- 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

Core Microbiology - Introduction to Parasites (4) Flashcards by Laura Chapman

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

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Host

An organism which harbours the parasite

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Symbiosis

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

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Mutualism

An associated in which both species benefit from the interaction

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Parasitism

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

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Commensalism

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

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Definitive host

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

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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

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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

Ascariasis treatment

Albendazole - Benzimidazole (prevents glucose absorption by worm)

Ascariasis control

Improve sanitation, education, deworming

Schistosmiasis

Macro-parasite, Trematode/fluke, Bilharzia disease

Schistosmiasis epidemiology

200 million, around freshwater lakes (Africa)

Schistosmiasis caused by

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

Schistosmiasis complications

Causes chronic renal disease > bladder cancer and liver cirrhosis

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

Schistosmiasis Swimmers itch

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

Schistosmiasis Katayama fever

General malaise, fever

Chronic Schistosmiasis presentation

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

Urinary complications of Schistosmiasis (S. haematobium)

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

Hepatic/intestinal Schistosmiasis

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

Schistosmiasis urinary diagnosis

Terminal stream microscopy and serology

Schistosmiasis hepatic/intestinal diagnosis

Stool microscopy, rectal snip microscopy, serology

Schistosmiasis treatment

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

Hydatid disease

Macro-parasite - Cestode/tapeworm

Hydatid disease host

Sheep and dogs, human accidental host

Hydatid disease caused by

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

Hydatid disease lifecycle

Liver > lungs > form hydatid cysts

Hydatid disease clinical

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

Hydatid disease diagnosis

Imagining and serology

Hydatid disease control

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

Malaria

Micro-parasite, protoza, sporozoan

4 species of Malaria (Plasmodium)

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

Which species of malaria is most clinically significant?

P. falciparum (most severe infections > death)

Malaria epidemiology

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

Malaria life cycle

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

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

Malaria diagnosis

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

Malaria control

Insecticide spraying, larvicidal spraying, filling in of breeding pools

Crypotsporidiosis

Micro-parasite, Cryptosporidium parvum and hominis, sporozoan

Crypotsporidiosis transmission

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

Crypotsporidiosis lifecycle

Direct, oocysts passed in stools contaminating water

Crypotsporidiosis incubation

2-10 days

Crypotsporidiosis clinical

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

Crypotsporidiosis severity

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

Crypotsporidiosis diagnosis

Faeces sample - acid fast staining, antigen detection by EIA

Crypotsporidiosis treatment

Rehydration, Nitazoxainde (Immunocompromised - paromomycin)

Common anti-protozoal treatment

Metronidazole, Pentamidine, Nitazoxanide, Pyrimethamine, Anti malarials

Common anti-helminthic treatment

Albendazole, Mebendazole, Ivermectin, Praziquantel

Core Microbiology - Introduction to Parasites (4) Flashcards

(65 cards)