Infectious disease 2 Flashcards
(24 cards)
What are the plasmodium species which cause malaria?
P. falciparum, P. vivax, P. ovale, P. malariae and P. knowelsi
What are some of the protective factors against malaria?
Sickle cell trait
G6PD deficiency
Some HLA B53 alleles allow T cells to kill parasite-infected hepatocytes in some non-Europeans.
How does falciparum malaria present?
Flu-like prodrome - headahce, malaise, myalgia, anorexia followed by fever paroxysms and faints.
Signs: anaemia, jaundice and hepatosplenomegaly
What are the possible complications of falciparum malaria?
Cerebral malaria Metabolic acidosis Anaemia - due to haemolysis Hypoglycaemia Acute renal failure Non-cardiogenic pulmonary oedema/ acute respiratory distress syndrome Shock Liver dysfunction Hyperparasitaemia (>5% of rbc parasitised)
What causes metabolic lactic acidosis in malaria?
Anaerobic glycolysis in host tissues where sequestered parasites interfere with microcirculatory flow
Parasite lactate production
Hypovolaemia
Insufficient hepatic and renal lactate clearance.
What is the presentation of cerebral malaria?
Confusion Coma and fits Focal signs are unusual There may be variable tone, extensor posturing, upgoing plantars, disconjugate gaze, teeth grinding. Seizures are common in children. Mortality 20%
What causes hypoglycaemia in malaria?
Occurs in severe malaria due to the following factors:
- reduced hepatic gluconeogenesis
- reduced liver glycogen stores
- increased glucose consumption by host
- quinine-induced hyperinsulinaemia
How is malaria diagnosed?
Serial thin and thick blood films. If P. falciparum is the cause, the level of parasitaemia must be known.
Rapid antigen detection
Other tests: FBC, clotting, glucose, ABG/lactate, U&E, LFT, blood culture
Urinalysis (haemoglobinaemia, proteinuria, casts)
What is the treatment of malaria?
If the patient has taken prophylaxis, do not use the same drug as treatment. If species unknown or mixed infection, treat as P. falciparum.
For uncomplicated non-falciparum malaria: chloroquine based treatment. If resistant, try malarone, quinine or Riamet.
For uncomplicated falciparum malaria: combination therapy preferable containing artemisinin derivatives e.g. artemether or artesunate
Severe falciparum malaria: Start full dose anti-malarials IV ASAP. Manage on ITU. Daily monitoring of FBC, parasite count, platelets, U&E, LFT, glucose, acidosis and fluid status.
What measures can be taken for malaria prophylaxis in travellers?
Conservative: avoid mosquitoes, wear long sleeves, use repellents and insecticidal bed nets
If little/no chloroquine resistance: proguanil and chloroquine
If chloroquine resistance: mefloquine or doxycycline or malarone.
What are the side effects of chloroquine?
Headache, psychosis, retinopathy
What kind of virus is Ebola?
Non-segmented, negative sense, single-stranded RNA virus in the family filoviridae.
Haemorrhagic fever virus.
How does Ebola present?
The incubation period is 4-21 days.
Symptoms start with fever, severe headache, muscle pain and weakness. It can progress to diarrhoea, vomiting, abdominal pain, lack of appetite and unexplained bleeding or bruising. A maculopapular rash may appear.
May result in delirium, shock, hepatic failure, massive haemorrhage and multi-organ failure.
How is Ebola spread?
Most cases are from exposure to an animal reservoir or direct physical contact with body fluids of a sick patient (faeces, saliva, sweat, urine, vomit and semen).
How is Ebola diagnosed?
Test all symptomatic patients with any possible risk of exposure. Ebola virus is generally detectable in blood samples by RT-PCR within 3-10 days after onset of symptoms.
What is the treatment of Ebola?
Supportive care whilst the immune system mobilises and immune response.
A number of experimental therapies have been tried: ZMapp (MAb) and whole blood or serum from convalescent Ebola virus survivors.
How is Dengue fever transmitted?
Aedes mosquitoes
How does dengue fever present?
Infants typically have a simple febrile illness with a rash. Older children/adults have flushes and centrifugal maculopapular rash from day 3,or late confluent petechiae with round pale areas of normal skin and headache, myalgia, jaundice, hepatosplenomegaly and anuria.
There may also be haemorrhagic signs.
How do you treat dengue fever?
Supportive. Prompt IV fluid resuscitation.
How do you diagnose dengue fever?
Antibodies (IgG and IgM)
RNA PCR
What causes progressive multi-focal leucoencephalopathy and how is it diagnosed?
This is a dementia-like illness caused by the JC virus.
Diagnosis: MRI shows diffuse white and grey matter lesions. JC virus PCR can be performed on CSF
Treatment: ART
Which tests can be done to diagnose TB?
Sputum ZN staining for acid-fast bacilli
PCR gene expert - can also tell you about rifampicin resistance
Biopsies - caseating granulomas
Mantoux test - see past exposure to TB/BCG
Interferon gamma release assay (IGRA)
What is your differential for fever in the returning traveller?
Influenza Dengue fever Typhoid - renal and liver failure, jaundice, myalgia Leptospirosis Typhus - rickettsia Chikungunya Hep A, B, C, E HIV PE Viral haemorrhagic fever e.g. Ebola
What are the causes of TB seeming to not respond to treatment?
Wrong diagnosis Non-compliance Drug resistance Drug fever - rifampicin Immune reconstitution syndrome in AIDS
