Filarids

life cycle

vector

larvae type

infective stage for host

parasites of all vertebrates except ____

indirect

blood sucking arthropod

microfilariae

fish

Suborder Camallanina

transmission of these helminths?

which sex is found in host?

vector?

drinking water

only females found in host

copepod in freshwater

4 Lymphatic Filariae

Wuchereria bancrofti

Brugia malayi

Brugia timori

Brugia pahangi

Lymphatic Filariae

niche?

adults are what shape?

females produce what type of larvae?

what are the infective stages for intermediate host?

lymphatic vessels

thread-like

microfilariae

the microfilariae that circ in blood for mosquito

Wuchereria bancrofti

___% of filariasis in humans

2 types of mosquito vectors

90

1. culicine mosquito

2. anopheline mosquito

Brugia malayi

Distribution?

Brugia timori

Distribution?

Brugia pahangi

definitive host?

Lymphatic Filarids

niche for adult worms

how many eggs can female produce per day

lumen of lymphatic vessels

especially in genitalia of males

produce 10,000/day

Periodicity of microfilariae

daytime?

nighttime?

during day collect in capillaries deep in organs (lungs)

circ in blood b/w 10pm-6am

MF >> through stomach >> molts 2x to J3 stage

J3 stage infective for def host

J3 migrates to mosquito mouth parts

J3 deposited on skin at bite site and into wound

J3 in bite wound >> subcut tissues >> lymph vessels

two successive molts to adult stage

adults on average survive 5-8 years

Wuchereria bancrofti, Brugia spp

similar larval and life cycle stages

no reservoir hosts

pathogenesis?

clinical syndromes? (5)

host inflammatory resp and immune resp

1. endemic "normals"

2. asymptomatic microfilaremics

3. acute lymphadenitis and filarial fevers

4. chronic obstructive lymphadenitis

5. Tropical pulmonary eosinophilia

What is the ultimate end point of chronic obstructive filariasis?

Occurs in __% of endemic populations

Elephantiasis

20%

no clinical signs

no microfilaremia detectable at any time

have high levels of microfilaria circ in blood

no clinical signs

onset of these clinical signs starts in adolescent years in endemic regions

have circ MF and recurrent bouts of fever and malaise with inflammation of lymphatics

lymphatics are varicose

lymphatics become blocked causing fluid backup

lymphedema results from blockage creating doughy skin, pitting edema and cellulitis

scarring of infected area with fibrous conn tissue

ultimate chronic obstructive filariasis

extensive, chronic lymphedema

fibrosis and scarring of lymphatics

skin thickening

permanent enlargement of involve extremities

occurs frequently in young men in S India

severe asthma-like syndrome with elevated eosinophilia

finding MF in blood smears

detection of circ adult antigens

DEC works on both adults and MF

Ivermectin on adults

combo of two is most effective

vector control is difficult

mosquitoes develop resistance to insecticides

urbanization has brought ppl and mosquitoes closer

Onchocerca volvulus

causes:

vector:

can lead to _____

River Blindness

Simulium spp (black fly)

skin pathology and eye pathology lead to blindness

Onchocerca volvulus

distribution:

niche:

morphology:

Africa, S and C America

subcutaneous tissues of skin and eye

filaria nematodes similar to W. bancrofti and Brugia

Simulium vector

reproduces where?

before Ivermectin, Africans...

in certain regions over __% were affected and blind

near fast water like rivers and streams

could not live along rivers in certain regions

50%

Life Cycle of Onchocerca volvulus

Adults in ___ in skin

MF produced and migrate out into _____

must wait in this area because...

vector bites

larvae penetrate ___

molt 2xs to ___

nodules

subcutaneous tissues

simulium spp cannot bite deeply

to gut epithelium

J3

Life Cycle of Onchocerca volvulus II

J3 migrates to ___

J3 escape onto skin into ___

invade ____ of host

molt 2x to ___

adults begin to reproduce

proboscis (mouthparts)

bite wound

subcutaneous tissues

adult

Pathogenesis of Onchocerca volvulus

lesions primarily involve ___ and ___

result from host mediated response to ___

dependent upon 2 things:

skin and eyes

parasite antigens

1. intensity of infection

2. degree of host responsiveness to dying adults or MF**(dead MF also produce intense inflamm)

Clinical Disease of Onchocerca volvulus

3 Types

1. skin dermatitis

2. onchocercoma formation in skin

3. eye lesions

Onchodermatitis (skin dermatitis)

intense itching

rash consisting of numerous elevated and itchy papules

skin becomes edamatous (lichinificaiton)

nodule formation around adults

antigenicity of worm products 

induces formation of fibrous nodule with blood vessels around it

all parts of eye become affected in chronic infections

conjunctivitis, keratitis, photophobia, secondary glaucoma, iritis

sclerosing keratitis (scarring and hardening of cornea) causes blindness

Dx of Onchocerca volvulus

biopsy of nodes

skin biopsy

Mazotti Test: NOT RECOMMENDED

if MF present, drug kills them and intense itching resp occurs

if heavy infection, increase onset of blindness

1. Treat with Ivermectin

kills MF but not adults; inhibits release of MF from females

2. excision of nodules esp in head and neck

Loa loa

causes:

often called:

vector:

distribution:

loasis

eye worm

Crysops (deer fly)

West Africa and Sudan

Loa loa

Life Cycle

MF ingested

develop to __ and molt 2x to __

J3 out of mouth parts into ___

J3 molts to __ but occurs later...

J1; J3

subcutaneous tissues

Adults; over extended period of time as larval stages wander through subcutaneous tissues of host

invoke inflammatory resp as they wander

Pathology of Loa loa

(3)

Asymptomatic

Calabar Swelling and Angioedema

Endemic Normals

decreased anti- Loa loa allergic resp

increased MF circ

increased immune resp to worms

increased levels of IgE and increased eosinophilia

secretory antigens of adults and MF that elicit host resp

develop where worms are located but decrease when worms move on in tissues so they are transient swellings

non-erythematous angioedematous swellings (non-red swelling around blood vessels)

MF in blood smears

adults in subcutaneous tissues

visited west or central Africa??

Rx of Loa loa

DEC - gets both MF and adults

must build up dose to prevent massive inflamm resp to dead/dying worms

Dirofilaria immitis

common name?

vector:

niche:

dog heartworm

mosquito

right side of heart and pulmonary artery

Life Cycle of Dirofilaria immitis

__ infect mosquito

develop to __ and molts 2x to __

J3 enters __ and gets into bite wound

migrate to bloodstream

molts and matures in ___

female produces ___

Microfilaria

J1;J3

mouth parts

right heart and pulmonary arteries

MF which circulate and are picked up by mosquito

soft cough and exercise intolerance

cardiopulmonary failure that can cause death

MF in blood

**must distinguish between Dirofilaria and Dipetalonema which is nonpath in dogs

ELISA to detect adult worm antigens

Dracunculus medensis

common names

Distribution:

vector:

general pathology:

fiery serpent; guinea worm

Middle East, Africa -- only 5 countries now have it

copepod (cyclops spp. etc)

disfigures skin and subcutaneous tissues and site for 2ndary bacterial infection

Dracunculus medensis

one of the largest worms

transmission to humans:

females induce __ around her vulva

contact with fresh water causes

swallowing water containing infected copepods

(this is the only helminth transmissted solely by drinking water)

ulcerated lesion in skin 

uterine prolapse and release of larvae into water

Dx of Dracunculus medensis

extraction by winding worm on a stick over time

apply cold water to induce worm to extrude out

removal of worm must be done cautiously because it could cause severe allergic resp, even anaphylaxis

Macracanthorhynchus hirudinaceus

int host? what does it eat?

def host? what does it eat?

Beetle

eats eggs with embryo called acanthor

acanthor develops into acanthella and then into cystacanth (inf for def)

Pig

pig eats cystacanth