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Medical Microbiology and Virology > 28 Vector-borne infections - protozoa > Flashcards

28 Vector-borne infections - protozoa Flashcards

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1
Q

Which protozoa are transmitted by arthropods?

A

Malaria

Trypanosomiasis

Leishmaniasis

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2
Q

Plasmodium transmitted by female anopheles mosquito. Can also be transmitted vertically, and via blood transfusion

Approx 200 million cases/ year.

What are the names of plasmodium species?

A

Falciparum

Vivax

Malariae

Ovale

Knowlesi

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3
Q

What is geographic spread of these species of plasmodium?

Falciparum

Vivax

Malariae

Ovale

Knowlesi

A

Falciparum - tropics

Vivax - India/ SE Asia, SA, NE Africa

Malariae - tropics

Ovale - tropical Africa

Knowlesi - SE Asia

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4
Q

Which plasmodium species have tertian/ quartan fever?

tertian fever - every 3rd day
quartan fever - every 4th day

A

Tertian -
falciparum
vivax
ovale

Quartan -
malariae

tertian have asexual reproduction every 48 hours
quartan have asexual reproduction every 72 hours

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5
Q

Why is there a lack of P vivax in West Africa?

A

Plasmodium binds to red blood cell Duffy antigen

high prevalence of Duffy-negative people in West Africa

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6
Q

What conditions provide some protection from malaria>

A

Duffy antigen negative
sickle cell
beta-thalassaemia
G6PD

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7
Q

What is life cycle of plasmodium?

not in mosquito

A

Sporozoites from saliva injected into new host

Move from blood to liver. Two weeks later mature into pre-erythrocytic schizonts

hepatocyte ruptures, releasing merozoites. They enter RBC, where they undergo asexual reproduction. Some species (vivax/ ovale) can have latent hypnozoites

merozoite in RBC matures ring form, trophozoite, and schizont. Which ruptures and releases merozoites into bloodstream (completing cycle)

some merozoites undergo sexual stage, and produce gaemtocytes, which are taken up by new anopheles mosquito during feeding

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8
Q

What is life cycle of plasmodium?

in mosquito

A

gametocytes taken up by anopheles mosquito during feeding

once inside mosquito gut, gametocytes fertilise to form zygoe, which invades gut mucosa, and forms oocyst

oocyst produces produces sporozoites which are released and migrate to salivary glands of insect

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9
Q

What are symptoms of malaria?

A

Fever
headache
myalgia

can then develop multi-organ failure as parasatised red cells sequester in capillaries, causing endothelial dysfunction -

  • cerebral disease
  • jaundice
  • anaemia
  • hepatosplenomegaly
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10
Q

What is incubation period of malaria?

A

Between 6-40 days
usually 9-14 days most common time to present

Can present up to 6 months after travel event

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11
Q

What are clinical manifestations of severe malaria?

A 
reduced GCS <11
convulsions
respiratory distress
prostration
shock
jaundice
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12
Q

What are biochemical manifestations of severe malaria?

A 
abnormal coagulation
anaemia
hypoglycaemia <2.2
metabolic acidosis
renal impairment
parasitaemia >10%
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13
Q

People living in endemic plasmodium area, if they survive first infection, they develop immunity, and subsequent infections are not as severe.

If they move to UK, how long before they lose immunity?

A

approx 1 year out of endemic area will reduce immunity

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14
Q

How to diagnose malaria?

A

Lateral flow test - rapid antigen test

thick/ thin blood film - 3x sets (admission/ 24 hours/ 48 hours). If from endemic country, having parasite in bloodstream, does not mean it is always causing disease. If blood film negative, and high suspicion, may need biopsy of tissue

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15
Q

What is treatment of -

uncomplicated falciparum

complicated falciparum (>2% parasitaemia)

A
  • PO co-artem (Artemetherelumefantrine (Riamet) is the drug of choice for 3 days
  • dihydroartemisinin-piperaquine (Eurartesim) is an alternative for 3 days

Alternatives -

  • Quinine and doxycycline 5-7 days
  • atovaquone- proguanil (Malarone) 5-7 days
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16
Q

What is treatment of -

vivax/ ovale/ knowlesi/ malariae

A

co-artem or chloroquine

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17
Q

How to remove hypnozoites from liver? (vivax/ ovale)

Radical clearance

A

primaquine 14 days

contraindicate in G6PD deficiency

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18
Q

How to prevent/ reduce malaria spread?

A

Mass chemotherapy

insecticide treated nets

indoor residual spraying

removal of stagnant water

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19
Q

Suspected malaria. What details are important in travel history?

Must notify public health with positive cases

A

Country and area of travel.

Stopovers and other countries transited through.

Date of return.

Type of travel and activities while abroad — people returning from visiting friends and family in endemic areas are more at risk of malaria than tourists.

Prophylaxis taken

Vaccinations e.g YF

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20
Q

What are important differential diagnoses of malaria?

A

VHF - ebola/ marburg/ lassa

dengue

YF

JE

typhoid

leptospirosis

babesiosis - anaemia

African Trypanosomiasis

Could be simple bacterial sepsis. But if high risk/ travel, do not miss malaria

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21
Q

Which malaria patients need to be admitted?

A

Is suspected of having severe or complicated malaria.
Is suspected of having falciparum malaria.
Is a pregnant woman.
Is a child.
Is older than 65 years of age.

Non-falciparum malaria can be managed as outpatient, if observed for 8 hours after starting treatment

22
Q

What is treatment of -

complicated falciparum (severe)

> 2% parasitaemia indicates IV therapy required

A
  • IV artesunate until manage oral/ parasite count reduced
  • if not available, start IV quinine until artesunate sourced
  • manage in HDU/ ITU
23
Q

What is treatment of malaria in pregnancy?

Increases risk of miscarriage

A

Co-artem 2nd/3rd trimester

Quinine + clindamicin all 3 trimesters

24
Q

Where is resistance emerging in malaria treatment?

A

SE Asia
SA

chloroquine resistance

25
Q

What are options for malaria prophylaxis?

A

Doxycycline
Mefloquine
Atovaquone-proguanil (malarone)
Chloroquine - widespread resistance

26
Q

What are options for malaria prophylaxis in pregnancy?

A

Advise avoid travel to high risk area

Mefloquine - can be used all trimesters, although less data in first trimester

Atovaquone-proguanil - lack of data, avoid if possible

Doxycycline - definitely avoid first trimester. Can use in 2nd/3rd if very high risk of malaria outweighs contraindications

27
Q

What do these terms mean?

causal prophylaxis

suppressive prophylaxis

A

Causal prophylaxis - active against liver stage (not hyponozoites), preventing release and infection of RBC. Take for 7 days after returning. Atovaquone-proguanil

Suppressive prophylaxis - active against red blood cell stages. Take for 28 days after returning. Chloroquine, mefloquine, doxycycline

28
Q

What are contraindications to chloroquine?

If on hydroxychloroquine for rheumatic disease, can continue hydroxychloroquine without swapping

A

If resistance present

epilepsy
psoriasis
myasthenia gravis
amiodarone interaction

29
Q

What are contraindications to doxycycline?

A

pregnancy

children <12

as acidic preparation, can cause severe oesophagitis/ gastritis

30
Q

When is emergence malaria standby treatment provided for travellers?

What are drug options? including pregnancy

A

If going to be >24 hours away from medical assistance

Artemther-lumefatrine or
atovaquone-proguanil or
quinine + clindamicin (pregnancy)

31
Q

Female on malaria prophylaxis, planning to become pregnant. How long should anti-malarials be stopped for?

Mefloquine
Doxycycline
Atovaquone-proguanil

A

Mefloquine: 3 months
Doxycycline: 1 week
Atovaquone/proguanil: 2 weeks

32
Q

Patient with epilepsy travelling to malaria country. What are options?

A

Doxycycline or
atovaquone-proguanil

mefloquine/ chloroquine unsuitable

33
Q

Patient with G6PD deficiency travelling to malaria country. What are options?

A

Avoid choroquine

doxycycline/ mefloquine/ atovaquone-proguanil

34
Q

When must these malaria prophlaxis drugs be started prior to travel?

Doxycycline
atovaquno-proguanil
chloroquine
mefloquine

A

Doxycycline or atovaquone-proguanil - 2 days before

Chloroquine - 1 week before

mefloquine - 2-3 weeks before (to ensure tolerance).

35
Q

What are three species of trypanosoma?

A

African trypanosomiasis -
Trypanosoma brucei gambiense (West) - 97% African cases
Trypanosoma brucei rhodesiense (East)

South American trypanosomiasis -
Trypanosoma cruzi

36
Q

African trypanosomiasis

what is vector?

A

tsetse fly

reservoir of trypanosomes in wildlife and cattle

flies feed during daylight hours

37
Q

What is clinical presentation of african trypanosomiasis?

A

following insect bite, widespread lymphadenopathy occurs. Enlarged cervical lymph nodes is known as Winterbottom’s sign

fever
splenomegaly
myocardial involvement
headache
behavioural change - sleeping sickness, which leads to death

Even after treatment, can be left with permanent neurological disability

38
Q

How does african trypanosomiasis evade host immune system?

A

Antigenic variation - switches between 900 different antigens on surface

39
Q

How to diagnose african trypanosomiasis?

A

microscopy of blood/ CSF/ lymph node for parasites

antitrypanosomal antibody - mostly only useful for screening populations

40
Q

What is treatment of african trypanosomiasis

A

Suramin IV followed by
melarsoprol IV if CNS involvement

West African -
Pentamidine IV
Nifurtimox orally + eflornithine IV if CNS involvement

41
Q

What is vector of South American trypanosomiasis?

A

reduviid bug - feeds on host, and excretes faeces. Host rubs trypanosomes into wound/ mucosa

inhabit poor housing in rural areas

most mammals can act as reservoir for infection

can also be transmitted via contaminated food, blood donors

42
Q

What are symptoms of South American trypanosomiasis?

A

Nodular lesion at inoculation site

Swelling eyelid - Romanas sign

fever

GI - megaoesophagus/ megacolon

Cardiac - myocarditis

43
Q

how to diagnose South American trypanosomiasis?

A

Blood film

PCR

serology

can perform PCR on reduviid bug stool

44
Q

What is treatment for South American trypanosomiasis?

A

benznidazole oral or

nifurtimox oral

45
Q

What is vector of leishmaniasis?

Leishmaniasis either multiplies in skin (cutaenous) or in spleen/ liver/ bone marrow (visceral leishmaniasis)

A

sandflies

dogs can act as important reservoirs

46
Q

Which species cause cutaneous leishmaniasis?

A

L major
L tropica
L mexicana
L braziliensis

47
Q

Which species cause visceral leishmaniasis?

also known as kala-azar

A

L donovani
L infantum
L chagasi

48
Q

Visceral leishmaniasis is fatal in 90% cases

What are symptoms?

A

Develops slowly

fever
weight loss
hepatosplenomegalt

49
Q

What are symptoms of cutaneous leishmaniasis?

A

Small papule develops into large ulcer. Can then heal with considerable scarring

50
Q

How to diagnose leishmaniasis?

A

Microscopy of splenic aspirate/ bone marrow/ skin

PCR

serology

51
Q

What is treatment of cutaneous leishmaniasis?

A

local injection of sodium stibogluconate

52
Q

What is treatment of visceral leishmaniasis?

A

amphotericin B IV or

sodium stibogluconate IV

Medical Microbiology and Virology (60 decks)

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