Tropical diseases Flashcards

1
Q

What is the most common cause of fever in travellers from Sub-Saharan Africa?

A

Malaria - 62% of systemic fever cases

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2
Q

What are some of the symptoms of Malaria?

A
GI toxicity 
Respiratory problems
- cough, breathlessness
Headaches
FEVER
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3
Q

What are some of the travellers diseases that present with systemic fever?

A
Malaria
Dengue fever
Mononucleosis
Salmonella typhi - Typhoid 
Ricketsial infection
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4
Q

What is the most common cause of fever in travellers from the Carribean and South East Asia?

A

Dengue fever

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5
Q

What is the most common cause of fever in travellers from Asia?

A

Typhoid

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6
Q

Which diseases are mosquitoes responsible for?

A

Malaria
Zika virus
Dengue fever

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7
Q

What are the two types of mosquitoes which commonly transmit disease?

A

Aedes - day-biter

Anopheline - evening biter

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8
Q

Which season means there’s an increase in mosquito numbers?

A

End of the rainy season - increased amount of stagnant water for mosquitoes to lay eggs in

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9
Q

How can people physically avoid mosquitoes?

A
Stay indoors - AC, screens
Impregnated netting
- Permethrin (insecticide)
- tucked in before the sun goes down (mosquito free)
Clothing
- Cover up (arms, legs, ankles, feet)
- Spray/soak clothing
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10
Q

Which insect repellent works (Evidence based results)?

A

DEET

- makes you taste really bad to mosquitoes

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11
Q

What do you have to do to ensure DEET works?

A

30% DEET
Re-apply every 3-4 hours (more if you go swimming)
Remember to put it on the ankles

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12
Q

What is the worldwide distribution of Malaria?

A

South America
- Amazon basin
Sub-Saharan Africa

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13
Q

What is the life-cycle of Malaria?

A

Mosquito bites you
Malarial virus enters the bloodstream
Travels to the liver and sits there, growing (incubation period)
Spill out of liver and into blood where they lyse RBCs
- symptom development
- sticky RBCs (causing clots)

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14
Q

How long is the incubation period of Malaria?

A

Varies depending on the type of Malaria

  • P.falciparum - 7-14 days
  • P.malaria - 18-40 days
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15
Q

What are the different types of malaria?

A

P.falciparum (most deadly kind)
P.vivax
P.ovale
P.malaria

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16
Q

How is malaria diagnosed?

A

Blood films
Antigen test
PCR

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17
Q

Describe thick and thin blood films in Malaria diagnosis

A

Thick
- a thick blob of blood is put on a slide and stained with a substance that lyses RBCs
- the parasite can be seen stacked up on the film under a microscope
- helps see if the patient has Malaria at all
Thin
- a thin blob of blood is smeared on a slide
- the parasites can be seen within the RBCs
- easy to miss Malaria due to thin nature of the film
- helps diagnose which type of Malaria the patient has

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18
Q

Describe antigen testing in regards to Malaria diagnosis.

A

Like a pregnancy test

Comes up with bands depending on which antigens are present

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19
Q

Describe how PCR can be used to diagnose Malaria?

A

Amplification of the DNA can help diagnose which type of Malaria the patient has

20
Q

What is the classic presentation of Malaria?

A
Fever
Malaise
Headache
Myalgia
Diarrhoea
21
Q

What are some possible clinical features of Malaria? (aside from the classical presentation)

A

Anaemia - lysis of RBCs
Jaundice - lysis of RBCs
Renal impairment
- block microcirculation

22
Q

What are some of the symptoms of severe malaria?

A
Parasitaemia (greater than 2% of RBCs infected)
Cerebral malaria - blockage of micro-circulation 
Severe anaemia
Renal failure
Shock
DIC
Acidosis 
Pulmonary oedema
23
Q

How is malaria treated?

A
Quinine and Doxycycline 
- dual therapy because of resistance 
Artemether compounds
- don't have side effects of quinine  
- better in severe Malaria
Prevention is best method of treatment 
- avoidance 
- chemoprophylaxis
24
Q

What are the different types of malarial chemoprophylaxis?

A

Mefloquine - once weekly with psychiatric side effects
Doxycicline - daily, and can cause photosensitisation
Malarone - minimal side effects, but very effective

25
Which Salmonella bacteria cause typhoid?
S.typhi | S.paratyphi
26
How is typhoid spread?
Human only reservoir - spread human to human - contaminated food/water
27
What is the infectious load of typhoid?
1000 organisms can cause disease in 10-20% | The more organisms ingested, the quicker you become unwell and the more infectious you become
28
Describe the pathogenesis of Typhoid.
Ingestion of the bacteria - acid resistant Passes through Peyer's patches in small intestine Passes into RES Grows in RES and then spills into the blood - causes bacteria and sepsis
29
What is the incubation period of typhoid?
5-21 days | - that is the time between symptoms and septic shock/death
30
What factors affect the incubation period of typhoid?
Age Gastric acidity Immune status Infectious load
31
What are the symptoms of typhoid?
``` Fever Myalgia Cough GI symptoms Neurological Bacteraemia Relative bradycardia (sign of advanced) Rose Spots (macular rashes) ```
32
What are the GI symptoms of Typhoid?
Diarrhoea/Constipation Abdominal pain (hepatospenomeagly) Rectal bleeding Bowel perforation (hyperplasia of Peyer's patches)
33
What are the neurological symptoms of Typhoid?
``` Headahce Enteric encephalopathy - altered consciousness/ confusion - increased mortality - steriods help ```
34
How is Typhoid diagnosed?
``` Based off of travel history - area visited - food/drink - vaccinations Blood cultures (for confirmation before antibiotics) Stool cultures Serology (unreliable) ```
35
What is the treatment for Typhoid?
``` Quinolones - most effective, but there are high resistance rates Cephalosporins - empirical therapy - longer courses (14 days) Azithromycin - very good activity - lack of evidence in severe disease - oral option ```
36
What is the most common mosquito borne disease in the world?
Dengue fever - 100 million cases/year - spread by the Augue mosquito (can live in pollution - cities)
37
What is the incubation period of Dengue fever?
5-14 days | - so people tend to get ill while still on holiday
38
What are the symptoms of Dengue fever?
``` Headache (retero-orbital pain) Fever Arthralgia Rash - diffuse, macular rash like sunburn Cough Sore throat Nausea Diarrhoea ```
39
What is found in the blood of people with Dengue fever?
Leucopenia Thrombocytopenia Transaminitis
40
What is Dengue hemorrhagic fever?
The most severe form of Dengue - occurs in less than 1% of cases Causes increased vascular permeability (oedema), thrombocytopenia, fever and mucosal bleeding
41
Is there a vaccine for Dengue fever?
No - only bite avoidance | - it's a self limiting illness anyway
42
Name some types of viral hemorrhagic fevers.
``` Lassa - West Africa Ebola - spread by the giant fruit bat CCHF - Crimean-Congo haemorrhagic fever SAVHFs - South American haemorrhagic fever RVF - Red Valley Fever DHF Yellow fever - vaccinated against ```
43
Which viral hemorrhagic fevers are communicable through blood/body fluids?
Ebola Lassa Crimean-Congo hemorrhagic fever
44
What is the maximum incubation period of a viral haemorrhage fever?
21 days - MAXIMUN
45
What are the clinical signs of viral hemorrhagic fevers?
``` Fever (non-specific) Pharyngitis Conjunctival infection Chest pain Haemorrhage Oedema, effusions - capillary leaking Decreased WCC ```
46
Why do people bleed in haemorrhage fevers?
Decreased platelet count | - prolonged TT and APTT