Lecture 69_70 - Intestinal and Tissue Dwelling Nematodes Flashcards
what are some common features of helminth infections?
Do not multiply within the host
Most infections are of low burden; rarely are there high burdens
Genetics, infection history, nutrition correlate with worm burden
Helminth parasites establish long term infections (nematodes - 1 to 3 years, river blindness – 10+ years, strongyloides – lifetime)
Helminthes – induce eosinophilia – elevated igE; skewing the patient towards a Th2 response
What are the Gastrointestinal Nematodes?
which are anthropodic ?
which are zoonoitc?
Antrhopodic Nematodes: Pinworm -- Enterobius vermicularis Hookworm -- Ancylostoma Duodenale Ascaris Lumbricoides --- Whipworm -- Trichuris Trichiura Strongyloides -- Threadworm
Zoonotic:
Trichinellosis – Trichinella spiralis
Toxocariasisi – Toxacara canis and Toxicara cati
Describe the General lifecycle of the nematode:
xxxx
Pinworm
what is it scientific name?
what is the name of the infection
what kind of nematode is it?
describe its life cycle and how it infects humans?
Enterobius vermiculiaris
Enterobiasis
Anthropotic GI nematode
Adults live in the intestine Females move to the perianal region; where she distributes very sticky eggs The human scratches eggs on hands re-innoculation; infect other people
In the Gut the eggs hatch
males and females unite
Pinworm
- geographic distribution
The most common helminthic infection in the US
common in preschool and school aged children in crowded conditions
Pinworm
- clinical features
- lab dx
Asymptomatic
Peri-anal pruritus (itching)
anorexia, irritability, abdominal pain, disturbted sleep
Labs:
Scotch tape test of the peri-anal region early in the morning
Followed by microscopic detection of eggs
Pinworm
treatment
Prevention
Treat: Pyrantel Pamoate – paralysis of the pinworm
Prevention – hygeine, laundering of bedding;
Hookworm
what is the scientific name?
what kind of nematode?
Describe the life-cycle and how it infects humans?
How long do they stay in the host?
aka – Ancylostoma duodenale and Necator americanus.
Anthropodic GI Nematode
Lifecycle:
- eggs are passed in the feces
- hatch and develop into L3 forms in favorable environmental conditions
- Humans walking with bare feet or other skin contact
- hookworm penetrates the skin
- travels to veins –> heart –> lungs
- Develop in to L4 form and become very motile
- Climbs to the esophagus
- induces cough, swallow reflex and enters the Gut
- Concentrate in the jejunum
-Develop into adults
- attach to intestinal wall with resultant blood loss
-
Eliminated by host in 1-2 years
Hookworm
who gets infected?
what is the geographical distribution
Second most common human helminthic infection (after ascariasis)
Effects children, pregnant women, malnourished persons
Hookworm
- describe the morphology and pathology
1 mm long
Female Teeth – Chitinous structures–
protrudes into the lamina propria – disrupts and sucks blood of capillaries
Hookworm
Describe the pattern of disease burden
describe immunological changes in the lungs
burden: increases over time – unlike other parasites whose peak burdens are at young ages
Immuno: makes the lung a Th2 biased environment
Ancylostoma duodenale and Necator americanus.
clinical features
Labs/diagnosis
Treatment
Clinical features:
- itch at site of skin penetration
- Iron deficiency anemia – can lead to growth and mental retardation
- diarrhea, weight loss, abd pain, cardiac complications (arrythmias)
Labs/Dx: Microscopy
Treat: light infections in most countries go untreated
Albendazole
Ascaris Lumbricoides; Ascariasis
- describe the lifecycle and how its infectious to humans
- what happens when sick, under stress or during treatment?
the largest nematode of human intestine – females up to 35 cm
- Embryonated eggs are passed in the feces
- infective eggs are swallowed -larvae hatch
- invasion of intestinal mucosa; carried in the blood to the LIVER and then the LUNGS
- Develop in the lungs for 2 weeks; penetrate the alveolar walls
- Crawl up to the esophagus
- cough and swallow
- back in the gut
- 2 more months of maturation
when host is sick: migration of the worms out of the body (nose, mouth, anus)
Ascaris Lumbricoides; Ascariasis
- epidemiology:
- how is it transmitted ?
- geographic distribution
The most common human helminthic infection (25% of the world)
World wide distribution
more so in tropical zones
Fecal oral ingestion
Ascaris Lumbricoides
- Clinical features: light vs heavy infection
- lab/dx
- Treatment
Low worm burden: Asymptomatic; flu like symptoms; coughing wheezing in lung phase
high burden: -abdominal obstruction - flu like symptoms - exclusion of the biliary tract - cough, wheezing if in lung "Ascaris Pneumonia"
Labs/Dx: microscopic identification of eggs in stool
adults worms in stool
larvae in sputum
Treatment: Albendazole, mebendazole, pyrantel pamoate
