30 terms

Blood and Tissue Nematodes

Which nematodes are transmitted via larva-contaminated insect bites?
All of the blood and tissue nematodes: Onchocerca volvulus, Wuchereria bancrofti, Brugia malayi, Loa loa, Dracunculus medinesis
Which filarial worms can cause elephantitis? How are they transmitted?
Wuchereria bancrofti, Brugia malayi; transmitted via bite of an infected mosquito
What is the pathological basis of elephantitis?
Infection with the filariae causes fevers, headaches and inguinal lymph node swelling; chronic infection results in fibrous tissue surrounding dead filarie that remain in the lymph nodes. This plugs up the lymph nodes calling swelling of testicles, genitals, and lower limbs
Diagnosis of elephantitis is made by the identification of microfilarie in blood draw at what time of day?
Night time (nocturnal periodicity); can also be diagnosed by positive antibody titers via immunofluorescence
What is the treatment for elephantitis?
Diethylcarbamazine (think of the 2 ethyls in the car with the elephant in between)
Where is Wuchereria bancrofti endemic to?
Pacific Islands, Africa
Where is Brugia malayi endemic to?
Southeast Asia and Malay peninsula
What eye worm is transmitted by biting fliers?
Loa loa
What roundorm causes river blindness?
Onchocera volvulus
Where is Onchocerca volvulus found?
Africa and Central and South America
How are Oncocherca volvulus transmitted to humans?
Larva transmitted via black flies
What is the life cycle of Onchocerca volvulus
Once larvae (microfimbrae) are transmitted to humans via flies they mature into adults (fimbrae) which coil up in fibrous nodules in the skin and subcutaneous tissue. The adults mate and the microfilariae migrate through the dermis and connective tissue
Symptoms of patient with river blindness?
Pruritic skin rash with darkened pigmentation; the skin may thicken with formation of papular lesions that are actually intraepithelial granulomas; the thickened skin is dry scaly and thick like lizard skin; microfilariae may migrate into the eye causing blindness
Diagnosis of river blindness?
Skin biopsies at the advancing site of the skin lesion; microfilarie can also be viewed in the cornea and anterior chamber of the eye by slit lamp examination
Treatment of river blindness?
Ivermectin (recall mnemonic i VER, i see), diethylcarbamazine
How do Dracunculus medinensis infections usually present?
Painful skin blister/ulcer in the lower extremity with a visible worm inside
What is the other name for Dracunculus mediensis?
Guinea worm
Where is Dracunculus mediensis mostly found now?
Sudan and Ghana; it is nearly eradicated thanks to the efforts of the Bill Gates Foundation
Is there effective treatment for Dracunulus?
Not at the moment; eradication of the disease depends on identifying persons who have worms migrating from their bodies and restricting their access to public water supply
How does Dracunculus mediensis get transmitted?
The female migrate to skin and pokes her body out of an ulcer exposing her uterus which sheds larvae into water supply; the larvae are picked up by copepods as an intermediate host; when a person drinks water containing the copepods, the larvae penetrate GI tract and move to subcutaneous tissue where they develop and mate. Males die. Females grow to be very long
How is Dracunulus mediensis removed?
Wrap the female around a stick slowly until the entire nematode is removed
What is cutaneous larval migrans?
Caused usually by Ancyclostoma braziliense (Necator americanus and Strongyloides stercoralis can also cause cutaneous larval migrans)
Symptoms of cutaenous larval migrans/creeping eruption?
Pruritic red raised migratory skin infection that corresponds to an allergic response to migrating larvae under the skin
Where does it occur geographically?
Southeastern US
How is cutaneous larval migrans transmitted?
larvae of dog and cat hookworms penetrate the skin and migrate beneath the epidermis
Treatment for cutaneous larval migrans?
Ivermectin or Albendazole
True/False: Filarial parasites are hosts to endosymbiots that they need for survival
True; Wolbachia which are like rickettsia
What is an antibiotic that targets the endosymbiotic bacteria in filarial nematodes?
Doxycycline (remember Wolbachia is rickettsia like)
True/False: Adult Filarial nematodes live in lymph nodes and give birth to larva (not eggs like the GI nematodes)
True/False: The blood and tissue nematodes are spread by bite of arthropods and not via fecal contamination or direct entry like the GI nematodes