Intestinal Nematodes Flashcards
Common name: Roundworms
Environment
Varied; free living; plant parasites; animal parasites
Reproduction
Sexual reproduction only
Dioecious: Separate male and female sexes
Females: Larger
Males: Curved tails or specialized copulatory organs
Intenstinal Nematodes
Shape
Cylindrical
Tapering at both ends
Unsegmented
Intestinal Nematodes
Cuticle Outer covering Relatively impermeable Protective Shed during molting
Intestinal Nematodes
Digestive tract: Complete
Specialized esophageal area
Intestines
Rectum
Osmoregulatory/excretory system: Ammonia waste system
Exit through anus
May have excretory pore and renette gland
Intestinal Nematodes
Nervous system
- Nerve rings : Anterior or posterior leads to receptors (sense organs): photo, mechanical and chemical - Longitudinal nerves: Two lateral
Intestinal Nematodes
Reproductive System
Monoecious: Reproductive organs of male and female in one organism or segment
Dioecious: Separate male and female organisms
Fertilization: Internal
Cross-fertilization: Most often (when more than one adult is present)
Self-fertilization: When only one organism is present
Repro of Intestinal Nematodes
Thousands of species; most are free living
Buccal structures: Specialized for attachment
Copulatory organs
Bursa: Used for grasping the female
Spicules: Used for injection of spermatozoa
Intestinal Nematodes
Ova: Nonoperculated Rhabditiform larva Filariform larva Molts Several between stages Intermediate forms observed
stages of development
Intestinal Nematodes
Common name: Giant intestinal roundworm
Ascaris lumbricoides
Eggs are passed in feces
Mature egg ingested by man
Infective larva in intestine, hatches
Enters the venules byway of intestinal wall
Travels through the heart to lungs
Travel into the alveoli byway of lung
Molt
Coughed up and swallowed
Mature and mate in intestine
Female begins laying eggslife cycle:
Ascaris lumbricoides
Habitat: Small intestines Intermediate host: None Reservoir host: Swine Infective form: Mature embryonated egg Mode of infection: Ingestion
Ascaris lumbricoides
Shape: Round and slender, male has a curved tail
Color: Creamy-white with a pinkish cast
Buccal structures: Three lips
Ascaris lumbricoides
Giant intestinal round worm.
Acquired by eating eggs from soil contamination
Worldwide dist., developing countries, poverty
Ascaris lumbricoides
Adults in small intestine
Heavy infection can cause obstruction 10k deaths/yr
Adults can perforate intestine and migrate to liver
Larvae migrate to liver and lungs causing systemic responses, eosinophilic pneumonitis (Loeffler’s)
Diagnosis: eggs or adults in feces
Ascaris lumbricoides
Common name: Pinworm or seatworm
Enterobius vermicularis
Habitat: Large intestine, cecum Intermediate host: None Reservoir host: None known Infective form: Embryonated egg (Rhabditiform larva) Mode of infection: Ingestion
Enterobius vermicularis
School children age 5-14 are often victims.
Eggs infective within 6 hours and up to 20 days.
Hand-to-mouth infection. Keep hands clean.
Anal pruritis encourages scratching, secondary bacterial infections are possible.
Worms may migrate to ectopic locations
Enterobius vermicularis
Specimen processing: Specimen of choice is transparent adhesive tape specimen collection (“scotch-tape prep”) or pinworm paddle
Enterobius vermicularis
Known as pinworm
Worldwide dist., most prevalent in temperate
Acquired by eating eggs, autoinfection, retroinfection
Enterobius vermicularis
Disease is slight, perianal itching, sleep disturbance
Spreads easily to family members
Diagnosis: D shaped eggs recovered from patient
Enterobius vermicularis
Hook worms:
Ancylostoma duodenale
Nector americanus
Common name: Old World hookworm
Ancylostoma duodenale
Creeping eruption, pruritis, iron deficiency anemia.
Anticoagulants in bite wound maintain bleeding even after worm leaves.
Physical, cognitive, intellectual growth diminished in children.
Ancylostoma duodenale
Color: Grayish-white Buccal structures: Two fused, sharp "teeth" on each side of ventral surface Copulatory bursa: Male Paired copulatory spicules: Separated Small paired dorsal rays: Tripartite
Ancylostoma duodenale
Common name: New World hookworm (archaic)
Necator americanus
Found worldwide, with focal locations for species.
Life cycle and symptoms similar with both species.
Hookworms
Symptoms vary with worm migrations, number of infections (repeats and burden), eosinophilia, pneumonia, abdominal discomfort.
Cause blood loss, anemia
Diagnosis: clinical signs, eggs in feces
Hookworms
Common name: Threadworm
Strongyloides stercoralis
Develop into infective filariform larvae that penetrate the skin and follow a lung migration (blood-lung-intestinal route), or
May develop into adults and exist for some time (two or more generations) as free-living nematodes, producing the filariform later
Life cycle:
Strongyloides stercoralis
Intestinal infection Desquamation Severe diarrhea and gastroenteritis Anemia Weight loss
**Hyperinfection may be fatal in immunosuppressed patients
Strongyloides stercoralis
Autoinfective**, can build large numbers in victim.
Some infections documented to last over 60 years.
Person to person transmission possible.
Epigastric pain, fluctuating eosinophilia, recurrent maculopapular rash of buttocks, perineum and thighs.
Strongyloides stercoralis
Discovery and ID of rhabditiform LARVAE IN STOOL examination.
May need a large volume and concentrate.
Serology available from CDC, maybe some commercial sources.
Some cross-reactivity with other helminths occurs
Strongyloides stercoralis
Resembles that of Hookworm
Males are either eliminated early in the parasitic cycle or the gravid females enter the mucosa and deposit their eggs through PARTHENOGENESIS.
Eggs hatch in the mucosa liberating the rhabditiform larvae
burrows back into the lumen of the intestine to pass out with the feces
Strongyloides stercoralis
Found worldwide, endemic in Appalachia in US.
Life cycle similar to hookworm, but also capable of free living.
Causes intestinal and organ damage.
Strongyloides stercoralis
Uses parthenogenesis while in parasitic mode.
Autoinfective an hyperinfective in immunocompromised.
Diagnosis: Larvae in stool, sometimes eggs in stool, possibly ELISA available.
Strongyloides stercoralis
Common name: Whipworm
Trichuris trichiura
Known as the Whipworm because of shape.
Found worldwide especially poor or developing countries.
Trichuris trichiura
Acquired by eating food contaminated by eggs found in soil.
Causes disease with heavy infections, adults in cecum and large intestine. Destruction and inflammation of intestine..leads to malnutrition, iron deficiency, and RECTAL PROLAPSE.
Diagnosis: Characteristic eggs in feces, colonoscopy.
Trichuris trichiura
Which of these parasites are best known for the ability to autoinfect an individual?
A. Trichuris trichiura
B. Ancylostoma duodenale
C. Ascaris lumbricoides
D. Strongyloides stercoralis
D. Strongyloides stercoralis
This worm is frequently called the “pinworm” and is usually associated with young children? A. Ascaris lumbricoides B. Enterobius vermicularis C. Strongyloides stercoralis D. Trichuris trichiura
B. Enterobius vermicularis
