Parasites

Life Cycle/DH

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Symptoms/Pathogenesis

Treatment

Prevention

Misc

Life Cycle/DH

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Life Cycle/DH

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Life Cycle/DH

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Life Cycle/DH

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Life Cycle/DH

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Life Cycle/DH

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Life Cycle/DH

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DH: Humans

Direct life cycle

Small intestine

Fecal-oral route

Sporulated thick-walled oocysts are shed

Sporulated or unsporulated thin-walled oocysts stay inside host to reinfect

Mostly asymptomatic, can go away on its own in hosts with strong immune systems

Pathology caused by small villi malabsorption

Watery diarrhea, weight loss, dehydration, nausea

Look at stool samples (easy to miss because of parasite small size)

Molecular and microscopic diagnostics

Fluid replacement and electrolytes, anti-diarrheal meds

Extra good sanitation, wash fruits and veggies, drink treated water only, isolate infected hosts, reduce stressors in animals (so their immune systems are strong and can resist)

Resistant against chlorination and temperature

Ammonia and hydrogen peroxide are effective in killing oocysts

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DH: Cats

Host spectrum: birds and mammals

IH: Warm blooded vertebrates

Primarily indirect life cycle

Cats have intestinal (asexual and sexual) and extraintestinal (asexual) stages, other IH hosts are only asexual extraintestinal

Infected cat sheds oocysts, become sporulated, when ingested become tissue cysts, only cats shed oocysts

Ingesting contaminated poop, ingestion of raw tissues, transplacentally with tachyzoites

Tissue cysts have bradyzoites and form in CNS, muscles, and organs

Reactivation associated with severe immune suppression, otherwise can go asymptomatic forever

Congenital: miscarriage, prematurity, mental issues, vision problems, often asymptomatic at birth

Usually sub-clinical signs, tests can detect toxoplasma specific antibodies

Treatment drugs target tachyzoite stage

Appropriate food preparation (cook meat, freeze meat, wash fruits and veggies)

Wear gloves when gardening

Cover sandboxes

Immunocompromised and pregnant people should not be cleaning litter box daily

Completely disinfect litter box

Don’t get a new cat while pregnant, keep cats indoors, clean litter box daily

Distributed worldwide

Zoonotic

Sporozoites: inside sporocysts within oocysts

Tachyzoites: acute infection, multiply rapidly, banana-shaped, form groups not cysts

Bradyzoites: chronic infection, tachyzoites walled off from immune system and slow down to become bradyzoites, long-lived cysts in muscle and tissue

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DH: Anopheles Mosquitos

IH: Vertebrates

Vector: Anopheles Mosquito

Malaria

Indirect

Mosquito bite injects parasites. Infected mosquito injects sporozoites in oocysts which infect liver cells, they form schizonts containing merozoites which invade RBCs, form gametocytes, mosquito takes a blood meal and ingests the gametocytes, they turn into gametes, zygotes, and produce ookinetes which become oocysts

• Liver stage has no disease, RBC stage has disease symptoms

• Early: asymptomatic to flu-like

• Middle: alternating fever and chills

• Late: anemia, swollen spleen and liver

• Reinfection is possible and you can be infected with multiple species at once

Collect and test blood, stained blood smears, PCR for low density infections

Treatment drugs are available, but drug therapy can make the parasites resistant

Duffy neg: P.vivax resistant

Sickle cell trait: hard for parasite to survive

Preventative drugs available

Reduce vector populations via environmental modifications, insecticides, and biological control; reduce human mosquito contact via insecticides and screens; reduce parasites in humans via quick diagnosis/treatment; vaccines for kids

Found worldwide, tropical/subtropical regions. A. gambiae mosquitoes are the major African vector and feed during rainy seasons. A. stephensi mosquitos are an invasive Asian species that feeds year-round and threatens Africa’s malaria control because of its adaptation to urban settings. Mosquito eggs and larva are found in quiet water and adults stay on land but nearby. Only females blood feed because the blood protein helps egg development.

Relapse: dormant stage hypnozoites reactivate infection

Recrudescence: detectable levels increase and decrease over time

Premunition: low levels of infection maintain effective ‘immunity’ in communities

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DH: Humans

Direct life cycle

Enters the nose, goes through membranes to reach and then move along the olfactory nerve, enters the brain, brain swells

• Can be mistaken for bacterial meningitis

• Stage 1: Headache, nausea, vomiting, fever

• Stage 2: Seizures, coma, altered mental status, hemorrhages

Diagnosis: Typically made after death, look for parasites in spinal fluid and tissues *quick and detailed diagnosis*

Avoid stirring up sediment at the bottom of bodies of water, avoid dunking your head underwater, hold nose shut or use nose clips when going head under in warm fresh water

Free-living, facilitative parasite. Found in fresh/warm water, soil, and poorly maintained pools. Trophozoites and resistant cysts are sensitive to disinfectants like chlorine

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DH: fish-eating carnivores

Embryonated eggs are digested and release ciliated larva (first IH: copepod eats larva, procercoid stage in body, second IH: fish eats copepod, plerocercoid stage develops in muscle), DH eats raw fish where adult worms grow in the small intestine and shed lidded non-embryonated eggs via their uterine pore (eggs embryonate in water after a couple weeks)

Can have paratenic hosts (predator fish eat infected fish)

fecal-oral

~80% asymptomatic

diarrhea, vomiting, weight loss

human DH: anemia (B12) deficiency from nutrient competition

Collect poop from DH → see chain of empty proglottids in vomit or poop, fecal floatation, smear

medicinal treatment is available

Prevent contamination of water (DH avoid pooping in water)

properly cook fish

Shallow and grooved bothria, genital pores, uterine pores release non-embryonated operculated eggs, ciliated larva (procercoid in first IH, plerocercoid in second IH)

“fish tapeworm”, colder environments, long lived, very long

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IH: Swine

DH: Human (also accidental IH)

Fecal-oral

adult worms in small intestine with armed scolexes

larval cysts in pig muscle

human IH have cysts in muscle, CNS, eyes, etc

Adult worms are mostly asymptomatic, maybe tummy ache, appetite loss, rarely there is a blockage in appendix or intestines, may see proglottids in feces

cysts in human IH symptoms depend on location, size, number, and stage; subcutaneous/muscle cysts usually have no symptoms or are tender lumps; cysts in brain/spinal cord cause neurocysticercosis which causes seizures, headache, blindness, balance issues→ pressure atrophy caused by degenerating cysts prompting an inflammatory reaction, necrotic larva can be resorbed but become calcified causing scarring and leading to seizures

Examine feces for rectangular segments and eggs

Eggs/proglottids are not consistently shed and are not evenly distributed in feces so multiple samples may be necessary

Eggs are long lived in the environment

Remove adult worms in DH, try to remove cysts in IH

Drugs that kill cysts can create cyst site inflammation and make symptoms worse

Prevent IH infection: DH good sanitation (use toilets, wash hands)

Prevent DH infection: avoid raw/undercooked meat, cook meat properly (especially pig and cows)

Eggs/gravid proglottids passed in feces contaminate environment, ingested by swine or accidentally ingested by human IH, cysts develop in any organ and subcutaneous muscle/nerve tissue in swine, humans ingest undercooked pork and adult worms shed proglottids/eggs into the environment

Scolexes are armed/hooked making human IH infection possible

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IH: Cattle

DH: Human

Fecal-oral

adult worms found in small intestine with unarmed scolex in human

cattle have larval cysts

Adult worms are mostly asymptomatic, maybe tummy ache, appetite loss, rarely there is a blockage in appendix or intestines, may see proglottids in feces

Examine feces for rectangular segments and eggs

Eggs/proglottids are not consistently shed and are not evenly distributed in feces so multiple samples may be necessary

Eggs are long lived in the environment

Remove adult worms in DH, try to remove cysts in IH

Drugs that kill cysts can create cyst site inflammation and make symptoms worse

Prevent IH infection: DH good sanitation (use toilets, wash hands)

Prevent DH infection: avoid raw/undercooked meat, cook meat properly (especially pig and cows)

Unarmed scolex (no hooks)

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DH: Dogs

IH: Livestock/humans

Adult worms are in the DH small intestine

Unilocular hydatid cysts in IH

Cystic echinococcus

Usually asymptomatic

Pressure atrophy from growing cysts, impaired organ function

liver: pain, nausea, vomitting

lungs: shortness of breath, cough, pain

Less severe

Thick-walled cysts that bud internally and grow slowly

Examine feces for eggs (too small to see segments), imaging for humans

Treat dog DH for adult worms, human IH can have surgical removal, watch and wait for granulosis forms

Prevent predation/dogs eating raw meat and inform dog owners, prevent IH infection by picking up dog feces and washing hands

Human ingests taenia-like egg with hexacanth larvae released in gut, penetrates the intestinal wall, enters circulation and migrates to liver/lungs, develops unilocular hydatid cysts with internal budding, cysts enlarge but won’t naturally rupture, if ruptured, multiple cysts are released

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DH: dog, fox

IH: small mammals, humans

Adult worms in DH

Multilocular hydatid cysts in IH

Alveolar echinococcus

Infects other organs besides liver and lungs, invades and destroys the tissues

Spreads and acts like cancer

Discomfort/pain, weight loss, liver failure, weakness, death

Examine feces for eggs (too small to see segments), imaging for humans

Treat dog DH for adult worms, human IH can have surgical removal, watch and wait for granulosis forms

Prevent predation/dogs eating raw meat and inform dog owners, prevent IH infection by picking up dog feces and washing hands

Ingested egg with hexacanth larva released in gut, larva penetrates and enters circulation and migrates to many organs, develops into multilocular hydatid cysts that bud externally and grow quickly

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DH: dogs, cats, humans

IH: fleas

Adult worms in small intestine of DH

usually asymptomatic

vomiting, diarrhea

Examine feces for proglottids or eggs, segments similar in appearance to cucumber seeds or rice grains

Drug treatment is available for all DH

Pick up feces, use flea control products in pets, prevent ingestion of fleas

Armed rostellum and suckers

Two sets of female and male reproductive organs in each proglottid, two lateral genital pores per segment

Gravid proglottids are passed in the feces, disintegrate in the environment to release egg packets, flea larva ingest egg packets, oncospheres hatch and develop into cysticercoids, flea develops with infective cysticercoids still inside, DH ingests a flea, adult worms develop in the small intestine

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DH: humans

IH: freshwater snails

female in a crevice of the male, dioecious

adult worms in blood vessels of DH

eggs shed from infected human, eggs hatch and release miracidia, miracidia penetrate snail tissue, sporocysts develop in snail, free-swimming cercariae released from snail into water, cercariae penetrate human skin, lose cells during penetration and become schistosomula which circulate and migrate to portal blood in liver, mature into adults, paired adult worms migrate to areas of the bowel to lay eggs that circulate in the liver and shed in stools (japonicum/mansoni) or in the bladder where eggs are shed in the urine (haematobium)

eggs that don’t pass out of the body lodge in the intestine, liver, or bladder where they cause inflammation and scarring; rash/itchy skin initially; fever, cough, weakness, aches in acute stage from hypersensitivity to migrating schistosomula; chronic stage involves intestinal or urogenital schistosomiasis as a response to egg deposition

intestinal (japonicum/mansoni): blood in stool, abdominal pain, diarrhea, liver/spleen enlargement

urogenital (haemotobium): blood in urine, painful urination, genital lesions, infertility, higher HIV risk, fibrosis, cancer

examine feces or urine, eggs often passed in small amounts and intermittently

drug treatments available

large scale treatments of affected populations, health education, provide clean water and good sanitation, control snail populations, keep out of high risk environments (streams, lakes, etc)

S. japonicum is zoonotic; found in china, indonesia, phillipines; intestinal/hepatic

S. mansoni found in africa, middle east, brazil; intestinal/hepatic

S. haematobium found in africa, middle east; urogenital

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Caused by Trichobiharzia spp, Heterobiharzia spp, etc

DH: birds, some other mammals

IH: snails

just the larval stage can make humans an accidental host

Skin

cercariae burrow in the skin and die creating allergic reactions, rash, itching, pimples/blisters, secondary bacterial infections from scratching

use corticosteroids and anti-itch products, cool compresses, Epsom salt or baking soda baths, baking soda paste

be careful around freshwater and saltwater

eggs are passed in DH feces, eggs hatch and release miracidia, penetrates and develops inside a molluscan IH, human accidentally exposed to cercariae in water, cercariae penetrate the skin of the DH and migrate to blood vessels to complete the cycle, adult schistosomes in DH

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DH: domestic/wild animals, humans

IH: freshwater snail

Intestine to liver and bile ducts

Mostly asymptomatic

Incubation stage (after metacercaria ingestion): asymptomatic, few days to a few months

Acute stage (1-3 months after ingestion): migrating larval flukes, ends when larvae reach and mature in bile ducts; tissue destruction, internal bleeding, GI issues

Chronic stage: begins when larvae reach bile ducts and mature to adults, start producing eggs; blockage and bile duct inflammation, pain, anemia, pancreatitis, hardening of liver because of long-term inflammation

Detect eggs in feces (later infections)

Blood tests (early infections)

Drug treatment available for both larvae and adults

no vaccines available

good sanitation (prevent feces in water)

containment of snail IH, drainage of grazing lands

cook water plants/vegetation, strict control of shipping and growth of water plants

education of how to irrigate and cook veggies, treat domestic animals and separate animals and humans

different drug treatment methods in different countries

zoonotic

flukes are in bile ducts, non infective eggs are passed in feces, become embryonated in water, miracidia hatch and seek snail IH, penetrate snail tissue (sporocysts→rediae→cercaria) develop in snail tissues, cercaria released from IH and encyst on vegetation (form metacercaria), ingested metacercaria encyst in intestine, perforate intestinal wall, and travel to liver and bile ducts of DH

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DH: ruminants (cattle and sheep)

1st IH: land snail

2nd IH: ant

humans can be accidental DH

Ant 2nd IH: most metacercaria encyst in the butt but 1-3 reach the brain and cause altered behavior where the ant climbs to the top of grass blades, increasing its chance a DH ingests it

Only a few flukes can cause disease

Ruminants with even severe infections may have minimal symptoms

Abdominal distress

Detect eggs in feces

Drug treatment available

Keep other animals to eat land snails (ducks, turkeys, chickens) to reduce IH population

cover ants nests with tree branches to keep animals away

treat infected animals

DH ingests infected ants, adults in the bile ducts, embryonated eggs are shed in feces, eggs are ingested by a land snail (miracidia→sporocysts→cercariae), cercariae are released in a slime ball via the respiratory pore, ant ingests cercariae which form metacercaria

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DH: humans

1st IH: water snails

2nd IH: crustaceans

RH: dogs, cats, humans

adults are encysted in the lungs and release non-embryonated eggs which are coughed or pooped out, they become embryonated in water and miracidia hatch to penetrate snail (sporocysts→rediae→cercariae), cercariae invade a crustacean and encyst into metacercaria, human eats undercooked/pickled infected crustacean, metacercaria excyst in the small intestine, penetrate walls, encapsulate and develop into adults in the lungs, creating cyst cavities as the adults excyst

often asymptomatic

acute (2-15 days): dry cough, abdominal pain, low fever

long-term: inflammed lungs, productive cough, bloody sputum, similar to bronchitis or tuberculosis

ectopic infection (adults elsewhere than the lungs): lesions from migrating flukes, cerebral paragomiosis(seizures, lesions, brain swelling)

eggs in sputum or feces (swallow instead of coughing out), serological tests for early and ectopic infections

drug treatment available

don’t spit or poop in outside water, snail control (not practical), avoid eating raw freshwater crabs/crayfish, travelers avoid traditional meals containing undercooked crustaceans

North American Lung Fluke

can be in other organs than the lungs, but life cycle won’t finish since eggs can’t escape

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T. trichuria DH: humans

T. vulpis DH: dogs

T. suis DH: pigs

direct

fecal-oral

large intestine

soil-transmitted infection with tropical weather, kids, and poor sanitation, night soil (untreated human poop in soil)

adult worms in large intestine, eggs are shed in feces, embryonate in the environment, infective eggs are ingested, hatch in small intestine, larvae penetrate intestinal villi, return to lumen and migrate to large intestine

mostly asymptomatic'

diarrhea, abdominal discomfort

severe diarrhea with mucus and fresh blood, rectal prolapse, iron-deficiency/anemia

eggs in feces (hard to find in mild cases)

drug treatment is available for both humans and dogs, humans are short-term with iron supplements, and dogs get initial and monthly control options

avoid ingesting night soil or crops fertilized with night soil, wash and peel and cook raw veggies and fruit, don’t poop outside, wash hands, pick up dog poop to prevent reinfection and spread

whipworms

not zoonotic

thin anterior end embeds in mucosa of LI to ingest blood

non-embryonated eggs when shed

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DH: pigs, carnivores, humans

1st cycle: domestic with pigs and rodents

2nd cycle: sylvatic with wildlife

one host is both the DH and IH since both adult worms and larvae are in the same host

adult worms live in between villi of the small intestine

ingestion of undercooked infected meat with encysted larvae, larvae are released in the small intestine where they develop into adults, adult females produce live larvae that circulate before travelling to muscles that move a ton and encysting

1st phase: nausea, diarrhea, vomiting, abdominal discomfort

2nd phase: fever, headache, muscle swelling, eye swelling, fingernail splinter hemorrhages, rash; respiratory failure and death due to diaphragm impairment if worm burden is high

mild to severe

most symptoms can go away on their own within a few months (immune response can get rid of adult worms, larvae in muscles can stay for months to years)

blood test, active muscle biopsy

drug treatment is available, but later on in the infection makes treatment harder

wash hands after handling raw meat, cook meat to a safe temperature (don’t sample undercooked meat)

other cooking methods like pickling and curing may not kill all worms and larvae alone

freeze pork to kill worms (freezing wild game may not be effective)

don’t allow pigs and wild animals to eat uncooked meat/carcasses

worldwide

no free-living larvae

1st phase: entric/gastrointestinal- stomach acid dissolves cysts and releases larvae that pass into SI to mature and mate

2nd phase: systemic/pareneral; adult female produce larvae that travel via blood to enter muscles and form cysts

more common to now rare because prohibiting laws prevent raw meat scraps being fed to hogs and there is public awareness of raw meat dangers