GI Nematodes Flashcards
Nematodes (Physical Characteristics)
Roundworms
Non-segmented bodies
Separate sexes
Complete digestive system
GI Nematodes (General)
- Most common parasitic helminths in the U.S. and the world
- Contribute to malnutrition and a diminished work capacity (do not cause fatal infections)
- Most common in areas with poor sanitation, particularly in TROPICAL countries
- Children are most likely to be symptomatic
- Disease is usually caused by the presence of ADULT FORMS in the body
GI Nematodes (Life Cycle, Reproduction, Disease)
Life cycle: egg, multiple larval, and adult stages
- Separate sexes* (female is larger)
- Need to be infected by 2 or more to be shedding infectious eggs
- Adult worms are not going to increase in number, they are going to have sex and shed eggs into your stool
Some GI nematodes pass through other tissues (lung, skin) during development
CAUSE EOSINOPHILIA
GI Nematodes: Enterobius vermicularis (Pinworm)
- Most common helminthic infection encountered in the U.S.
- “Geohelminths”
1) Nematode infection acquired through contact with infected soil
2) Larvae or eggs require a period of time to develop in warm moist soil
3) Two Groups: - Ascaris and Trichuris: ingestion of infectious EGGS
- Strongyloids and hookworms: penetration of the skin by infectious LARVAE found in the soil
Enterobius vermicularis (Pinworm) (Life Cycle)
- Grow in the mucosa (No bleeding or deep tissue invasion)
- Adults mate and release eggs; female worms crawl out of rectum onto anus and perianal folds and lays thousands of eggs (Flat on one side) every night; sticky, remain on the surface of the skin
Enterobius vermicularis (Pinworm) (Transmission)
- Fecal-oral*
- Ingestion of eggs
- Reinfection is common; so is TRANSMISSION WITHIN FAMILIES
- Pinworms of other animals DO NOT infect man
Enterobius vermicularis (Pinworm) (Disease, Diagnosis)
- Most infections are ASYMPTOMATIC
- Symptomatic infection = perianal itching (Secondary bacterial infection) and Appendicitis??
Diagnosis:
- Identification of eggs (adult worms) in perianal region
- FLAT-SIDED EGGS on SCOTCH-TAPE PREP*
Enterobius vermicularis (Pinworm) (Control/Prevention)
Treatment:
- Several ANTI-HELMINTHIC COMPOUNDS (Mebendazole, Pyrantel Pamoate). Usually a single dose, repeated again two weeks later.
- TREAT ALL HOUSEHOLD MEMBERS*
Prevention:
-Good hygiene and housekeeping
Whipworm - Trichuris trichiura (Life Cycle)
1) Ingestion of infective stage embryonated egg
2) Eggs hatch in small intestine, releasing larva (larva penetrates and develops in mucosa of large intestine)
3) Larva migrates to large intestine
4) One-cell eggs in feces are released DIAGNOSTIC STAGE
5) Egg cells mature/divide for a few weeks before becoming in fectious
White, thread-like things on prolapsed rectum
Whipworm - Trichuris trichiura (Transmission)
Fecal-oral; contaminated soil
-Warm, moist soil promotes development of eggs
Whipworm - Trichuris trichiura (Asymptomatic vs Symptomatic Infections)
90% of infections are ASYMPTOMATIC
Symptomatic:
- Heavy worm burden (>200 adult worms)
- Bloody, mucus containing diarrhea
- Frequent stools
- RECTAL PROLAPSE in children
- May contribute to growth retardation, malnutrition, and anemia in children
Whipworm - Trichuris trichiura (Diagnosis and Control/Prevention)
Diagnosis:
-Identification of eggs in stool
Control/Prevention:
-Proper sanitation and personal hygiene
Ascariasis - Ascaris lumbricoides (Life Cycle)
Eggs are ingested by someone, break open, larvae are released and penetrate intestines, get into the circulation, travel through the LIVER, travel into the LUNGS, crawl up trachea and then are swallowed
Leads to GI and Pulmonary symptoms due to larvae going through lungs
Ascariasis - Ascaris lumbricoides (Characteristics)
- LARGEST of intestinal roundworms (about a foot long and as thick as a pencil)*
- 1 billion people infected, including a few million Americans
Ascariasis - Ascaris lumbricoides (Transmission)
-Fecal oral; soil contaminated with human feces
-Eggs need to develop in soil before they are infective (Geohelminth: needs to develop in soil)
-Humans are the only reservoir for A. lumbricoides
(Pig ascarid, A. suum rarely (if ever) infects humans)
Ascariasis - Ascaris lumbricoides (Asymptomatic vs Symptomatic: Intestinal Disease)
Most infections are ASYMPTOMATIC
Symptomatic Disease:
-Range from abdominal discomfort to death (rare)
Intestinal Disease:
1) Physical presence of adult worms in small intestine
- Abdominal pain, indigestion, loss of appetite, vomiting, diarrhea
- Heavy infections can cause a physical obstruction
- In children: nutritional deficiency, growth retardation
Ascariasis - Ascaris lumbricoides (Symptomatic: Pulmonary Disease)
- A combination of physical presence of larvae and immune response to them
- Mild cough, pneumonitis (inflammation of alveoli)
- Parasite antigens are highly allergenic (Repeated exposure –> ASTHMA ATTACK)
- EOSINOPHILIA IS COMMON*
Ascariasis - Ascaris lumbricoides (Diagnosis)
Eggs in stool; larvae or EOSINOPHILS in sputum
Hookworm - Necator americanus and Ancylostoma duodenale (Life Cycle)
Eggs are released into soil and will hatch in the soil. Have larvae in the soil. Wave around and wait for something to step on them. Attack and attach to the skin. Enter circulation.
KNOW that there are larvae in the soil, rather than eggs
Hookworm - Necator americanus and Ancylostoma duodenale (Characteristics)
- 1 billion people infected
- Major cause of anemia in children and pregnant women
- Necator americanus is found in the Southeastern U.S.
Hookworm - Necator americanus and Ancylostoma duodenale (Transmission)
Larvae from fecal contaminated soil penetrate intact skin
No animal reservoir for human hookworms
Dog and cat hookworms –> CUTANEOUS LARVAL MIGRANS
Hookworm - Necator americanus and Ancylostoma duodenale (Disease)
1) Iron-deficiency anemia: due to blood loss from hookworm feeding
- Can result in fatigue, exertional dyspnea, koilonychias (brittle, spoon-shaped nails), pale sclera, and heart murmurs
2) Children with severe infection can become protein malnourished due to blood loss
3) Penetration of the skin - moderate dermatitis “Ground Itch”
4) Pneumonia and EOSINOPHILIA may accompany larval passage through lungs
5) Ancylostoma consumes more blood than Necator; therefore, it is usually considered more pathogenic
Hookworm - Necator americanus and Ancylostoma duodenale (Diagnosis)
- Presence of eggs (plain, non-decorated) in stool
- Distinguishing between Necator and Ancylostoma requires examination of adult worms or larvae*
Prevention:
- Sanitation
- WEAR SHOES
Strongyloidiasis - Strongyloides stercoralis (Life Cycle)
First example of a FACULTATIVE PARASITE
(DO NOT NEED HUMANS to survive; can reproduce in the soil and do just fine)
Infected individual: passes larvae in the stool
Diagnostic form: looking for a larva, not an egg
-Worms have sex in the environment, produce eggs in the soil
