Other Aschelminths Flashcards
Organisms considered “Eutelyosts” share what trait?
Have a fixed number of somatic cells their whole life cycle, which only grow bigger throughout life.
The Aschelminths are generally considered to have what basic traits?
Live in water, usually “worm shaped”, no blood-vascular system or true coelom, digestive tract is a complete tube, and they usually have some form of ashesive organs.
Nematode bodies are completely encased in a non-living _____. Describe this.
Cuticle. Composed of many sub-layers of polymers of chitin. It is bendable and resilient but it cannot stretch outwards
Where do nematodes most often live?
Must live in water. Typically live in soil (along plant roots), water, or host animals. Found basically all over the entire world.
What does the drug Pyrantel pamoate do to susceptible nematodes?
Induces a state of tetanus (constant muscle contraction)
Briefly describe the general physical characteristics of nematodes
Round in cross section, often round and thin, usually only a few mms long but can be as much as a meter long. Have a thick cuticle that must be molted/shed periodicially. Have a tubular gut with anterior mouth surrounded by lips and sensory structures. Buccal cavity is sometimes armed with teeth or rasping structures.
TRUE OR FALSE: All nematodes hatch out of eggs outside of the mother
FALSE, some hatch inside the mother and are birthed live
How many juvenile stages are there in nematodes? What happens during each transition? Which stage is usually infective?
4 stages, with a cuticle molt at each stage. Usually the third is infective.
What is the purpose of the lateral, dorsal, and ventral ducts in nematodes?
Lateral ducts likely used for excretory functions.
Dorsal and ventral hold the dorsal and ventral nerve cords.
Describe the structure of the gut in most nematodes
Usually have a muscular pharynx which can bypass the high pressure of the body cavity by rhythmically contracting and opening and closing a flap below the pharynx (connecting pharynx and esophagus)
What is unique about the body fluid in nematodes?
Under extremely high pressure, actually compresses the gut when it is not full
What kind of muscles exist in nematodes?
Lateral (only longitudinal, no circular) muscles all along the body with long extensions of the muscles reaching out to the dorsal and ventral nerve cords
Why don’t nematodes have circular muscles?
They can’t contract the body because of the cuticle anyway, so they would not be useful
How is nematode sperm unique among metazoans?
Sperm have no flagella, and are in fact amoeboid
Briefly describe nematode gonads
Very simple with the gametogenic organism at one end and the gonopore at the other end. Ex. ovary at one end which becomes uterus which becomes the vagina.
Describe the external physical differences between male and female nematode.
Males typically have a hooked tail for grabbing female during reproduction.
Hookworm males have a ______ used to wrap around the female during copulation. Describe this.
Some other nematodes have something similar called a _____
Bursa - a large flat disk used to attach to female
Pseudobursa - like little legs for wrapping around the female
_____ can be inserted by nematodes into the vagina to open the vagina. Why is this necessary?
Spicules. This is needed because the body is under such high hydraulic pressure that the vagina is naturally shut
The Order Trichurida is also referred to as ____. Why is this?
whipworms. They look like whips, with an enlarged posterior end and a very thin anterior half
A whipworm infection is referred to as _____ and is a result of infection with ____
Trichuriasis. Trichurus trichiura
Describe the lifecycle of T. trichiura
Direct life cycle.
Egg comes out in feces, starts at 1 cell stage, moves into 1 cell stage, and develops through more advances cleavage into embryonated egg. Fecal-oral contamination results in ingestion of embryonated egg, which becomes a larva, penetrates host mucosa, and becomes an adult.
____ is localized inflammation and increased blood flow that causes a red colour
Erythema
What kind of symptoms does T. trichiura infection in the large intestine produce?
Usually nothing, but when someone has more than 100 worms, diarrhea, inflammation, bloody diarrhea, abdominal pain, rectal prolapse can occur.
How is T. trichiura distributed across the world
Tropical areas (eggs cannot survive above frost line), areas with poor sanitation practices or pooping in places other than bathrooms. Also present in southern US
How is T. trichiura diagnosed?
By finding whipworm eggs in feces (microscope). Sometimes concentration is necessary. Also possible to examine rectal mucosa by proctoscopy
What is the drug of choice for nematodes? What does it do?
Mebendazole. Causes worm death be selectively and irreversibly blocking glucose/nutrient uptake in adult intestine where helminths dwell.
What is the absolute best way to mitigate T. trichiura risk?
EDUCATION
What is the basic egg morphology of T. trichiura?
idk
How was Trichinella spiralis discovered?
Mortician found that cutting through people’s muscles was dulling his scalpel. IT was found that within the muscle cells of of some people there were tubercles made of collagen containing small worms. A network of tiny “venules” called a “Rete” was found to form around the worm, creating a tiny little incubator (just based on hormone signals). Sometimes the tubercles become calcified, which was what caused the dulling of the scalpel.
What is the transmission cycle of Trichonella spiralis?
IT develops completely in one host, but can be transferred by carnivory. Only animals that eat flesh can be infected.
Describe the physical external differences between males and females of T. spiralis
All are a few mm long but males are slightly smaller. Males have a curved end with a pseudobursa
What is the life cycle of Trichonella spiralis?
Juveniles mature in host’s small intestine and females produce new juveniles (ovoviviparous). Juveniles enter the blood stream of host (intracellularly) and eventually enter host’s muscle tissue, where they mature and infect next host when it consumes infected tissue.
What is unique about reproduction in Trichonella spiralis?
Males die after fertilization and females die within about 6 weeks after
How do people react to Trichonella infection?
Soreness and tenderness of muscles. Very rarely people die of it
A rete of Trichonella is formed by the stimulated production of _____
Vascular endothelial growth factor
The development of blood vessels in Trichonella retes is referred to as _____
Angiogenesis
What is the single biggest risk factor for Trichonella infection in humans?
Consuming undercooked or uncooked meat (ex. pigs, seals, bears)
What are risk factors for Trichonella in pigs?
Ingestion of animal protein such as rats, confined conditions for pigs (they eat each other’s tails)
What are the symptoms of Trichonella infection?
Light infections may be asymptomatic.
In intestines one can have diarrhea, abdominal pain, vomiting.
Juvenile migration into muscle cells causes edema (facial/periorbital), conjunctivitis, fever, myalgia, splinter hemorrhages, rashes, eosinophilia
Can Trichonella infection be deadly?
Yes, occasionally it causes myocarditis, penetration of juveniles into CNS, and pneumonitis
How do symptoms change over the course of Trichonella infection?
As juveniles encyst into the muscles, the symptoms subside
How is Trichonella infection treated?
Mebendazole
Why are hookworms called such?
Have a large hook at the anterior end of the worm (just behind the oral opening)
Briefly describe the Hookworms
All are blood feeders, usually living in the intestine (small intestine).
How do hookworms gain access to blood?
Have a large buccal capsule armed with plates, teeth and lancets for tissue destruction (macerate tissue, access blood)
Hookworms are restricted to the tropics and subtropics. How?
Eggs must be laid in loamy, moist soil in warm areas (no frost)
What are the two human hookworms? How do they differ?
Ancylostoma duodenale, Necator americanus
slightly smaller
A. ceylanicum can cross the species barrier between ____ and _____
Monkeys and humans
Which hookworms penetrate human skin and do not develop any further
A. braziliense, Uncinaria stenocephala
Briefly describe the hook worm life cycle (though you should know this considering how long you’ve worked on your essay)
Eggs are passed in stool and hatch in 1-2 days. Juveniles grow in the soil and after 5-10 days they can penetrate human skin, flow through veins to lungs. The penetrate the alveolae, ascend to the pharynx and are swallowed. Once in the small intestine they can complete development.
Can hookworms directly infect small intestine with ingestion?
There is some evidence that N. americanus can
The juvenile that hatches out of the eggs of hookworms is referred to as _____ larvae. What do they look like?
Rhabditiform. Have 2 enlarged pharynxes with a circumesophageal nerve cord in the middle
Briefly describe the filariform larva of hookworms
There is only one muscular pharynx in the filariform larvae with the nerve cord anterior to it
Hookworm is the ___ most common helminthic infection
2nd
Heavy hookworm infections can be in _____ of worms per individual
thousands
____ occurs at the site of hookworm infection during penetration by the filariform juveniles
Ground itch
Filariform hookworm juveniles respond to what signals that indicate life?
Warmth, CO2
How is Hookworm infection diagnosed?
Microscopic identification of eggs performed by:
collecting stool, concentrating eggs (can use saline solution to cause them to float on top)
How is hookworm infection treated?
Albendazole, mebendazole
Describe the drug Ivermectin?
One of the most important anthelmintic/antiparasitic drugs of all time. Was donated to Africa to treat river blindness in the 70s
How does one differentiate between N. americanus and A. duodenale?
Rearing filariform juveniles in a fecal smear on a moist filter paper strip for 5-7 days
The large intestinal roundworm is known as _____
Ascaris lumbricoides
How does A. lumbricoides differ from hookworms?
Live in the small intestine, consuming digestive material.
If someone has extremely intense ascariasis, what can happen in the small intestine?
Ascaris lumbricoides worms can block up intestine
How are Ascaris lumbicoides eggs passed on
Passed in feces, can survive for months in good conditions
Ascariasis causes what symptoms?
Abdominal pain, intestinal obstruction, pulmonary symptoms (can cough of blood, result in eosinophilia). Adult worms usually cause no symptoms
How is Ascaris lumbricoides diagnosed?
Microscopy using wet mounts (must identify eggs)
Filarial nematodes must be transmitted to humans how>
Through a blood feeding vector such as mosquito or tick
Describe the appearance of filarial nematodes?
multinucleated worm-mass
What are the 3 types of filarials most responsible for morbidity?
Wuchereria bancrofti, Brugia malayi - Lymphatic filariasis
Onchocerca volvulus - Onchocerciasis (river blindness)
In lymphatic filariasis, how does the swelling occur? What is the vector?
As a result of the immune response to infection of lymphatic tissue. Vectors are mosquitos
How can one use tail morphology to differentiate microfilaria?
Count number of nuclei in the end of tail, observe their arrangement, blunt vs pointed tail, and the presence/absence of a tail sheath
What happens over years and years of Onchocerciasis?
Scar tissue develops so much on the eye that eyes become opaque
How is onchocerciasis transmitted?
black flies
People suffering from onchocerciasis develop what symptoms?
Nodules form all over the body with 2 or more worms present per nodule. Over time the nodules cause sin wrinkling, depigmentation.
What all contributed to a massive decline in river blindness in west africa? Why are rates going up?
Education (don’t hang out near rivers), insecticidal treatment of rivers, treatment of humans. Because of civil war in west africa, rates are going up because proper insectidal treatment is not happening
onchocerciasis is ____notic
anthroponotic
