Nematodes- infective eggs Flashcards
What is the distribution of Trichuris species?
worldwide, but especially in tropical areas with poor sanitation, esp in children
Is Trichuris an old parasite?
yes, petrified eggs have been found in prehistoric humans
What is the name of the human whipworm specie?
Trichuris trichiura
What are the species names for cat, pig, mouse, and dog whipworm?
Trichuris campanula, Trichuris suis, Trichuris muris, Trichuris vulpis
What are some distinguishing features of whipworm species?
has a narrow anterior end and a wider posterior end
females are always larger than the males
Under what conditions will whipworm eggs embryonate?
must be in external environment: high humidity, sandy soil and 20-30 degrees celcius
Describe the whipworm egg morphology
barrel-shaped, unembryonated, has bipolar plugs, a smooth shell
Where does the first stage larva hatch from the egg?
in the host small intestine and migrate to colon
Where do adult whipworms inhabit?
in the cecum and ascending colon, with anterior portions threaded through mucosal layer
What is the life span of adult whipworms?
1 year
What is the pathology of whipworm infection?
frequently asymptomatic
heavy infections in children can cause abdominal pain, diarrhea and rectal prolapse (caused by weakened ligaments holding rectum), sometimes growth retardation
How can a whipworm infection be diagnosed?
microscopic identification of eggs in feces
Which drugs can be used to treat whipworm infections?
mebendazole and albendazole
What is the distribution of Enterobius vermicularis (pinworm)?
broadest geographic range. most common in temperate regions of Western Europe and North America (rare in the tropics)
How are pinworm eggs spread?
oral-fecal route
What are the hosts of pinworm?
humans are the only known natural host, no reservoirs
Describe the adult pinworm morphology
small, white, threadlike bodies, females are bigger.
females have a long, pin-shaped posterior
Where do the adult pinworms reside?
in the cecum. gravid females migrate at night to lay eggs
Describe the pinworm egg morphology
flattened asymmetrically on one side, ovoid in shape, embryonate in 6h. viable for 20 days in moist environments
What is retro-infection of pinworms?
When the larvae hatch on the anus and crawl back up the intestinal tract to the cecum to mature into adults
What is the pathology of pinworms?
usually asymptomatic.
females and eggs may cause irritation of butt hole region.
female migration at night may lead to discomfort and scratching, aiding in the spread of eggs
How can pinworm infection be diagnosed?
scotch tape test: cellulose tape is applied to anal area
anal swabs: has adhesive material
How are pinworm infections treated?
primarily mebendazole, but also albendazole
What is the largest and most common intestinal nematode?
Ascaris lumbricoides (human roundworm)
What is the distribution of Ascaris lumbricoides?
worldwide, but mostly in Africa, in the countryside. eggs can remain viable for years in moist environments
How are people common infected with Ascaris lumbricoides?
using feces to fertilize soil, children playing in soil
What are the hosts of Ascaris lumbricoides?
humans are the only definitive host
Describe the morphology of the adult roundworms
adults are the largest nematodes to infect humans
females larger than males
male posterior end is curved due to spicules
three lips at anterior end, lined with miniscule teeth
Describe the roundworm egg morphology
unembryonated when passed in the feces, become embryonated in soil, eggs are the infectious stage. thick, rough outer shell
Which path do the larva follow in the body?
hatch, burrow in the intestine, through intestinal mucose to blood, reach the lungs and migrate up the respiratory tract so that they can be swallowed. mature into adults in the small intestine
What is the pathology of ascariasis from adult worms?
light infection is usually asymptomatic, but can lead to vague abdominal pains
heavy worm burden results in malnutrition
wandering adults can cause blockages resulting in intestinal obstruction, appendicitis, biliary ascariasis, perforation of intestine, pancreatitis, etc
What is the pathology of ascariasis from larvae?
larvae can penetrate alveoli, causing plasma to enter them and cause an inflammatory reaction. leads to pneumonia-like symptoms such as low fever, cough, blood in sputum, asthma
How is ascariasis diagnosed?
identify egg in feces
Which drugs are used to treat roundworm infections?
albendazole in combination with mebendazole. ivermectin can be used alternatively.
this treats adults. no treatment for larvae
What is the distribution and host of Baylisascaris procyonis?
it is a raccoon roundworm that does not develop in humans but can cause problems.
common throughout North America
What is the pathology of Baylisascaris procyonis?
migration of large larvae through many tissues, including liver, heart, lungs, brain, eyes causes visceral larval migrans or ocular larval migrans symptoms.
symptoms are severe because the larvae are large and move a lot
How can Baylisascaris procyonis infection be diagnosed and treated in humans?
rare infection, not often diagnosed. serological test and identification of larvae (biopsy or autopsy).
no drugs are completely effective
