Tropical diseases Flashcards
What is the most common cause of fever in travellers from Sub-Saharan Africa?
Malaria - 62% of systemic fever cases
What are some of the symptoms of Malaria?
GI toxicity Respiratory problems - cough, breathlessness Headaches FEVER
What are some of the travellers diseases that present with systemic fever?
Malaria Dengue fever Mononucleosis Salmonella typhi - Typhoid Ricketsial infection
What is the most common cause of fever in travellers from the Carribean and South East Asia?
Dengue fever
What is the most common cause of fever in travellers from Asia?
Typhoid
Which diseases are mosquitoes responsible for?
Malaria
Zika virus
Dengue fever
What are the two types of mosquitoes which commonly transmit disease?
Aedes - day-biter
Anopheline - evening biter
Which season means there’s an increase in mosquito numbers?
End of the rainy season - increased amount of stagnant water for mosquitoes to lay eggs in
How can people physically avoid mosquitoes?
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
Which insect repellent works (Evidence based results)?
DEET
- makes you taste really bad to mosquitoes
What do you have to do to ensure DEET works?
30% DEET
Re-apply every 3-4 hours (more if you go swimming)
Remember to put it on the ankles
What is the worldwide distribution of Malaria?
South America
- Amazon basin
Sub-Saharan Africa
What is the life-cycle of Malaria?
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)
How long is the incubation period of Malaria?
Varies depending on the type of Malaria
- P.falciparum - 7-14 days
- P.malaria - 18-40 days
What are the different types of malaria?
P.falciparum (most deadly kind)
P.vivax
P.ovale
P.malaria
How is malaria diagnosed?
Blood films
Antigen test
PCR
Describe thick and thin blood films in Malaria diagnosis
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
Describe antigen testing in regards to Malaria diagnosis.
Like a pregnancy test
Comes up with bands depending on which antigens are present
Describe how PCR can be used to diagnose Malaria?
Amplification of the DNA can help diagnose which type of Malaria the patient has
What is the classic presentation of Malaria?
Fever Malaise Headache Myalgia Diarrhoea
What are some possible clinical features of Malaria? (aside from the classical presentation)
Anaemia - lysis of RBCs
Jaundice - lysis of RBCs
Renal impairment
- block microcirculation
What are some of the symptoms of severe malaria?
Parasitaemia (greater than 2% of RBCs infected) Cerebral malaria - blockage of micro-circulation Severe anaemia Renal failure Shock DIC Acidosis Pulmonary oedema
How is malaria treated?
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
What are the different types of malarial chemoprophylaxis?
Mefloquine - once weekly with psychiatric side effects
Doxycicline - daily, and can cause photosensitisation
Malarone - minimal side effects, but very effective
Which Salmonella bacteria cause typhoid?
S.typhi
S.paratyphi
How is typhoid spread?
Human only reservoir
- spread human to human
- contaminated food/water
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
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
What is the incubation period of typhoid?
5-21 days
- that is the time between symptoms and septic shock/death
What factors affect the incubation period of typhoid?
Age
Gastric acidity
Immune status
Infectious load
What are the symptoms of typhoid?
Fever Myalgia Cough GI symptoms Neurological Bacteraemia Relative bradycardia (sign of advanced) Rose Spots (macular rashes)
What are the GI symptoms of Typhoid?
Diarrhoea/Constipation
Abdominal pain (hepatospenomeagly)
Rectal bleeding
Bowel perforation (hyperplasia of Peyer’s patches)
What are the neurological symptoms of Typhoid?
Headahce Enteric encephalopathy - altered consciousness/ confusion - increased mortality - steriods help
How is Typhoid diagnosed?
Based off of travel history - area visited - food/drink - vaccinations Blood cultures (for confirmation before antibiotics) Stool cultures Serology (unreliable)
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
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)
What is the incubation period of Dengue fever?
5-14 days
- so people tend to get ill while still on holiday
What are the symptoms of Dengue fever?
Headache (retero-orbital pain) Fever Arthralgia Rash - diffuse, macular rash like sunburn Cough Sore throat Nausea Diarrhoea
What is found in the blood of people with Dengue fever?
Leucopenia
Thrombocytopenia
Transaminitis
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
Is there a vaccine for Dengue fever?
No - only bite avoidance
- it’s a self limiting illness anyway
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
Which viral hemorrhagic fevers are communicable through blood/body fluids?
Ebola
Lassa
Crimean-Congo hemorrhagic fever
What is the maximum incubation period of a viral haemorrhage fever?
21 days - MAXIMUN
What are the clinical signs of viral hemorrhagic fevers?
Fever (non-specific) Pharyngitis Conjunctival infection Chest pain Haemorrhage Oedema, effusions - capillary leaking Decreased WCC
Why do people bleed in haemorrhage fevers?
Decreased platelet count
- prolonged TT and APTT
