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Microbiology > 6. Parasitic infections > Flashcards

6. Parasitic infections Flashcards

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Biology 101 flashcards
1
Q

What is an infection and disease?

A

Infection - invasion and growth of pathogenic microorganisms within the body

Disease - disordered or incorrectly functioning organ, structure or system of the body resulting from the effect of genetics/developmental errors, infections, poisons, nutritional imbalance, toxicity or environmental factors / illness

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2
Q

What is a vector?

A

Organism that transmits a disease or parasite from one animal or plant to another

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3
Q

What is a parasite?

A

Organisms living in or on the host and dependent on it for nutrition, causing damage

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4
Q

What are parasite that live in or on the host called?

A

In - endoparasites

On - ectoparasites

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5
Q

Describe Protozoa

A
  • Endoparasitic
  • Single-celled
  • Eukaryotes (genome in a nucleus, have complex organelles in cytoplasm)
  • Varied pathogenesis
  • Not characterised by eosinophilia
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6
Q

Give examples of protozoan parasites

A
  • Amoebae e.g. Entamoeba histolytica
  • Coccidian e.g. Toxoplasma
  • Ciliates e.g. Balantidium coli
  • Flagellates e.g. Giardia
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7
Q

Describe Metazoa

A
  • Endoparasitic
  • Multicellular - helminths/worms
  • Some just inhabit the gut (geohelminths), others invade tissues
  • Characterised by eosinophilia, if it invades the blood
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8
Q

How does infection by amoebae occur?

A

Ingestion of mature cysts in food or water, or on hands contaminated by faeces

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9
Q

Where does amoebae rank in causes of death by parasitic infections and what is the animal reservoir for infection?

A
  • 3rd most common cause of death
  • Humans are the only reservoir

(90% are asymptomatic)

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10
Q

Describe how amoebae infects humans

A
  • Cysts enter the small intestine and release active parasites (trophozoites)
  • These invade the epithelial cells of the large intestines, causing flask-shaped ulcers
  • Can spread to other organs e.g. liver, brain etc. via venous system
  • Asymptomatic carriers pass cysts in faeces (can remain viable for 2 months)
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11
Q

What problems does invasive amoebiasis most often cause, and which species causes this?

A

Amoebic liver abscess

caused by E. histolytica, not E. Dispar, which is commensal

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12
Q

What do the following Coccidia cause:
• Plasmodium
• Toxoplasma
• Cryptosporidium

A
  • Plasmodium - malaria
  • Toxoplasma - toxoplasmosis: mild disease in immunocompetent individuals, but danger in pregnancy
  • Cryptosporidium - diarrhoea
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13
Q

What are the different types of Plasmodium?

A
  • P. falciparum
  • P. knowlesi
  • P. ovale
  • P. vivax
  • P. malariae
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14
Q

What are the 2 types of hosts for Plasmodium?

A

Humans and female Anopheles mosquitoes

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15
Q

How many mosquito and human stages are there of the malaria life cycle?

A

1 mosquito and 2 human

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16
Q

What are the human stages of the malaria life cycle?

A

1) Liver stage - parasite invades liver cells, multiplies, ruptures
2) Blood invasion

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17
Q

When do symptoms generally appear for malaria?

A
  • Can appear as early as 7 days

* Time between exposure and signs of illness can be as long as one year

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18
Q 
When do symptoms appear for the following:
• P. falciparum
• P. knowlesi
• P. ovale
• P. vivax
• P. malariae
A
  • P. falciparum - 9-14 days
  • P. knowlesi - 11-12 days
  • P. ovale - 12-18 days
  • P. vivax - 12-18 days
  • P. malariae - 18-40 days
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19
Q

What are the symptoms of malaria?

A
  • Fever, headache, chills, vomiting, muscle pain

* Paroxysm (cycle in 4 to 8 hours)

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20
Q

What are the complications of malaria?

A
  • Severe anaemia
  • Cerebral malaria (swelling of brain, seizures, coma)
  • Liver failure
  • Shock
  • Pulmonary oedema
  • Low blood sugar
  • Kidney failure
  • Swelling/rupture of the spleen
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21
Q

What is the treatment for uncomplicated and severe malaria?

A 
Uncomplicated
• Chloroquine
• Atovaquone-proguanil
• Artemether-lumerfantrine
• Quinine sulfate
• One of: doxycycline, tetracycline etc.

Severe
• Artemisinin-based combination therapy (ACT) for P. falciparum malaria

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22
Q

How can you diagnose malaria?

A
  • Blood film, Giemsa stained microscopy
  • Detect the type by looking at the shape of the parasite
  • P. falciparum is the worst

• Antigen detection tests are faster, but more expensive and less sensitive

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23
Q

How can humans become infected by toxoplasma?

A
  • Eating undercooked meat
  • Consuming food or water contaminated with cat faeces
  • Contaminated environmental samples
  • Blood transfusion, organ transplant, transplacental
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24
Q

What complications may occur in immunocompromised patients with toxoplasma?

A

CNS disease, brain lesions, pneumonitis, retinochoroiditis

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25
Q

Who does toxoplasma infect and how can you test it?

A
  • Warm-blooded animals

* Serological test

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26
Q

What does cryptosporidium cause?

A
  • May not realise you have it if you are healthy

* If immunocompromised: diarrhoea, fever, nausea, vomiting

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27
Q

What is the route of infection, diagnosis and treatment for cryptosporidium?

A
  • Route: faecal-oral route
  • Diagnosis: stool examination
  • Treatment: fluid rehydration
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28
Q

What is Balantidiasis and what does it cause?

A
  • Ciliate
  • Asymptomatic in most people
  • Dehydrating in HIV patients (diarrhoea, dysentery, abdominal pain, weight loss, nausea, vomiting)
  • Colon perforation if untreated
29
Q

What is the diagnosis for Balantidiasis?

A

Stool examination

30
Q

What is Giardia, how is it acquired and what does it cause?

A
  • Flagellate
  • Attache by their suckers to the surface of the duodenal or jejunal mucosa
  • Ovoid cysts can survive the standard chlorination procedure, but trophozoite can’t
  • Filtration required remove them, can acquire from unfiltered water
  • Transmitted via faecal-oral route
  • Mostly asymptomatic
  • Acute symptoms: can cause diarrhoea, greasy stools, abdominal cramps, nausea, dehydration
31
Q

How is Giardia diagnosed and treated?

A

Diagnosis: stool examination
Treatment: metronidazole/tinidazole

32
Q

How is trichomonas transmitted and what are the symptoms?

A
  • Flagellate transmitted sexually
  • Can be asymptomatic (up to 50%)
  • Women: vaginal discharge, vulval itching, dysuria, offensive odour, low abdominal discomfort
  • Males: discharge, dysuria
33
Q

What are the complications of trichomonas?

A

Detrimental outcome on pregnancy, associated with pre-term delivery and low birth weight

34
Q

What effect does trichomonas have on HIV?

A

Enhance HIV transmission, and increase risk of trichomonas in those with HIV

35
Q

What is the diagnosis and treatment for trichomonas?

A

Diagnosis: microscopy (swab/urine) and rapid test
Treatment: metronidazole

36
Q

What are helminths and their definitive host?

A
  • Metazoa
  • Complex multicellular parasites
  • Humans are the definitive host (few are zoonoses)
37
Q

What is the most common worm infection worldwide?

A

Ascariasis

38
Q

What are the 3 different types of worm and give examples?

A
  • Roundworms (Nematodes) e.g. Ascaris
  • Flatworms (Cestodes) e.g. Taenia
  • Flukes (Trematodes) e.g. Schistoma
39
Q 
For Ascaris (roundworm):
• Where do they live?
• When do eggs become infective?
• How are the larvae carried?
A
  • Live in lumen of small intestine
  • Eggs embryonate and become infective after 18 days - several weeks
  • Larvae hatch and invade the intestinal mucosa
  • Carried via the portal then systemic circulation to the lungs
  • Mature in the lungs for 10-14 days
  • Penetrate into alveoli
  • Ascend the bronchial tree to the pharynx
  • Swallowed and reach the small intestine
40
Q

How long can adult Ascaris worms live for?

A

1-2 years

41
Q

What are the symptoms of Ascaris infection?

A
  • Often asymptomatic
  • Large number may cause abdominal pain or intestinal obstruction
  • Problems in malnourished individuals as they feed on contents of small intestine
  • Localised reactions in various organs from larvae migration
  • Loeffler’s pneumonia from lung penetration - blood and dead epithelial cells can clog air spaces
  • Secondary bacterial infections
42
Q

What is the diagnosis and treatment for Ascariasis and hookworms?

A

Diagnosis: stool examination
Treatment: albendazole and mebendazole

43
Q

Describe hookworms (roundworm) e.g. Ancylostoma duodenale and what they can cause

A
  • 1cm long and curved
  • Buccal capsules that attach them to the vili of the small intestine
  • Hard to expel and can cause intestinal bleeding - iron deficiency anaemia
  • GI and metabolic symptoms
  • Local skin manifestations during penetration
  • Respiratory symptoms during pulmonary migration
44
Q

How do hookworms e.g. Ancylostoma duodenale enter the body and reside in the small intestine?

A
  • Initially enters body through skin e.g. sole of foot
  • Larvae carried through the blood vessels to the heart and lungs
  • Penetrate alveoli and ascend the bronchial tree to the pharynx
  • Swallowed and reach the small intestine
45
Q

How does the hookworm Trichuris trichuria (whipworm) grow in a human and where do they live?

A
  • Faecal-oral transmission
  • Eggs hatch in the small intestine and release larvae
  • Larvae mature and establish themselves as adults in the colon
  • Adult worms live in the caecum and ascending colon
46
Q

What are the symptoms of a whipworm?

A
  • Asymptomatic if small amount

* If there’s a lot - bloody diarrhoea, anaemia, open wounds (intestinal inflammation), rectal prolapse

47
Q

Which worm is being used in helminthic therapy, to help against allergies and autoimmune diseases?

A

Whipworm

48
Q

How does the nematode, Lymphatic filariasis, cause its symptoms?

A
  • Blocks lymphatic vessels
  • Can progress to elephantiasis
  • Can occur in the legs (and arms, breast and scrotum)
49
Q

How is Lymphatic filariasis transmitted?

A
  • Mosquito takes up blood from infected host with the microfilariae
  • Larvae transform in the mosquito
  • Transfers to another person
50
Q

What is the diagnosis and treatment for Lymphatic filariasis?

A

Diagnosis: blood smear/antigen detection with immunochromatic test / ELISA
(peak amounts in peripheral blood from 10pm - 4am)
Treatment: albendazole and ivermectin

51
Q

What transmits the nematode Loa Loa (filaria), what does it cause and how long can it live in a person?

A

• Transmitted by a fly (becomes infective in the fly)

  • Loiasis
  • Migrate through subcutaneous tissues and cross the front of the eye under conjunctiva

• Lives for 4-12 years

52
Q

What are the definitive hosts for the (cestode) tapeworm Taenia spp., how can it be acquired and what are the symptoms?

A
  • Humans
  • Eating raw meet (eggs can survive in environment for months)
  • T. saginata (from beef) can cause more symptoms than the other types - size up to 10m
  • Mostly asymptomatic
  • Abdominal pain, loss of appetite, weight loss, upset stomach
  • Most common acquired cause of epilepsy (can cross the BBB)
53
Q

What is the most visible sign of taeniasis?

A

Active passing of tapeworm segments

54
Q

What is the treatment for Taenia spp.?

A

Praziquantel

55
Q

How does Schistosomiasis (trematode) transfer to a human?

A
  • Eggs eliminated in water via faeces or urine
  • Hatch and release miricidia
  • Penetrate a snail, transform and release cercariae in the water
  • This can penetrate the skin and migrate through tissues, transforming into an adult
  • Eventually resides in venules
  • Eggs move progressively towards the lumen of the intestine (S. mansoni/japonicum) or the bladder/ureters (S. haematobium)
56
Q

What are the symptoms of Schistosomiasis?

A

Days
• Rash or itchy skin

1-2 months (mostly asymptomatic)
• Fever
• Chills
• Cough
• Muscle aches

(inflammation or scarring in the intestine/liver/bladder)

57
Q

How is Schistosomiasis diagnosed and treated?

A

Diagnosis: stool or urine samples
Treatment: praziquantel

(Can be prevented by killing the snails with Endod berries)

58
Q

What are the common names for the following ectoparasites:
• Pediculus humanus capitis
• Pediculus humanus corporis
• Pthirus pubis

A
  • Pediculus humanus capitis - head louse
  • Pediculus humanus corporis - body louse
  • Pthirus pubis - pubic louse
59
Q

What are the 3 stages of the life of lice?

A
  • Eggs
  • Nymphs
  • Adult
60
Q

What type of parasite is Leishmania and how is it transmitted into the body?

A

Protozoan flagellate parasite

Vector - sandfly
• takes blood meal
• regurgitates parasite into mammalian host
• taken up by phagocytic cells
• transforms into non-flagellated form
• parasite dies and amastigote form is released into blood

61
Q

Describe the 2 forms of leishmania

A

Promastigote
• Transmitted by the sandfly
• Has a flagellum
• Form of leishmania within the sandfly

Amastigote
• Acheived inside the phagocytic cell
• Form within humans or other vertebrate host cells
• Resorbed their flagellum - no longer motile

62
Q

How are sandflies different to mosquitos?

A

Attack is silent - cannot be heard

63
Q

Describe the most severe form of Leishmaniases

A

Visceral leishmaniasis (black fever)
• Irregular fever, weight loss, hepato/splenomegaly, anaemia
• Affects internal organs
• Risk factors: malnutrition, immunosuppression

64
Q

How can Leishmaniasis be diagnosed?

A
  • Parasite detection - visualisation of the amastigote form by microscopy
  • Antibody detection - direct agglutination test (DAT) and rK39 chromatographic test
65
Q

What are the 3 categories of cutaneous leishmaniasis?

A
  • Localised
  • Diffuse
  • Mucocutaneous
66
Q

Describe localised cutaneous leishmaniasis

A
  • Skin lesions on exposed body parts
  • Can create serious disability and scars (can be disfiguring) - causes social problems
  • Can heal
  • Immunity to reinfection
67
Q

Describe diffuse cutaneous leishmaniasis

A
  • Disseminated lesions characterised by nodules (non-ulcerating lesions)
  • Resembles leprosy, difficult to treat
  • No spontaneous healing
  • Nodules are full of parasites
  • Relapses
68
Q

Describe mucocutaneous leishmaniasis

A
  • Disfiguring, destroys mucous membranes
  • Very severe
  • No spontaneous healing
  • Relapses
  • Malnutrition is a serious manifestation (hurts to eat)
69
Q

What is the diagnosis and treatment for cutaneous leishmaniasis?

A

Diagnosis: microscopy and culture, PCR
Treatment: Sodium stibogluconate (SSG)

Microbiology (6 decks)

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