Lectures 11-15 - Lecture notes 12-15 PDF

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Summary

Instructor: Paul Sharp...

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Digenean: Leucochloridium variae —- remember this lesson goes above. - Definitive host: include warblers—active birds. Eggs are defecated in feces; this species is completely terrestrial. (changes morphology, physiology and behavior of intermediate host; leads to pathology in intermediate host) - Embryonated eggs are ingested by the terrestrial snail (Succinea ovalis). ***Sharp’s favorite dessert is brownie*** -

Tailless cercariae develop in branched sporocysts; metacercaria encyst in broodsac

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Sporocyst divided into 3 parts: o Central body in snail’s hepatopancreas o Tube connecting the central body to the broodsac o Broodsac in the head-foot of the snail and entering its tentacles (infectious stage). ▪ These broodsacs can wind up in antenae of snail; they are colorful; as they grow they stretch out the antenae and you can see its color pattern ▪ Warbler is going to go for the broodsac as it is an “eat me sign”. It can regenerate after being eaten by the bird. Bird will spread eggs and infect other snails in the forest. ▪ When the snail is infected behavior changes as it will climb and expose itself to predators—hence it perpetuates the parasites life cycle.

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Brightly colored broodsac pulses in enlarged snail tentacle

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Broodsac gives rise to tailless cercariae (since there’s no freshwater in this life cycle), which develops in branched sporocyts, metacercarie (infectious stage) encyst in broods

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Definitive hosts include warblers (warbler- bird that is the definitive host; intermediate host- snail)

Digenean: Alaria americana—vet and medical importance. -

Parasite of wolves, foxes, coyotes and the domestic dog (humans are accidental hosts)— founds in intestines.

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Eggs released through feces that will end in freshwater aquatic habitat.

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Mircadia hatch out of egg and penetrate snail (appropiate species)

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Sporocysts -> daughter sporocysts (density dependent) -> cercariae (bores out of the snail)

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Cercaria penetrate tadpole

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Mesocercaria (not like metacercaria cyst; this one is not trapped within a cyst, still considered infectious) develop in tadpole. The tadpole will develop and become a frog and it can “go” to definitive host. (infective to next host, either paratenic or definitive host) Water snake (paratenic host) eats infected tadpole or frog. Dog, Wolfes etc… consume snakes.

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Canid eats infected snake and mesocercariae are freed by digestion

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Mesocercariae penetrate coelom, then move to the diaphragm and lungs (once in lungs forms metacercaria)

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(after 5 weeks) they migrate up the trachea, pharynx, throat (swallowed) and then to the small intestine

o Pathology: ▪ Mature Alaria spp. very pathogenic causing severe enteritis (inflammation of the small intestine) ▪ Often kills host in severe infections (high intensity; dozens or hundreds) ▪ Can be fatal in humans when accumulated in large numbers ▪ o Epidemiology: ▪ Found in various species of Canidae in northern North America ▪ Mesocercariae are pathogenic to human ▪ Acquired by eating undercooked frogs’ legs ▪ Also transmammary transmission (vertical transmission; from mother to offspring) of mesocercariae to offspring via milk

▪ Humans are accidental host hence infection can result in even worse outcomes. •

Vertical (from one host to another) vs horizontal transmission

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Epidemiology: all ecological aspects regarding the transmission, prevalence, incidence, and abundance of an organism.

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Population structure: set of quantitative descriptors of a population, including prevalence, density (mean abundance), variance of a frequency distribution, and curve of best fit. o e.g. which demographic group is more infected?

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Prevalence: percentage of a single host species infected at a given time; “snapshot in time”. (infected/total)*100 Yellow tag: infected snails. Red: new infected snails that happened during the second month at time 0, no infected snails, which means 6/10 is prevalence for month 1, prevalence for month 2 is 8/10

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Incidence: the number of uninfected hosts at the beginning of the measured time; “rate of infection”. o Incidence for month 2 from example above would be 50% (2/4)

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Abundance or density: average number of parasites per host in a sample of hosts, equal to the arithmetic mean; (total # of parasites)/(total # of organisms). Applies to particular species of host and parasite. o 20 parasites and 10 snails: abundance is 20/10 = 2

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Intensity: the number of parasites of one species in a single infected host; total # of parasites of one species within one organism.

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Mean intensity: the average number of parasites of one species per infected host; only looking at infected organisms; (total # of parasites)/(total # of infected organisms).

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Aggregated or over dispersed: a situation in which most of the parasites occur in a relative minority of hosts and most host individuals are either uninfected or lightly infected; most of the individuals in the population are not parasitized or have a small number of parasites.

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Parasite community: the number of different parasite species infecting a single individual host. Ex. different species of Digeneans that can infect a specific host.

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Macroepidemiology: study of the effects of large scale factors, such as climate and culture, on distribution of disease in a population.

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Microepidemiology: study of the effects of small scale factors, such as parasite strains, host genetic variation, and distribution of disease in a population.

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Landscape epidemiology: approach of epidemiology that employs all ecological aspects of a nidus; by recognizing certain physical conditions, the epidemiologist can anticipate whether a disease can be expected to exist.

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Nidus: specific locality of a given disease; result of a unique combination of ecological factors that favors the maintenance and transmission of the disease organism (Ex: stagnant water, a lot of vegetation, specific species of mosquito, etc.)

1. Cercariae

2. Metacercariae cyst

3.Egg

Digenean: Clonorchis sinensis (human liver fluke) . Target organ bile duct of the liver. Hermaphrodites, can cross and do sexual reproduction. Eggs will end up in feces and you need freshwater treatment facility to prevent spread Operculum does not follow curvature of the egg. -

Seconda intermediate host—> freshwater fish (redia only has about 24 hrs to get to the scales of the fish, which they will arrive by using penetration glands.) Metacercarial cyst is infectious stage. Pathology: - erosion of epithelium in larger bile ducts - inflammation becomes prominent, fibrosis, necrosis and atrophy of surrounding liver tissue - trapped eggs become surrounded by granulomas, interfering with liver function because granuloma tissues is tissue that is not functioning - eggs and sometimes entire worms become nuclei of gallstones - cancer of bile duct is often associated with cholorchiasis because parasites can interfere normal flow of bile - Clear structures seen in video. -

Epidimiology: - can live up to 8 years in humans - Clonorchis is common in countries that eat raw fish - Reservoir hosts include dogs, cats, pigs and rats that contaminate streams (hard to eradicate) - Widely distributed in Asia. - Eating frozen, dried or pickled fish imported from endemic areas has caused infections (cant kill by freezing) - Metacercaria can withstand salting, pickling, freezing, smoking fish - May be futile to get millions of people to break century old habit. - Educating people to cook fish; not option for many because fuel is luxury and people have to eat raw fish - Fish farms contaminated with human feces (“night soil”) used as fertilizer through out much of Asia. — great production of algea, and these fish are herbivores. You would need water treatment facility to decrease this incidence. If the eggs make it to freshwater habitat you are perpetuating life cycle.

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don’t have flushable toilets or access to waste water treatment facilities. India: sanitation breakthrough!!!half of Indian households don’t have toilets. They are digging holes (pits) in the ground that after two years when they are full, they switch to another one and residual feces acts as fertilizers. Digenean: Paragonimus westermani (lung fluke) Adults in lungs— eggs leave in feces that they swallowed eggs or by spitting eggs out in spututm. Make it to freshwater habitat, when it hits water miracidium leaves, penetrates snail, and cercaria leaves seeking freshwater crab. They can penetrate the shell of the crab by getting in through the joints of the legs of the crab (can’t penetrate hard shell). Hence undercooked crab, can result in human infection. Seen in Eastern Asia, a different strain in the US— Paragonimus kellicotti (penetrate crayfish). Fluke can go to brain and skin; cough, fevers, chills are common symptoms. It can easily be treated with medication with proper diagnosis (Video). (Picture to the right) cross section lung biopsy with 2 parasites. They bust out of small intestine, penetrate abdominal wall, penetrate diaphragm Schistosome) Pathology: - Once in lungs or ectopic site, worm stimulates inflammatory response - Parasite becomes enshrouded in a granuloma - Eggs in surrounding tissues result in pseudo tubercles - Worms may end up in spinal cord and cause paralysis - Fatal cases are seen when Paragonimus app. Is located in heart or brain - Pulmonary cases are rarely fatal: resulting in chronic cough, SOB, sputum containing blood (hemoptysis). Epidimiology: - Reservoir hosts include felids, canids, rodents, pigs - Worms can live for 10-20 years - Humans become infected by eating raw or insufficiently cooked crustaceans - Marination in brine, vinegar or wine have no effect on metacercariae - Exposure can also come from contaminated fingers and cooking utensils - Some ethic groups use of juices strained from crushed crab or crayfish for medical purposes (poultice— used in cuts, can reduce inflammation, pain) - Variety of mammals and some birds can serve as paratenic hosts o Ex: Guinea pigs: considered a delicacy in Ecuador and Peru; we get infected by eating these hosts

Medicine (drugs for dingeneans in the US):

Worms die by paralysis No glucose— death. FYI: Clochine seen in karyotypes, hence chromosomes don’t move and they stay in place.

Cestoidea worms (tapeworms): Still Platyhelminthes. - Monoecious parasites, hermaphrodites - acoelomate, no digestive system — everything is consumed through tegument. - Adults live in digestive tract of vertebrates. - Scolex: may have suckers, grooves, spines, glands or tentacles - Contains neuro ganglia of the worn. - Neck: undifferentiated zone located between the scolex and strobila. - contains stem cells responsible for giving rise to new proglottid. - Strobila: region of tapeworm behind the scolex & neck, chain of proglottids - Proglottid: a segment in a strobila that includes male and female reproductive organs o proglottid can copulate with itself, with other in its strobila; or with those in other worms, depending on the species. Echinococus granulosus (only three proglottids). **Strobila can be polyzoic (more than one proglottid) or monozoic (only one proglottid) Cestoidea: Form and Function - Strobilation: formation of chain of proglottids by budding - gravid: a proglottid containing fully developed eggs or shelled embryos

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Apolysis: disintegration or detachment of a gravid tapeworm segment (only happens in those with genital pore; uterine pore allows eggs to be released little by little) o Proglottd can burst and eggs are released in feces or it can detach and be excreted as gravid ploglottid Anapolysis (pseudoapolysis): detachment of senile proglottid after it has shed its eggs (those with uterine pore) Hyperapolysis: detachment of proglottid while it is still immature, before eggs are formed. o may lead an independent existence in the gut while maturing.

Proglottids can be craspedote or acraspedote: cras e: anterioir edge of each segment overlaps the anterioir edge of next sengment. (left) e: posterioir edge of proglottid does not overlap the anterioir edge of the next (right)

Acetabula: a sucker on the scolex of a tapeworm; normally 4 acetabula on a scolex Bothridia: usually in groups of 4; can have highly mobile, leaflike margins with adaptations for adhesion (a; first image) Rostellum: dome-shaped area on the apex of the scolex, often with hooks (b = armed rostellum) Bothria: usually 2 number (dorsal and ventral, and take the form of shallow pits (third image) - seen in Duphyllobothrium latum. Tegument: - Tegument of cestodes is in a syncytium (syncytial) - No digestive tract - All required substances are absorbed through their tegument - distal cytoplasm is connected to cytons by channels or internuncial processes

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Microtriches are unique for Cestoidea. Not seen in Digenians. They are numerous minute finger -shaped times that extend out of the tegument. increases absorptive area of the teguments (remeber no GI system— l Completely cover the worm’s surface Glycocalyx is found on the surface membrane of microtriches Below microtriches is a layer of distal cytoplasm

Muscular system: - muscle cells consist of 2 portions: contractile myofibril and non contractile myocyton - Contractile portion contains actin and myosin fibrils, and it is nonstraited - Myocytons comprise most of the custodies parenchyma - Bundles of longitudinal and circular muscle fibers lie below the distal cytoplasm - More powerful musculature lies below the superficial muscles Nervous sytem: - displays the orthogonal plan typical of Platyhelminthes - Main nerve center in located in scolex - Innervation of ganglia, commissures, and motor and sensory neurons occur at therein nerve center; complexity often depends on the complexity of scolex - Sensory function most likely includes tactoreception and chemoreception.

Microvili, increase absorption of monomers

Muscular cirrus is analogous to penis; 20.17 = anapolysis; 20.18 = apolysis Development: - Embryogenesis within the egg gives rise to larva (oncosphere) - Oncosphere hatches and penetrates extra intestinal site o Oncosphere: six hooked (3 pairs) larvae hatched from an egg of a eucestode, also known as hexacanth. - Metamorphosis of the larva into a juvenile (metacestode) in extra intestinal site - Metacestode develops into adult in the intestine. o Cystercerci: invaginated and inverted o Cyticercoid: only invaginated. o Plerocercoid o Hydatid cyst

Cestoidea: Diphyllobothrium Tatum - broad fish tapeworm - Occurs in humans, beats cats, dogs, and other fish eating carnivores (host specificity us low) - Adults live in small intestine - 10 meters of length, > 4000 proglottids; sheds 1 million eggs per day - Eggs released through uterine pore. —- end of strobila, senile proglottid (anapolysis)

Pathology: - Can sequester vitamin B-12, causing pernicious anemia - Sparganosis: infectious disease caused by migrating

plerocercoids (thinks you are an intermediate host and does not do further development) in host tissues. o Can reach 35 cm in length and live for at least 30 years ▪ Swallowing procercoid infected copepods while drinking water—- ex. Water coming from sink in New York. ▪ Eating amphibians, reptiles and mammals (paratenic hosts that could have eating the small fish, 2nd intermediate) containing plerocercoids; will never develop into a full adult. ▪ Applying plerocercoid infected flesh to wounds as a poultice (put sometimes in cut and inflammations, mentioned in last class) o Example: sparganosis in the eye Case study: 46 y/o F symptoms of abdominal pain, loose stool, excretion of tape like material. Hx of eating raw fish, most recently 2 months ago Colonoscopy located D.latum in terminal ileum of small intestine. Has golden-yellow color; it also appears to be very active, moves a lot. Epidimiology: - Eating undercooked freshwater fish - Accidental ingestion of copepod from unfiltered water - Insufficiency cooked frog, snake or pig (these are paramedic hosts) - Poulticing inflamed area or wound with split frog. Video showing plerocercoid in freshwater fish—> can alter behavior of the host, stickleback fish. The live plerocercoid can be as big as its host, manipulated the body of two different animals. Can also be found in the bodies of fish eating birds. - Changes the copepod behavior making them swim erratically and get caught by the freshwater fish. - Changes the behavior of the freshwater fish to not get scared by the predator, freshwater eating birds, it changes its behavior to stay out in the open and not hide. Cyclophyllidea: Taenia saginata - Beef tapeworm - Occurs in humans in countries were beef is eaten - 3-5 m in length , >2000 proglottids - Adult beef tapeworm lives in small intestine - Gravid segments detach and pass out with feces or migrate out of anus; no uterine pore instead have genital pore. - Proglottid begins to dry and ruptures, releasing eggs - Larvae (hexacanth) remain viable for weeks. **in areas with no flushable toilets, not uncommon for cows to eat the human poop, and if person infected the life cycle perpetuates, cysticerci in the small intestine of the cow (they prefer human poop)***

— many cystecerci in beef to the right; if infected, every single one of them becomes an adult in small intestine

Pathology - Might be asymptomatic if few — in the mean time they could be harboring more and more eggs - Symptoms include dizziness, headache, abdominal pain, diarrhea and nausea - Intestinal obstruction with need for surgical intervention sometimes occurs - Loss of appetite is not frequent - Delirium is rare. Epidemiology - Infection is highest where beef is a major food and sanitation is deficient - One person who defecates in pasture can infect entire herd - Use of human feces as fertilizer (night soil) - Cattle are coprophagous (eat feces) Cyclophyllidea: Taenia sodium - Worst tapeworm you can get - Humans can serve as definitive or intermediate host (autoinfection) - Pork tapeworm - Life cycle same as beef tapeworm except the normal intermediate host is pig - Humans can become an intermediate host when the eggs are accidentally ingested or a gravid proglottid ruptures releasing eggs before leaving the body (autoinfection). Infection may happen when eating poorly cooked pork, but it is even worse if you eat eggs within poorly prepared food, as oncosphere will hatch out Pathology: - Cysticerci can be found in any organ and tissue including: o Subcutaneous connective tissue o Eye o Brain causing epilepsy, blindness, paralysis, disequilibrium, disorientation— oncosphere can pass the BBB and insert themselves in the brain; it's like a cancer in the brain crowding the neural tissue. o Muscles o Heart o Liver lungs o Coelom Epidimiology: - Infection is highest where pork is a major food source and sanitation is deficient - Eggs can be transmitted by Blowflies (PARATENIC HOST; mechanical vectors) - Infected (domestic help) person can contaminate households or food o 1.3% orthodox jewish community in New York infected T. solium — infected with neural cystecercosis (not with the adult)— can cause the brain to be dangerously inflamed. - Cystecercosis is highly endemic in Mexico, Central and much of South America, sub-saharan Africa , china and other parts of Eastern Asia....