Parasitology Nematodes Flashcards
What is the mouth of a nematode known as?
Buccal (buckle) cavity
What is the exterior of a nematode known as?
Cuticle
What is a pregnant female nematode referred to as?
Gravid female
Common name for nematodes
Roundworm
Scientific name for roundworm
Nematode
Most common stages of nematode development (3)
- ova (eggs)
- Larva
- Adult (worm)
This stage of nematode development is resistant and transmissible
Ova
This stage of nematode development is considered the feeding and growth stage and may be transmissible
Larva
This is the reproductive stage of nematodes and causes pathogenesis
Adult (worm)
3 types of ova
- Unfertilized
-Fertilized
-Embryonated
This type of ova may have an embryo that appears segmented
Fertilized
This type of ova contains a developing embryo or larval form
Embryonated
Scientific name for Pinworm
Enterobius vermicularis
Common name for Enterobius vermicularis
Pinworm
This nematode has jellybean shaped ova
Enterobius vermicularis
This is the most common helminth infection in the US
Enterobius vermicularis
TRUE or FALSE:
Humans are the only known host for pinworm
TRUE
Why is Enterobius vermicularis known as pinworm?
The adult females have a sharp, pin-shaped posterior
What is the infective stage for Enterobius vermicularis?
Embryonated ova
Method of infection for pinworm
Ingestion of embryonated ova
Diagnostic stage for Enterobius vermicularis
Embryonated ova
Method of diagnosis for Enterobius vermicularis
Cellophane tape prep or Scotch tape prep
Definition: intense itching
Pruritus
TRUE or FALSE:
Enterobius vermicularis ova are too heavy to be transmitted in the air
FALSE - they are light enough to float in the air
TRUE or FALSE:
Gravid pinworm females can lay up to 15,000 eggs/day
TRUE
Where do adult Enterobius vermicularis reside in humans?
Colon, cecum, and appendix
Definition: process of reinfecting oneself
Autoreinfection
Definition: hatched larva travel back into the rectum and large intestine and mature into adults
Retroinfection
3rd most common helminth infection in the US
Trichuris trichiura
Common name for Trichuris trichiura
Whipworm
This helminth has ova shaped like barrel/footballs/lemons
Trichuris trichiura
What are the ends of whipworm ova known as?
Polar/hyaline plugs
Infective stage for Trichuris trichiura
Embryonated ova
Method of infection for whipworm
Ingestion of embryonated ova
Diagnostic stage for Trichuris trichiura
Unembryonated ova
Method of diagnosis for Trichuris trichiura
Identify unembryonated ova in feces
TRUE or FALSE:
Gravid whipworm females can lay up to 5000 eggs/day
TRUE
Serious infections with this helminth can lead to a prolapsed rectum
Trichuris trichiura
This is the most common helminth infection WORLDWIDE
Ascaris lumbricoides
Ascaris lumbricoides is the ______ most common helminth infection in the US
2nd most common
TRUE or FALSE:
Ascaris lumbricoides is the largest adult nematode
FALSE it is the largest adult INTESTINAL nematode (up to 35 cm in length)
2 types of ova that can be seen in samples for Ascaris lumbricoides
Fertile and infertile
Biggest difference between Ascaris lumbricoides fertile and infertile ova
Fertile are round-oval and has an inner translucent layer whereas Infertile are elongated and have inner globular material
Ascaris lumbricoides ova may be _______ or _______
Mammillated or Decorticated
Infective stage of Ascaris lumbricoides
Embryonated ova
Ascaris lumbricoides method of infection
Ingestion of embryonated ova
What type of migration do Ascaris lumbricoides have?
Liver-Lung migration
Diagnostic stage for Ascaris lumbricoides
Fertile or Infertile ova
Ascaris lumbricoides method of diagnosis
Identify fertile/infertile ova in feces
TRUE or FALSE:
Ascaris lumbricoides gravid females can lay up to 250,000 eggs/day
TRUE
Ascaris are known as ________ migrators meaning they will exit the host through any orifice when they feel threatened or upset
Active migrators
This helminth may cause a bolus of worms that obstruct the bowel or appendix
Ascaris lumbricoides
Scientific name for New World Hookworm
Necator americanus
Scientific name for Old World Hookworm
Ancylostoma duodenale
Common name for Necator americanus
New World Hookworm
Scientific name for Old World Hookworm
Ancylostoma duodenale
Which hookworm has cutting plates?
Necator americanus
Which hookworm has teeth-like structures?
Ancylostoma duodenale
These helminths are known for being notorious bloodsuckers
Hookworms
These helminths can cause iron deficiency as well as hypochromic/microcytic anemia
Ancylostoma duodenale/Necator americanus
The ova for this helminth are:
-oval shaped
-colorless
-have a thin smooth shell
-segmented embryo (2-8 segments)
-inner translucent layer
Hookworm
-Necator americanus and Ancylostoma duodenale
Development stages for hookworm (4)
-Ova
-Rhabditiform larva (1st stage/feeding/growth stage)
-Filariform larva (3rd stage/infective stage)
-Adult
Infective stage for hookworm
Filariform larva
Method of infection for hookworm
Filariform larva penetrate the skin
What type of migration are hookworms known to have?
Heart-Lung migration
Hookworm diagnostic stage
Ova
Method of diagnosis for hookworm
Identify ova in feces
What could cause difficulties for identifying hookworms in feces?
If the specimen is not preserved properly or if there is a delay in ID’ing, the ova can hatch in to the rhabditiform larva and resemble a different type of helminth infection (Strongyloides stercoralis)
Repeat infections by hookworms may cause what condition?
Ground itch
Hookworms in which humans are not the natural host may cause what type of condition in humans?
Cutaneous larval migrans
OR
Visceral larval migrans
What type of blood test finding is commonly associated with migrating nematodes?
Eosinophilia
Common name for Strongyloides stercoralis?
Threadworm
Scientific name for threadworm
Strongyloides stercoralis
Strongyloides stercoralis is known as a __________ parasite meaning it does not require a human host
Facultative
Definition:
Organism is capable of asexual reproduction
Parthenogenic
Which helminth is parthenogenic?
Strongyloides stercoralis
Threadworms ova are identical to which other helminth?
Hookworm
Infective stage for Strongyloides stercoralis
Filariform larva
Threadworm method of infection
Filariform larva penetrates the skin
Strongyloides stercoralis has what type of migration?
Heart-Lung migration
Threadworm diagnostic stage
Rhabditiform larva
Strongyloides stercoralis method of diagnosis
Rhabditiform larva found and identified in stool
Can threadworm autoreinfect?
Yes
Hookworm vs Threadworm:
Rhabditiform have long buccal cavity
Hookworm
Hookworm vs Threadworm:
Rhabditiform have short buccal cavity and a prominent genital primoridum
Threadworm
Hookworm vs Threadworm:
Filariform have pointed tail and short esophagus
Hookworm
Hookworm vs Threadworm:
Filariform have notched tail and long esophagus
Threadworm
Definition: Creeping rash infection - auto-infection that appears as an eruption beginning in the perianal region that rapidly spreads and causes intense itching
Larva currens
This helminth can cause disseminated hyperinfection which can be fatal
Strongyloides stercoralis
Accidental human parasite
Trichinella spiralis
Zoonotic disease for Trichinella spiralis
Trichinellosis
Where does Trichinella spiralis typically reside?
Wild game (pig, bear, mountain lions)
How is Trichinella spiralis passed to humans?
Ingestion of undercooked encysted meat
Infective stage for Trichinella spiralis
Encysted larva
Method of infection for Trichinella spiralis
Ingestion of undercooked meat containing encysted larva
Diagnostic stage for Trichinella spiralis
Encysted larva within “nurse cells”
Method of diagnosis for Trichinella spiralis
Identify encysted larva in biopsied muscle tissue or ELISA (serologic testing looking for antibodies)
Largest parasitic adult nematode to infect humans (tissue nematode)
Dracunculus medinensis
Common name for Dracunculus medinensis
Guinea worm
Scientific name for Guinea worm
Dracunculus medinensis
This tissue nematode is considered a “Neglected Tropical Disease”
Dracunculus medinensis
Infective stage for Guinea worm
Copepod infected with Guinea worm larva
Method of infection for Dracunculus medinensis
Drinking water containing infected copepod
Diagnostic stage for Guinea worm
Female worm
Method of diagnosis for Dracunculus medinensis
Visually observe skin blisters with adult worm
The copepod infected with Guinea worm is known as what type of host?
Intermediate host
Where do the Dracunculus medinensis larvae mature into adults inside humans?
Abdominal cavity
Name the helminth:
Gravid females migrate through the tissues to the skin surface creating a blister. When the blister comes into contact with water, the female worm emerges partially and releases larvae into the water.
Dracunculus medinensis
How are Guinea worm females treated?
Slowly wrapping the worm around a revolving stick or by surgical removal
These nematodes produce “living” embryos
Filarial nematodes
What are “Living” embryos also known as?
Microfilariae
Where do filarial nematodes reside in humans?
Subcutaneous or lymphoid tissues
TRUE or FALSE:
Filarial nematodes have an ova stage
FALSE
Which type of nematode requires a biological vector (arthropod) as an intermediate host?
Filarial nematode
Filarial nematode infective stage
Larva
Filarial nematode method of infection
Larva enters skin at arthropod vector’s feeding site
Filarial nematode diagnostic stage
Microfilariae
Filarial nematode method of diagnosis
Identify microfilariae on blood smear or tissue biopsy
Causes elephantiasis
Wuchereria bancrofti/Brugia malayi
Vector for Wuchereria bancrofti/Brugia malayi
Mosquito
Where are adults of Wuchereria bancrofti/Brugia malayi found?
Lymphatic system
Where are the microfilariae of Wuchereria bancrofti and Brugia malayi found? Do they exhibit periodicity?
Blood
Yes, nocturnal
Wuchereria bancrofti vs Brugia malayi:
Sheathed; nuclei don’t extend to tip of tail
Wuchereria bancrofti
Wuchereria bancrofti vs Brugia malayi:
Sheathed; widely spaced subterminal and terminal nuclei
Brugia malayi
Common name for Loa Loa
Eyeworm
Scientific name for Eyeworm
Loa Loa
Vector for Loa Loa
Chrysops fly
Where are adult Loa Loa found?
Subcutaneous and conjunctival tissues
Where are Loa Loa microfilariae found? Do they exhibit periodicity?
Blood
Yes, diurnal
Nematode that causes calabar swellings (transient subcutaneous swellings caused by microfilariae migration and death in capillaries
Loa Loa
Nematode that is the leading cause of river blindness
Onchocerca volvulus
Onchocerca volvulus vector
Simulium black fly (aka Black fly)
Where are Onchocerca volvulus adults found?
Subcutaneous tissues
Onchocerca volvulus form nodules that are known as __________
Onchocercomas
Where would you find Onchocerca volvulus microfilariae?
In the skin and eye
Loa Loa vs Onchocerca volvulus:
Sheathed; nuclei extend all the way to the tip of the tail
Loa Loa
Loa Loa vs Onchocerca volvulus:
No sheath; no tail nuclei; tail is often sharply bent
Onchocerca volvulus
Vector for Mansonella species
Biting midges
The adults of this Mansonella species are found in peritoneal and pleural cavities
Mansonella perstans
The adults of this Mansonella species are found in subcutaneous tissue
Mansonella ozzardi
The adults of this Mansonella species are found in skin/subcutaneous tissue
Mansonella streptocerca
Where are the microfilariae of Mansonella species found?
Blood
Which Mansonella species may also be spread by Black flies?
Mansonella ozzardi
TRUE or FALSE:
All Mansonella species microfilariae have sheaths
FALSE
They all have NO sheaths
Which Manosonella microfilariae have a characteristic “Shepards crook”
Mansonella streptocerca
These nematodes are diagnosed by skin snips
Onchocerca volvulus and Mansonella streptocerca
Nematodes diagnosed by finding microfilariae in peripheral blood (5)
-Wuchereria bancrofti
-Brugia malayi
-Loa Loa
-Mansonella ozzardi
-Mansonella perstans
Nematodes diagnosed by identifying their ova in stool (3)
-Trichuris trichiura
-Ascaris lumbricoides
-Ancylostoma duodenale/Necator americanus
Nematode diagnosed by indentifying their larva in stool
Strongyloides stercoralis
Nematode diagnosed by finding larva within tissues
Trichinella spiralis
Nematode diagnosed by finding adult worm in tissues
Dracunculus medinensis
Nematode diagnosed by identifying ova from the perianal region
Enterobius vermicularis
Name the nematode:
-Jelly bean ova
-Scotch tape prep
Enterobius vermicularis
Name the nematode:
-Rhabditiform larva: long buccal cavity
-Iron deficiency anemia
Ancylostoma duodenale/ Necator americanus
Name the nematode:
-Nurse cells
Trichinella spiralis
Name the nematode:
-River blindness
-Black fly vector
Onchocerca volvulus
Name the nematode:
-Prolapsed rectum
-Football ova with hyaline plugs
Trichuris trichiura
Name the nematode:
-Larva currens
-Filariform larva: notched tail
Strongyloides stercoralis
Name the nematode:
-Elephantiasis
-Mosquito vector
Wuchereria bancrofti/ Brugia malayi
Name the nematode:
- Liver-Lung migration
-Ova may be mammillated
Ascaris lumbricoides
Name the nematode:
-Adult worms in serous membranes of pleural and peritoneal cavities
-Biting midge vector
Mansonella perstans
Name the nematode:
-Causes formation of skin blisters
Dracunculus medinensis
Name the nematode:
-Chrysops fly vector
Loa Loa
TRUE or FALSE:
Stool specimens are the ideal specimen for diagnosing pinworm
FALSE- scotch tape prep or pinworm paddle
