wuchereriabancrofti

1. WUCHERERIA BANCROFTIBY:Norhan Ahmed Faculty of MedicineEGYPT

2. Geographical distribution Africa ,Asia &parts of south America In Egypt ; cases are detected in kalyobia , Dakahilia ,Sharkia ,Cairo ,Giza &Assuit

3. Life Cycle The adults live in the lymphatics of man (noreservoir host) . Microfilariae laid by the female reach the blood by migration through the wall of the lymphatics to the neighboring small blood vessels . Microfilariae gradually appear in the peripheral blood by night (nocturnal periodicity ) reaching maximum about midnight (10am – 2am),and gradually disappear by day time .

4. The microfilaria are ingested by the mosquito intermediate host with its blood meal . Species of the genera CULEX , AEDES & Anopheles act as vectors .In Egypt it is CULEX PIPIENS . • In the mosquito’s stomach , the microfilaria loses its sheath , penetrates the gut wall and invades the thoracic muscles within 24 hours . • There it settles & moults assuming a short sausage shaped larvae (200×15 u).

5. After a few days it moults again (300×20 u). About the tenth day the larvae becomes long & slender (2000×20 u ) . The filaform larvae ( the infective stage ) migrates from the thorax to the head , reaches the proboscis & enters the labium . • When the mosquito bites man , the infective larvae attracted by warmth of the skin , pierce the labium & penetrate the skin or enter the bite wound .

6. Larvae pass to the lymphatics vessels & nodes where they grow to maturity in 6 to 12 months . They live & produce microfilaria for 5 to 10 years . Microfilaria live for 2 years .

7. FILARIA PEROIDICITY Causes unknown , theories that explain periodicity are : • Biological theory : inborn periodicity related to the habit of the insect vector biting activity , mosquitoes are night biters . • Chemical theory : positive chemotaxis between the microfilaria & saliva of the mosquito .

8. PH of the blood theory : decreased oxygen content & increased carbon dioxide content while sleeping may stimulate the microfilaria to migrate to the peripheral circulation . By day time the reverse occurs. • Lymphatic blockage theory : as adult worms are mainly found in the lower limbs & during day the patient attains an upright position the born microfilaria go to the circulation during sleeping .

9. Pathogenesis & clinical picture Asymptomatic In endemic areas where children are exposed to infection at an early age . Many adults exhibit microfilariae in their blood without symptoms referable to their infection . On physical examination , the patient may exhibit a moderate generalized enlargement of lymph nodes especially of inguinal region . Blood examination shows numerous microfilaria & a low grade eosinophilia .

10. Acute inflammatory phase Due to toxic products of worms & immunological reaction to it . Incubation period ( about one year after the infective bite ) then the following symptoms appear . • Filaria or elephantoid fever :recurrent attacks of fever with rigors ends with sweating ( lasts few hours to several days)

11. Recurrent attacks of lymphatics & lymphadenitis mainly of the legs & genitallia . The legs show: raised , red , hot , swollen & tender streaks. Bacterial & fungal super- infection . The genitallia shows: Funiculitis: Inflammation of the spermatic cord

12. Orchitis : Inflammation of the testis . Epididymitis : Inflammation of the epididymis Epididymis- orchitis : Inflammation of the epididymis & testis . Chronic obstructive phase • Distension & varicosities of lymph vessels distally . Fibrous tissue is deposited around lymph vessel .

13. Persistent lymphatic edema . • Lymph flow is obstructed . • Elephantiasis & hydrocele . • Rupture of distended lymphatics leads to release of chyluria , chylocele , chylothorax & chylous diarrhea .

14. Diagnosis • Clinical History Presence of history of exposure to mosquito in an endemic area , together with clinical finding . • Laboratory investigations 1- Blood examination for microfilaria 2-Polycarbonate filters ( Nucleopre) technique : the microfilaria are trapped on the filter after the RBCs have been lysed by 3% acetic acid .

15. The 3 sum pore size filters may be examined directly on a microscope slide because they are transparent when wet. 3-Knott’s concentration technique : add 2 ml blood to 10 ml 2% formalin , leave for 10 min then centrifuge & examine sediment either as a direct wet film or after staining with methylene blue .

16. 4 – Hetrazan provocation test : microfilaria may be demonstrated in blood at daytime by administration of 100 ml of diethylcarbamazineorally , 45 to 60 min before the blood specimen is taken . 5 – Serological test :detection of antibodies to filarial antigen may be of diagnostic value when malaria can’t be found . 6 – Intradermal test : skin test using antigen from dog heartworm , DIROFILARIA IMMITIS , is group – specific for filarial infections .

17. Detection of adults in lymph node biopsy • Imaging techniques : • Lymphoscintography : shows lymphatic dilatation . Soluble or fine colloidal material is injected interstitially . They will be taken up into the lymphatics vessels then into the draining lymph node. • Ultrasonography : shows adults in lymphatics ( when viable they give filarial dance sign )

18. ultrasonography

19. Treatment 1 – Diethylcarbamzine ( DEC, Hetrazan) : the drug is effective in killing microfilaria ( rapidly) adults worms (slowly) , can be given orally in dosage 2 mg/kg for 12 days . 2 – Ivermectin: taken as single oral dose 200 ug / kg , is highly effective . 3 – Supportive measures : elevation of affected part , use elastic stockings or pressure bandage , mechanical devices or boots that apply intermittent pressure to promote lymphatic flow .

20. 4 – Surgical treatment : • Cosmetic surgery : to remove excess connective tissue. • Micro vascular surgery : small lymphatics are anastomosed to a large central vein . It can produce marked reduction in limb size.

21. Prevention & control 1 – Mosquito control e.g. spraying , use of larvicides , insecticides . 2 – Mass treatment to eliminate source of infection .