Core Microbiology - Introduction to Parasites (4) Flashcards Preview

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Flashcards in Core Microbiology - Introduction to Parasites (4) Deck (65):
1

Parasite

- Organism that lives in/on another organism (its host) and benefits by deriving nutrients at other's expense
- Habitually relies on/exploits others and gives nothing in return
- Doesn't necessarily cause disease
- Host may be harmed/suffer consequences of this association

2

Host

An organism which harbours the parasite

3

Symbiosis

Living together, close, long term interaction between two different species

4

Mutualism

An associated in which both species benefit from the interaction

5

Parasitism

An association in which the parasite derives benefit and the host gets nothing in return but suffers injury

6

Commensalism

An association in which the parasite only is deriving benefit without causing injury to the host

7

Definitive host

Harbours adult stage of parasite, where parasite utilises the sexual method of reproduction, usually human

8

Intermediate host

Harbours the larval/asexual stages, some parasites have 2

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Paratenic host

Host where parasite remains viable without further development

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How to approach parasites

- Distribution (where find them?)
- Life Cycle (how survive+breed)
- Clinical Manifestations
- Diagnosis
- Treatment
- Control (prevent others)

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Direct life cycle

1 host

12

Simple/complex indirect

2 hosts

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Classification of parasites

Protozoa (micro-parasites) and Helminths (marco-parasites)

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Cestode

Taenia/tape worm

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Tretmatode

Schistosoma/fluke

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Intestinal nematode

Ascaris lumbricoides - largest most common worm

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Tissue nematode

Wuchereria bancrofti

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Ascariasis

Macroparasite, intestinal nematode, Ascaris lumbricoides, round worm

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Ascariasis epidemiology

1/7 world population, common China

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Ascariasis prevalence

3-8 years old

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Ascariasis transmission

Ingestion of eggs > lava pass into intestines > portal circulation > lungs (alveolar) > swallowed > intestines

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Ascariasis Lung migration

Loefflers syndrome - dry cough, dyspnea, wheeze, haemoptysis, eosinophilic pneumonitis

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Ascariasis intestinal phase

Malnutrition, migration, intestinal obstruction, worm burden

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Raised ?? commin in helminth infection

Eosinophils

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Ascariasis diagnosis

Stool/blood sample, X-ray, USS, CTI/MRI

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Ascariasis treatment

Albendazole - Benzimidazole (prevents glucose absorption by worm)

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Ascariasis control

Improve sanitation, education, deworming

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Schistosmiasis

Macro-parasite, Trematode/fluke, Bilharzia disease

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Schistosmiasis epidemiology

200 million, around freshwater lakes (Africa)

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Schistosmiasis caused by

Schistosoma/snails: S.haematobium, S.mansoni, S.intercallatum, S.japonicum, S.mekongi

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Schistosmiasis complications

Causes chronic renal disease > bladder cancer and liver cirrhosis

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Schistosmiasis life cycle

Male and female mate in bowel > produce eggs > released in faeces/urine > develop/hatch > eaten by snail > reproduce > penetrates skin of humans

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Schistosmiasis Swimmers itch

Lasts few weeks, pain and itching at site (allergic reaction)

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Schistosmiasis Katayama fever

General malaise, fever

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Chronic Schistosmiasis presentation

Persist for years, distended stomach effects of eggs in distant sites - spine and lung

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Urinary complications of Schistosmiasis (S. haematobium)

Haematuria, bladder fibrosis and dysfunction, squamous cell bladder cancer (due to eggs)

37

Hepatic/intestinal Schistosmiasis

(S. mansoni, S. intercallatum, S. japonicum, S.mekongi) Portal hypertension, liver cirrhosis

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Schistosmiasis urinary diagnosis

Terminal stream microscopy and serology

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Schistosmiasis hepatic/intestinal diagnosis

Stool microscopy, rectal snip microscopy, serology

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Schistosmiasis treatment

Praziquantel (increased ionic permability tetanic contraction, detachment and death)

41

Hydatid disease

Macro-parasite - Cestode/tapeworm

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Hydatid disease host

Sheep and dogs, human accidental host

43

Hydatid disease caused by

Echinococcus (E. granulosus - cystic and E.multilocularis - alveolar)

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Hydatid disease lifecycle

Liver > lungs > form hydatid cysts

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Hydatid disease clinical

Cysts liver and lung, asymptomatic for years, mass effect, secondary bact infection, cyst rupture > shock and death

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Hydatid disease diagnosis

Imagining and serology

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Hydatid disease control

Regularly worm dogs (reduce eggs), hand hygiene, safe disposal of animal carcasses

48

Malaria

Micro-parasite, protoza, sporozoan

49

4 species of Malaria (Plasmodium)

1. P. falciparum
2. P. vivax
3. P.ovale
4. P.malariae

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Which species of malaria is most clinically significant?

P. falciparum (most severe infections > death)

51

Malaria epidemiology

300-500 million people/year, 1-3 million deaths/year

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Malaria life cycle

Anopheles as a vector, injects parasite into RBC, sporozites enter liver, replicates until cells so heavy they rupture, asexual phase

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Malaria clinical

Parasites ruputure RBC > block capillaries and cause inflammation, fevers and rigors (alternate days), cerebral malaria (confusion, headache, coma), renal failure (black water fever), hypoglycaemia, pulmonary oedema, circulatory collapse, anaemia, bleeding and DIC

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Malaria diagnosis

Thick and thin microscopy, serology (antigen), PCR (malarial DNA)

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Malaria control

Insecticide spraying, larvicidal spraying, filling in of breeding pools

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Crypotsporidiosis

Micro-parasite, Cryptosporidium parvum and hominis, sporozoan

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Crypotsporidiosis transmission

human - human with animal resevoir (cattle, sheep, goats), faecal-oral

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Crypotsporidiosis lifecycle

Direct, oocysts passed in stools contaminating water

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Crypotsporidiosis incubation

2-10 days

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Crypotsporidiosis clinical

Watery diarrhoea with mucus, bloating, cramps, fever, nausea, vomiting

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Crypotsporidiosis severity

Self-limiting, severe - young, old and immunocompromised (HIV)

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Crypotsporidiosis diagnosis

Faeces sample - acid fast staining, antigen detection by EIA

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Crypotsporidiosis treatment

Rehydration, Nitazoxainde (Immunocompromised - paromomycin)

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Common anti-protozoal treatment

Metronidazole, Pentamidine, Nitazoxanide, Pyrimethamine, Anti malarials

65

Common anti-helminthic treatment

Albendazole, Mebendazole, Ivermectin, Praziquantel

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