Presentation on theme: "Nematodes, Cestodes, Trematodes Slackers Facts by Mike Ori."— Presentation transcript:
Nematodes, Cestodes, Trematodes Slackers Facts by Mike Ori
Disclaimer The information represents my understanding only so errors and omissions are probably rampant. It has not been vetted or reviewed by faculty. The source is our class notes. The document can mostly be used forward and backward. I tried to mark questionable stuff with (?). If you want it to look pretty, steal some crayons and go to town. Finally… If you’re a gunner, buck up and do your own work.
Describe a nematode
Round spindle shaped worms that range in size from 1mm to 70cm. They undergo multiple larval stages. They are dioecious (separate sexes)
What are the three methods of nematode infection
1.Ingestion of eggs 2.Ingestion of larva 3.Direct penetration of skin
Describe the relative frequency of nematode disease in children v adults
Children > adults
What are the intestinal nematoed and what are their common names
What is the life cycle of Enterobius vermicularis
Ingested eggs hatch in small intestine Adults live in colon Eggs deposits in perianal region nightly by females
How is Enterobius vermicularis diagnosed
Sticky side out Scotch tape wrapped slide is pressed against perianal region. Tape is examined under microscope to identify the presence of eggs
What is the hallmark clinical sx for Enterobius?
What is the lifecycle of Trichuris trichuria?
1.Ingestion of embryonated eggs from contaminated dirt. 2.Larva hatch in small intestine 3.Adults mature in colon where they burrow into the surface 4.Eggs are passed in the feces 5.Egg embryonate in the soil over 2-4 weeks
What are the clinical sx of Trichuris
None if worm burden is low. Otherwise tenesmus with chronic mucoid diarrhea occurs. Rectal prolapse may occur
Why does rectal prolapse occur with Trichuris?
The adult worms burrow into the epithelium and weaken it.
O and P for O
What is the lifecycle for Ascaris lumbricoides?
1.Ingestion of embryonated eggs which hatch in intestines 2.Larva migrate to alveoli 3.L3 larva break through into the alveolar spaces 4.Larva migrate up trachea and are swallowed 5.Adults mature in small intestines 6.Eggs pass in feces 7.Embryonate in soil for 2-4 weeks
What is the relative size of ascaris?
They can range up to 70cm
Correlate the intensity of disease to Ascaris chracteristics
Disease intensity is dictated by worm burden. Higher burden results in greater likelihood of clinical sx.
Relate eosinophilia to Ascaris infection
Elevated when the worms are migrating to and especially when they are molting within the alveoli.
How does Ascaris cause disease in the intestines
Primarily through blockage
Describe Necator americanus lifecycle
1.Eggs hatch in the soil and larvate 2.L3 larva directly penetrate the skin 3.Larva migrate to the lungs and pass through to the alveolar space 4.They are regurgitated and swallowed 5.Adults mature in the small intestines 6.Eggs pass in the feces
How dow Necator and Ancylostoma vary in their paths of infection?
Ancylostoma infection can also occur by direct ingestion of eggs in a manner akin to Ascaris. Wakana’s disease relates to ancylostoma infection by ingestion
Describe the clinical disease
Asthma from migration that is less sever than ascaris because molting does not occur. Anemia related adult repositioning every few days in the intestine coupled with anti- coagulant
What is the dx for Necator and Acylostoma
Direct microscopic observation of eggs passed in feces
What is Strongyloides lifecycle
1.L3 larva penetrate skin 2.Larva migrate to lungs and break out of alveoli 3.Larva migrate up trachea and are swallowed 4.Adults mature in the small intestines 5.Eggs ebryonate and hatch in the host 6.L2 larva pass in feces 7.L3 larva reinfect host
How does Strongyloides infection differ from that of other intestinal worms?
Strongyloides eggs hatch within the host resulting in the potential for autoinfection.
Describe Strongyloides disease
1.Pneomonitis 2.Moderate to severe watery, moucousy diarrhea % eosinophilia
What dictates the level of eosinphilia between Ascaris, Necator, Ancylostoma, and Strongyloides
Ascaris has the highest reactivity because it molts L1-L2 and L2-L3 within the tissues. Thus eosinophilia is highest in ascaris.
Trichenella spiralis lifecycle
1.Ingestion of encysted organisms in undercooked, non-frozen pork, bear meat, and rat. 2.Adults mature in the intestines. 3.Larva migrate to the skeletal muscles and encyst for up to 30 years.
Ca and dog hookworm larva penetrate the skin but cannot enter the circulation. They persist for about 10 days before dying
What is visceral larval migrans
Toxacara canis and ascaris of dogs cannot break out of alveoli. Organism disseminates and encysts primarily in liver and eye.
What is filiariasis?
Infection with tissue nematodes transmitted by arthropods.
What are the agents of Filariasis?
Wuchereria bancrofti Brugia malayi Onchocerca volvulus Loa Acanthocheilonema perstans
How do the insect biting pattern and the worm levels in the blood compare in filariasis?
Worm levels increase in a way such that their levels coincide with the activity of their insect vectors. The mechanism is not understood.
Describe the role of antibiotics in the treatment of filariasis
Many filariasis agents have an endosybiont bacteria without whom they cannot live. Therapy directed against the bacteria can be beneficial
What are the vectors for filariasis
Mosquitoes – most organism Blood sucking flies – Onchocerca
What are the agents of elephantiasis?
Wucheria bancrofti and Brugia malayi
What is Loa Loa
A filariasis that migrates through the subcutaneous tissue of the eye.
What is the life cycle of Onchocercosis
1.Blood sucking flies deposit larva in skin 2.Nodules form filled with organisms 3.Black flies ingest larva from nodule
Describe the role of the immune system in causing Onchocerca disease
The immune system largely ignores adults but reacts vigorously against the endosymbiotic bacteria (Wolbachia) contained within. It is believed the the immune response leads to disease.
What are tremetodes
Flukes of nature
List the tremetodes
Clonorchis sinensis – Chinese river fluke Fasciola hepatica – Sheep liver fluke Pargonimus westermani – Human lung fluke Schistosomes – blood flukes
Where do adult schistosomes live?
Depends on species. Mansoni, japonicum, mekongi live in mesenteric venules Maematobium in the venus plexus of the urinary bladder
Where do schistosomes lay their eggs and what happens to the eggs
Eggs are laid on the venous endothelium. They pass through the epithelium to be passed in urine or feces depending on speces
Describe the lifecycle of schistosomes
1.Eggs hatch in fresh water to form miracidia 2.Miracidia pentrate snails and mature to cercariae 3.Cercariae leave snail and penetrate host. 4.Migrate to lungs and liver and mature to adults 5.Adults mate and migrate to venous plexus of mesentery or urinary tract. 6.Eggs are deposited into epithelium where they burrow through to the epithelium to pass
What is the origin of granulomatous disease in schistosomiasis
Eggs float to the liver instead of passing into the epithelium. In the liver they elicit a strong immune response that results in granuloma formation.
What are the time course of the diseases caused by schistosomiasis
Swimmers itch lasting a 2 days Katayama fever beginning 2-3 weeks after exposure Chronic schistosomiasis beginning 2+ years
1. Ingested eggs hatch in cattle 2. Larva hatch in small intestines 3. Larva penetrate intestinal epithelium 4. Larva migrate to the skeletal muscle to encyst and develop to cystecerci 5. Encysted meat is improperly cooked and ingested. 6. Unencyst and develop into adults 7. Proglottids containing eggs break up and eggs pass in feces
Describe the clinical disease caused by the adult tapeworm
Usually only one worm present so there is no clinical disease. PT may notice proglottids in stool.
What is a proglottid
It is a segment of the worm that contains the eggs. It developed from a hermaphroditic segment that contained uterine and testes elements.
What is cystecercosis
Cystecercosis occurs when a human ingest the eggs of T. solium and thus becomes the intermediate host.
What are the clinical sx of cystecercosis
It depends on the worm burden. May form space occupying lesions in any organ system. Epilepsy can occur in if cystecerci form in the brain.
What is the difference between saginata and solium proglottids?
T. Saginata has 12+ lateral branches of the uterus vs 5-10 for T. solium
Does T. saginata cause cystecercosis?
What is interesting about the lifecycle of Diphyllobothrium latum?
It is very complicated and involves multiple fresh water hosts including crustaceans and fish.
What are the clinical sx of D. latum?
Usually none. Can have B12 deficiency.
What is the lifecycle of Echinococcus granulosus?
Sheen act as intermediate host. Dogs eat sheep muscle encysted with the organism. Adults develop.
How do humans enter the Echinococcus granulosus loop
Humans enter the loop by ingesting material contaminated with eggs.
What are the sx of Echinococcus granulosus
Large ( 20cm) fluid filled hydatid cysts form in the liver or viscera.
Describe the disease caused by Echinococcus granulosus
Usually these are mass forming issues due to the large size. The Echinococcus is unique in that it can replicate in the cyst form thus over time a number of cysts can form.
Describe the consequence of hydatid cyst rupture.
The fluid is allergenic and can cause anaphylaxis on rupture. Surgical tx must be done gingerly to prevent shock.