W.bancrofti & B. malayi microfilariae W.bancrofti B.malayi

8. Life Cycle

9. LifeCycle • Host: • W. bancrofti : human • B. malayi : human and reservior host • Residing place (adult worm): lymphatics • W. bancrofti: lymphatics of limbs and genital system • B. malayi: lymphatics of limbs • Infective stage：Third-stage filariform larvae (L3) • Intermediate host：mosquito • W. bancrofti: culex (Culex pipiens pallens, C. fatigans) • B. malayi: anopheles ( A. sinensis) • The larvae only undergo growth but no propagation there • Diagnostic stages: microfilariae

10. nocturnal periodicity • The phenomena that the presenting of microfilariae in the peripheral blood is very low in density at daytime but the number of microfilariae gradually increase from evening to early next morning. This periodicpattern was called nocturnal periodicity. The microfilariae mostly stay in the pulmonary capillary vessels during the day. • The peak time of microfilariae in the peripheral blood is: • W. bancrofti: 10pm – 2am • B. malayi: 8pm –4am

11. Clinical manifestations • Wuchereria bancrofti • Asymptomatic (incubation) • Inflammatory - lymphangitis (acute) • arms 25% • legs 11% • epididymitis, funiculitis 42% • ‘filarial fevers’ • Orchitis • filarial abscess

12. Clinical manifestations • Wuchereria bancrofti • Obstructive • elephantiasis • chyluria • hydrocele elephantiasis

13. chyluria

14. Filarial hydrocele • Lymphocele of the right spermatic cord • hydrocele  testis

15. Clinical manifestations Brugia malayi • commonly same with that of W. bancrofti, but hydrocoele and chyluria are rarely seen. • Elephantiasis due to Brugia malayi, complicated by severe dermatitis and secondary bacterial infection.

16. Diagnosis • Direct examination • Thick blood smear • Thin blood smear • Make sure to take the peripheral blood at proper time • Knotts concentration technique: lyse the blood cells and centrifuge (1~2ml of blood from vena) • Immunological methods: • Intra-dermal tests using antigens for early infection • ELISA for detecting specific antigen or antibody

17. Epidemiology • Source of infection: carrier, patients, reservoir host for Brugia Malayi • Vector: mosquitoes including culex, anopheles and Aedes • Distributed in tropical and subtropical region, Brugia Malalyi only in Asia

18. Epidemiology

19. Prevention • Mass chemotherapy: • Hetrazan(diethylcarbamazine，DEC) • Avermectin • Control of and protection from mosquitoes • Use of screens • Use of insect repellents • Use of insecticides

20. QUESTIONS • 1. MCQ: • The vector of B. m and W.b is: A.mosquito B.lice C.sandfly D. termite • 2. Fill in the blanks: • The infective stage of B. m is _____ • 3. Explain the definitions： • nocturnal periodicity • 4. Essay questions: • What is the consequence of W. b infection?

21. Onchocerca volvlus(旋盘尾丝虫) Black fly(蚋) River Blindness

22. Onchocerca volvlus • Pathogenic stage: microfilariae • Intermediate host：blackfly (Simulium spp.) • Severe symptoms due to microfilariae in skin and in the eye • Adult worms in nodules cause insignificant pathology

23. Onchocerca volvlus Onchocerca nodule

24. Onchocerca volvlus

25. Onchocerca volvlus • The world’s 2nd leading infectious cause of human blindness -- onchocerciasis

26. Epidemiology • Approximately 96% in tropical Africa with significant number in the highland of Western Guatemala, Colombia and northeastern Venezuela, even Mexico

27. Prevention • Treatment of the patients • Surgical treatment (remove the adult worms in the nodules) • Chemotherapy: Avermectin,Ivermectin (effective to kill microfilariae) • Control of insect vector population • Protective netting and screening to shield individuals

28. Loa loa（罗阿罗阿丝虫） Chrysops (deer fly,斑虻) The eye worm

29. Loa loa ●Pathogenic stage: Adult worm ●Intermediate host：Chrysops ●Mildly pathogenic ●Adult worms wander through out the body (1.5cm/min) and cause pathology The most troublesome infection sites --conjunctiva

30. Loa loa Cabalar swelling

31. Loa loa Loa loa adult in Calabar swelling x section

32. Loa loa Epidemiology • Loaiasis is now limited to the African equatorial rain forest and southern Sudan • Infection rates are highest in regions with muddy ponds and swamps

33. Prevention • Treatment of the patients • Surgical removal of wandering adult worms from the conjunctiva is advisable • Chemotherapy: Diethylcarbamazine/Ivermectin (effective to kill microfilariae), but may both have severe side-effects • Control of insect vector population • Protective netting and screening to shield individuals