Lecture 5: Parasites III

malaria: caused by what species

Plasmodium species

malaria: 4 organisms that cause this disease

P. vivax, P. falciparum, P.ovale, P. malariae

malaria: location

hepatocytes/erythrocytes

malaria: reservoir

humans

malaria: transmission

vector-borne: female Anopheles mosquitoes

also congenital & needle transfer

malaria: most fatalities are in

children

malaria: increasing resistance

increasing drug (from the parasite) and insecticide (from the vector) resistance

malaria: most morbidity and mortality due to

P. falciparum

the malaria life cycle

malaria: fever cycle

fever cycle with ‘synchronous’ bursts of merozoites

P. vivax & P. ovale: 48 hr spike

P. malariae: 72 hr spike

P. falciparum: 48 hr broad

malaria: anemia

results from erythrocyte destruction

cerebral malaria

extreme result of P. falciparum only disruption of cytokines networks: TNFα & IL-1?

mechanical damage due to sequestration?

malaria: latent form

latent hepatic forms in P. vivax & P. ovale

malaria: diagnosis

geimsa stain of blood smears

malaria: P. falciparum diagnostic features

multiple rings per RBC

no trophozoites or schizonts

banana shaped gametocytes

tertian malaria

P. vivax and P. ovale

quartan malaria

P. malariae

malignant tertian malaria

P. falciparum

malaria: immunity development

slow to develop; requires multiple infection

short lived; lost when leaving endemic area

easily reinfected; return to endemic area

malaria: what kind of treatment resistance is common

multidrug resistance

malaria: prevention

avoid mosquitoes when feeding...repellents, bednets!

phylum phlatyhelminthes: 3 classes

cestoda, trematoda, nematoda

cestoda class

Tapeworms; flattened segmented bodies

cestoda: digestive system

No internal digestive system; nutrients absorbed across cuticle

cestoda: how do adults attach

Adults attach by the anterior end (scolex) to the gut wall of definitive host

cestoda: how do segments mature

Segments (proglottids) mature from anterior to posterior; specialized for hermaphroditic reproduction

cestoda: transmission

Transmission by ingestion of larval cysticerci (in undercooked meat from intermediate host) or eggs

class trematoda

Flukes of the lungs, liver and blood

trematoda: digestive system

Broad flattened bodies with a simple digestive system; a single opening serves as mouth and anus

trematoda: intermediate hosts

One or more intermediate host, one of which is a snail

trematoda: transmission

can be invasive or ingestive

class nematoda

Roundworms of the tissues and gut

nematoda: body and systems

Cylindrical body; well developed digestive and nervous systems

nematoda: transmission forms

ingestive (no intermediate host)

invasive (no intermediate host)

vector-borne (one intermediate host)

2 significant cestoda species

Taenia saginata (beef)

Taenia solium (pork)

significant nematoda species

Enterobius vermicularis

Taenia saginata and Taenia solium eggs

look same; cannot be distinguished

Taenia saginata: location

lumenal, jejunum

Taenia saginata: transmission

Eating undercooked beef containing cysticerci

Taenia saginata: humans as host

humans as the definitive host only

Taenia saginata: intermediate host

cattle

Taenia saginata: pathology

Abdominal discomfort; nausea, vomiting and diarrhea

Rarely serious; occasionally weight loss; obstruction

Taenia saginata: immunity

Humoral response to adults...reinfection is possible

Taenia saginata: self-diagnosis

active proglottids

Taenia saginata: clinical diagnosis

observation of proglottids or eggs in stool

Taenia saginata: what must it be distinguished from and how

T. solium; proglottid morphology

Taenia saginata: prevention

Good public hygiene; prevent infection of cattle

Well cooked beef; prevent infection of humans

Freezing kills cysticerci

Beef Tapeworm: Taenia saginata lifecycle

traits of Taenia saginata Proglottid

longer; pore on side for egg release

Taenia solium: humans as host

humans as definitive or intermediate host

Taenia solium: location

adults: lumenal, jejunum

cysticerci: any tissue

Taenia solium: intermediate host

pigs or human

Taenia solium: transmission

Ingest cysticerci; definitive host

Ingest eggs; intermediate host

Taenia solium: neurocysticercosis

brain lesions; neurological disorders; mortality

Taenia solium: life cycle

Taenia solium: diagnosis

Adults same as beef tapeworm

X-ray, calcified dead larva; CAT/MRI, viable cysticerci

Taenia solium: treatment consensus

Consensus is to not treat cysticerci outside of CNS

Taenia solium: prevention

Well-cooked pork, freezing kills cysticerci

pinworm organism

Enterobius vermicularis

Enterobius vermicularis: location

adults in colon

Enterobius vermicularis: transmission

ingestion of eggs

Enterobius vermicularis: definitve host

humans

Enterobius vermicularis: epidemiology

An equal opportunity parasite

More prevalent in children, daycare centers

Enterobius vermicularis: pathology

Intense perianal pruritis; Secondary infection due to scratching

Rare urogenital invasion in females ➙ bacterial infection

Enterobius vermicularis: immunity

None...reinfection is possible and common

Enterobius vermicularis: diagnosis

Persistent perianal itch, restlessness, insomnia Confirm by observation of eggs, "scotch tape” test

Enterobius vermicularis: lifecycle

what feature is diagnostic for Enterbius vermicularis

eggs

whipworm: prevalence and intensity

high prevalence in school aged children; high disease intensity at same time of high prevalence