Cause:Wuchereria bancrofti(elephantiasis), Onchocerca volvulus(blinding worm), Loa loa(eye worm), Brugia malayi(elephantiasis), Dirofilaria spp(dog filariasis), mansonella perstans and perhaps tropical eosinophilia is also a form of filariasis from an unknown worm
Pathophys:Adults block lymphatics, fibrotic nodules form about them in lymphatics or in sc locations (onchocercaand loa). TE probably is an infection w worms whose microfilaria never get into blood; are in nodes and lung biopsies
All transmitted by flies or mosquitoes (brugiaand wuchereria); take a long time to mature, hence up to 1 yr for onset of sx. Two-week maturation in insect; infect via puncture holes; males and females in lymphatics produce microfilarial worms, which migrate to peripheral blood in diurnal fashion where ingested by insect and thus complete cycle
In tropical areas; Dirofilariaoccasionally in US
Sx:
Onset may be delayed up to 5+ yr after leave area
Local swelling and redness of skin where microfilaria enter; fever
Calabar(loa):a swelling of 2-3 cm sc anywhere but often in areas of trauma
Si:Recurrent lymphangitis, esp of extremities and male genitalia; can see worms crawling sc often (loa),esp in loose sc tissue, eg, eye, scrotum, breast, penis
Lab:
Hem:Eosinophilia; microfilaria in blood sporadically (not in TE or onchocerca), 40% pos thin smears; thick smear better, or spin crit and look at buffy coat smear under low power
Path:Biopsy of lymphatics or skin nodules (loa, onchocerca)show adults
Serol:immunoassay testing for filariasis antigen is positive
Rx:
Prevent w diethylcarbamazine 300 mg po q 1 wk (Loa loa—Nejm 1988;319:752); used with ivermectin po q 1 yr to all over age 5 yr markedly (90+%) decr prevalence and even improves morbidity of those w elephantiasis (Nejm 2002;347:1841, 1885)
of disease: diethylcarbamazine po, ivermectin; surgical excision of adult worms; doxycycline 200mg qd x 6 week kills rickettsial endo-symbiont of Wuchereria bancrofti (Nejm 2009;361:1448, 1502)