HELMINTH PARASITES & Arthropod Vectors

helminths

-term for all parasitic worms

-carried or transmitted in microscopic forms

helminths

-includes nematodes, cestodes, trematodes

monoecious

(hermaphroditic) male and female reproductive systems in one animal

-cestodes (tapeworms)

dioecius

separate male and female worms

-nematodes (roundworms)

nematodes

non-segmented roundworms

cestodes

class of tapeworms

trematodes

class of flukes

cestodes

long segmented flatworms

trematodes

short non-segmented flatworms

Platyhelminthes

phylum of flatworms - cestodes & trematodes

reproductive

most well developed system in helminth parasites

host

where helminth parasites get their nutrients & protection from the environment

definitive host

an organism in which sexual reproduction and the adult/mature form of a parasite occurs

intermediate host

organism in which asexual reproduction or an immature form of a parasite occurs

accidental or dead-end host

a host that can become infected with a parasite that completes its lifecycle in another host.

-can develop disease

-but cannot usually transmit the infection

dogs and cats

definitive host of Toxocariasis

-humans ingest eggs & become accidental hosts

-cause visceral & ocular larva migrans

prevention of cutaneous larva migrans/creeping eruption

avoid becoming an accidental host by wearing shoes

human is accidental host

1. swimmer's itch - larval flukes

2. toxocariasis - visceral & ocular larva migrans

3. creeping eruption

methods of transmission

1. fecal-oral route - ingestion of eggs

2. burrow through skin

3. consuming undercooked meat

4. insect bites of arthropod vectors

transmission by fecal-oral route

1. ascaris

2. pinworm

3. cysticercosis

transmission by larva burrow through skin

creeping erruption

hookworm

schistosomiasis - blood fluke

transmission by insect bites

river blindness - onchocerciasis

elephantiasis - lymphatic filariasis

class of helminths without a digestive system

cestodes - tapeworms

scolex

head of an adult tapeworm

contain suckers or hooks

proglottids

segments of tapeworms

contain male & female structures

proglottids

shed in feces of one infected by a tapeworm

contains eggs

scolex

part of tapeworm that attaches to intestine of host

transmission by eating undercooked meat

tapeworms &

trichinosis

Taenia saginata

causative agent beef tapeworm

Taenia solium

causative agent pork tapeworm

cysticerus

-a.k.a. a bladder worm -

-a larval tapeworm in which the scolex is inverted in a sac

-usually in skeletal muscle/meat of host

location of a cysticerus

typically found encysted in the muscle tissue of the host

cysticercosis

general term for disease where tapeworm LARVAE encyst in tissues

-striated muscle, brain and eyes

cysticercosis

-disease caused by ingesting pork tapeworm EGGS -

-from autoinfection or person to person

-only tapeworm disease NOT by eating undercooked meat

-term not specific to location

neurocysticercosis

-disease tapeworm larvae develop cysts in the brain

-cause headache, seizures and can cause death

neurocysticercosis

#1 parasitic disease of the CNS central nervous system

dioecious - split body

schistosomes/blood flukes body plan

intermediate host of schistosomes/blood flukes

snails

definitive host of schistomes/blood flukes

human or other vertebrate

liver & bladder

main organs affected by schistomiasis

increased worm load

increased severity of symptoms & failure to thrive in children

Schistosoma

Genus of blood flukes

ascariasis

-#1 worldwide helminth parsitic infection

-WHO treats entire villages at a time

Ascaris lumbricoides

roundworm that causes ascariasis

ascaris life cycle

-eggs transfered by fecal-oral route to stomach & intestines

-carried by blood to lungs

-coughed up and swallowed

-eggs passed in feces

only involve humans as host

ascariasis and pinworm

global locations high in helminth disease

-Africa

-Central & South America

-Asia

water treatment, sanitation & FDA

why MOST (not all) parasitic infections in U.S. originate from other countries

ascariasis & hookworm

infections where worms enter lungs and are coughed up to live in the intestine

pinworm

-#1 parasitic infection in the U.S.

-mostly in children & institutionalized individuals

Enterobius vermicularis

roundworm that causes pinworm

pinworm

-nightly intense anal itching

-female comes out at night from large intestine to lay eggs

pinworm

-roundworm disease

-transmission by fecal-oral route, fomites & inhalation

-highly contagious

trichinosis

only roundworm disease transmitted by eating undercooked or raw meat

- pig or bear

-consumption of cysts

Trichinella spiralis

-the roundworm that causes trichinosis

prevent spread of trichinosis

why most commercial pork is frozen & you should fully cook meat

Wuchereria bancrofti

roundworm that causes filariais a.k.a. elephatiasis

mosquito

-vector of elephatiasis/filariasis

-transmits microfilariae (immature form)

filariasis (elephantiasis)

disease: tropical parasitic roundworms invade the lymph nodes and block them causing lymphedema (swelling)

lower extremities & genitals

where lymphedema usually occur in filariasis/elephantiasis

Onchocerca volvulus

roundworm that causes river blindness

black fly

vector of river blindness

Onchocerca volvulus

causative agent of 2nd leading cause of infectious blindness

limited vector range

reason some helminth parasites are endemic to particular regions

mosquito

vector for malaria, filariasis/elephantiasis

West Nile virus, yellow fever & Dengue fever

tsetse fly

vector of African sleeping sickness

Trypanosoma bruceii

flea

vector for plague

Yersinia pestis

tick

vector for Lyme disease

control of arthropod vector spread diseases

-eliminate the vector

-protection from bites - clothing & netting

eosinophilia (high)

-hallmark of a helminth infection

-helps in diagnosis

creeping eruption

cutaneous larva migrans

-accidental host disease

Diphylobothrium latum

-fish tapeworm

-transmission by eating undercooked or raw fish

fish

type of meat ingested to transmit the largest tapeworm in humans (up to 30 ft)

type of tapeworm to cause pernicious anemia

fish tapeworm

#1 cause of seizures worldwide

cysticercosis

Neglected parasitic infections

Chagas disease

Cysticercosis

Toxocariasis

Toxoplasmosis

Trichomoniasis

O&P test

-stands for ova and parasites

-most common diagnostic for parasites.

O&P test

microscopic examination of feces sample looking for parasites or eggs

visceral toxocariasis

dog or cat roundworm infection of organs - particularly the liver

ocular toxocariasis

dog or cat roundworm infection of the eye - can cause visual disturbances & blindness

hookworm

caused by roundworm Ancylostoma duodenale and Necatur americanus

Necatur americanus (hookworm)

anemia inducing roundworm & reason for the "Lazy Southerner" stereotype

visceral, occular and cutaneous

types of toxocariasis

stay out of endemic waters

how to avoid schistosomiasis

Wear shoes

how to avoid hookworm & creeping erruption