L16: Intestinal nematodes Flashcards
Name general characteristics of nematodes
long, cylindrical, unsegmented bilately, symsttry, covered by cuticle
Describe the face of nematodes
- pseudocoelomates with body cavity
- no suckers/hooks/respiratory/circulatory
- male smaller than female
- nematode infection impact human/animal health a lot very important
What is the body wall made of
outer cuticle, hypodermis, somatic musculature
Go in depth about quantites of body wall
- cutile
*covers whole body and lines cavity, recturm, vagina and pore
*has metabolically active enzymes
*smooth with spines, ridges for locomotion
*molted and reformed 4 times in life - hypodermis to secrete cuticle
- somatic musculature with longi muscles arranged in > 1 rows with different shapes
has 2 muscle regions
contactical with myofibrils and non contracile to hold organelles
What are the layer of cutiicl
It consists of 4 basic layers
i. Epicuticle
ii. Exocuticle
iii. Mesocuticle
iv. Endocuticle
What is the digestive tract of nematodes made of
have compelte digestive tract
foregut: for digestion, mouth, phyraniz, esophogous
midgut: intestine, sight of absoroption with microvilli and digestion
hingut: in females it has recturm and anus in males it has reprodutive parts
What does the nervous system of nemotodes consit of
circumesophageal commissure – also called the nerve ring, surrounds the esophagus
Rectal commissure – encircles the rectum
Longitudinal nerve trunks from the nerve ring extends the length of the nematode and peripheral nerves
branch from here to supply sensory organs
What is the exretory system of nematodes
1 or 2 renettes
digestive tract is the principal excretory organ, so this is only osmoregulatory
no flame cells
Desrcibe reproctuve system of nematodes
seperate sexes => diosecious
tubular organs lysin in pseudocoelom
Detail the male reproductive system of nematodes
posterio end is curved
structures exten to cloacoa
single testis
1 or more copulatory spicules to keepvulva open
spicule guide
Detail male reproductive system of female
didelphic with 2 ovaries and 2 uteri
single vagina and vulva
Life cycle of Nematodes
Sexual reproduction occurs within an infected definitive host
* Typically includes 6 stages – egg, 4 juvenile larval stages and adult
* Infectious stages for humans and animals are either the egg or larva
* Eggs only hatch under specific, favorable external conditions to protect the larva
* Larval stages are separated by rounds of molting
Molting nematodes general characteristics
nematodes go trough 4 rounds of molting or excheatment
during the process it forms a new cuticle, loosens the old one, reaptures to break out of the old one and escapes the larva
controlled by exsheating fluid
host and site specific
Enterobius vermicularis
def host: humans
int host: none
causes enteribasis
worldwide, common in temperate places
kids, overcrowded
most common in N.aermica
whip shape, females have pointed tail = pinworm
Life Cycle of Enterobius vermicularis
- Gravid adult female worms deposit eggs on perianal folds
- Infection occurs via autoinfection (transferring eggs to the mouth with
hands after scratching the perianal area) OR retroinfection by L3
larvae
that hatch from perianally located eggs and migrate back up the host’s
GIT OR cross-infection (exposure to eggs in the environment e.g.,
contaminated surfaces, clothes, bed linens, infected persons etc.) OR
inhalation of airborne eggs - Following ingestion of infective eggs, larvae hatch in the small intestine
- The adults establish themselves in the colon, usually in the cecum
- Gravid females migrate nocturnally outside the anus and oviposit while
crawling on the perianal skin. Females lay up to 15,000 eggs daily
Larvae inside the eggs develop (become infective) in 4-6 hours under optimal
conditions. Eggs can remain viable for up to 20 days in a moist environment
Clinical Presentation of Enterobiasis
asymptio
heavy infection => perianal prutirus at night => bacterial superinfection/excoriations => scratchy butt eggs to finger nails infection
Diagnosis of Enterobiasis
eggs around perianal area during scotch test
treatment of enterobiasis
mebendazole, alternatively, albendazole but only for adults
What is Trichuris trichiura
def host: humans
int host: no body
soil transmitted helminth and tricharis
worldwide but tropic/subtropic - moist is good for embryonic
3rd most common worm
Trichuris trichiura general characteristics
whip worm, females longer than males
T.campanula cat
T. suis pig
Life Cycle of Trichuris trichiura
- The unembryonated eggs are passed with the stool
- In warm, moist soil, the eggs develop into a 2-cell stage
- This is followed by development into an advanced cleavage stage
- Finally, an embryonated egg develops with an L3 stage larva Eggs
become infective 15-30 days after being passed - After ingestion of infective (embryonated) eggs in soil-contaminated
hands or food, eggs hatch in the small intestine and release larvae - Larvae mature and establish themselves as adults in the colon. The
anterior portion of the worm is ‘threaded’ into the mucosa of the
cecum and ascending colon where the worm resides. Female worms
shed 3000-20000 eggs per day. Adult worms have a life span of about
1 yea
Clinical Presentation of Trichuriasis
light is asymptomic
chronic = rectol prolapse
go to colon and rectum => inflammation which cause tenemus and prolapse
gastro issues
anemia, weight loss
Which infections happen together often
E. histolytics and Trichuriasis
What is Ascaris lumbricoides, small on general characteristics
def host: human
int host: none
soil transmitted helminth
adutl causes ascaris and larvae causes pneumonia
worldwide, common in tropic / subtropics
adults are largest nematode parasite = large roundworms
3 lips lines with teeth
Life Cycle of Ascaris lumbricoides
- The adult worms live in the lumen of the small intestine.
- A female may produce ~200,000 eggs daily. These are passed with the feces
- The unfertilized eggs may be ingested but are not infective. Larvae develop to
infectivity within fertile eggs after 18 days to several weeks, depending on the
optimum environmental conditions – moisture, warmth, shaded soil, oxygen
levels - The Infective (embryonated) eggs are swallowed
- The larvae hatch in the duodenum
- Larvae then invade the intestinal mucosa, enter the circulatory system, and
over the period of one week, are carried to the heart and then the lungs - Larvae mature further in the lungs (10-14 days), penetrate the alveolar walls,
and ascend the bronchial tree to the throat. Coughed up larvae are swallowed.
Upon reaching the small intestine, they develop into adult worms. About 3
months after initial ingestion of infective eggs, adult worms begin to oviposit.
Adult worms can live for 1-2 years
Clinical presentation of Ascariasis
85% asympto
more eggs => worse, malnutrion
break down the phases:
pulmonary migration phage
*inflammatroy and hypersensitive, penumonia sympmtoms, eosinophila, urticaria
developing mature in intestinse
abdmonidal pain, nausea, vomitting, impaired absoroptn
heavy infection
*intestinal abstroction, liver absecces, appendecitis
Diagnosis of STH Infections
T. Trichiura
*eggs in poop, heavy infection diagnosis, rectal prolapse using protpscope
A. lumbricoides
*eggs in poop, eggs expelled by butt or mouth
*larvae in spetum/gastric aspirate in pulomanry migration
Treatment of STH Infections
Albendazole or mebendazole
Drugs target adult worms only
