Nematodes Filarial Flashcards
What are the species in the superfamily Filaroidea & which are of significant human health importance?
- Wuchereria bancrofti 2. Brugia malayi 3. Onchocerca Valvulus 4. Loa Loa 5. Dirofilaria immitis
Where do filarial worms live in the DH?
blood or tissues
How are filarial worms transmitted to the DH?
vector
What are microfilaria?
advanced embryos
What is the sheath?
flexible eggshell as covering membrane in blood dwelling species
Do all species have a sheath?
no tissue dwelling species are unsheathed
How long do mf survive in the host?
survive for many years
What is periodicity?
mf in peripheral blood only at certain times of day
Give an example of periodicity using Wuchereria bancrofti.
max number between 10pm & 2am bc vector is a night feeding mosquito vs. during the day mf are in blood vessels of deep tissue (lungs & liver) -> evolutionary advantage increases chance mf ingested by suitable vector
What disease is caused by Wuchereria bancrofti?
lymphatic filariasis (LF)
What is the size of the adult Wuchereria bancrofti worms and where do they live?
females: 8-10cm vs. male: 40cm
Are the mf of Wuchereria bancrofti sheathed?
yes
What is the vector for Wuchereria bancrofti?
mosquito
What are the 3 phases of Wuchereria bancrofti pathology?
- incubation phase 2. acute (inflammatory) phase 3. obstructive (chronic) phase
Describe the incubation phase of Wuchereria bancrofti infection.
asymptomatic, no detectable microfilarenia, ELISA - detect antigen in blood
What is microfilaremia?
early stage of parasite
Whatis episodic adenolymphangitis and in which phase of pathology does it occur?
attacks of fever, chills, & edema, iuguinal lymph nodes in the inflammatory (acute) phase
When does chronic pathology develop in microfilaremia infection?
obstructive phase 10-20 years after exposure
What is lymphoedema?
swelling of lymph tissue during obstructive phase of W. bancrofti
Compare the 3 grades of lymphoedema.
- grade I: transient & soft if apply pressure there is a pit in the skin rest and elevation needed 2. grade II: swelling is hard & permanent & does not pit with pressure 3. grade III: subcutaneous thickens, hyperkerastosis (hypertrophy of outer skin ayer), fissures, nodules, warty appearance
What is elephantiasis?
- phychological/social impact 2. swollen lymph nodes 3. ~10% of population 4. ages >40 rare is ages <25
What are the advantages of the CFA test for diagnosis of W. bancrofti infection?
test circulating filarial antigen
What can be observed using ultrasound for W. bancrofti infection?
adult worms in lymphatics
How if W. bancrofti infection treated?
- exercising limb to promote lymph flow 2. chemotherapy 3. treat bacterial & fungal infections
What drugs are effective against W. bancrofti infection?
- DEC (diethylcarbamazine - may release components of parasite cuticle & stimulates immune response 2. albendazole - disrupts metabolic function 3. ivermectin (mectizan) - increases GABA at neutral junctions leads to faccid paralysis
Why is hygiene important in preventing W. bancrofti infection?
H20, soap, & shoes prevent bacterial and fungal infections
What are the costs of infection with lymphatic filariasis?
- costs of the disease 2. costs of treatment
Compare the costs of disease and treatment for lymphatic filariasis.
disease: 1. permenant long term disability 2. social loss 3. decline in economic productivity vs. treatment: 2 cents/person/yr for DEC, 30 cents/person/yr for DEC fortified salt albendazole & ivermectin are donanted CFA test is $1/test: total cost $1.32/person/yr
How do these costs and other factors contribute to the control of lymphatic filariasis?
- no amplification 2. no animal reservoir 3. simple & accurate diagnostic test 4. treatment is effective, inexpensive, large scale, combo of drugs, collateral health benefits 5. plans of action 6. drug company support
What is the size of Brugia malayi adults?
female = 55mm vs. males = 25mm
Is there periodicity in Brugia malayi?
yes: in peripheral blood at night
Are Brugia malayi mf sheathed?
yes
Brugia malayi is very similar to what other species?
W. bancrofti
What are onchocercomas and where are they found?
cause river blindness found in Africa, Central/South America
How long do onchocerca volvulus adults live?
10 years
What is the vector in the life cycle of onchocerca volvulus?
blackfly (Simulian spp)
What stage is infective to the vector in onchocerca volvulus?
L3
How does the vector become infected in onchocerca volvulus?
blackfly has bloodmeal and scarifies skin -> pool of blood forms on skin -> fly laps up -> ingest mf
What is the development of the parasite inside the vector in onchocerca volvulus?
mf -> mitohemocoel -> L1 -> L2 -> L3 -> migrates to mouthparts -> L4 -> adults in skin
What is Wolbachia?
causes pathology in onchocerca volvulus. intracellular, inherited spp that controls reproductive functions and sex determination in many insect spp. gram negative - LPS causes host immune response and pathology
What is LPS and how is it related to pathology in onchocerca volvulus infections?
produced by gram negative bacteria and produces host immune response and pathology
Compare acute, chronic and ocular lesions in onchocerciasis.
acute: light, recent infections mf in skin -> presistant, itchy rash -> secondary infection skin begins to thicken & lymph nodes enlarge vs. chronic: heavy, long term infects, skin is thick & discolored “lizard” appearance loos of skin elasticity, femoral & ingunial lymph nodes enlarge & hang loose skin -> hanging groins vs. ocular lesions: mf invaded eye -> blindness
Why do Simulium flies live near rivers?
lay eggs in water of fast flowing rivers
How is onchocerciasis diagnosed?
skin snip - lift skin w/ forcep & use razor to slice thin layer of skin -> skin & saline -> microscope slide
Why is it important not to draw blood during the skin snip?
won’t know which spp it is: tissue vs blood
What is the treatment for onchocerciasis?
- ivermectin - kills mf 2. deoxycycline - kills adults 3. surgery - move onchocerca
Briefly describe the Onchocerciasis Program of W. Africa & the Carter Center River Blindness Program.
Onchocerciasis Program of W. Africa: 1974 with 11 countries and ~20mil cases Dec 2002 program ended vs. Carter Center River Blindness Program: 1996 - Americas & Africa w/ MDP, mectizan distribution program
In what part of the body do Loa loa adults live?
migrate freely in subcutaneous tissue
What is the vector for Loa loa?
deerflies
What is the pathology of Loa loa?
mild: adults winder through subcutaneous tissue and cause inflammatory rxn. caladbar swelling is localized, painful, temporary. migrate across conjuctive & cornea
How is Loa loa infected diagnosed?
mf in blood
How can Loa loa infection be treat?
surgery
What is the common name of Dirofilaria immitis?
heartworm
What is vector for Dirofilaria immitis?
mosquito
What pathology results from Dirofilaria immitis?
fatigue & general loss of condition, cough
How is Dirofilaria immitis infection diagnosed?
mf in blood
How is Dirofilaria immitis infection treated?
- immiticide - contains arsenic that kills worms 2. surgery - caval syndrome (heavy infection & immiticide is contraindicated)
What stage of Dirofilaria immitis is killed by immiticide?
adult worms. problem: dead worms can block blood vessel and arsenic can be toxic (low margin of safety)
Why should a drug such as Heartgard be used?
ivermectin & pyrantel kill L3s injected by mosquitos
