Parasites of importance

Plasmodium species

P. falciparum

P. vivax

P. malariae

P. ovale

Plasmodium spp. phylum

Apicomplexa

Protozoa

Plasmodium spp. disease

Malaria

Malaria disease presentation and possible complications

Uncomplicated malaria, cerebral malaria, Asymptomatic Malaria

Headache, vomiting, chills, muscle pain, cyclical fever

Febrile paroxysm for each plasmodium spp.

P. knowlesi - 24h

P. falciparum, p. vivax, p. ovale - 48h

P. malariae - 72h

Febrile paroxysm

Chills and rigors

Abrupt fever lasting 1-2 hours

Resolves with profuse sweating and a return to normal temperature

Cycles every 24-72 hours depending on species

Location of malaria in human host

Hepatocytes

Red blood cells

Blood vessels

Malaria biology

Sporozoites: in mosquito, immature and infective stage

Merozoites: multinucleated schizonts in hepatocytes

Trophozoites: Activated intracellular phase in blood

Gametes: result of gametogony

Exo-erythrocytic cycle of Plasmodium spp.

1) Mosquito takes a blood meal and injects sporozoites

2) Hepatocyte infected

3) Schizont formation in liver cell

4) Schizont rupture and release into blood

Erythrocytic cycle of plasmodium spp.

1) Schizont travels to blood cell

2) Schizont turns to an immature trophozoite

3) Trophozoite maturation OR Gametocyte

4) Mature trophozoite becomes schizont

5) Schizont ruptures and reinfects blood cells OR gametocytes ingested by mosquito

Malaria mode of transmission

Female anopheles species vector

Blood meal

P. falciparum prevalence

Most pathogenic and deadliest

Highly prevalent in sub-saharan Africa

Some prevalence in tropical areas

Can present in many forms

P. vivax prevalence

Very pathogenic

Present in south east asia and south america

Sporozoites can be dormant in hepatocytes - hypnozoites

Invade reticulocytes

Parasitemia is low

P. knowlesi prevalence

Monkey malaria

high parasitemia

Short erythrocytic cycle

south east asia

P. ovale prevalence

Sub-saharan Africa

Some in islands of western pacific

Invade reticulocytes

Parasitemia is low

Sporozoites can become dormant in hepatocytes - hypnozoites

P. malariae prevalence

South America, Asia and Africa

infects old erythrocytes

proteinuria

Asymptomatic parasitemia

Malaria diagnostics

Rapid tests

Thin and thick blood smears with Giemsa stain

Nucleic acid amplification tests

Leishmania spp. phylum and grouping

Protozoa, flagellated

Leishmania disease presentations

Cutaneous leishmaniasis: most common, lesions at site of bite, localised, inflammation

Visceral leishmaniasis: Most lethal, fever, abdominal swelling, malnutrition and death

Mucocutaneous leishmaniasis

Leishmaniasis human lifecycle

1) Sandfly takes a blood meal and injects promastigotes

2) Promastigotes are phagocytosed by macrophages

3) Promastigotes transform into amastigotes and multiply

4) Sandfly takes a blood meal, taking up infected macrophages

Leishmania geographical distribution

Tropical and subtropical areas

Leishmania transmission

Female phlebotomine spp. sandfly vector

Blood meal

Schistosoma species

S. haematobium

S. japonicum

S. mansoni

Schistosoma spp. phylum

Trematode

Schistosoma spp. disease and presentation

Acute infection: swimmers itch - fever, muscle ache, chills and abdominal pain, inflammatory response to egg. Adults coat themselves in protein and evade host immune response

Chronic infection: granuloma formation blocking blood flow to liver and cerebral embolism

Schistosoma spp. human lifecycle

1) Free swimming cercariae released into water from intermediate host and penetrate skin

2) Cercariae lose tails during penetration and become schistosomula

3) Circulation in blood

4) migration to portal blood in liver and maturation into adults

5) Paired female and male worm migrate to venules of bowl or venous plexus of bladder depending on species

6) eggs circulate and shed in stool or urine

Schistosoma spp. geographical location

Africa, SE Asia, South America

Sarcopetes scabiei phylum, class and subclass

Arthropods, Arachnids, Mites

Sarcopetes scabiei disease and presentation

Scabies or Crusted Scabies

Intense itching, vesicle and crust formation, skin thickening, septic pustule formation, characteristic rash

Interdigital spaces, groin, breasts, umbilicus, penis, back, buttocks

Sarcopetes scabiei secondary infections

tissue damage due to scratching

Group A streptococcus and MRSA

Can lead to chronic disease

Sarcopetes scabiei human lifecycle

Female mite burrows into epidermis of skin

Lays 2-3 eggs/day

Sarcopetes scabiei risk factors

Close personal contact

Overcrowded environments

Immunocompromised or weakened immune system

Contaminated fomites

Giardia duodenalis Phylum and grouping

Protozoan

Flagellate

Giardia duodenalis disease and presentation

Giardiasis

Diarrhea, Dehydration, Abdominal pain, Malabsorption of glucose, sodium and water

Giardia duodenalis lifecycle in humans

1) Trophozoites mature and multiply in gut

2) Trophozoite encyst

3) Infective cyst released in faeces

4) Cysts are ingested and release trophozoites

Giardia duodenalis distribution

world wide

Giardia duodenalis transmission

Faecal-oral route

cantimated water and food

Giardia structure

1) Trophozoite stage

Two large nuclei, adhesive sucker, 12-15 micrometers long

2) Cyst stage

Four tetraploid nuclei, Cyst wall

Giardia duodenalis virulence

Attachment via ventral adhesive disc and surface lectins

Alteration of host innate defences

Survival in stomach acid and external environment

Anti-inflammatory modifications

Toxoplasma gondii phylum and class

Apicomplexa, protozoa

Toxoplasma gondii disease and presentation

Toxoplasmosis, Congenital toxoplasmosis, Ocular toxoplasmosis

Intracellular parasite

Definitive host: cats

Generally asymptomatic, affect brain, eyes and other organs

Toxoplasma gondii lifecycle in humans

1) Livestock consume infective oocyst

2) Infective oocyst enter food, litterboxes or water

3) Human ingests oocysts

4) Cysts form in brain, cardiac muscle and skeletal muscle

5) Cysts remain for life

Toxoplasma gondii proliferation

Host cell dies and tachyzoites are released and enter another cell

Stress drives formation of bradyzoites

Toxoplasma gondii transmission

Eating raw or uncooked meat

Contact with cat faeces

Can be congenital

Toxoplasma gondii diagnosis

Retinal examination, serological testing, observation of parasite in tissue or CSF

Ascaris lumbricoides phylum

Nematode

Ascaris lumbricoides disease and presentation

Roundworm

Abdominal pain, malnutrition, bowel obstruction

Ascaris lumbricoides human lifecycle

1) Larvae hatch in gut

2) Larvae migrate through the gut wall into blood and lymph

3) Travel through the lungs

4) Arrive at epiglottis

5) Swallowed back into gut

6) Maturation into adults

Ascaris lumbricoides transmission

In soil

Faecal-oral transmission

Subtropical to tropical areas

Places of poor sanitation

Ancylostoma spp. phylum

Nematode

Ancylostoma spp. disease and presentation

Hookworm

Anaemia, malnutrition, cutaneous larval migrans, respiratory issues

Ancylostoma spp. lifecycle

1) Migratory larvae circulate in blood

2) Travel from heart to lungs

3) Migrate up bronchial tree to pharynx

4) Swallowed

5) Maturation to adults in gut

Ancylostoma spp. transmission

Transdermal

In soil

Can be zoonotic

Warmer areas

Enterobius spp. phylum

Nematode

Enterobius spp. disease and presentation

Pinworm

Itching anus at night

Abdominal pain

Enterobius spp. lifecycle

1) Eggs laid on perianal folds at night by female worms

2) Eggs dislodge and contaminate toys, books and other objects

3) Egg ingested by human

4) Larvae hatch in small intestine

5) Gravid female migrates to perianal region at night to lay eggs

Enterobius spp. transmission

Faecal-oral route

Enterobius spp. prevalence

World-wide distribution

Institutionalised individuals

Members of a household

Wuchereria bancrofti phylum

nematode

Wuchereria bancrofti disease and presentation

Filariasis

Cyclical filarial fever, cellulitis, inflammation, Asthma like syndrome, blockage of lymphatic circulation

Wuchereria bancrofti lifecycle

1) Mosquito takes blood meal and injects larvae into skin

2) Mature to adults in the lymphatics

3) Adults produce sheathed microfilariae that migrate into lymphatic and peripheral blood circulation

No egg stage birth live young

Wuchereria bancrofti transmission

Mosquito vector

prevalent in pacific

taenia spp. species

Taenia solium - Pork tapeworm

Taenia saginata - Beef tapeworm

taenia spp. phylum

Cestode

taenia spp. disease and presentation

Tapeworm

Abdominal pain, nausea, weight loss, passage of tapeworm segments in faeces

taenia spp. lifecycle

1) Gravid proglottids containing eggs host in faeces

2) Intermediate host ingests eggs and the larvae encyst in the muscle

3) Definitive host eats uncooked infected meat from intermediate host

4) Scolex attaches to intestine

5) Mature into adults in the small intestine

taenia spp. prevalence and transmission

World wide

More in tropics and subtropics

Faecal-oral route

Strongyloides stercoralis phylum

Nematode

Strongyloides stercoralis presentation

Largely asymptomatic

Abdominal pain and diarrhea

Cough, wheezing and chronic bronchitis

Eosinophilia

Larva currens

Strongyloides stercoralis lifecycle

1) Larvae enter body through exposed skin

2) Migration of larvae to intestine

3) Maturation in intestine

4) Lay eggs and hatch eggs in intestine

5) Larvae excreted in stool

Strongyloides stercoralis prevalence

Tropical or subtropical climates

Indigenous australian populations

Strongyloides stercoralis transmission

Autoinfection and dissemination into other organs