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ID study > Parasitology > Flashcards

Parasitology Flashcards

1
Q

Onchocerciasis - organism

A

Onchocerca volvulus

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2
Q

Onchocerciasis - geographical distribution

A

Africa

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3
Q

Onchocerciasis - transmission

A

Simulium (blackflies) that are day biting outdoors and breed in rapids

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4
Q

Onchocerciasis - life cycle

A
  1. Blackfly with L3 larvae bites human and injects into skin
  2. L3 larvae migrate to the subcutaenous tissue and mature into adult worms, forming nodules
  3. Adult worms produce microfilariae which migrate to the skin and eyes causing symptoms
  4. Blackfly ingests Mf
  5. L1 –> L3 larvae in the blackfly midgut
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5
Q

Onchocerciasis symptoms

A

Itching
Skin nodules and can develop atrophy, lizard skin chronically
Eye disease - punctate keratitis, anterior uveitis, secondary cataracts, optic atrophy

Late stage - retinal changes, sub-conjunctival haemorrhage

Epilepsy

Poor growth

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6
Q

Onchocerciasis - diagnostics

A

Skin snip

Antibody testing (Ov16)

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7
Q

Onchocerciasis - treatment

A

Ivermectin - although does not kill adult worms and cannot give in concurrent loa loa infection

Doxycycline to eradicate Wolbachia

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8
Q

Onchocerciasis - prevention

A
  1. Blackfly vector control - insecticides
  2. MDA
  3. Cross border collaboration
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9
Q

What are the two types of helminths?

A

Platyhelminths (like a flattened patty-cake) –> Flat worms (flukes and tapeworms)
Nematodes - Round worms

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10
Q

Intermediate host (helminths)

A

Hosts the larval stage

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11
Q

Definitive host

A

Hosts the sexually mature adult

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12
Q

Cestodes = ribbon-like flat worms
What are the most important species?

A

Taenia saginata (beef tapeworm)
Taenia solium (pork tapeworm) (larval infection=cysticercosis)
Dihyllobothrium spp (fish tapeworm)
Echinococcus spp (dog and fox tapeworms) (larval infection=hydatid cyst)

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13
Q

Nematodes - what are the most important species?

A

Intestinal:
Hookworm
Ascaris
Trichuris
Strongyloides

Subcutaneous tissue:
Wucheria bancrofti
Brugia

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14
Q

What is Chagas disease?

A

A parasitic infection caused by trypanosoma cruzi, transmitted by triatoma bugs (rhodnius and panstrongylus)

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15
Q

Chagas disease - life cycle

A
  1. Triatoma bug bites and there is faecal inoculation
  2. Tryponmatigotes penetrate cells at the bite wound site and inside the cells they turn into amastigotes
  3. Intracellular amastigotes turn into trypomastigotes
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16
Q

Chagas disease transmission

A

Triatoma bug bite
Vertical transmission
Oral ingestion
Transplants/transfusion

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17
Q

Chagas - diagnostics

A

Serology (x2 - ELISA and IFAT)
PCR
Microscopy

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18
Q

Chagas symptoms

A

GI: Dysphagia, mega-oesophagus
Cardiac: Heart block, cardiomyopathy and heart failure

In immunocomprimised: fever, rash, myocarditis and SOL in HIV

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19
Q

Chagas treatment

A

Benznidazole 60 days
Side effects: Rash, numbness/peripheral neuropathy, weight loss

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20
Q

What is romana’s sign?

A

T cruzi infection through the conjunctiva

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21
Q

Management of asymptomatic Chagas

A

Consider benznidazole 60 days to prevent vertical transmission, in immunocompromised or immunocompetent with asymptomatic disease
ECG screening +/- echocardiogram

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22
Q

Hookworm - organism

A

Ancyclostoma duodenale
Necator americanus

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23
Q

Hookworm - transmission

A

Penetration of skin by L3 larvae
Oral ingestion of unwashed vegetation with L3 larvae on

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24
Q

Hookworm lifecycle

A
  1. Filariform larva penetrates the skin
  2. Exit circulation in the lungs
  3. Coughed up and swallowed into the intestine
  4. Eggs leave in the faeces
  5. Larvae atched and develop into a filariform larva in the environment
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25
Q

Hookworm - skin features

A
  1. Ground itch
  2. Cutaneous larva migrans (from cat + dog hookworm only as it cannot complete the lifecycle)
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26
Q

Hookworm - lung clinical features

A

Dry cough/wheeze
Loeffler’s syndrome (eosinophilic pneumonitis)

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27
Q

Hookworm - abdominal clinical features

A

Nausea, abdo pain, diarrhoea
Anaemia
Cognitive impairment in children

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28
Q

Hookworm - diagnostics

A

Stool OCP
60microns, clear wall

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29
Q

Hookworm treatment

A

Albendazole or mebendazole
Ivermectin

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30
Q

Strongyloides - organism

A

Strongyloides stercoralis

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31
Q

Strongyloides - transmission

A

Penetration through the skin, often the soles of the feet

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32
Q

Strongyloides hyperinfection

A

Driven by autoinfection in the context of immunosuppression
Asexual reproduction by adult females in the gut –> L3 larvae can autoinfect internally through the intestinal mucosa or externally via perianal skin
Leading to disseminated strongyloides in multiple organs

Associations: Steroids, HTLV1, transplant. NOT HIV

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33
Q

Strongyloides skin manifestation

A

Pruritic dermatitis at site of initial penetration
Urticarial rash in the context of autoinfection
Cutaneous larva currens

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34
Q

Differentials for migratory swellings (9)

A
  1. Cutaneous larva migrans (Ancylostoma braziliense, Ancylostoma caninum).
  2. Strongyloidiasis (Strongyloides stercoralis).
  3. Gnathostomiasis (Gnathostoma spp.).
  4. Loiasis (Loa loa).
  5. Dracunculiasis (Dracunculus medinensis).
  6. Toxocariasis (Toxocara canis, Toxocara cati).
  7. Filariasis (Mansonella spp., Wuchereria bancrofti, Brugia malayi).
  8. Fascioliasis (Fasciola hepatica).
  9. Trichinosis (Trichinella spiralis)
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35
Q

Disseminated strongyloidiasis symptoms

A

Lung: ARDS Cough, SOB, wheeze, pulmonary haemorrhage, ARDS

Intestine: Ulceration with bacterial translocation and GN bacteraemias, small bowel obstruction, chronic diarrhoea

Nephrotic syndrome

Larva currens STRAIGHT LINEAR RASH

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36
Q

Strongyloidiasis

A

Diagnosis: Stool OCP
Sputum for larvae in disseminated disease
Eosinophilia
Serology (in returning travellers, not those from endemic setting)

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37
Q

Strongyloides treatment

A
  1. Ivermectin
  2. Albendazole
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38
Q

Trichuris - clinical features

A

Chronic trichuris colitis
Gut wall odoema + haemorrhage + rectal prolapse

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39
Q

Trichuris - microscopic features

A

50-55 microns
Tea tray

40
Q

Trichuris - treatment

A

Benzimidazoles

41
Q

Ascaris lymbricoides - clinical features

A

Migrates to lung so causes Loeffler’s

GI: intestinal obstruction, biliary obstruction, hepatic abscess
malnutrition

42
Q

Cestodes - definition

A

Ribbon like flatworms with segments (proglottids) and a head (scolex) with suckers that attach to the intestinal wall

43
Q

Taenia saginata - transmission and clinical syndrome

A

Beef tapeworm
Humans eat contaminated beef, adult worm evolves in the gut and poo out the eggs

Intra-abdominal symptoms, may have the worms around the anus

44
Q

Taenia saginata - microscopic findings

A

4 suckers, no hooks
Egg looks like a bike wheel, just over 30 microns

45
Q

Cystercicosis - organism

A

Taenia solium

46
Q

Cystercicosis life cycle

A

Humans eat pig meat containing cysts or may eat the eggs directly from infected human poo

47
Q

Taenia solium- clinical presentation

A

Intestinal infection from eating the adult worm is often mild (i.e. pig meat)

But tissue infection with the larval form from eating eggs (i.e. cystercisosis) can be really severe with seizures secondary to neurocystercicosis

48
Q

Taenia solium

A

Differentiate from taenia saginata because of presence of hooks

49
Q

Diphyllobothrium - life cycle

A

Copepods eaten by freshwater fish eaten by human.

Develops into an adult in small intestine

Proglottids release the immature eggs which pass into the faeces and back into the water supply

Coracidia hatch from the egg and are eaten by crustaceans

50
Q

Diphyllobothrium clinical features

A

GI disturbance
Anaemia (B12 deficiency)

51
Q

Diphyllobothrium microscopic features

A

Oval with an operculum, measuring just over 60 microns

52
Q

Echinococcus granulosus

A

Dogs are the definitive host
Humans are accidental intermediate hosts by accidentally eating the eggs
No adult worms in the body

53
Q

Echinococcus granulosus - clinical features

A

No adult worms in the body
Hydatid diseases
Liver/lung cysts
Anaphylaxis secondary to rupture of these cysts

54
Q

Echinococcus multilocularis - disease

A

Alveolar echinococcus

55
Q

Echinococcus granulosus - disease

A

Cystic echinococcosis

56
Q

Echinococcus multilocularis - transmission

A

From eating eggs in fox poo

57
Q

Echinococcus multilocularis - clinical features

A

Slow growing hydratid disease - more like a tumour

58
Q

Intermediate host

A

The host harboring the larval stages

59
Q

Definitive host

A

Host harbours the sexually mature adult worms

60
Q

Enterobius vermicularis - life cycle and clinical features

A

Pinworm i.e. itchy bottom in children

Adults live in the intestine, mature in 2-6 weeks and eggs are laid on the perianal skin

Can cause reinfection from scratching bottom and oral ingestion (i.e. does not need soil to mature)

61
Q

Enterobius vemicularis - treatment

A

Mebendazole - treat twice and the entire family. Prevent with hot wash of clothes/linens

62
Q

Enterobius vemicularis - microscopic features

A

Egg is 50-60 microns
Looks like a D shape with a flatter edge (Think what comes before E - Denterobius)

Diagnosis from tape test

63
Q

Trichuris trichiura - geographical distrubution and brief life cycle points

A

Seen in the tropics

Eating embryonated eggs from contaminated soil or foods

No migration

Need the soil to mature

64
Q

Trichuris trichiuria - clinical features

A

Asymptomatic to colitis
Increased risk of bacterial invasion/invasion by entamoeba histolytica/disbar
Anaemia and malnutrition, especially in children

65
Q
A
66
Q

Cestode with >15 uterine branches on microscopy of gravid proglottids

A

Taenia saginata

67
Q

Cestode with < 10 uterine brances on the gravid proglottid

A

Taenia soium

68
Q

Life cycle of taenia saginata (beef tapeworm) and taenia solium (pork tapeworm)

A
  1. Infected meat which is raw/undercooked is eaten by the human
  2. Cysts develop into adult worms in the small intestine
  3. Eggs passed by humans in the stool
  4. If taenia solium eggs are swallowed by humans then this can cause neurocysticercosis
  5. Or the eggs are ingested by the pigs, which turn into cysts in the muscle
69
Q

Scolex with 4 suckers but no hooks

A

Taenia saginata

70
Q

Scolex with 4 suckers and hooks

A

Taenia solium

71
Q

Echinococcus granulosus - key facts

A

AKA Cystic echinococcus

Dogs
Causes hydatid disease - well defined fluid filled cysts, mostly in the lung and liver
Diagnosis - imaging, serology

72
Q

Echinococcus granulosus (cystic echinococcosis)- treatment

A

< 5cm and no solid or daughter cysts: albendazole alone (+ repeat scan at 6-12 months)

> 5cm and contains solid areas or daughter cysts – percutaneous + albendazole

Complex - i.e. invading other structures, lung cysts (usually rupture with albendazole) and larger cysts need surgical management

Key thing is to prevent rupture and avoid disseminated disease

Watch and wait if non-viable cysts (CE4/5) or if unclear diagnosis/lack of resources/poor candidate etc

73
Q

Echinococcus multilocularis - key facts

A

Alveolar echinococcosis
Foxes
Primarily infects the liver but can metastasise elsewhere
Diagnosis - serology, imaging, biopsy if unable to exclude malignancy

74
Q

Echinococcus multilocularis (Alveolar echinococcosis) - management

A

Radical surgery with albendazole
Palliative surgery with lifelong albendazole

75
Q

Hymenolepis nana - microscopic features

A

Fried egg, 40 x 60

76
Q

Diphyllobothrium - microscopic appearance and key facts

A

Eating undercooked fish
Operculum present
Causes B12 deficiency

77
Q

Paragonimus spp - Transmission risks

A

Asia
Undercooked crustaceans

78
Q

Paragonimus - symptoms

A

Affects lungs - may be mistaken for TB
Ectopic spread to SC tissue, brain

79
Q

Liver fluke - species and transmission risks

A

Clonorchis sinensis (SE Asia)
Opisthorcis (China, Russia)

Eating undercooked fish

80
Q

Liver fluke clinical presentation

A

Goes to bile ducts
AcuteL abdo pain, jaundice, diarrhoea

Chronic: increased risk cholangiocarcinoma

81
Q

Fasciola hepatica/buski - transmission risks

A

Eating waterplants or vegetables

Fasciola hepatica seen worldwide, connections with livestock

Faciola buski seen in SE Asia

82
Q

Loa loa - pathogen

A

Filaria of Loa loa (with the nuclei going lower and lower in the sheath to the end of the tail)

83
Q

Loa loa - vector

A

Chyrsops silacea (deer flies)

84
Q

Loa loa - epidemiology

A

Forest and adjacent savannah regions of central africa

85
Q

Loa loa - Clinical symptoms and signs

A

Eye worm migration
Calabar swelling
Dermal rash, arthralgia, myalgia, headache
Rare: encephalitis, Endomyocardial fibrosis, renal, pulmonary

86
Q

Loa loa - diagnostics

A

Adult - clinical
MF - microscopy, PCR, LoaScope

Serology in returning travellers only

87
Q

Loa loa - treatment

A

DEC/albendazole but avoid in high microfalarial loads
Plasmapharesis an option to bring down the load prior to treatment (in high resource settings)

88
Q

Loa loa - prevention

A

Clothes, repellents
High risk travellers - weekly DEC

89
Q

Lymphatic filariasis - pathogens

A

Wucheria bancrofti
Brugia malayi

90
Q

Lymphatic filariasis - epidemiology

A

Wucheria bancrofti - more in sub-saharan africa

Brugia malayi - India, SE Asia

91
Q

Lymphatic filariasis life cycle

A
  • Mosquito bites human and deposits L3 larvae which enter the lymphatics
  • They migrate through lymphatics and mature to L4 and turn into adult worms in 6-12 months
  • Adults can stay in the lymphatics 10-14 years
  • Adult female words release Mf whic re-enter the blood stream (nocturnally) - ready for the mosquito to take it up again
  • Develops in the midgut and migrate to thoracic muscles
92
Q

Lymphatic filariasis - clinical presentation

A

Lymphatic obstruction –> inflammation –> secondary bacterial infections –> lymphodoema

Stage 0 - no lymphoedema
Stage 1 - mild, may be relieved with elevation
Stage 2 - moderate, irreversible changes with minimal skin changes
Stage 3 - severe with skin changes like large knobs, sclerosis, discolouration, mossy lesions

93
Q

Lymphatic filariasis - diagnostics

A

Blood smears
Circulating filarial antigen (CFA)
US to detect adult worm nexts in the lymphatic system (can be used pre and post treatment to assess whether its been cured

94
Q

Lymphatic filariasis - management

A

Lymphoedema care - hygiene, elevation, emollients, compression bandages
Treat secondary infections
Doxycycline 4-6 weeks - Wolbachia
Hydrocele surgery

95
Q

Lymphatic filariasis MDA

A

Africa - Albendazole + ivermectin
Asia and Americas - Albendazole + DEC
Triple therapy in areas without co-endemic loa loa/oncho

96
Q

In what situations would you avoid DEC in MDA?

A

Onchocerciasis endemic area (also loa loa at high microfilarial loads)

97
Q

In what situations would you avoid ivermectin in MDA?

A

Loa loa endemic area

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