Blood/Tissue Nematodes Flashcards
Blood and tissue nematodes are referred to as:
Filarial worms
Females are viviparous, meaning:
they produce elongated and worm-like embryos called microfilariae
Filarial worms inhabiting blood are ______
Sheathed
Meaning they retain egg shell as a membrane
Tissue-dwelling filarial worms are ________
unsheathed
They loose their shell during development
Wucheria bancfrofti causes
Bancrofti filariasis or lymphatic filariasis or elephantiasis
Wucheria bancfrofti adults live in:
The major lymphatic ducts of humans
In W. bancrofti females produce:
Sheathed microfilariae which will circulate in the blood
Why are microfilariae found in the blood?
Arthropods take a blood meal which further perpetuates spp.
Are there nuclei in the tail of W. bancrofti?
No
Periodicity in W. bancrofti microfilariae
Only found in peripheral blood at night, when vector takes a blood meal
also depends on the circadian rhythm of host
primary vectors of Wuchereria
Culex, Anopheles, Aedes, and Mansonia
During the day, the bacrofti microfilariae are concentrated in:
blood vessels of the deep tissues of the body
physiological factors associated with sleeping _______________________ which trigger the behavior of _________
decreased body temperature and oxygen tension, increased carbon dioxide, lower adrenal activity
microfilarae
In W. bancrofti, once ingested by mosquitoes:
lose their sheath in insects stomach
penetrate gut and enter thoracic muscles
Sausage stage develops which has most of the organ systems present
Filarifrom stage develops and travels ot mosquitoes proboscis where they are infective to definitive host
In W. bancrofti, when the mosquito feeds on human:
The filariform larvae escape
They migrate through peripheral lymphatics
They reach larger lymphatics where they settle, mature and mate producing microfilariae
3 phases of W. bancrofti pathogenesis:
incubation (asymptomatic), acute inflammatory phase, and the obstructive phase
Incubation phase in W. bancrofti
the time between infection and the appearance of microfilarae in the blood. It is largely symptomless, but there may be mild fever and general weakness
Acute inflammatory phase in W. bancrofti
female worms attain maturity and start releasing microfilarae
females block lymph vessels and glands, resulting in edema
Intense lymphatic inflammation mostly affects the lower half of the body
chills, fever, and toxemia
Obstructive phase in W. bancrofti
lymph varices
chyluria (lymph in urine)
hydrocele (fluid accumulation around testicles)
elephantiasis
Elephantiasis in men vs women
In men the organs most commonly affected are: scrotum, legs, and arms
in women: legs and arms are usually affected, with vagina and breasts sometimes affected
______ attacks of ________ causes the condition called elephantiasis
Repeated
acute lymphatic inflammation
What occurs in elephantiasis:
Skin becomes thick and cracked which allows secondary infections via fungi and bacteria
Dx of W. bancrofti
Demonstration of microfilarae in the blood
Blood smears must be taken at the right time
US detect adult worm movement
X-ray detects dead and calcified worms
Treatment of W. bancrofti
Hetrazan kills microfilariae and adults
Metronidazole
Surgery
Pressure bandages on swollen areas
Prevention
Avoid mosquito bites in endemic areas
Insect repellents and mosquito nets
______ also causes lymphatic filariasis
Brugia malayi
Brugia malayi causes
Brugian filariasis
2 key differences between Brugia malayi and W. bancrofti
B. mayali has 2 nuclei in tail
B. mayali is not as widely distributed
Loa Loa causes _____ and is referrred to as the _____
Loa filariasis
Eye worm
Vector for Loa
Chrysops
Day feeding
Once fly bites host:
The L3 larva enter the bite and develop slowly, adjacent to the skin
Adult makes excursions to sub-dermal tissue where it becomes visible
They mate and produce microfilariae, which travel to the peripheral circulatory system
Periodicity in Loa loa
In synchrony with fly vector, present during the day
After loa vector takes a blood meal:
they develop to L3 stage in the gut and travel to proboscis where they are infective to the definitive host
Infective stage to human in Loa loa
L3
Pathogenesis in Loa loa:
When adults travel they cause pain, they can often be seen in the eye where they can be removed before causing further damage
Immune reaction in Loa loa host
Calabar swellings in arms and legs
Also caused by the worm being stationary
Dx of Loa loa
demonstration of microfilariae in the blood
Treatment
Surgical removal
Hetrazan kills microfilariae and adults
Metronidazole
Prevention/control of Loa loa
Control of deer flies is difficult; they breed in swampy forests
Avoid the bites of deerflies
Wear long pants and sleep in well-screened areas
