Parasites Vocabulary Medical parasitology: - PowerPoint Presentation

Slide1

Parasites

Slide2

Vocabulary

Medical parasitology:

“the study and medical implications of parasites that infect humans”

Eukaryote:

a cell with a well-defined chromosome in a membrane-bound nucleus. All parasitic organisms are eukaryotes

A

parasite:

“a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”. Parasites may be simple unicellular protozoa or complex multicellular

metazoan

Protozoa:

unicellular

organisms

Metazoa

:

multicellular

organisms

An

endoparasite

:

“a parasite that lives within another living organism”

Slide3

Vocabulary

An

ectoparasite

:

“a parasite that lives on the external surface of another living organism” –

Definitive

host:

“the organism in which the adult or sexually mature stage of the parasite lives”

Intermediate host:

“the organism in which the parasite lives during a period of its development only”

Zoonosis:

“a parasitic disease in which an animal is normally the host - but which also infects man”

Vector:

“a living carrier (e.g.an arthropod) that transports a pathogenic organism from an infected to a non-infected

host

Slide4

Epidemiology

Several

diseases falling it this field only occur in the tropics, but many parasite disease are/were very common in temperate climates

Overall there is a much stronger association with the level

of:

housing

, nutrition, sanitation and general public health than

climate

Parasitic

diseases are in their majority the diseases of the poor around the

globe

Poverty

is a major risk factor for disease – but disease is also a major contributor to poverty.

Slide5

Parasites

There are three main classes of parasites that can cause disease in humans:

Protozoa

Helminths

Ectoparasites

Slide6

Protozoa

Protozoa are

microscopic

One-celled

organisms that can be free-living or parasitic in

nature

They

are able to multiply in

humans

contributes

to their survival

Transmission of protozoa that live in a human intestine to another human typically occurs through a fecal-oral route Protozoa in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly).

Slide7

Helminths

Helminths

are large, multicellular organisms that are generally visible to the naked eye in their adult

stages

Can

be either free-living or parasitic in

nature

In

their adult form,

helminths

cannot multiply in

humans

There are three main groups of helminths that are human parasites:Flatworms, Thorny headed worms, roundworms

Slide8

Ectoparasites

This

term is generally used more narrowly to refer to organisms such

as:

ticks

, fleas, lice, and mites that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to months)

Slide9

Life cycle of parasites

Slide10

Protozoa

Slide11

Giardia

Microscopic parasite

Protozoal

flagellate parasite

Single-celled, bi-nucleated intestinal parasite

Has

trophozoite

and cyst phases

Causes diarrheal illness- Giardiasis

Also know as

Giardia

intestinalis

Giardia lamblia orGiardia duodenalis

Slide12

Giardia

Found on surfaces or soil, food, or water that has been contaminated with feces (poop) from infected humans or animals

Protected

by an outer shell that allows it to survive outside the body for

long periods

of time and makes it

tolerant

to

chlorine disinfection

.

Slide13

Transmission

Infected

with

Giardia occurs

by swallowing

Giardia

cysts (hard shells containing

Giardia

) found in contaminated food or

water

swallowing as few as 10 cysts might cause someone to become

ill (1,2)Fecal-oral transfer of cysts person-to-personAnimal- to- person transmission

Often transmitted by asymptomatic carriers

1

.CDC. Giardiasis surveillance - United States, 2006-2008. MMWR

Morb

Mortal

Wkly

Rep. 2010;59(SS06):15-25.

2. 6.Rendtorff RC. The experimental transmission of human intestinal protozoan parasites. II. Giardia

lamblia

cysts given in capsules. [PDF - 12 pages] Am J

Hyg

. 1954;59(2):209-20.

Slide14

Trophozoite

Colonizes in the intestines of mammals

Definiteve

host- Human intestine

Duodenum and Jejunum

Cyst

Contaminated material

Definiteve

host- Human colon

Sigmoid colon

Slide15

Giardia

Risks

Traveling to countries where it is common

People in child care settings

Close contact with someone with disease

People who swallow contaminated drinking water

Backpackers or campers who drink untreated water from lakes or rivers

People who have contact with animals who have the disease

Prevention

Good hygiene

Washing hands

In child care settings- children with diarrhea should be removed from setting until diarrhea has stopped

In pools- if you have diarrhea do not go swimming, shower before entering water

Do not swallow water while swimming in pools, hot tubs, interactive fountains, lakes, rivers, springs, ponds, streams or the ocean.

Slide16

Chlorine Disinfection Timetable

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Giardia

Incubation period 1-2 weeks

Onset is gradual

Signs

and symptoms may vary and can last for 1 to 2 weeks or

longer

[2,3]

In

some cases, people infected with

Giardia

have no

symptoms

[2-4]Acute SymptomsDiarrhea, Gas, Greasy stools that tend to float, Stomach or abdominal cramps, nausea, vomiting, dehydration

Sometimes, the symptoms of

giardiasis

might seem to resolve, only to come back again after several days or weeks.

2.Robertson LJ,

Hanevik

K, Escobedo AA,

Morch

K,

Langeland

N. Giardiasis--why do the symptoms sometimes never stop? Trends

Parasitol

. 2010;26(2):75-82.

3. 5.Escobedo AA,

Cimerman

S. Giardiasis: a pharmacotherapy review. Expert

Opin

Pharmacother

. 2007;8(12):1885-1902.

4. 4.Gardner TB, Hill DR. Treatment of giardiasis.

Clin

Microbiol

Rev. 2001;14(1):114-28.

Slide18

Giardia

Diagnosis

Because

Giardia

cysts can be excreted intermittently, multiple stool collections (i.e., three stool specimens collected on separate days) increase test

sensitivity

(1)

Water-like feces

Trophozoite

Formed feces

Cysts

Treatment

Several drugs can be used to treat infection

Effective treatments include metronidazole,

tinidazole

, and

nitazoxanide

(2)

Combination therapy may be effective

1.Clinical and Laboratory Standards Institute. Procedures for the recovery and identification of parasites from the intestinal tract; approved guideline. [PDF - 7 pages] CLSI document M28-A2. 2nd ed. Wayne, PA: Clinical Laboratory Standards Institute; 2005.

Drugs for Parasitic Infections

: The Medical Letter; 2010

Slide19

Entamoeba

hystolytica

Protozoal

infection

Causes:

Amebiasis

Morphology

Trophozoite

Cysts- Killed by desiccation or boiling

Entamoeba

spp: Infects ~ 10 % of world’s population

Geographic distribution is

worldwide

Found where sanitation is poor

High incidence in developing countries

In the U.S ~ 4

%

Hosts are humans, cats, dogs, and rats

Slide20

Transmission

Fecal-oral-route

Ingestion

of food & water contaminated with feces

Putting

anything into

one’s mouth

that has touched the feces (poop) of a person who is infected with

E.

histolytica

.

Swallow

E. histolytica cysts (eggs) picked up from contaminated surfaces or fingers.

Slide21

Excystation

:

happens in the small intestine

This leads to a

trophozoites

Can cause liver

absess

, amoebic colitis

Asymptomatic colonization

Encystation:

happens in the colon

Gets excreted in feces

Slide22

Slide23

Entamoeba

Hystolitica

Risks

Anyone can get it, but most common in people who live in tropical regions with poor sanitation

In the U.S.

People who have traveled to tropical places that have poor sanitary

conditions

Immigrants from tropical countries that have poor

sanitary

conditions

People who live in institutions that have poor sanitary conditions

Prevention

Handwashing

(soap & clean water)

Boiling water used for drinking & food preparation (10-15 minutes)

When traveling

Drink only bottled or boiled

water

Don’t drink juices, fountain drinks or any drinks with ice

cubes

Don’t drink fresh fruit or

vegetables not

personally

prepared

Avoid street foods and drinks if possible

Slide24

Clinical Symptoms

Incubation period: 2-4 weeks

Only

about 10% to 20% of people who are infected with

E.

histolytica

become sick from the

infection

Acute symptoms- sudden high fever, chills, abdominal cramping, bloody stool

Chronic symptoms- 1-4 years with periodic symptoms same as acute

Complications may lead to more serious illness including abscess of the liver

Slide25

Slide26

Diagnosis and treatment

Diagnosis

Diagnosis

can

be very

difficult

Other

parasites and cells can look very similar to

E.

histolytica

when seen under a

microscope

Your health care provider will ask you to submit fecal

samples

E

.

histolytica

is not always found in every stool sample, you may be asked to submit several stool samples from several different days.

Treatment

Several diff. medications depending on severity and nature of disease

Asymptomatic- Meds of choice are

iodoquinol

and

paromomyosin

Symptomatic- Mild, moderate, severe- metronidazole,

tinidazole

Slide27

Toxoplasma gondii

Protozoan parasite

Causes Toxoplasmosis

Toxoplasmosis is considered to be a leading cause of death attributed to foodborne illness in the United States

> 60 million men, women, and children in the U.S. carry the

Toxoplasma

parasite

very few have symptoms because the immune system usually keeps the parasite from causing illness.

Slide28

Toxoplasmosis

In various places throughout the world, it has been shown that up to 95% of some populations have been infected with

Toxoplasma

.

In

, women newly infected with

Toxoplasma

during pregnancy and anyone with a compromised immune system should be aware that toxoplasmosis can have severe consequences.

Slide29

Toxoplasmosis-Transmission

Not passed from person-to-person

Except in mother-to-child, blood transfusion, organ transplantation

People typically become infected by three principal routes of transmission.

Foodborne

Animal-to-human (zoonotic)

Mother-to-child (congenital)

Rare instances

Slide30

Foodborne Transmission

Tissue form of parasite (microscopic cyst) can be transmitted to humans by food

By eating undercooked, contaminated food (pork, lamb, and venison)

Accidental ingestion of undercooked, contaminated meat after handling it and not washing hands thoroughly

Slide31

Animal-to-human

Cats play an important role in spreading toxoplasmosis

They become infected by eating infected birds, or rodents, or other small animals

The parasite is then passed in the cat's feces in an

oocyst

form

Kittens and cats can shed millions of

oocysts

in their feces for as long as 3 weeks after infection.

Slide32

Animal-to human

People can accidentally swallow the

oocyst

form of the parasite. People can be infected by

:

Accidental ingestion of

oocysts

after:

cleaning

a cat's litter box when the cat has shed

Toxoplasma

in its feces touching or ingesting anything that has come into contact with a cat's feces that contain Toxoplasma

Accidental ingestion of

oocysts

in contaminated soil (e.g., not washing hands after gardening or eating unwashed fruits or vegetables from a garden)

Drinking water contaminated with the

Toxoplasma

parasite

Slide33

Mother-to-child

Generally if a woman has been infected before becoming pregnant, the unborn child will be protected because the mother has developed

immunity.

If woman becomes infected while pregnant may

not have symptoms, but there can be severe consequences for the unborn

child such as:

diseases

of the nervous

system (mental disability, seizures)

Potential visual loss

Slide34

Slide35

Symptoms

V

ery

few have symptoms because a healthy person's immune system usually keeps the parasite from causing

illness

If acquired in first trimester of pregnancy:

Often results in stillbirth

Many problems may arise

Ex: hydrocephalus

Acute:

Similar to those for mononucleosis

Immunodeficient

patients may have generalized infection with encephalitis, fever, headache, vomiting, delirium, convulsions, and rash

Slide36

Diagnosis

Diagnosis typically made by serologic testing

Test that measures

IgG

For time of infection: measures of

IgM

Less frequent techniques used:

Direct

observation of the parasite in stained tissue sections, cerebrospinal fluid (CSF), or other biopsy material.

Slide37

Treatment

Healthy people (

nonpregnant

)

Most recover w/o treatment

Persons who become ill may be treated w/ combination of drugs such as

pyrimethamine

and sulfadiazine, plus folic acid

Pregnant women, newborns, infants

Can be treated although parasite not completely eliminated

The parasites can remain within tissue cells in a less active phase

Slide38

Treatment

Persons with ocular disease

Sometimes prescribed meds to treat active disease by ophthalmologist

Whether or not medication is recommended depends on the size of the eye lesion, the location, and the characteristics of the lesion (acute active, versus chronic not progressing)

Immunocompromised

Need to be treated until they show improvement in their condition

Slide39

Prevention

Reduce risk from food

Cook food to safe temps

Do not sample meat until well cooked

For Whole Cuts of Meat (excluding poultry

)

Cook

to at least 145° F (63° C) as measured with a food thermometer placed in the thickest part of the

meat. Allow

the meat to rest* for three minutes before carving or consuming

.

For Ground Meat (excluding poultry)

Cook to at least 160° F (71° C); ground meats do not require a rest* time.

For All Poultry (whole cuts and ground)

Cook to at least 165° F (74° C), and for whole poultry allow the meat to rest* for three minutes before carving or consuming.

Slide40

Prevention

Reduce risk from environment

Avoid drinking untreated water

Wear gloves when in contact with soil as it may contain cat feces

Wash hands with soap and warm water

Keep outdoor sandboxes covered

Feed cats only canned or dried commercial food or well-cooked table food, not raw or undercooked meats

.

Slide41

Prevention

Change the litter box daily if you own a

cat.

The

Toxoplasma

parasite does not become infectious until 1 to 5 days after it is shed in a cat's feces.

If

you are

pregnant or

immunocompromised

:

Avoid changing cat litter if possible. If no one else can perform the task, wear disposable gloves and wash your hands with soap and warm water

afterwardsKeep cats

indoors

Do not adopt or handle stray cats, especially

kittens

Do

not get a new cat while you are pregnant.