Session 9 - Travel Related Infections Flashcards
What is the most important piece of knowledge to have when you suspect someone has a travel related infection?
- How long they have had symptoms for
- What their recent travel history is
- Where they have recently travelled to
What is a bacterium that is commonly seen in travel related infections?
Rickettsia
What is special about Rickettsia as compared to other bacteria?
- Can only live within other cells
- Doesn’t have the same gram staining capabilities as normal bacteria
- Needs a vector
What are some other travel related infections?
- Malaria
- Dengue
- Enteric fever
Why is a patient’s travel history so important?
- Recognise imported diseases
- May be a different strain of a pthogen
- Can prevent infection from spreading
How can people acquire travel related infections?
- Contaminated food and water
- Insect or tick bite
- Swimming in contaminated water
- Sexual contact
- Animal contact
- Beach or recreational activities
What is the organism that causes malaria?
Plasmodium (a parasite)
What are the four main species of malaria?
- Plasmodium flaciparum (msot common)
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
What is the vector that trasmits malaria?
Female anopheles mosquitos
(night biter mosquitos)
What is malaria’s incubation period?
- A minimum of 6 days
- P. falciparum: up to 6 months
- P. vivax/ovale: up to a year
What are the common symptoms of malaria?
- Headache
- Fever
- Chills and sweating
- Dry cough
- Spleen enlargement
- Nausea and vomitting
- Muscle fatigue and pain
How would you classify severe falciparum malaria?
This is when the parasites occupy more than 2% of red blood cells.
What are the risks with severe malaria?
Cardiovascular:
- tachycardia
- hypotension
- arrhythmias
Respiratory:
- acute respiratory distress syndrome (ARDS)
Gastrointestinal:
- bilirubin (haemolysis)
Renal:
- acute kidney injury
Blood:
- thrombocytopenia
Metabolic:
- metabolic acidosis
- hypoglycaemia
Also susceptible to secondary infections.
How does the malaria parasite infect the body?
- Parasite enters the blood stream
- Enters the liver
- Multiplies in the liver
- Re enters the bloodstream and red blood cells
- Leads to red blood cells bursting
- Some parasites become gametocytes that can be picked up by mosquitos
How do you test for malaria?
Blood smear
- Done three times and to be cleared of infection, must receive 3 negatives
FBC, Urea and Electrolytes, Liver Function Tests
Chest X ray
How do you treat P. falciparum malaria?
- Artesunate
- Quinine and Doxycycline
How do you treat the other three forms of malaria?
- Chloroquinine and primaquine
- Hypnozoites (liver stage)
Can recur months-year later
How can malaria be prevented?
- Know the risk areas
- Prevent bites (insect repellant, clothing etc.)
- Chemoprophylaxis
- specific to the region
- start before and continue after return (normal course is 4 weeks)
Where can someone get enteric fever?
- Found in mainly asian countries
- Due to poor sanitation
What is the mechanism of infection for enteric fever?
Faecal-oral transmission from contaminated food and water.
Source comes from cases or carriers (human pathogen only).
What is the name of the bacteria that causes enteric fever?
Salmonella typhi
What kind of bacteria is Salmonella typhi?
- Aerobic
- Gram-negative rod bacteria
What are some of the virulence factors for enteric fever?
- Gram negative endotoxin
- Invasin - allows intracellular growth
- Fimbriae that can adhere to epithelium over the ileal lymphoid tissue
What are the common symptoms of enteric fever?
- Fever
- Headache
- Abdominal discomfort
- Constipation
- Dry cough
- Bradycardia
What is the incubation period of enteric fever?
7-14 days.
What are some complications that can arise from enteric fever?
- Intestinal haemorrhage and perforation
- Has a 10% ortality if left untreated
How do you test for enteric fever?
- Blood culture should be taken (main one)
- Faeces test
- Serology not reliable in these cases
How do you treat enteric fever?
Enteric fever has increasing ability to resist drugs (highly drug resistant).
Therefore is normally treated with IV ceftriaxone.
Can also be treated with azithromycin for 7-14 days.
How can enteric fever be prevented?
- Food and water hygiene precautions
- Typhoid vaccine can be given if going to areas of high risk
- this is either an antigen or a live attenuated (less dangerous) version of the bacteria
What is the microorganism that causes dengue fever?
Dengue fever is caused by the arbovirus.
It has 4 different serotypes.
How is dengue fever transmitted?
It is transmitted by day-biting mosquitos.
What are the symptoms of dengue fever?
- Abrupt fever
- Back pain
- Headache originating from behind the eyes
- Flat and widespread rash
How would you test for dengue fever?
- Blood culture and malaria screenings normally show negative.
- Need to conduct a Dengue PCR and serology (IgM)
The serology and PCR take time, but treatment must be started immediately.
How long does dengue fever last?
First infection can range from asymptomatic to severe illness.
- Lasts 1-5 days
- Improves few days post-rash
- Only supportive treatment needed
What happens if someone gets re-infected with dengue fever, with a different serotype?
Antibody dependent enhancement occurs, leading to:
- dengue haemorrhagic fever
- dengue shock syndrome
