Infection Session 5 Flashcards
What are important patient factors to consider in travel-related infections?
Calendar and relative time
Recent places
Social factors (inc. those at destination)
What important information might a travel history reveal in suspected infection?
Healthcare exposure abroad
Any prophylactic Tx
Recreational activities
Whether travel companions are also affected
What does an increase in atopy as a S/S indicate?
Slight increase –> eosinophilia
Large increase –>helminth infection
How might a travel related infection be acquired?
Ingestion of food/water Insect/tick bite Swimming Sexual contact Animal contact Beach/recreational activities
What finding on histological examination indicates a medical emergency in malaria?
Multiple parasites in one RBC
What are the four main species of Plasmodium?
Falciparum
Vivax
Ovale
Malariae
Which species of Plasmodium causes the most severe malarial disease?
Falciparum
What is the vector for Plasmodium?
Female Anopheles mosquito
Can malaria be spread from pt–>pt?
No
Which species of Plasmodium causes the majority of malaria deaths?
Falciparum
What is the typical incubation period of malaria?
1-3 weeks
What is the typical Hx for malaria?
Fever, chills and night sweats which cycle every 3/4 days Headache Muscle fatigue +/- pain Nausea Vomiting Dry cough
O/E what would you expect to find in malaria?
Few signs except fever +/- splenomegaly
What investigations would you perform in suspected malaria?
3x blood smears (thick and thin) FBC U&Es LFTs Coagulation tests Head CT if GCS decreased CXR if respiratory distress syndrome suspected
Describe the general management plan for malaria infection.
Start with IV floroquinolones or artemisinin depending of species and then treat orally once controlled
Describe the ABC approach to malaria infection prevention.
Assess risk
Bite prevention (repellant, clothing etc)
Chemoprophylaxis (specific to destination region)
Do regular/returning travellers need to take chemoprophylaxis?
Yes, resistance is rapidly lost
Describe how an uninflected mosquito can go on to transmit malaria to a human.
Uninfected mosquito bites infected man ingesting gametocytes which are present in blood
Plasmodium undergoes sexual stage in mosquito
Now infected mosquito bites uninfected man, transmits plasmodium which can undergo asexual reproduction to produce gametocytes
Which stage of the plasmodium life cycle is exo-erythrocytic?
Liver
Which stage of the plasmodium life cycle is erythrocytic?
Blood
Why is there no easy target for malaria prevention?
It has a complex life cycle
What are the S/S of severe falciparum malaria when the parasite count is high?
Tachycardia, hypotension, arrythmias Acute RDS (lungs fill with fluid) Diarrhoea, deranged LFTs AKI Metabolic acidosis Confusion, fits, cerebral malaria
What are malaria pts at especially high risk of?
Secondary infection from G-ve pathogens
Which enteric fever is generally milder, typhoid or paratyphoid?
Paratyphoid
How is enteric fever transmitted?
Faecal-oral
Why is the source of enteric fever only cases/carriers?
It is a human pathogen only
What is the incubation period of enteric fever?
7-14 days
What is the typical history of a pt with enteric fever?
Fever Headache Abdominal discomfort Constipation Dry cough
What ah be found O/E of a pt with enteric fever?
Reactive bradycardia
Fever
What would you expect to find on investigation of a pt with enteric fever?
Moderate anaemia
Relative lymphopenia
Raised transaminase and bilirubin
Positive blood and faecal culture
How can enteric fever be prevented?
Food and water hygiene precautions Typhoid vaccine (live or attenuated)
What is the problem with typhoid vaccine?
Only gives 75% protection
What are ‘food poisoning’ salmonellas?
Non-typhoidal salmonella infections that have widespread distribution inc. UK
What are the S/S of ‘food-poisoning’ salmonella infections?
Diarrhoea
Fever
Vomiting
Abdominal pain
What are the outcomes of S.thyphimurium and S.enteritidis?
Usually self-limiting
Can develop bacteraemia
Can develop deep seated infection
How is dengue fever transmitted?
Arthropod vector
Where is dengue fever mainly seen?
Africa
Asia
Indian subcontinent
What happens on first infection with dengue fever?
Asymptomatic –> severe febrile illness lasting 1-5 days which improves 3-4 days after non-specific rash appears
Can specific treatments be used in the first dengue infection of an individual?
No, supportive only
What happens in reinfection of an individual with a different dengue fever serotype?
Pre-existing antibodies can bind but not neutralise the new serotype and instead facilitate easier monocytes infection
What can an increased viral load on reinfection of dengue fever lead to?
Dengue haemorrhagic fever
Dengue shock syndrome
What are the S/S of dengue haemorrhagic fever?
Haemorrhage
DIC
Petichae rash
Why is the rash seen in first dengue fever infection said to be non-specific?
Also seen in measles, rubella, parvovirus, EBV, CMV, acute HIV and rickettsia
What can increase the risk of influenza strains ‘jumping species’ and causing a pandemic?
Intensive farming
What is SARS?
Novel coronavirus - Severe Acute Respiratory Syndrome
Is MERS easily transmittable?
No
Which human influenza viruses cause seasonal epidemics?
A & B
How is human influenza A split into two subtypes?
According to hemagglutinin and neuraminidase expression on the viral surface
Which two lineages do currently circulating influenzae Bviruses belong to?
Yamagata
Victoria
Does influenza B circulate in animals?
No, humans exclusively
What is the primary natural reservoir for all influenza A subtypes?
Birds
How often does antigenic shift occur?
Occasionally
How often does antigenic drift occur?
Continuously
What happens in antigenic shift?
Two subtypes of virus infect the same host, reassort and form new virus with most genes from one but hemagglutinin +/- neuraminidase from the other to create new subtype
Why does antigenic shift cause pandemics?
It creates a new subtype which few people have resistance to as it has not been seen before in human influenza
Which type of influenza virus can undergo antigenic shift?
A
Which types of influenza virus NA undergo antigenic drift?
A & B
What happens in antigenic drift?
Virus infects healthy cell –> DNA polymerase makes mistakes creating new virus with antigenic variants –> pre-existing host antibodies exert selection pressure –> slightly different strain circulates in population
Why does the flu vaccine have to be reviewed every year?
Antigenic drift cussing slightly different strains to circulate in the population
Why are a greater range of foreign endemic diseases being seen in UK healthcare?
More exotic destinations Travellers with underlying health conditions More aid workers Migration Global warming
