Lecture 41: Febrile Returned Traveller Flashcards
What can you be contaminated via air?
What are the c_linical features_ and the i_ncubation periods?_
Influenza
- Respiratory
- Few days
Tuberculosis
- Respiratory
- Many months
What can you be contaminated via contaminated water and food?
What are the clinical features and the incubation periods?
Salmonella typhi
- Non specific
- Days to weeks
Salmonella enteritidis
- Diarrhoea
- Days
Campylobacter jejuni
- Diarrhoea
- Days
Hepatitis A virus
- Jaundice
- Weeks
What is the most important thing when trying to diagnose a travellor with a fever?
History (Very Important!)
Where have you been and what did you do there?
- (What organisms was the person exposed to?)
When were you there and when did you start to get sick?
- (Does timeline fit with incubation period?)
What can you be contaminated via Infected Vectors?
What are the clinical features and the incubation periods?
Malaria
- Non specific
- Weeks
Dengue
- Muscle aches
- Days
What can you be contaminated via Infected People?
What are the clinical features and the incubation periods?
- HIV
- Non-specific
- Syphilis
- Variable
A 50 year old man, returned 6 days ago from a 18 day trip back to Zimbabwe
He has been too tired to work since the flight home (sat) and now (Friday) is febrile and non-communicative
He is 38.9 degrees with GCS = 9
What is the patient’s travel history, possible exposures and other notes?
History: Incubation peiod may be as long as 18+ days or as short as a few days
Exposures: Air, water and food, vectors, people. Therefore any of the previously listed illnesses are possible
Note: no diarrhoea, cough, muscle aches.
_____ is the most important illness to consider in travellers
(Potozoa infection)
Plasmodium Parasite
Malaria is often most important illness to consider in travellers. It is mosquito-borne blood disease caused by Plasmodium parasite
Common species include:
- Plasmodium falciparum (potentially fatal)
- Plasmodium vivax (relatively benign)
Rare species include:
- Plasmodium ovale
- Plasmodium malariae
The plasmodium species that cause malaria in humans are closely related to the species that cause malaria in other mammals (e.g. African apes, Asian monkeys, chimpanzees, gorillas)
What are the 2 common species that cause Malaria?
Common species include:
- _Plasmodium falciparum (_potentially fatal)
- Plasmodium vivax (relatively benign)
What type of mosquitos can cause malaria?
Anopheles mosquitoes causes malaria (forest dwelling, night feeding):
- There are anopheles mosquitoes in PNG (Papa New Guinea), Solomons, Vanuatu. Therefore, there is HIGH risk of malaria in these islands.
- There are no anopheles mosquitos in New Caledonia, Fiji, Tonga, Samoa, Cook Islands, TahiX, etc. Therefore, there is NO risk of malaria in these islands!
There are ______mosquitoes in______________________________Therefore, there is HIGH risk of malaria in these islands.
There are anopheles mosquitoes in PNG (Papa New Guinea), Solomons, Vanuatu. Therefore, there is HIGH risk of malaria in these islands.
Describe the stages of the Plasmodium infection
- Infected female anopheles mosquito feeds on blood, and they inject saliva containing sporozoites
- Sporozoites invade liver cells and replicate (MIN 10 DAYS). Sporozoite is the form that infects new host (present in mosquito saliva)
- Merozoites are released from liver and invade erythrocytes
- Merozoites replicate in erythrocytes and r_upture erythrocyte_s, causing fever. Merozoite is the form that results from replication in liver cells (released from liver and replicates in RBCs) (merogeny = schizogeny (asexual replication))
- Some merozoites mature into male or female gametocytes, which are source of sexual replication in mosquito salivary gland
- Sporozoite (don’t need to memorize names)
- Form that infects new host (present in mosquito saliva)
- Merozoite
- Form that results from replication in liver cells (released from liver and replicates in RBCs).
Describe the typical temperature chart of Plasmodium infections
The most characteristic symptom of malaria is fever. Other common symptoms include chills, headache, myalgias, nausea, and vomiting. Diarrhea, abdominal pain, and cough are occasionally seen.
As the disease progresses, some patients may develop the classic malaria paroxysm with bout_s of illness alternating with symptom-free periods._ Malaria paroxysm comprises three successive stages.
- First is a 15-to-60 minute cold stage characterized by shivering and a feeling of cold.
- Next comes 2-to-6 hour hot stage, in which there is fever, sometimes reaching 41°C, flushed, dry skin, and often headache, nausea, and vomiting.
- Finally, there is 2-to-4 hour sweating stage during which fever drops rapidly, and patient sweats.
In all types of malaria, periodic febrile response is caused by rupture of mature schizonts.
These classic fever patterns are usually not seen early in the course of malaria, and therefore the absence of periodic, synchronized fevers does not rule out a diagnosis of malaria.
How do you diagnose Malaria?
- Residence in a malarious area
- Symptoms (fever, rigors, malaise, headache, coma)
- _Blood film examination (_determine species (falciparum or vivax) by appearance of merozoites in RBCs) (proportion of RBCs that contain merozoites)
- Antigen detection in blood
Why do people die from infections with P.Falciparum but not P.Vivax?
-
P.falciparum
- Able to infect any RBC
- High parasite load (>1% erythrocytes infected)
- Inserts a protein into RBC membranes that adheres to CD36 and ICAM1 on capillary membranes
-
Sequestration of erythrocytes in capillaries,
- esp. brain and kidneys
- Cause “sludging up” of blood in brain and kidneys = Coma and black water in urine
- Death from coma and renal failure
- Able to infect any RBC
-
P.Vivax__
- Only infects y_oung RBCs_
- Low parasite load (<1%)
- Does not cause RBC sequestration
- No risk of severe disease
- Relapses result from repeated release of liver hypnozoites
- Only infects y_oung RBCs_
Describe the Treatment for Malaria
P. Falciparum
- Quinine and doxycycline (t_o kill merozoites in erythrocytes_);
- Or, artemether and lumefantrine (to kill merozoites in erythrocytes).
P. Vivax
- Chloroquine (to k_ill merozoites in erythrocytes_)
- Then primaquine _(to kill hypnozoites in live_r).
Describe Typhoid Fever (causes, symptoms, mortality rates)
Typhoid Fever (Enteric Fever)
Typhoid Fever and Samlonella Typhi
Typhoid fever (enteric fever) is bacteraemic illness arising from intracellular infection in macrophages in Peyer’s Patches.
It is caused by Samlonella typhi.
Symptoms include fever, rigors, sweats, cough, headache, confusion, but NOT usually diarrhoea, may be constipation!
There is 10% mortality without treatment.
- Risk of perforation of Peyer’s patch, resulting in peritonitis
- Risk of erosion of ileal blood vessels, resulting in catastrophic intestinal bleeding
Minority of infected people have long term gall bladder colonisation and excrete S. typhi in faeces (source of infection for others)
