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340 Cards in this Set

  • Front
  • Back
Sexes of intestinal nematodes
Dioecious (seperate)

The nematodes vary in size from:

a few mm to over a meter in lenth.
Another name for intestinal nematodes
Roundworms.
Posterior end of male
Curved or coiled with copilatory spicules.

Adults have what in buccal cavity?
Oral hooks, teeth, or plates.

Hooks, teeth, and plates are used for what?

attachment

Small body projections are called:

setae or papillae.

Function of setae/papillae:

thought to be sensory in nature.

Exterior layer of roundworm
Cuticle
What does the cuticle lie over?
Muscle layers.
Internal organ systems of roundworms
Nerve cord, a well developed digestive system, and complete reproductive organs that are proportionally large and complex.
Digestive system of roundworm
Buccal cavity, esophagus, gut, and anus.
Reproductive organs of male roundworm
Testes, vas deferen, seminal vehicle, and an ejaculatory duct.
Reproductive organs or female roundworm
Ovaries, oviduct, seminal receptacle, uterus, and vagina.
How many offspring can female roundworm produce?
Several hundred up to millions depending on species.
Definitive host for roundworms
Humans
Mode of transmission for roundworms
Ingestion of infective stage egg or larva, larval penetration through skin, or transmission of larvae by bite of an insect.
Another name for ascaris lumbricoides
The large intestinal roundworm.
Most common human worm infection
Ascaris lumbricoides.
Largest nematode parasitizing the human intestine
Ascaris lumbricoides.
Second most on intestinal helminth infection in US.
Ascaris lumbricoides.
Most common intestinal worm worldwide
Ascaris lumbricoides.
Most common intestinal helminth in US
Enterobius vermicularis or pinworms.
What % of population is infected with ascaris lumbricoides?
25.

Ascaris lumbricoides is occurs mostly where in the US?

rural areas in SE United States.

Where does the adult ascaris worm live?
Small intestines

Eggs of Ascaris lumbricoides are passed in:

feces
When do adult ascaris worms mature?
2-3 months.
What protects ascaris larvae?
Bumpy coat.
How can ascaris effect growth?
Stunts grwoth, but usually cause no acute symptoms.
What can cause abdominal pain and intestinal obstruction? (Ascaris)
High worm burdens.
What can migrating adult ascaris worms cause?
Symptomatic occlusion of biliary tract or oral expulsion.
What happens during the lung phase of larval migration? (Ascaris)
Pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis)

Loeffler's sydnrome is:

eosinophilic pneumonitis

When in the lungs, Ascaris breaks out of:

capillaries
How long does it take adult ascaris worms to mature?
2-3 months.
Most common method of diagnosis for ascaris.
Microscopic identification of eggs in stool.
What is the migratory activity of ascaris worms?
Active migraters.
Which worm is sensitive to anesthesia?
Ascaris.

For diagnosing Ascariasis, fix specimen with:

10% formalin

Concentrate stool specimen using:

the formalin-ethyl acetate sedimentation technique

Examine:

a wet mount of the sediment

Where concentration procedures are not available:

a direct wet mount of the examination is adequate

A direct wet mount is only adequate if:

there is a moderate to heavy infection

For quantatative assessments, methods like _____________ can be used.

Kato-Katz

Ascaris larvae can be identified in:

sputum or gastric aspirate during the pulmonary migration phase

Examine what for morphology?

formalin-fixed organisms

Adult Ascaris worms are occasionally passed in:

the stool or through the mouth or nose



Adult Ascaris worms are recongnizable by:

their macroscopic characteristics
Which three forms of eggs may be seen in feces? (Ascaris)
Fertilized and covered with albiminoid coat, fertilized without the albiminoid coat, and unfertilized with the albiminoid coat.
Another name for Enterobius vermicularis
Pinworms or seatworms.
What % is infected with pinworms?
10.
Most common worm infection in US.
Pinworms.
What are symptoms of most pinworms associated with?
Migration of the gravid female out of the rectum onto the perianal skin to lay her eggs.
Cardinal symptom of pinworms.
Hypersensitivity reaction causing severe perianal itching.

1/3 of all cases of pinworm infections are:

asymptomatic

What symptoms can occur with enterobius vermicularis?
Teeth grinding (bruxims), insomnia due to disturbed sleep, and abdominal pain or appendicitis.

What infection has been reported with females?

infection of the female genital tract

Which species is the only one to transfer parasite? Enterobius
Humans.
Which species can't get infected with pinworms?
Dogs and cats.
How long can pinworms eggs survive in the indoor environment?
2 to 3 weeks.
What's the incubation of pinworms once someone has ingested pinworms?
1 to 2 months or lines for the adult gravid female to mature in small intestines.
Where does the adult female pinworm migrate once mature?
To the colon and lays eggs around the anus at night when hosts are asleep.
How long can people with pinworms transmit it to others?
For as long as there is a female pinworms depositing eggs on perianal skin.
How can one be re infected with pinworms?
By eggs from another person, or from themselves.
Diagnosis of pinworm
Three techniques:
1. Look for worms in perianal region 2-3 hours after infected person is asleep.
2. Touch perianal skin with transparent tape to collect possible pinworm eggs around anus first thing in the morning. Worms will be visible under microscope. Should be done 3 consecutive mornings before washing. "tape test"
3. Analyzing samples from under fingernails since anal itching is a common symptom and look at it under microscope.
What diagnosis tool isn't recommended for pinworms?
Examining stools because pinworm eggs and works are often sparse in stool. Serological testing is unavailable.
Appearance of pinworm eggs
Flattened on one side.
How many pinworm eggs can a female produce each day?
15,000.

Most pinworm eggs are only infective for how long?

a few days
What is important to breaking the life cycle of pinworms?
Cleaning eggs from environment and testing all persons in the household.

Retro infection is:

reinfection when an egg hatches on the peri-anal area, then crawls back in human host
Medications used to treat pinworms
Mebendazole, pyrantel pamoate, and albendazole.
Dosage of pinworm medication
Given 1 dose at first, then another dose 2 weeks later.
Which pinworm medication is available without a prescription?
Pyrantel pamoate.
Purpose of second dose of pinworm medication
Eliminate possible re infection since the first dose of medication.
How should repeated infections of pinworms should be treated?
Same method as first infection.
If there is numerous infections in one household, when should treatment occur?
At the same time.

In institutions, mass and simultaneous treatment should be repeated after how long?

2 weeks
Another name for ancylostoma duodenale
Old world hookworms.
Another name for necator americanus
New world hookworms.
How many people are estimated to be infected with hookworms worldwide?
576-740 million.
What has greatly improved hookworm infections in US?
Improvements in living conditions, particularly in SE region.

Associated with the "Myth of the lazy southerner"

hookworms
Hookworm, ascaris, and shipworm are known as _______________ helminths.
Soil transmitted.
Which helminths account for major burden of disease worldwide?
Soil transmitted helminths.

Rhabditiform larva of hookworms is________shaped.

club

Where do hookworms live in the body?
Small intestines.
What happens if infected person defecates outside or if infected person's feces are used as fertilizer?
Eggs are deposited in the soil.
What do eggs do once they mature?
Hatch, releasing larvae.
How are hookworm infections mainly acquired?
By walking barefoot on contaminated soil.

Hookworms can go ______ in intestines and mucles.

dormant
How many eggs can female hookworms produce each day?
10,000-25,000 depending on species.
Attachment of hookworms to host's small intestines causes ________.
Bleeding.

Hookworms can cause a __________ in hemoglobin.

decrease
What do hookworms feed on?
Host blood.
Which age group can hookworms be really serious?
Children due to loss of excessive blood.
Difference in adult worms of the hookworms.
Attachment structure in buccal cavity: A. Duodenale has "teeth" and N. Americanus has "plates."
Ground itch is:
a severe allergic reaction at site of skin penetration. Associated with hookworms.
Symptoms of hookworms
Intra alveolar hemorrhages and mild pneumonia with cough, sore throat, and bloody sputum.
Heavy hookworm burden symptoms
Enteritis, pain, iron deficiency anemia, blood loss

Hookworm blood loss can be up to _____ml/day

100
Light hookworm burden symptoms
Slight anemia and nonspecific GI symptoms.
Optimal conditions for getting hookworms.
Moist, warm regions and bare skin contact with soil are optimal conditions for contracting heavy infections in areas of poor sanitation.

Pinworm and hookworms use the same________ for treatment.

drugs
Delayed fecal examination of hookworms can result in?
Eggs hatching and larval development.
Larvae of hookworms could be confused with which larvae and difference.
Strongyloides, hookworms have a longer buccal cavity.
Another name for cutaneous (dermal) larval migrans
Creeping eruption.
What is the cutaneous larval migrans caused by?
Larvae of dog or cat hookworms.
Why do cutaneous larva migrans not enter bloodstream like they would in a dog or cat?
Humans are unnatural host, so they remain in the skin for weeks or sometimes months until they die.
What happens as cutaneous larva migrate through skin?
Inflammatory response and a trail left by larvae as they migrate under skin.

Trails left under skin by Dermal larva migrans are called:

serpinginous trails
How long do cutaneous larvae survive in human host?
5-6 weeks.
Treatment of cutaneous larvae
Usually resolve without treatments, but treatment can be used to control signs/symptoms and help prevent secondary bacterial infections. Anti-parasitic treatments may be prescribed or surgical removal of larvae.
Prevention of cutaneous larva
Keep sandboxes covered, wear shoes to prevent contact with sand and soil, other sources could be flower beds or vegetable gardens, and animal feces need to be picked up often and animals wormed to be kept free of hookworm infections.

Strongyloides stercoralis was first described in:

French troops stationed in modern day Vietnam during the late 19th century who were suffering from severe, persistent diarrhea.

Strongyloides stercoralis is a parasitic disease caused by:
nematodes that enter body through exposed skin.
Symptoms of strongyloides
Most have no symptoms, other can develop severe form and die if untreated.
Where is strongyloides geographically found?
Everywhere except Antarctica. Most common in tropics and warm temperate regions.

It is estimated that how many persons are infected with Strongyloides worldwide?

3-100 million
What is most frequently associated with subclinical infection in patients receiving high dose corticosteroids for treatment of COPD?
Hyper infection syndrome and disseminated strongyloides.
What does subsequent impaired host immunity lead to in strongyloides?
Accelerated autoinfection and an overwhelming number of migrating larvae.
Chronic strongyloides and hyperinfection syndrome:
Larvae are limited to GI tract and lungs whereas disseminated invade multiple organs.
If left untreated, what is the mortality rate of hyperinfection sydrome and disseminated strongyloides:
90%.
Two types of strongyloides worms
Parasitic females and free living males and females

Parastitic females are found in:

the small intestines

Free living males/females live where?

soil
How do female strongyloides worms produce larvae?
Parthogenically (without fertilization) and larvae are passed in host feces.
Diagnosis of strongyloides
Finding larvae in feces.
What happens once strongyloides larvae are passed in feces?
Become parasitic or free living.
Where do free living strongyloides larvae complete development?
In soil and mature into free living males and females.
What do the offspring of free living males and females become?
Free living or parasitic.
Reservoir for human infections of strongyloides.
Free living, soil inhabiting strongyloides.
Why is the strongyloides life cycle most complex?
Alternation between free living and parasitic and potential for autoinfection and multiplication within host.
Free living cycle
The rhabditiform larvae passed in the stool can either molt twice and become infective filariform larvae or molt four times and become free living adult males and females that mate and produce eggs from which rhabditiform larvae hatch.
Direct development or strongyloides
Infective filariform larvae.
Rhabditiform larvae develop into:
New generation of free living adults or into infective filariform larvae.
What penetrates the human host skin to initiate parasitic cycle? (Strongyloides)
Filariform larvae.
Parasitic cycle of strongyloides
Filariform larvae in contaminated soil penetrate the human skin and transported to the lungs where they penetrate the alveolar spaces. Carrier through bronchial tree to pharynx and swallowed, then teach small intestines.
What happens in intestines once parasitic strongyloides reaches intestines?
Molt twice and become female adult worms.
Where do the female parasitic strongyloides live?
Threaded in the epithelium of small intestines.
How do female strongyloides produce eggs?
By parthenogenisis: produce eggs which yield rhabditiform larvae.
What happens once the rhabditiform larvae is produced?
It can be passed in stool or cause autoinfection.
What happens with autoinfection with parasitic cycle?
rhabditiform larvae become infective filariform larvae which can penetrate the intestinal mucosa or the skin of the perineal area
Internal and external autoinfection.
Internal: penetrates the intestinal mucosa.
External: penetrates skin of perianal area.
Result of autoinfection
Can be carried to the lungs, bronchial tree, and small intestines where they mature into adults or may disseminate widely in the body.
Which species does autoinfection occur in?
Strongyloides stercoralis and Capillaria phillippinesis infections.
What does strongyloides autoinfection explain?
Possibility of persistent infections for many years in persons who have not been in endemic area and of hyperinfections in immunodepressed individuals.
Another name for Trichuris trichuris
Whipworms.
3rd most common intestinal helminth.
Trichuris trichuris or whipworms.
Why can children be infected with ascaris and trichuris at the same time?
Similar manners of infection.
Structure of buccal cavity of trichuris.
No teeth or plates, but tiny spear in the oral cavity.
Where do adult trichuris worms live?
Cecum, but also appendix, colon, and rectum.

Female Trichuris can produce up to _______ eggs/day.

10,000
How many people are estimated to be infected with whipworms?
604-795 million.
Heavy infections of whipworms symptoms.
Frequent and painful passage of stool that contains mixture of mucus, water, and blood. Rectal prolapse can occur.
Symptoms of children with heavy whipworm infections.
Severe anemia and growth retarded.
Eggs of Trichuris are:

barrel shaped, and have polar plugs
Another name for Anisakiasis.
Aka herring worm disease.
Anisakiasis
Parasitic disease caused by anisakid worms that can invade the stomach wall or intestine of humans.
Transmission of Anisakiasis
Infective larvae are invested from fish or squid that humans eat raw or undercooked.
Treatment of Anisakiasis
Removal of larvae via endoscopy or surgery.
Onset and symptoms of infected larvae (Anisakiasis)
Within hours; violent abdominal pain, nausea, and vomiting. Occasionally the larvae are coughed up.
What happens if larvae are passed into the bowel? (Anisakiasis)
Severe eosinophilic granulomatous response may occur 1-2 weeks following infection, causing symptoms mimicking Chrohn's disease.
Sensation some people may experience after or while eating raw or undercooked fish or squid and what is it caused from?
Tingling. It's the worm moving in the mouth or throat. Can extract by coughing up.
Where is Anisakiasis most commonly found?
Areas where eating raw fish is popular, such as Japan.

Anyone who eats undercooked or raw fish are:

at risk

Baylisacarasis infection is caused by:

a roundworm found in racoons

This roundworm can infect people as well as a variety of other animals including:

dogs

Human infections are:

rare

Human infections can be severe if:

the parasites invade the eye (ocular larva migrans), organs (visceral larva migrans), or the brain (neural larva migrans)

Baylisacarasis procyonis worms are:

intestinal parasites found in a wide variety of animals.

Baylisacarasis procyonis is found in:

racoons

Baylisacarasis columnaris is found in:

intestines of skunks

Balysacarasis infections are not common but can be:

severe

Balisascaris procynois is thought to be:

the greatest risk to humans because of the often close association of racoons to human dwellings

Baylisascaris procyonis has been identified in the US mostly in:

mid-atlantic, NE, and midwestern states

Eggs passed in racoon feces are not immediately:

infectious

In the environment, eggs may take how long to become infectious?

2-4 weeks

Racoon feces should be:

removed carefully, burned, buried, or sent to a landfill

Care should be take to:

avoid contaminating clothes and hands

Treat decks, patios, and other surfaces with:

boiling water or a flame gun

What reduces infections?

Prompt removal and destruction of racoon feces before eggs become infectious

Appearance of Baylisascaris eggs:

thick shelled and slightly oval in shape

Have a similar morphology to:

fertile eggs of Ascaris lumbricoides (which are smaller)

Definitive host of B. procyonis:

racoons and dogs

Humans are not:

definitive hosts for B. procyonis

Eggs are not considered:

a diagnostic finding and not excreted in human feces

Human infections are hard to:

diganose

Diagnosis is often made by:

exclusion of other causes

Resuslts from CBC and CSF examination would be consistent with:

parasititc infection, but tend to be nonspecific

What can be extremely helpful if a section of larva is contained?

A tissue biopsy (hard find a place where larava are actually present)

Ocular examinations can reveal:

mirgarting larva, larval tracks, or lesions consistent with a nematode larva

What kind of tests are helpful though not commonly used?

Serological tests

Males have:

curved posterior ends

Infected blood/tissue dwelling nematodes are transmitted by:

the bite of an arthropod during a blood meal
The larvae migrate to:

the apporpriate site of the host's body

Migrating larvae develop into:

microfilariae producing adults

Adults dwell in:

various human tissues



Adults can live for:

several years in tissues

The agents of lymphatic filariasis reside in:

lymphatic vessels and lymph nodes

Onchocera volvulus is found in:

nodules in subcutaneous tissues

Loa loa is found in:

subcutaneous tissues where it migrates actively

Brugia malayi is found in:

lymphatics

Wuchereria bancroft is found in:

lymphatics

Mansonella streptocera is found in:

dermis and subcutaneous tissue

Mansonella ozzardi is found in:

subcutaneous tissues

Mansonella perstans is found in:

body cavities and the surrounding tissues

Adult filariae live in:

various human tissues

The fertilized female is:

ovoviviparous (gives birth to live young)

Live young are called:

microfilariae

Microfilariae migrate into:

lymphatics, blood or skin

These parasites require:

an arthropod intermediate host for the transmission of infection

The arthropod ingests:

microfilariae while taking a blood meal

The microfilariae then:

molts twice before becoming the infective stage

These larvae are then released through:

the insect's proboscis to the human definitive host during the arthropod's next blood meal

The female worms produce:

microfilariae

Microfilariae circulate in:

the blood except for those of Onchocera volvulus and Mansonella streptocera which are found in the skin and O. volvulus which invade the eye

Inside the arthropod, the microfilariae develop in how long?

1-2 weeks into infective filariform (3rd stage) larvae

During a subsequent blood meal by the insect, the larvae infect:

the vertebrate host

They migrate to:

appropriate sites of the host's body

Once in appropriate area in the host, the larvae develop into:

adults

Maturation of larvae into adults can take:

up to 18 months

In some species, microfilariae are more prevalent in:

peripheral blood at specific times of day

Microfilariae exhibit:

periodicity (coincide with feeding schedule of arthropod intermediate host) either nocturnal or diurnal

Eight main species infect humans:

Wuchereria bancrofti, Brugia malayi, Onchocera volvulus, Loa loa, Mansonella perstans, Mansonella streptocera, Mansonella ozzardi, and Brugia timori

Causes lymphatic filariasis:

Wuchereria bancrofti, Brugia malayi, and Brugia timori

Causes onchocerciasis:

Onchocera volvulus
Wucheria bancrofti (lymphatic filariasis) is found:

tropical areas

Brugia malayi is found:

in Asia

Brugia timori is found:

islands in Indonesia

Agent of riverblindness:

Onchocera volvulus

Onchocera volvulus is found:

mainly in Africa but also in Latin America and the Middle East

Loa loa and Mansonella streptocera are found:

Africa

Mansonella perstans is found:

in Africa and South America

Mansonella ozzardi is found:

the Americas from Mexico south to South America and the Carribean

Brugia malayi and Brugia timori is spread by:

The mosquito species; Anopheles, Aedes, Culex, and Mansonia

The microfilariae have a ________ periodicity

nocturnal

Adult Brugia live in:

lymphatics

Infection with Brugia can lead to:

elephantiasis

Diagnosis of Brugia is made by finding:

microfilariae in peripheral blood.



Microfilariae of Brugia are:

sheathed and have 2 nuclei at the tip of the tail

Wuchereria bancrofti is spread by:

mosquitoes; Anopheles, Culex, Aedes, and Mansoni

Adult Wuchereria live in:

lymphatics

Microfilariae of Wuchereria are found in:

the blood

Microfilariae of Wuchereria demonstrate a ________ periodicity

nocturnal

Outcome of Wuchereria if left untreated:

elphantiasis

Diagnosis of Wuchereria is made by finding:

microfilariae in periphral blood

Microfilariae of Wuchereria are:

sheathed. They have a gently curved body, and a tail that is tapered to a point.

The nuclear column of Wuchereria is:

loosely packed; the cells do not extend to the tip of the tail

The nuclear column is:

the cells that constitute the body of the microfiaria

Microfilarie of Brugia malayi are:

sheathed. The tail is tapered with a significant gap between the terminal and sub terminal nuclei

Microfilariae of Brugia timori are:

sheathed.

Microfilariae of B. timori and B. malayi differ in that:

B. timori has a longer cephalic space, a sheath that does not stain with Giemsa, and a larger number of single file nuclei towards the tail.

Loa loa is also known as:

the Africa eyeworm

Adults of Loa loa migrate throughout:

subcutaneous tissue

Diagnosis of Loa loa is made by:

finding microfilariae in the blood

Microfilariae of Loa loa are:

sheathed and have a continuous row of posterior nuclei

One of the main symptoms and diagnosis of Loa loa:

Calabar swelling (fugitive swellings)

Calabar swellings are:

localized subcutaneous edema and are thought to be a type of allergic reaction to dead worms or their metabolic byproducts

They can appear:

anywhere on the body, be up to several inches and are often preceded by itching and localized pain
The swellings last how long?

days to weeks and subside slowly

Calabar swellings are named after:

a coastal Nigerian town where they were first seen

Oncherca volvulus is known as:

blinding filaria

Oncherca is found in:

Africa

Oncherca periodicty:

doesn't exhibit any

May cause:

blindness (called river blindness) hanging groin, and leopard skin

Diagnosis of Oncherca is made by finding:

adults excised from nodules or microfilariae found in skin snips

Microfilariae are:

unsheathed and have no nuclei in tail

What has dramatically reduced dracunculiasis?

an eradication campaign

Dracunculiasis is now restricted to:

rural, isolated areas in a narrow belt of African countries

Laboratory confirmation of dracunculus is not needed because:

clinical presentation is so typical and well known to the local population

The disease occurs in areas where what is unlikely available?

confirmation tests

Examination of what is used for diagnosis?

fluid discharged by the worm, can show rhabiditiform larvae

Treatment includes:

local cleansing of the lesion and local application of antibiotics, if indicated because of the bacterial superinfection. Mechanical progressive extraction of the worm over a period of several days (no curable antihemlminth)

Trichinella spiralis is also called:

trichinosis

Mode of transmissionof trichinosis:

eating raw or undercooked meat from animals infected with Trichinella

Persons infected with may initially experience:

gastrointestinal symptoms such as diarrhea, abdominal cramps, nausea, and vomitting

May be followed by:

fever, muscle pains, facial swelling, and fatigue

Symptoms can last how long?

from weeks to months

Symptoms can vary from:

mild to severe

Trichinella infections may also be:

asymptomatic

Treatment of Trichinella infection:

prescription drugs

People most often associate trichinellosis with the consumption of:

raw or undercooked pork

In more recent years, more cases have been associated with eating:

raw or undercooked wild game meats (bear)

Trichinella can infect:

a wide range of animals worldwide

Outbreaks of Trichinella in the lower 48 have been caused by:

consumption of brown/black bear, boar, cougar, walrus, grizzly bears, and polar bear

Trichinella has also been detected in:

coyotes and foxes

There has been one reported case due the the consumption of undercooked:

racoon meat

For whole cut meat, cook to: (excluding poultry and wild game)

145*, then allow to rest 3 minutes

Ground meats, cook to:

160* (no rest time)

Wild game, cook to:

160*

For all poultry cook to:

165*, rest 3 minutes

Animals infected with Trichinella usually don't appear:

sick, but may show some changes in behavoir such as being less active

There are no feasible methods for:

reducing Trichinella infection in wild animals

Curing, drying, smoking, or microwaving meat does not:

consistently kill infective worms

What type of meat were the cause of thichinellosis reported?

homemade jerky and sausage

Freeze pork less than 6'' thick for _____ days at _____*

20, 5
Freezing may be ineffective because:

some worm species are freeze resistant

Make sure to clean what after use?

meat grinders

To help prevent infection, don't allow:

pigs or wild animals to eat undercooked meats of any animals including rats

For laboratory diagnosis, biopsy:

gastrocenemius muscle

Onchocerciasis parasiste, and vector:

Ochocera volvulus, black flies (simulium species)

Bancroftian filariasis parasite and vector:

Wuchereria bancrofti, mosquitoes (anopheles, aedes, culex, and mansonia species)

Malayan filariasis parasite and vector:

Bancrofti malayi, and Bancrofti timori, mosquitoes (anopheles, aedes, culex, and mansonia species)

Loiasis parasite and vector:

red flies (Chrysops species)

Mansonelliasis parasite and vector:

Mansonella streptocerca, midges (culicoides species)

Collect stool in:

a dry, clean, leak proof container. Make sure no urine, water, soil or other material gets in the container.

Stool specimen should be examined:

immediately (within 30 minutes), processed or preserved immediately

When preservatives are not available:

specimens can be kept in refrigerator but are only suitable for antigen testing

What will render the stool specimens unsatisfactory for examination?

certain drugs and compounds

Specimens should be collected:

before the administration of certain drugs or delayed until after the effects have passed.

Substances that effect stool samples:

antacids, koolin, mineral oil, and other oily materials, non-absorbable anti diarrheal preparations, barium/bismuth (7-10 days for clearance), antimicrobial agents (2-3 weeks for clearance), and gallbladder dyes (3 weeks for clearance)

Preservative:

10% formalin

Advantages of 10% formalin:

good preservation of morphology of helminth, eggs, larvae, protozoan cyts, and coccidia.

Disadvantages of 10% formalin:

not suitable for some permanent smears stained with trichrome, inadequate preservation of morphology of protozoan trophs

Cysts are found in:

formed stools

Trophs are found in:

watery stools

Modified PVA copper or zinc advantage:

permanent smears can be made and stained with trichrome

Because 10% formalin and PVA have complementary advantages it is recommended:

specimen be divided and preserved with both types of preservatives

Examination of fresh specimens permits the observation of:

motile trophs, but must be carried out without delay.

Which type of specimens are more likely to contain trophs?

liquid (diarrheic), should be examined within 30 minutes of passage, not 30 minutes of arrival

Soft specimens usually contain:

trophs and cysts, should be examined within 1 hour of passage

Special tests for specimens preserved with 10% formalin:

wet mount (helminths and protozoa)


Elisa


chromotrope stain

Special tests for specimens preserved with PVA:

trichrome stain

Concentration procedures separate:

parasites from fecal debris and increase chances of detecting parasitic organisms when they are in small numbers.

They are divided into:

flotation techniques and sedimentation techniques

Flotation techniques:

use zinc sulfate or Sheather's sugar which have higher specific gravity than the organisms to be floated so that the organisms rise to the top and the debris sinks to the bottom.



Main advantage of flotation technique:

produce cleaner material than the sedimentation technique

Disadvantage of flotation technique:

walls of eggs and cysts will ofeten collapse, and some don't float

Formalin-Ethyl Acetate Sedmentation Concentration:

mix specimen well, strain 5ml of fecal suspension through wetted cheese-cloth type gauze placed over disposable paper funnel into 15ml conical centrifuge tube. Add 0.85% saline or 10% formalin through the debris on the gauze to bring volume up to 15ml (distilled water may be used) Blastocystis hominis may be deformed or destroyed. Centrifuge at 500 x g for 10 minutes

Modified acid fast staining procedure is used for:

the identification of oocysts of the coccidian species (cryptosporidium, cystoisospora, and clyclospora)

Chromotrope staining procedure is used for:

differentiating microsporidia spores from background fecal elements.

Trichrome staining procedure is used for:

a rapid simple procedure which produces uniformly well stained smears of the intestinal protozoa, human cells, yeast and artifact material.

Wet mount is used for:

identifying trophs, cysts, oocyts, and helminth eggs and larvae.

To prepare a wet mount:

obtain a small amount of specimen and place it on a slide. If the stool specimen is somewhat solid, add a drop or two of saline to the specimen and mix. Ideally, two smears can be prepared on one slide, of which one can be stained with iodine.

Thickness of the wet mount:

should be able to read newspaper print through it

For PVA fixed specimens:

apply two or three drops of the specimen to the slide and with a rolling motion or an up and down dabbing motion, spread the specimen evenly to cover an area the size of a 22mm coverslip. After staining, systematically examine with 100x oil objective. Examine at least 200-300 fields.

PVA, report:

protozoa seen as trophs or cysts. Protozoans do not need to be quantitated because they reproduce in the gut at different time intervals.



Helminth eggs should be quantitated because:

number of eggs reflects worm burdens.