Objectives 24
Three Stages Found in all Helminth Life Cycles
**3 stages found in all helminth life cycles •Larval stage •Adult •Eggs **Hookworm does life cycle B 1)In all of these life cycles worms are going to exist in a larval stage in the human host. Eggs will form and then passed in feces, what happens from there differs. Life Cycle A 1) Fecal oral route transmission. 2) Eggs are ingested, larvae hatch, get into intestine, adult worms form, and those release eggs Life Cycle C 1) Adult worms existing in intestine, they form eggs, eggs pass in feces 2) Here an animal is going to ingest the eggs from feces 3) Larvae go to intestine and end up in the musculature of the animal 4) They will form cysts and so you get this from ingesting cysts within the musculature of the animal Life Cycle D 1) Larvae give rise to adult worms 2) Egg formation passes in the feces 3) Feces ends up in a body of water, and part of life cycle occurs within snails 4) Larvae are released from snails and can enter your skin thru hair folicles.
Diagram the life cycle of Ascaris. Are all life stages of Ascarislimited to the digestive tract? Explain.
Ascariasis - nematode 1) Caused by Ascaris lumbricoides, a large nematode 2) Eggs are ifective, excreted in a person's feces and ingested by another person 3) Cause few symptoms, may not know it 4) Eggs hatch in small intestine, dont stay there, larvae once formed, burrow out of intestine and enter bloodstream. They're carried to the lungs and grow. They migrate to throat, Larvae are then coughed up, swallowed, returned to small intestine, where they mature into adults. Eggs are passed in feces, females deposit 200k a day and passed. 6) Fairly common in southeastern US and worldwide. 30% of world infected. ***LARGEST NEMATODE INTESTINAL PARASITE 6) Diagnosis is often made when an adult worm emerges from the anus, Mouth, or nose **females can be 40cm, males 30cm 7) Hand to mouth transmission, or human manure, contaminated vegetables, contaminated soil Symptoms: Mild: cough, abdo pain Heavily: intesinal blockage, impaired growth
[Big Picture] Compare and contrast the life cycles of Ascaris, Schistosoma and tapeworms.Consider the host and location of the egg, larval and adult stages, as well as the method oftransmission.
Ascaris: •Eggs hatch in intestine larvae burrow out of intestine enter bloodstream carried to the lungs migrate to throat•Larvae are then coughed up, swallowed, returned to small intestine, where they mature into adults. Eggs are passed in feces. Schistosoma 1) The free swimming larvase are infecteive and can penetrate human skin 2) larvae lose thier tails and develop into adults in blood vessels of the liver or bladder, adults mate 3) Eggs are passed into environment in feces or urine 4) In water, eggs hatch into free swimming larvae 5) LArvae penetrate freshwater snail 6) Larvae reproduce asexually in snail, forming a different larval form
Draw and label a tapeworm. Include the scolex, immature proglottids and mature proglottids.Briefly describe the life cycle of a beef tapeworm and include intermediate hosts and the development of cysts.
Cestode: Tapeworm **Can physically block intestine, are gastrointestinal worms. **Segmented flat worms Morphology: 1) Cuticle = skin or outer surface (steals host nutrients by absorption) 2) Scolex= suckers/hooks attach to host tissue, wall of small intest,. often asymptomatic. People dont always know infected until passes segments 3) Neck = narrowest behind scolex; segments called proglottids originate here. 4) New proglottids grow from neck, push the older ones down creating a chain, thats what a strobolla is - Proglottids mature as they are pushed from neck, producing male and female reproductive organs -Proglotids closest to neck are least mature, least developed reproductive - most posterior have mature where reproductive organs are functional -Very end of the worm there is gravid proglotid = egg filled. Those can detatch from the Strobola and can exit the body and feces - •Each proglottid has both sex organs (male and female) that produce the sex cells. Fertilization is internal*** Fertilization 1) Most species it takes 2 worms (cross fertilization between 2 adjacent worms 2) Self fertilization occurs with 2 proglotids within the worm or within the same proglotid 3) Some species, once eggs are fertilizaed they can rupture and are just shed continuously and leave the body in feces 4) In others, the fertilized egg is just stored in proglotid until its full and then the entire proglotid is shed in the feces Then eggs once in environment, form hard outer shell and then they dont hatch until eaten by intermediate host. Either cattle or pigs . Symptoms: Nausea, abdo pain, weight loss, diarrhea Life Cycles
What are some common features of parasitic helminth worms? Describe the three stages that are found in all parasitic helminth life cycles.
Helminths *Multicellular eukaryotic animals many of which are identified by their microscopic eggs and larvae *TWO MAJOR GROUPS OF HELMINTHS: 1) Platyhelminths: the flatworms (Trematodes/Cestodes) 2) Roundworms *Adults can be 15meters long and have well developed organ systems and complex life cycles Common features of parasitic helminths: 1) May lack a digestive system, because they can absorb nutrients from host. Hang out in small intestine and feed of predigested food 2) Nervous system is reduced because they dont have to search for food or respond much to the envirnoment, dont need to search for habitat 3) Means of locomotion is often reduced or lacking 4) Reproductive system is often complex 5) They have digestive, circulatory, nervous, excretory, and reproductive systems Trematodes: flukes 1) Leaf shaped,Oval-shaped flatworms with a digestive tube that ends in a cecum•Expels waste out of mouth 2) Ventral/oral sucker used to hold organism in place and absorb food 3) 5mm-2cm Cestodes: tapeworms 1) Lack own digestive system. Absorbs nutrients through skin 2) For morphology: see slides 18 and 19 can be up to 15-30ft long and live 25yrs Nematodes: roundworms 1) Cylindrical and tapered at both ends, tube within a tube. A body wall and a digestive tract 2) digestive tube that ends in an anus, and expels waste there 3) Can be microsopic or a meter in length, they are unsegmented Ex. Ascaris, hookworms, whipworms Nematodes (roundworms) 1) Whipworm•Trichuris trichiura•Adults form in intestine and burrow into the intestinal wall•Heavily infected individuals can experience dysentery, loss of muscle tone, prolapsed rectum 2) Pinworm•Enterobius vermicularis•Migrates out of anus to lay eggs, causing itching•Transmitted from hands, contaminated bedding, and sexually 3) Loaisis (African eye worm)•Loa loa•Transmitted through bite of deer fly 4) Lymphatic filariasis (elephantiasis)•Wuchereria bancrofti•Transmitted through bite of mosquito•Presence of adult worms in lymphatic system results in obstruction. Lymph accumulates behind the blockage.
Briefly describe the 3 main groups of helminths; then match the following parasites or disease to their respective class: Ascaris, liver fluke, whipworm, tapeworm, loa loa,elephantiasis, pinworm, blood fluke (Schistosoma).
Nematodes (roundworms) ****Whipworm 1)Trichuris trichiura uses LIFE CYCLE A 2)Adults form in intestine and burrow into the intestinal wall, causes damage to intestinal wall, pass eggs in feces = abdominal pain, weight loss 3)Heavily infected individuals can experience dysentery, loss of muscle tone, prolapsed rectum ****Pinworm 1) Enterobius vermicularis, most common nematode infection in US = LIFE CYCLE A 2) Causes sleeplessness and itching around anus 3) Females at night, Migrates out of anus to lay eggs, causing itching 4) Become infected by ingesting pinworm eggs, can survive weeks on contaminated objects. Transmitted from hands, contaminated bedding, and sexually 5) Eggs can become airbourne - breathing 13-13mili pinworms ****Loaisis (African eye worm)•Loa loa 1) Spread by insect vectors 2) Transmitted through bite of deer fly, can visibly see in the eye ****Lymphatic filariasis (elephantiasis) 1) Wuchereria bancrofti 2) Transmitted through bite of mosquito VECTOR 3) When bitten the larval form passes thru the lymphatic system and it matures into adults in lymph glands 4) Male and females mate and eggs are released giving rise to the larval form which can move around in general circulation and be picked up by masquitos during feeding. 5) Presence of adult worms in lymphatic system results in obstruction. Lymph accumulates behind the blockage = massive swelling of extremeties ***Ascaris=nematodes Cestodes (Tapeworms) Tapeworm is the common name for a cestode •Flat, segmented, intestinal parasite •Can be >4 m long!•Signs and symptoms•Usually asymptomatic •Nausea, abdominal pain, weight loss, and diarrhea may occur •People usually don't know they are infected until they pass segments of the helminth! •Pathogens •Taenia saginata: beef tapeworm •Taenia solium: pork tapeworm
Diagram the Plasmodium life cycle. Describe the etiologic agent, vector, symptoms/signs, virulence factors, definitive and intermediate host.
Plasmodium-Genus of parasitic protozoa 1) Apicomplexan: characterized by schizogony: a form of asexual reproduction. Rapid nuclear divisions, merzoites Complex life cycle involving stages in the host and vector (Anopheles mosquito needs blood meal for egg production) **circulates in bloodstream and infects RBCs , diagnosis is by blood smear. INTRACELLULAR 1) Plasmodium exists in the host as: •Sporozoites: injected into host's blood from mosquito, 300-500 2) Within 30 min, Undergo schizogony in liver cells and produce merozoites. End up with 30k merzoites in blood 3) Merozoites: infect RBCs 4) undergo Trophozoites stage: grow in RBCs, produce MORE merozoites via schizogony 5) RBCs rupture, releasing 20 merozoites which infect more RBCs 6) Some merozoites develop into male and female Gametocytes, which are taken up by the mosquito 7) Life cycle in mosquito: gametocytes zygoteookineteoocystsporozoites cycle begins again) Malaria 1) Caused by four species of Plasmodium Protozoan: apicomplexan •P. falciparum ** most dangerous •P. vivax ** most Prevelant •P. ovale •P. malariae 2) Epidemiology 3) Endemic throughout tropics and subtropics 4) Affects 10% of the world's population 5) Malaria causes 500,000- 1 million deaths annually, mostly children 6) Vector transmission: Anopheles mosquito •Symptoms associated with parasite's life in erythrocytes•Recurrent Fever + chills (caused by waste products), diarrhea, vomiting, severe headache•Occasional pulmonary or cardiac dysfunction, jaundice may occur•Anemia, weakness, and fatigue gradually occur P VIVAX - symptoms every 2 days, fever caused by organism being released from RBC to ensure at night its in the correct stage of the life cycle. Mos feed at night VF 1) Reproductive cycle occurs within RBCs- hides parasite from immune surveillance (RBCs don't display MHC) 2) Adhesins allow red blood cells to adhere to certain tissues (avoid clearance by spleen) 3) Changes in body chemistry attract other mosquitoes: the gametocytes trigger changes in body odor that attracts Anopheles mosquitoes !! 4) *** Hemozoin •In RBCs, Plasmodium digests hemoglobin, which releases free heme .•Free heme is toxic! So the parasites covert it into a non-toxic insoluble crystalline form called hemozoin. •Many anti-malarials (ex. Chloroquine) work by inhibiting hemozoin formation. Definitive vs. Intermediate Host 1) The mosquito is the DEFINITIVE HOST because it harbors the sexually reproducing stage of Plasmodium. 2) The human is the INTERMEDIATE HOST because it is the host in which the parasite undergoes asexual reproduction. •Diagnosis, treatment, and prevention 1) Diagnosis made by identifying Plasmodium in blood Chloroquine, raises pH of lysosomal and reduces ability to breakdown host hemoglobin 2) Treated with various antimalarial drugs 3) Some Plasmodium strains are resistant to antimalarial drugs 4) Prevention requires control of mosquitoes•Use of mosquito nets is important way to reduce contact 5) What about a vaccine???•Several vaccines are currently under development •Difficult to accomplish due to complex life cycle •Parasite is very efficient at evading immune response
Diagram the life cycle of Schistosoma (blood fluke), including transmission.
Schistosomiasis - a FLUKE, TREMATODE 1) Caused by 3 species of Schistosoma, a blood fluke (trematode) 2) Serious parasite disease, 2nd to malaria in death or disables 3) Worm has separate sexes 4) Female helminth lives permanently in a groove in the body of the male, union = continually mating, eggs 5) Either ingest the eggs, or larvae or transmitted via insect vector, but here you get THEM THRU SKIN - water, from snails 6) Symptoms caused by eggs shed by adult schistosomes in host CYcle 1) Freshwater contaminated by Schistoma by infected people urinating or defecating in water, eggs will hatch, and if snails are present, they multiply and develop inside the snail. 2) Parasite leaves snail, back into water and can survive 48hrs. Worms can penetrate skim 3) Within several weeks worms mature into adult worms and live in blood vessels where females keep producing eggs. 4) Some eggs can travel to bladder or intestine and passed. 5) Many eggs can be swept away in host circulation and become trapped in tissues and organs. 6) Symptoms are from eggs shed from adult worms - not a worry here because of snail and also sewage treatment Symptoms --Can include inflamm. of bladder and intestine, itchiness, fever, chills, cough --Can also cause - lodge in lungs, liver brain or kidneys and cause renal failure, increase BP, bladder obstruction or cancer -- Defensive reactions of the human host cause granulomas to form --Not an issue in the US because sewage and water treatment minimizes contamination of water supply, and a snail host is needed to complete the life cycle It is dangerous when worms mate because eggs can lodge in tissues such as liver, lungs, brain, kidneys Adults reside in intestinal or urinary bladder blood vessels
Beef Tapeworm Life Cycle
Tineas Saginata - Beef 1) Human host passes eggs or proglotids in feces 2) They end up in environment 3) Cattle eats the eggs and a form of the larval stage hatches and penetrates intestinal wall 4) Goes to musculature of animal, gives rise to Cysticerci 5) Get this by eating raw or undercooked contaminated 6) Definitive host: human because sexual repro occurs 7) Intermediate host: cattle for T saginata. Swine for T solium. **Humans can become an intermediate host if they ingest eggs or proglotids. LArvae released from eggs can invade muscle or brain tissue of humans and cysticerci forming. if in brain, serisures and other issues ** food or eggs contaminated with human feces, or hands Prevention relies on thorough cooking and/or freezing of meats.
