Eukaryotic Parasites

An Illustrated Guide to Parsitic Life Cycles

to Accompany Lecture

By Noel Ways

Cysts

Trophozoites

FomitesFoodFecesWater

Fecal / OralRoute

Giardia lamblia Life Cycle

Page 2

LargeIntestine

Stomach

Small Intestines

Excystment inSmall Intestine

Reservoir: Beavers stronglyimplicated. Also, many other wild

animals as well as domestic animals

Excystment inSmall Intestine

Disseminated infection results in organ

lesions /peritonitis and death

Encystment inLarge intestine

Note: bloodinvasion is

rare

Amoebiasis Life Cycle Entamoeba histolytica (invasive) Entamoeba dispar (non-invasive)

Cysts

Trophozoites(in Small Intestine)

FomitesFoodFecesWater

Fecal / OralRoute

LargeIntestine

Stomach

Ulcerations

BLOOD

Trophozoite Migration

FomitesFoodFecesWater

Balantidium coli Life Cycle

Excystment inSmall IntestineEncystment

in large intestine

Both trophozoitesand cysts found

in stools

Page 4

Cysts

Trophozoites

Swine

Swine

Reservoir consists mainly of swine, but also humans, rats and others. Transmission is fecal / oral route.

Fecal / OralRoute

LargeIntestine

Stomach

Small Intestines

Trophozoites INVADE mucosa and may cause ulceration ( ). Rarely, invasion occurs resulting in peritonitis.

Trophozoite Migration

Embr

yona

ted

Eggs

hat

ch.

Mira

cidi

a de

velo

pan

d se

ek o

utsp

ecie

s spe

cific

snai

l.

Mira

cidi

a pe

netra

tesp

ecie

s spe

cific

snai

l. F

orm

s Red

ia

Cerc

aria

seek

out c

rayf

ish

or c

rabs

.

Cer

caria

pe

netra

tean

d en

cyst

form

ing

Met

acer

caria

with

in ti

ssue

.

Red

ia

Cer

caria

Para

goni

mus

wes

term

ani L

ife C

ycle

Page

5

Man

eat

s und

er-

cook

ed c

rust

acea

ns

and

met

acec

aria

e de

-ve

lop

into

fluk

es

whi

ch m

igra

te to

lung

s an

d ot

her o

rgan

s. In

lu

ngs,

eggs

pro

duce

d ar

e co

ughe

d up

and

sw

allo

wed

, the

reby

le

avin

g vi

a fe

ces.

Refe

renc

es:

Para

sito

logy

by

Nob

le a

nd N

oble

Mic

robi

olog

y by

Tort

ora

Red

ia a

sexu

ally

repo

rduc

e.

With

in re

diae

, cer

caria

are

pr

oduc

ed.

Not

e ta

ils.

Cer

caria

will

bor

e ou

t and

leav

e sn

ail.

Gravid proglotids pass in fecesof man

Page 6

Eggs freed from gravid proglotids

Embryo liberated

Larvae travels via blood stream to skeletal muscle

Larvae encysts in skeletal muscle

UndercookedBeef

Head Evaginates and hooks into small intestine of man

Tapewormdevelops

Taeniarhynchus saginatus Life Cycle

Cows, Buffalo, etc.

Gravid proglotids pass in fecesof man

Eggs freed from gravid proglotids

Embryo liberated

Cysticerosis when embryos injested by man. Cysticerci develop in brain, liver, muscles, and heart of man.

Larvae travels via blood stream to skeletal muscle

Larvae encysts in skeletal muscle

UndercookedPork

Head Evaginates and hooks into small intestine of man

Swine

Tapewormdevelops

Taenia solium Life Cycle

Page 7

Sylv

atic

Cyc

leW

ild M

amm

als

of “a

ll” ty

pes

Ster

ilize

dSc

raps

Ster

ilize

dSc

raps

Dom

estic

Cyc

leFo

od In

dust

ry

B I O H Y G E N E

B I O S E C U R I T Y

Sylv

atic

and

Dom

estic

Life

Cyc

les

Sylv

atic

: “o

f the

fore

st”.

If s

omet

hing

is re

ferr

ed to

as s

ylva

tic, t

hen

it oc

curs

in th

e w

ild.

The

oppo

site

of s

ylva

tic is

dom

estic

. In

dis

cuss

ions

re

gard

ing

para

site

s, sy

lvat

ic c

ycle

s ofte

n re

fer t

o th

e m

aint

enan

ce a

nd

rela

tions

hips

bet

wee

n a

para

site

and

it’s

hos

t(s) i

n na

ture

thro

ugh

time.

H

owev

er, t

here

are

man

y in

stan

ces w

here

a p

aras

ite th

at is

mai

ntai

ned

in n

atur

e “

slip

s” in

to o

ur d

omes

tic a

ffairs

/ co

ncer

ns.

In th

e ca

se o

f Tri

chin

ella

sp

iral

is, t

he p

aras

ite is

aliv

e an

d w

ell a

ll ar

ound

us i

n ra

ccoo

ns, r

ats,

lynx

, opo

s-su

ms,

beav

ers,

etc.

etc

. (th

e lis

t is h

uge)

. A

nd, 1

00 y

ears

ag

o, tr

ichi

nosi

s was

a m

ajor

he

alth

issu

e w

ith a

bout

20

% o

f the

Am

eric

an

popu

latio

n ha

rbor

ing

cyst

s by

old

age.

M

igra

tion

from

the

sylv

atic

com

mun

ity

into

the

dom

estic

co

mm

unity

was

st

raig

ht fo

rwar

d.

Bios

ecur

ity a

nd B

iohy

gien

e pr

actic

es re

gard

ing

tric

hino

sis:

• Co

ok m

eat t

horo

ughl

y (fo

llow

dire

ctio

ns)

• Cl

ean

cook

ing

uten

sils

thor

ough

ly•

By la

w, p

oten

tially

infe

cted

food

scr

aps

mus

t be

ster

ilize

d•

Prev

ent v

erm

in c

onta

ct w

ith li

vest

ock

• Pr

ovid

e “c

lean

” liv

ing

cond

ition

s fo

r liv

esto

ck

Raw

Scr

aps

Dom

estic

Cyc

leFo

od In

dust

ryRa

w S

crap

sCa

rniv

orou

sCa

rniv

orou

s

Sylv

atic

Cyc

leW

ild M

amm

als

of “a

ll” ty

pes

Carn

ivor

ous

Carn

ivor

ous

Ade

quat

ely

Coo

ked

Und

erco

oked

B I O H Y G E N E

B I O S E C U R I T Y

Fede

ral B

iose

curit

y an

d hy

gien

e gu

ide-

lines

as w

ell a

s ge

nera

l pub

lic

awar

enes

s of t

he

exis

tenc

e of

this

di

seas

e, h

as re

sulte

d in

a h

uge

decr

ease

in

inci

dent

rate

. M

ost c

ases

in th

e U

S no

w c

ome

from

hu

nter

s who

im

prop

erly

pre

pare

th

eir w

ild m

eats

.Pa

ge 8

Trichinella spiralis Life Cycle

Page 9

Larvae migratethrough blood venoussystem to body tissues,particularly skeletal muscle

Larvae burrow intobody organs and skeletal muscle tissue

Larvae encyst inskeletal muscle

Larvae developinto adults in Small Intestine

Blood Vessel

UndercookedPork

Larvae encyst inorgans / muscles

of man

Flesh eatenby animals

Undercooked Meat eaten by man

Larvae excyst in small

intestine

Adults mate. Female burrows into mucosa and

deposits ~1,500 larvae. Reference:Parasitology

by Noble and Noble

ScrapsScraps

CarnivorousCarnivorousSylvatic Cycle

Wild Mammalsof “all” types

Domestic CycleFood Industry

2

9

3

4

5

1

10

11

6

7

12

13

14 8

12. Larvae are now reflexively swal-lowed.

13. Pass through stomach.

14. Enter small intestine and develop into adults.

Cycle now repeats: (start back at 1).

5. Fecally contaminated food with embryonated eggs ( ) injested

6. Embryonated eggs swallowed

7. Pass through stomach and enter small intestine

Fertilized Eggs

Fertilized EggEmbryonated Egg

Development

Larvae in Egg

8. Larvae ( ) hatch and bore through intestinal mucosa.

9. Enter hepatic portal system and migrate to liver, then right heart and then lungs.

10. Larvae enter alveoli. Patient may experience severe “ascaris pneumonitis at this time.

11. Tracheal Migration. Larvae migrate up respiratory tree to pharynx.

Ascaris lumbricoidesLife Cycle

References:CDC (http://www.dpd.cdc.gov/dpdx/html/Ascariasis.htm)An Illustrated Laboratory Text in Zoology by Boolootian and Heyneman c 1991

1. Sexual Reproduction results in copious egg ( ) production (~200,000 / day)

2. Fertilized eggs passed in feces

3. Embryo develops within egg case

4 Development continues, larvae

form.

Page 10