Filariasis and Guinea Worm

filariasis

tropical disease caused by parasitic thread-like worms transmitted through mosquito bites, primarily affecting the lymphatic system

types of filariasis

lymphatic, cutaneous, nonpathogenic

lymphatic filariasis is caused by—

Wucheria bancrofti and Brugia malayi

cutaneous filariasis is caused by—

Loa loa and Onchocerca volvulus

nonpathogenic filariasis is caused by—

Mansonella spp.

sheathed

enclosed in a protective coating

microfilariae

embryo stage of filarial parasite, usually in blood or tissue of humans and can be ingested by intermediate host where the microfilariae will develop into its infective stage

clinical features of filariasis

adult filariae live in lymphatic vessels and cause them to over time become thickened and destroyed

• lymph is pooled and endothelial and connective tissue proliferate

• total lymphatic obstruction

elephantiasis is the end result

lab diagnosis of filariasis

thick blood smears, micropore filtration

• repeating over the course of 24 hours to catch periodicity (nocturnal)

• circulating filarial antigen detection is commercially available

• eosinophilia is marked in all forms

Brugia malayi morphology

• sheathed

• nuclei densely packed in single row to tip but separated

• tapered tail to poimt

Wuchereria bancrofti morphology

• sheathed

• tapered tail to point

• nuclei singly do not extend to tip\

• individually visible nuclei

Loa loa morphology

• sheathed

• tapered, often coiled

• nuclei to tip

Onchocerca volvulus morphology

• not sheathed

• tail tapered toa point, sharp angle at end

Loa loa is known colloquially as the—

African eye worm

the vector of Loa loa is —

mango fly or deerfly (Chrysops spp.)

clinical features of Loa loa

• calabar swellings, nodules mostly on extremities

• localized pain, itching, urticaria

• microfilaremia usually asymptomatic

• diurnal

lab diagnosis of Loa loa

• thick blood smear for microfilariae

• removal of cutaneous worm

• microscopy

onchocerca volvulus is known colloquially as causing—

river blindness

Onchocerca volvulus is predominant in —

equatorial Africa, central and south America

the vector of Onchocerca volvulus is —

blackflies (Simulium spp.)

clinical features of Onchocerca volvulus

• chronic dermatitis (leopard sin), subcutaneous nodules or masses, ocular lesions with or without lymphadenitis

• skin lesions early focal or generalized itching, redness, diffuse papules and scabbing to chronic edema, hypopigmentation and lichenification because of scratching

• eye lesions early punctate keratitis, corneal fibrosis, glaucoma, optic atrophy

lab diagnosis of Onchocerca volvulus

skin snip, scleral punch

• Americas - gluteus and calf skin

• Africa - deltoid and scapular

UA following small DEC dose to mobilize microfilariae into urine

immunochromatographic test for specific antigens

clinical features of Dracunculus medinensis

itchy blister and ulceration

• secondary bacterial infection leading to abscess

lab diagnosis of Dracunculus medinensis

clinical diagnosis is sufficient

therapy of Dracunculus medinensis

slow removal of female worm by winding on a stick a few inches per day

• prevent breaking the worm and killing it

• metronidazole

Dracunculus medinensis is known colloquially as —

Guinea worm

Dracunculus medinensis morphology

• fishhook shape

• sharp thin tapered tail

• unsheathed

• similar to filarids