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Y2 Microbiology > Parasitic Infections > Flashcards

Parasitic Infections Flashcards

1
Q

Define infection

A

invasion by and growth of pathogenic microorganisms within the body

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2
Q

Define disease

A

a disordered or incorrectly functioning organ, part, structure, system … etc..

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3
Q

Define parasite

A

organism living in or on the host and dependent on it for nutrition - causing damage

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4
Q

What are the two categories of endoparasites

A

Protozoa

Metazoa

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5
Q

Describe the protozoa

A

Eukaryotic and single-celled
Pathogenesis varied
Some have insect vectors e.g. malaria
No eosinophilia

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6
Q

Give examples of types of protozoa

A

Amoeba e.g. entamoeba histolytica
Coccidiae e.g. plasmodium species
Ciliae e.g. balantidium coli
Flagellates e.g. Giardia, leishmania

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7
Q

Describe the metazoa

A 
Multicellular organisms (Helminths/worms)
Free living, intermediate hosts and vectors
Some may just inhabit the gut (geohelminths), while others invade tissues
Eosinophilia if it invades blood
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8
Q

Give examples of types of metazoa

A

Roundworms e.g. ascaris, hookworm
Flatworms e.g. taenia (tape)
Flukes e.g. schistoma

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9
Q

Describe the epidemiology of amoeba infections

A

10% of the world is infected with E. histolytica
3rd most common cause of death of parasitic infection (after schistosomiasis and malaria)
90% asymptomatic
More common int eh tropics than in temperate climes

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10
Q

What does infection with amoebae cause

A

Amoebiasis which causes dystentery (bloody diarrhoea) and liver abscess

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11
Q

How does E. histolytica infection spread

A

Faecal-oral route (human only reservoir)
In the small intestine, E. histolytica cysts release active amoebic parasites (trophozoites) which invade the colon’s epithelial cells and cause flask-shaped ulcer
Infection can then spread via blood to other organs (liver, lungs, brain)

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12
Q

Give a reason to explain why E. histolytica infection is so widespread

A

asymptomatic carriers pass cysts in faeces
asymptomatic carriage state can persist indefinitely. Cysts
remain viable for up to 2 months.

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13
Q

What is the difference between E. dispar and E. hystolitica

A

E. dispar is a normal commensal in the GI tract

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14
Q

What do the different types of coccidia (plasmodium, toxoplasma and cryptosporidium) cause

A

Plasmodium - malaria
Toxoplasma - toxoplasmosis (a mild disease for immunocompetent people but very dangerous to a fetus)
Cryptosporidium - diarrhoea

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15
Q

Explain how plasmodium is spread

A

Hosts in humans and female anopheles mosquitos

2 stages: liver and blood

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16
Q

What are the symptoms of malaria

A

Can appear from 7days - 1 year
Fever, headache, chills, vomiting, muscle pain
Paroxysm (cycle in 4-8hrs)

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17
Q

What re the complications of malaria

A 
Severe anemia 
Cerebral malaria (swelling of the brain,seizures, coma)
liver failure
Shock 
Pulmonary edema
abnormally low blood sugar 
kidney failure
swelling and rupturing of the spleen
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18
Q

Explain how toxoplasma spreads

A

pet faeces
undercooked meat (of animals harbouring cysts)
organ transplantation or blood transfusion.

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19
Q

What are the risks of toxoplasma to immunocompromised patients

A

may develop central nervous system disease, brain lesions, pneumonitis or retinochoroiditis

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20
Q

Where do toxoplasma cysts form

A

tissues, mainly muscle, the brain and eyes, which may remain for life

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21
Q

How does cryptosporidium spread

A

infected water, either drinking water or in swimming pools etc.

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22
Q

What are the symptoms of cryptosporidium infection

A

Diarrhea, fever, nausea, vomiting in humans

very common in HIV+ patients presenting with diarrhea.

23
Q

What are the symptoms of Balantidium coli

A

No symptoms

Immunocompromised - persistent diarrhoea, sentry, abdominal pain, weight loss, nausea, vomiting, perforation of colon

24
Q

Explain how balantidium coli is spread

A

globally carried by pigs, rodents, and primates.

The life cycle of B. coli is very similar to E. histolytica

25
Q

What does giardia lambia cause and how

A

Giardiasis (traveller’s diarrhoea)
(most common water-borne protozoal infection)
flagellated trophozoites attach to duodenal or jejunal epithelium

26
Q

What are the symptoms of giardiasis

A 
Diarrhoea
Greasy stools that tend to float
Stomach or abdominal cramps
Upset stomach or nausea/vomiting
Dehydration (loss of fluids)
27
Q

How is trichomonas transmitted

A

Sexually
Flagellate
The trophozooites attach inside the vagina or urethra, and cause abnormal discharge. It can be spread by secretions and urine.

28
Q

What is the vector for leishmania

A

Sand fly

Leishmania have flagella which are retracted after being injected into humans via sandfly bites, becoming immobile

29
Q

Where are sand flies found and describe the appearance (+gender difference)

A

Warmer parts of the world (everywhere but N. America, N. Europe and Asia and poles)
3mm long and hairy, smaller than mosquitoes and silent
Only females feed on blood

30
Q

What are the 4 major types of leishmaniasis

A

visceral leishmaniasis
localised cutaneous leishmaniasis
diffuse cutaneous leishmaniasis
mucocutaneous / mucosal leishmaniasis

31
Q

Describe visceral leishmaniases (Common name, fatality, risk factors, PKDL)

A

Black fever / kala Azar
Fatal if untreated, 30-100 subclinical infections
Risk factors include malnutrition and immuno- suppression (either by drugs or HIV)
post-kala azar dermal leishmaniasis (PKDL) is common during or after treatment

32
Q

What are the symptoms of visceral leishmaniases

A 
irregular fever 
weight loss
hepatomegaly 
splenomegaly 
anaemia
33
Q

What is the treatment for visceral leishmaniases

A

IM or IV sodium stibogluconate or meglumin antimoniate

34
Q

Describe localised cutaneous leishmaniasis

A

Causes skin lesions on exposed body parts, which can be ulcerating
Are often self-healing and lead to immunity against re-infection, but can create serious disability and scars
Species include L. major and L. tropica.

35
Q

Describe diffuse cutaneous leishmanias

A

causes multiple, nodular, non-ulcerating skin lesions often on the face and hands.
L. aethopica.

36
Q

Describe mucocutaneous leishmanias

A

caused by L. braziliensis, affects the skin around the mouth, causing disfigurement.

37
Q

Describe mucosal leishmanias

A

Mucosal leishmaniasis just destroys the mouth and lips themselves (mucous membranes)
L. infantum as well as L. major, L. tropica, and L. aethopica.

38
Q

Which of the leishmania types is most common

A

LCL is by far the most common > MCL > DCL

39
Q

What is the treatment for Leishmanias

A

SSG either systemically or intra-lesion, and/or cryotherapy.

40
Q

Give 2 important cell surface molecules on leishmania

A 
lipophosphoglycan (LPG) and gp63, a protease
They can inhibit the fusion of the phagosome and lysosome in macrophages and neutrophils, and also inhibit activation, suppressing MHC class I and II expression and other signalling
41
Q

What are the most common worm infections

A

Ascariasis
Trichuriasis
Hookworm
Schistosomiasis

42
Q

What does ascaris lumbricoides cause

A

ascariasis
Adult worms are ~20-30cm in length. One female can produce hundreds of thousands of eggs per day, which get passed in the faeces.

43
Q

What is the timescale at which female Ascaris lumbricoides can produce eggs and live

A

It takes 2-3 months from egg ingestion to having an adult female able to produce her own eggs.
Adult worms can live for 1-2 years.

44
Q

What are the symptoms of ascariasis

A

Often asymptomatic
May cause abdominal pain, intestinal obstruction, exacerbation of existing malnutrition
Migration of larvae - Loeffler’s pneumonia

45
Q

What occurs in loeffler’s pneumonia

A

larvae penetrating from capillaries into the lungs causes pools of blood and dead epithelial cells to clog air spaces.
This increases the patient’s susceptibility to potentially fatal bacterial infections.

46
Q

Describe hookworms

A

about 1cm long, and attach by their ‘mouth’ to the villi of the small intestine.

47
Q

What are the symptoms of hookworm infection

A

A few worms may cause no symptoms, but having hundreds can cause bloody diarrhoea and anaemia because the worms leave open wounds in the intestinal mucosa.
This also leads to inflammation of the bowel.

48
Q

Describe the trichuris trichuria

A

whipworm, is used as therapy for allergy and autoimmune disease

49
Q

What does filaria cause and how

A

Lymphatic filiariasis
Obstruction of lymphatic vessels, usually in a leg, leading to elephantiasis
(may also obstruct the arm, breast or scrotum)

50
Q

Describe infection by tapeworms/cestodes

A

Taenia solium from pork and Taenia saginata from beef

Tapeworms attach to the small intestine and can be ~3m long in adulthood.

51
Q

What are the symptoms of tapeworm infection

A

Most have no symptoms
Those with taenia saginata have more symptoms
Abdominal discomfort
Diarrhoea
Weight loss
Visible active passing of tapeworm segments in the stool

52
Q

Give examples of ectoparasites

A

Scabies (Sarcoptes scabiei), mites whose females burrow into the epidermis to lay their eggs
Lice, including head lice (Pediculus capitis, ‘nits’ are their eggs) and pubic lice (Pthirus pubis)

53
Q

What does loa loa cause

A

Loaiasis - eye worm

Y2 Microbiology (7 decks)

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