nematodes pt. 1 Flashcards
what group do nematodes belong to
helminths
- multicellular organisms that contain internal organ systems
nematodes are commonly known as
intestinal roundworms
what are the 3 basic morphologic forms
- eggs
- produced after fertilization from female worms
- size and shape depends on the microorganism - larvae
- adult worms
- adult female worms are usually larger than adult males
- equipped w a complete digestive and reproductive system
What does it mean when life cycle are similar but organism-specific
Organ specific - infection of nematodes can be initiated in several ways
Briefly explain the life cycle of nematodes in general
After entering the body, eggs or larvae grow into adult worms.
The adult worms live in the intestines to obtain nutrients and reproduce.
Female worms lay eggs in the intestine, which can be passed out in stool.
Some eggs need warm, moist soil to continue developing for 2-4 weeks.
Once fully developed, these eggs can infect a new host, repeating the cycle.
Some nematodes don’t need a host and can live freely in the environment.
Nematodes SOC
Stool - however, it depends on the organism
What conditions do nematode eggs need to develop
Warm, moist soil for 2-4 weeks before becoming infectious
True or false:
Nematodes cannot live without a host.
False - they can live without a host as they are a free living nematodes that can survive independently in the environment
What are the 3 factor that may contribute to the severity of a nematode infection
Number of worms present
- more worms = heavy infection
Length of time the infection persists
- as they are known to last up to 12 months or longer
- there are cases that it will last 10-15 years or more
Overall health of the host
- if the patient is immunocompromised, the higher the possibility of the infection is severe
- moreover secondary infections like bacterial infections affect other organs beside the intestines
true or false:
Occurrence of reinfections and autoinfections is possible
True
Infective pinworm eggs that migrate back into the host body, develop and reproduce rather than becoming dislodged
Retroinfection
Infected individuals reinfected themselves if reinfecting pinworms eggs are digested via hand to mouth contamination
Autoreinfection
- parasite completes its life cycle within the same hotspot in an individual leading to continuous infection without exposure to external source
What are the typical symptoms of nematodes
Typical symptoms:
Abdominal pain
Diarrhea
Nausea
Vomiting
Fever
Eosinophilia
May be present:
Skin irritation
Formation of skin blisters
Muscle involvement
Phylum and class of nematodes
Phylum: nemathelminthes
Class: nematoda
What are the 2 hookworm spp.
Necator americanus
Ancylostoma duodenale
Enterobius vermicularis
Common name:
Common associated disease:
Common Name: Pinworm, Seatworm
Common Associated Disease: Enterobiasis, Pinworm Infection
Enterobius vermicularis egg morphology
48-60 μm long, 20-35 μm wide
Oval, one-side flattened (“D”)
Double-layered, thick, colorless shell
May be seen unembryonated,
embryonated, or mature
Briefly explain the unembryonated, embryonated or mature Enterobius vermicularis egg
Unembryonated:
Unfertilized eggs where it is the initial stage where the eggs lays
No developed larva, non infectious
Embryonated:
Feretilized eggs where
In the process of maturing into an infective stage
Mature:
Fully developed infective larva (infectious)
Can cause infectious once digested
Infective mature embryonated eggs can be infective within 6-8 hours
How can the embryonated eggs be infective in E. vermicularis
Can cause infections once digested Infective mature
Can be infective within 6-8 hours
Briefly explain the adult worm morphology of Enterobius vermicularis
Male:
2-4 mm log, no more than 0.3 mm wide
Yellowish-white in color and are rarely seen
Female:
7-14 mm long, 0.5 mm wide
Yellowish-white in color equipped with organ system such as digestive tract, intestinal tract and reproductive structure
Tail is pointed that resembles pinhead (distinctive feature of a small)
Laboratory diagnosis for Enterobius vermicularis
Cellophane tape preparation
Stool samples
- eggs or adults females may be recovered in stool samples on rare occasions a
What is the cellophane tape preparation specimen of choice for the recovery of E. vermicularis
Collected from the perianal region of the person suspected of infection
- mostly seen are eggs
- however adult females may also be present
- multiple sample may be required
- another term: scotch tape method
Why do the cellophane tape preparation requires multiple samples
To confirm the presence of a light infection or to determine a patient is free of infection
E. vermicularis
Host -
Infective stage -
Diagnostic stage -
Host - only known hosts is human
Infective stage - mature embryonated eggs where
Diagnostic stage - eggs in perianal region
Briefly explain the life cycle of E. vermicularis
- Infection is initiated following the ingestion of the infective eggs.
2.Eggs migrate through the digestive tract into the S.I. where they hatch and release young larvae.
- Resulting larvae continue to grow and mature= transform into adult worms.
- It reside on the colon.
- Following copulation, the gravid female worm migrates outside the body to the perianal region, where she may deposit up to 15,000 eggs.
- The developing eggs achieve infective status after 4-6 hours.
- Infective eggs may then become dislodged from the body. Once apart from the host, the eggs may take up residence in a number of locations.
- Ingestion of these infective eggs initiates a new cycle.
mating process where the male and female parasites reproduce sexually.
copulation
term used to describe a female parasite that is caring for fully developed eggs or embryos.
gravid
How long is the incubation period before the eggs of Enterobius vermicularis become infective?
4-6 hours.
how can the infective Enterobius vermicularis eggs become dislodged from the body
due to intense scratching of the anal area
afterwards, the eggs may take residence in surfaces like dust, linens and clothing.
true or false:
the infected eggs of E. vermicularis can become airborne
true
[these eggs are light and can be carried by dust or air currents making them easy to inhale or settle on surfaces]
how long can the infective eggs of E. vermicularis can survive
for a few days to several weeks under suitable environmental conditions
- ideal surroundings consist of moderate temperature accompanied with high humidity.
true or false:
all Enterobius vermicularis infections are symptomatic
false - many cases are asymptomatic
symptom of enterobiasis
most common:
Intense itching (Pruritus ani) and inflammation around the anal and/or vaginal areas.
other common:
Inflammation of the anal/vaginal areas
Intestinal irritation
Mild nausea or vomiting
Irritability and difficulty sleeping
less common:
Minute ulcers
Mild intestinal inflammation
Abdominal pain
epidemiology of Enterobius vermicularis
found worldwide
most common helminth known to cause infection in the US
who appears to be at the greatest risk of contracting Enterobius vermicularis
children
how is Enterobius vermicularis transmitted
hand-to-mouth contamination
treatment and prevention and control for E. vermicularis
TREATMENT
albendazole
mebendazole
pyrantel pamoate
PREVENTION AND CONTROL
practicing proper personal hygiene
- handwashing
- applying ointment to an infected perianal area
- avoiding scratching the infected area
thorough cleaning of all potentially infected environmental surfaces
providing treatment to all household members
Trichuris trichiura
Common Name:
Common Associated Disease:
Common Name: Whipworm
Common Associated Disease: Trichuriasis, Whipworm Infection
morphology of Trichuris trichiura
eggs
50-55 μm long, 25 μm wide
Barrel-shaped or football-shaped
Hyaline polar plug at each end
Unicellular, undeveloped embryo
Smooth shell that retains a yellow-brown color from its contact with the host bile.
morphology of Trichuris trichiura adult worm
anterior end vs posterior end
2.5-5 cm long (males usually smaller than females)
Anterior end:
Colorless and contains slender esophagus
Small that resembles a whip handle
Posterior end:
Pinkish-gray color, consisting of the intestine and reproductive systems
Large and resembles whip itself
Male possess a prominent curled tail
why is the Trichuris trichiura’s egg shell yellow-brown in color?
As it has contact with bile in the host, hence the outer covering/ shell is yellow-brown in color.
what is the SOC for the recovery of T. trichiura eggs
stool
how can adult Trichuris trichiura worms be detected
visible on macroscopic examination of the intestinal mucosa
Where can Trichuris trichiura be found in heavy infections
seen in areas of the intestinal tract down to and including the rectum
Which laboratory method helps detect Trichuris trichiura eggs in stool samples
The Zinc Sulfate Flotation Method
- eggs are prominent in infected samples processed using this method
How do Trichuris trichiura eggs appear in treated patients?
may be distorted, showing a variety of unusual shapes
life cycle of T. trichiura
- Ingestion of infective T. trichiura eggs containing larvae = initiates human infection.
- Larvae emerge from the eggs in the small intestine.
- Growth and development of the larvae occur as they migrate within the intestinal villi.
- Larvae return to the intestinal lumen and proceed to the cecum, where they complete their maturation.
- Resulting adults take up residence in the colon, embedding in the mucosa.
- Following copulation, the adult female lays her undeveloped eggs which are passed into the outside environment via feces.
- Approximately 1 month outside the human body, the eggs embryonate, become infective, and are ready to initiate a new cycle.
How long do Trichuris trichiura eggs take to become infective
approx 1 month outside the human body
Where do Trichuris trichiura eggs develop outside the human body?
in the soil
How long can adult Trichuris trichiura worms live in untreated infections?
up to 4-8 years
Do all Trichuris trichiura infections cause symptoms
No, mild infections are often asymptomatic
What is another name for Trichuris trichiura infection?
Trichuriasis (Whipworm Infection)
- heavy infection: 500-5000 worms
- symptoms depend on the age of the host
what symptoms do children and adult with Trichuris trichiura infection often experience
CHILDREN
- Symptoms resembling ulcerative colitis
- Chronic dysentery (with as few as 200 worms)
- Severe anemia
- Possible growth retardation
- Increased rectal prolapse and peristalsis
ADULT
- Symptoms mimicking inflammatory bowel disease
- Abdominal tenderness and pain
- Weight loss
- Weakness
- Mucoid or bloody diarrhea
third most common helminth
Trichuris trichiura
Most common helminth known to cause infection the US.
Enterobius vermicularis
Most common intestinal helminth infection in the world.
Ascaris lumbricoides
epidemiology of Trichuris trichiura
Found in warm climates where poor sanitation practices are common.
- Example using feces as fertilizations for farming.
who has the most risk contracting whipworm infections
children as well as those in psychiatric facilities.
treatment and prevention and control for Trichuris trichiura
TREATMENT
mebendazole
albendazole
PREVENTION AND CONTROL
exercising proper sanitation practices
- avoidance of defecating directly into the soil, using feces as fertilizer, and placing potentially infective hands into the mouth
thorough treatment of infected persons.
educating children and aiding mentally handicapped persons in their personal hygiene and sanitation practices.
Ascaris lumbricoides
Common name:
Common associated disease:
Common name: Large Intestinal Roundworm
Common associated disease: Ascariasis, Roundworm Infection
morphology of A. lumbricoides unfertilized egg
85-95 μm long, 38-45 μm wide
Shape varies
Thin shell
Unembryonated; amorphous mass of protoplasm
Usually corticated
morphology of A. lumbricoides fertilized egg
40-75 μm long, 30-50 μm wide
More rounded than the unfertilized egg
Undeveloped unicellular embryo
Thick nitrogen-containing polysaccharide coating called chitin, also known as shell.
- Less evident in corticated eggs.
morphology of A. lumbricoides adult worm
male vs female
Largest known intestinal nematode.
Creamy white color with a tint of pink.
Fine striations are visible on the cuticle.
Male:
- Small, reaching up to 30 cm in length.
- Slender and possesses a prominent incurved tail.
Female:
- 22-35 cm in length
- Resembles a pencil lead in thickness.
Largest known intestinal nematode
A. lumbricoides, adult worm
present of heavy albuminous coating:
absence of heavy albuminous coating:
Corticated: present of heavy albuminous coating.
Decorticated: absence of heavy albuminous coating.
*Fertilized egg shell is thin and the insides are amorphous mass of protoplasm (unembryonated)
what is the SOC for the recovery of A. lumbricoides eggs
stool
Where can adult Ascaris lumbricoides worms be found in severe infections?
Small intestine
Gallbladder
Liver
Appendix
may be present in:
- stool
- vomit
- external nares (nostrils)
In what types of samples can adult Ascaris lumbricoides worms be recovered?
Stool
Vomit
External nares (nostrils)
What serological test is available for diagnosing Ascaris lumbricoides?
Enzyme-linked immunosorbent assay (ELISA)
Do all Ascaris lumbricoides infections cause symptoms?
No
patients infected with 5-10 worms often remain asymptomatic.
What is another name for Ascaris lumbricoides infection?
Ascariasis (Roundworm Infection)
may be infected with only a single worm
- can produce tissue damage as it migrates through the host
- sec bacterial infection may also occur
true or false:
a person can be infected with only a single Ascaris lumbricoides worm?
true
How does Ascaris lumbricoides cause tissue damage?
By migrating through the host’s body.
What can happen if an Ascaris lumbricoides worm perforates the intestine?
A secondary bacterial infection may occur.
[perforates the intestine (makes a hole in the intestinal wall)]
symptoms when there are many worms of Ascaris lumbricoides
Abdominal pain
Vomiting
Fever
Distention
*Mature worms may entangle themselves into a mass that may ultimately obstruct the intestine, appendix, liver, or bile duct
How can Ascaris lumbricoides cause intestinal obstruction?
Mature worms may entangle into a mass that blocks the intestine, appendix, liver, or bile duct.
it is one of the parasites that can undergo lung migration
A. lumbricoides
patients may also experience pulmonary symptoms when the worms migrate through the lungs.
- Low-grade fever, cough, eosinophilia, and/or pneumonia.
- Asthmatic reactions to the presence of the worms may also occur.
How can Ascaris lumbricoides exit the body
discomfort from adult worms exiting the body through the
- anus
- mouth
- nose
What nutritional condition can heavily infected children develop in the presence of Ascaris lumbricoides
Protein malnutrition
life cycle of Ascaris lumbricoides
- Infection begins following the ingestion of infected eggs that contain viable larvae.
- Once inside the small intestine, the larvae emerge from the eggs.
- Larvae then complete a liver-lung migration by first entering the blood via penetration through the intestinal wall.
- FIRST STOP IS THE LIVER. From there, the larvae continue via the bloodstream to the SECOND STOP, THE LUNG.
- Inside the lung, the larvae burrow their way through the capillaries into the alveoli. Migration to the bronchioles then follow.
- The larvae are transferred through coughing into the pharynx, where they are swallowed and returned to the intestine.
- Larvae matures which results to adult worms that take up residence in the small intestine.
- Adults multiply and a number of the undeveloped eggs (up to 250,000/day) are passed in the feces. - Outside environment provides the necessary conditions for the eggs to embryonate.
- The resulting embryonated eggs are the infective stage for a new host and when consumed by a human host, initiate a new cycle.
- Infective stage: mature embryonated eggs
How do Ascaris lumbricoides larvae travel from the lungs back to the intestine?
They migrate to the bronchioles.
They are coughed up into the pharynx.
They are swallowed and return to the intestine.
How many undeveloped eggs can an adult Ascaris lumbricoides female lay per day?
Up to 250,000 eggs.
Where do Ascaris lumbricoides eggs embryonate?
In the outside environment.
What is the infective stage of Ascaris lumbricoides?
Mature embryonated eggs.
true or false:
Ascaris lumbricoides infective eggs cannot survive in 10% formalin fixative?
false - they can survive
epidemiology of Ascaris lumbricoides
most susceptible areas are
- warm climates
- areas of poor sanitation
which population is most at risk of A. lumbricoides
children who place their contaminated hands into their mouths
treatment and prevention and control for A. lumbricoides
TREATMENT
- albendazole
- mebendazole
PREVENTION AND CONTROL
avoidance of using human feces as fertilizer.
exercising proper sanitation
personal hygiene practices.
