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Medical Microbiology > Day 10: Introduction Parasitology, Protozoa and Helminths > Flashcards

Day 10: Introduction Parasitology, Protozoa and Helminths Flashcards

HC23, 24, 25

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1
Q

HC23: Symbiosis

A
  • Living together
    > all organisms have associations
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2
Q

Intraspecies and interspecies association

A

Intraspecies: associations between animals of same species: herd or flock and parental care
Interspecies: Associations between animals of different species

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3
Q

Interspecies association types

A
  • Mutualism: both benefit: mutually beneficial association between 2 species
  • Commensalism: No effect host and benefit of other species: both species can live independent from each other, but one or both may gain advantage from the association
  • Parasitism: An organism is living on or in another organism (the host), is dependent on the host and benefits from the association at host’s expense (disadvantage)
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4
Q

Parasite

A

Maintains and multiplies at expenses of the host with which it lives

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5
Q

Protozoa vs Metazoa

A

Protozoa: unicellular organisms: Plasmodium, Giardia
Metazoa: multicellular organisms: Schistosoma (worm), Arthropoda (ticks)

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6
Q

Endo vs ectoparasites

A
  • Endoparasites: parasites that live inside their host: intestine, blood tissue and organs: protozoa (unicellular) and helminths (multicellular) (majority is endo)
  • Ectoparasites: Parasites that exclusively live of or on the skin of their hosts: Arthropoda: lice, mites, fleas, ticks
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7
Q

biggest and smallest parasites

A

Biggest: helminths
Smaller: protozao, bacteria and even viruses

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8
Q

Life cycle of parasite requires … from host

A

Complex interactions between parasite and host

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9
Q

Final (definitive) host

A

Organism in which the adult parasite is present and where sexual reproduction takes place

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10
Q

Intermediate host

A

Organism in which the parasite undergoes a specific development where asexual reproduction might occur but not suxual reproduction

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11
Q

Human is not always the final host, name big example

A

Plasmodium (malaria)

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12
Q

Life cycles:
Direct transmission

A
  • From final host to other final host, no intermediate stages
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13
Q

Life cycles:
Direct life cycle

A

Final host > free living stage (larval) > final host
- Like Whipworm,: adult worms in intestines of dog > eggs pass in feces > mature eggs ingested by other dog
- Free living larval stage in feces

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14
Q

Indirect life cycle

A

Final host > Intermediate host (larval) stage > Final host
- But also other combinations: Final host > Intermediate host > Free living stage > Intermediate host 2 > Final host

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15
Q

Schistosoma spp. life cycle

A

Final host: human
> Adult worms (m/v) paired in blood vessels around intestines
> Sexual reproduction in blood
> Eggs go across endothelium into intestines or bladder
> Excretion eggs through feces or urine
> Eggs go into environmental water
> From eggs a miracidium develops: taken up by snail (intermediate host)
> Asexual reproduction of parasite inside the intermediate host: inside snail sporocysts are made
> Sporocysts develop in snail and are released from snail into water and grow
> Free cerecariae come into contact with human skin and can penetrate (invade) and go into circulation
> Cerecariae lose tails during penetration and become schistosomulae again

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16
Q

Vector

A

Invertebrate organism that facilitates transmission from one host to another

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17
Q

The snail in the schistosoma spp. life cycle is the …

A

Intermediate host and the vector

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18
Q

Reservoir

A

Some parasites occur in both humans as well as in other animals, these animals are called reservoir hosts and are the source of infection for humans: zoonotic infections
> zoonotic infections include reservoir hosts: always

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19
Q

Cryptosporuidium parvum - zoonotic transmission

A

Cattle: sporulated oocysts pass feces > get into soil > ingestion again via soil
> humans also infected via soil

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20
Q

Life cycle of Cercal dermatitis causing Trichobilharzia ocellata

A

Common skin disease in summer time
Final hosts: water birds
> eggs passed in feces
> eggs hatch in water and liberate miracidia
> Parasite develops in snail
> cernanae released which penetrate skin of water birds
> accidental: transmission carcanae to humans

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21
Q

Life cycle of Trichobilharzia is a …

A

Indirect life cycle

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22
Q

Hosts in Trichobilharzia ocellata cycle

A

Birds: final host (sexual reproduction)
Snail: intermediate host and vector
Human: accidental host

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23
Q

Life cycle Toxoplasma gondii

A

Cat litter disease: ocular and congenital toxoplasmosis
- Cat is final host
- Fecal oocysts released and passed to mice and birds
- Tissue cysts
- Eaten by cat and infection
- cattle can be infected by cat feces as well
- cat litter can cause disease: pregnant women cannot do this: infection over placenta causes congenital problems in fetus
> Cats and cattle: reservoir
> Direct transmission: from mother to fetus or human to human blood transfusion
> Direct life cycle: cats eat grass which other cat infected
> zoonotic disease: from cat litter or cattle

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24
Q

Health impact parasites

A
  • 2 million people infected
  • 25% global mortality
  • economic impact via health system: unproductivity, agriculture loss
  • social impact
  • development: less school days attended and less cognitive development
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25
Q

HC24: Protozao cell

A

Like eukaryotic cell, but may lack some familiar organelles like mitochondria and Golgi apparatus in Giardia

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26
Q

Cryptosporidium

A

Intestine parasite causing diarrhea, immunocompromised host affected, zoonotic infections possible

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27
Q

Trypanosoma characteristics

A

Blood and brain affected, immune evasion, lack of medicines

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28
Q

Cryptosporidium spp. life cycle

A

Oocysts with feces excretion from intestines
> C. parvum major host: cattle, humans via zoonotic infection
> C. hominis: infection of humans > contamination water and food with oocysts > thick walled oocyst ingested by host: go into GI tract
> asexual and sexual cycles in human

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29
Q

Specific locatalization of Cryptosporidium spp. in human

A

Wall of the small intestine

30
Q

Absorbing nutrients and Cryptosporidium infection

A

Is imparied because diarrhea and mucus and epithelium affected
> severe diarrheal disease: risk for children, eldery, immunocompromised > dehydration

31
Q

Transmission type of Cryptosporidium

A

Fecal-oral route with contaminated water

32
Q

Oocysts are very …

A

resistant

33
Q

Therapy Cryptosporidium

A

Paramomycin, for the immunocompromised

34
Q

Infection Cryptosporidium treatment normally

A

Should disappear spontaneously in immunocompetent

35
Q

Diagnosis Cryptosporidium

A

Microscopy: Staining methods
> difficult morphology: confusion with yeast
> PCR

36
Q

Symptoms Cryptosporidium

A
  • Diarrhea: das to weeks and often watery-loose
  • Fever often present
37
Q

Symptoms Cryptosporidium in immunodeficient persons / AIDS

A
  • Persistent infectin (low CD4)
  • Diarrhea, frequent water, sometimes liters per day
  • Anorexia, nausea, sometimes vomiting
  • Pain in right upper quadrant abdomen
    » Cryptosporidiosis is life threatening in AIDS
38
Q

Most common protozoan GI infection worldwide

A

Cryptosporodiosis

39
Q

Milwaukee outbreak

A

Contaminated tap water with Cryptosporidium
> resistant oocysts against water-treatment-plant

40
Q

Diarrheal disease in Malawi

A

Large part by Cryptosporidium or Giardia (almost no co-infection)
> No infections in domestic animals
> Main source oocysts are soil and toilets
- Antroponotic transmission: human to huma
- wash measures

41
Q

Human African Trypanosomiasis (HAT)

A

Sleeping disease
> by T. brucei
» by T. b. gambiense: Gambian HAT (chronic form, West Africa)
» by T. b. rhodesiense: Rhodesian HAT (acute form, East Africa)

42
Q

Kinetaplasts of Trypanosoma

A

Have next to nucleus, second organelle with mtDNA for energy management

43
Q

Life cycle African Trypanosoma

A

Tsetse fly: blood sucking fly
Indirect life cycle with the vector: tsetse fly
> zoonotic reservoir: cattle
> there are subtypes which infect cattle specifically

44
Q

Transmission Trypanosoma brunei: reservoir

A
  • Wild and domestic animals reservoir for t. b. rhodesiense
  • Infected humans reservoir for t. b. gambiense
    » fertile regions affected: green desert
45
Q

Stage 1 HAT symptoms

A
  • Recurrent fever ddx (differential diagnosis) incl malaria, HIV, brucellosis
    Lymphadenopathy - ddx tuberculosis, HIV and cancer
46
Q

Do the trypanosoma have intracullar stages

A

No

47
Q

Stage 2 (late) HAT symptoms

A

Mental status change
ddx tuberculosis, meningitis and HIV-related opportunistic infections
Sleeping

48
Q

HAT has been sometimes seen as witchcraft (evil spirits) resulting in..

A

More visits of spiritual healers instead of meds

49
Q

Diagnosis HAT

A

Spinal fluid sample

50
Q

Problem with HAT treatment

A
  • Few old drugs
  • Treatment depends on stage disease
  • Drugs that are efficient in treatment of HAT in early stage are not effective in late stage
  • Treatment success in late stage is low, relapse in common
51
Q

Stage 2 HAT treatment: Melarsoprol

A
  • Drug of choice: can pass blood brain barrier
  • Painful treatment: deaths and relapses occur
  • Toxic, causes myocarditis, renal damage and encephalopathy
  • Resistance occurs
52
Q

Eflornithine and Nifurtimox

A

Possible treatments for stage 2 HAT which are not used because patent on it

53
Q

Compromised eradication of HAT

A

Pandemic COVID and civil wars

54
Q

Evasion host immune system by Trypanosoma

A

Lives in blood > hostile environment: immune system
» Fluctuations in parasitemia during infection
> Variant surface glycoproteins (VSGs) of Trypanosoma are essential for survival
> switch genes on or off to vary the surface glycoproteins
> VSG: protein which densely packs cell surface of parasite
» no biochemical activity
» protect against host environment and immune responses
» waves of VSG variants during chronic infection based on selective pressure

55
Q

HC25: Helminths classes

A
  • Trematoda: flukes
  • Cestoda: tape worms
  • Nematoda: round worms
56
Q

Helminths

A

Large worms, visible with the eye and composed of many specialized cells

57
Q

Specialized cells and organs of helminths and properties

A
  • Brain with neuropeptides
  • Digestive system
  • Reproductive system
  • Parasite - parasite communication
  • Parasite - host communication
  • Females are larger than males
  • can survive for long time
58
Q

Nematodes, trematodes examples

A
  • Nematodes: ascatis, hookworm, onchocerca
  • Trematodes: schistosoma
  • Guinea worm
59
Q

Nematodes character

A
  • Huge numbers
  • Huge biomass
  • Huge impact
  • Soil-transmitted helminths: adult worms of greatest public health significance
60
Q

Burden of ascaris worms

A

Can become up to 40 cm, in intestine

61
Q

Ascaris worm life cycle

A

In GI tract > lay eggs
> fertilized eggs in feces
> consumption via soil
> worms to intestine
> larvae can be coughed up via lungs for re-infection

62
Q

Hookworm cycle

A

Hooks to intestinal wall with hooks and suck blood
> causes anemia in children at risk
> larvae exit circulation in lungs > coughed up and swallowed
> eggs in feces
> larvae develop in environment (in warm, moist soil: this limits the distribution to certain climatic conditions) and penetrate skin at foot

63
Q

Onchocerciasis

A

Causes river blindness
O. valvulus
> vector: black fly
> adult worms in skin nodules
> migrating microfilariae causing severe itching: Leopard skin
> Treatment with Ivermectin > only treats the larvae: larvalcidal (but why take pills when you are not sick (still larvae): problem
> nodes with parasites removed through surgery

64
Q

Life cycle Onchocerciasis valvalus

A

in skin nodules
> blackfly takes blood meal
> larval stages in fly
> infection by the fly
> worms go to subcutaneous tissues

65
Q

Schistosomiasis

A

Parasitic disease caused by Schistosome worms
> five species cause human disease
> second most prevalent parasitic disease
> a neglected tropical disease (NTD)
> Schistosoma mansoni the most important

66
Q

Life cycle of Schistosoma spp.

A

Final host human
> schistosomulae in circulation
> adult worms lay eggs
> miracidia in feces
> snails as intermediate host
> formation sporocysts
> formation cercaria which leave and penetrate human skin

67
Q

Clinical signs Schistosomiasis

A
  • Cercarial rash when first infection
  • Goes into blood afterwards
    > acute schistosomiasis
    > Katayama syndrome: immune complexes deposited in tissues
  • Chronic: into blood vessels around intestine and bladder
    > chronic schistosomiasis
    > granuloma formation in tissues
    > urinate blood
68
Q

Intestinal schistosomiasis

A

S. japonicum, S. mansoni and others
> eggs trapped in different tissues like liver
> granulamatous reaction
> fibrosis of liver

69
Q

Urinary schistosomiasis

A

S. haematobium
> eggs trapped in different tissues like bladder
> granulamatous reaction
> fibrosis of the bladder

70
Q

Dracunculiasis

A

Guinea worm disease
> eradiacation almost
> females when full of eggs > migrate to the foot and cause large blisters
> For relief, humans put foot in water
> Larvae released into water from emerging female worm which creeps out the blister of the foot and releases eggs
> large worm
> reproduce in subcutaneous tissues

71
Q

Life cycle Guinea worm

A

In human > reproduce in GI tract
> fertilized female worm migrates to surface skin in foot and causes blister and releases and releases larvae into water
> larvae develop in water
> larvae consumed by copepod in water
> infected copepods in unfiltered drinking water or eaten via larger fish

72
Q

Treatment Guinea worm

A

No vaccine, no treatment, no immunity
> try to facilitate safe water access: interrupt transmission
> active case detection and containment
> heightened surveillance
> education awareness

Medical Microbiology (11 decks)

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