Week 13 - healthy and unhealthy communities Flashcards
Where is malaria prevalent? (LO1)
Tropical regions:
- Africa and Asia.
- Central and South America.
- Dominican Republic and Haiti.
- Parts of the Middle East.
- Some pacific islands.
- NOT found in the UK and you cannot catch it from another person.
Describe the basic epidemiology of malaria. (LO1)
- NOT found in the UK and you cannot catch it from another person.
- In 2020, estimates 241 million cases worldwide.
- Estimated number of malaria deaths in 2020: 627,000.
- Death rate: 54% if no preventative or other measures are taken beforehand.
- 95% of malaria cases and 96% of malaria deaths were located in Africa in 2020.
- Childern under 5 account for around 80% of all malaria deaths in Africa.
List the at-risk groups for malaria. (LO1)
- Pregnancy.
- Young children.
- > 65s.
- Compromised immune system.
- Absent spleen.
Describe the general presentation of malaria. (LO1)
Malaria is rarely seen in clinical practice.
- History of travel to endemic area.
- High temperature, sweats and chills.
- Headaches and feeling confused.
- Feeling very tired and sleepy (especially in children).
- Nausea, vomiting, stomach pain and diarrhoea.
- Loss of appetite.
- Muscle pains.
- Yellow skin or white of the eyes.
- Sore throat, cough and difficulty breathing.
These symptoms usually appear between 7 and 18 days after being bitten by an infected mosquito. Sometimes, symptoms may not appear for months after travel.
Explain what is meant by periodicity of fever in malaria. (LO1)
- Fever follows a rupture of erythrocytic scizonts, thus there is periodicity in fever and characteristic patterns of fever.
- 48 hours (tertian: day 1 and 3).
- 72 hours (quartan: day 1 and 4).
- 24 hours (quotidian: daily).
How does splenomegaly come about in malaria? (LO1)
Occurs as erythrocytes burst due to osmotic fragility caused by parasitic infection.
Do all species of malaria cause the same symptoms? (LO1)
NO. There are four species with varying degrees of severity:
- P. vivax.
- P. ovale.
- P. malariae.
- P. falciparum.
Describe a P. vivax infection (malaria). (LO1)
- Develops into a chronic febrile illness with severe mortality.
- Causes severe malaria with pronounced anaemia and respiratory distress.
Describe P. ovale and P. malariae infections. (LO1)
Usually self-limiting but can recur as they often form hypnozoites that can re-present with anaemia years after the original infection.
Describe a P. falciparum infection (malaria). (LO1)
- Frequently fatal during first 2 weeks due to a variety of complications.
- In hyperendemic areas, complicated falciparum malaria is most common in children aged 6 months to 5 years and in pregnant (primigravid) women.
List the main complications of a malaria infection. (LO1)
- Cerebral malaria.
- Severe anaemia.
- Acute renal failure.
- Hypoglycaemia and lactic acidosis.
Describe cerebral malaria as a complication of malaria. (LO1)
- Most dangerous complication.
- Convulsions and diminished levels of consciousness progressing to a coma.
- If treated successfully, little or no impairment of cerebral function but neurological and psychiatric sequelae may occur in 5-10% of childhood cases.
- Treatment relies on the time when antimalarial medications have been given to the patient.
List the causes of cerebral malaria as a complication of malaria. (LO1)
- Binding (sequestration) of parasitised red blood cells in cerebral capillaries.
- Endothelial dysfunction.
- Increased permeability of blood-brain barrier.
- Dysregulation of coagulation pathways.
- Excessive induction of pro-inflammatory cytokines.
What are the causes of severe anaemia as a complication of malaria? (LO1)
- Partly due to red blood cell destruction.
- Partly due to dyserythropoiesis in bone marrow.
More common complication.
What is the cause of acute renal failure as a complication of malaria? (LO1)
Due to acute tubular necrosis which is also an important complication.
Describe the management of malaria. (LO1)
- Intravenous artesunate in combination with other antimalarials to avoid drug resistance for severe malaria.
- IV quinine if artesunate cannot be obtained without delay.
Uncomplicated falciparum malaria:
- Treated with oral artemisinin combination therapy.
- Complications of any other species should be treated as severe falciparum.
P. vivax, P. ovale, P. malariae:
- Treated with oral artemisinin combination therapy.
- Or oral chloroquine.
- Primaquine used to kill hypnozoites of P. vivax or P. ovale in the liver and prevents relapses of these.
Describe the prognosis of malaria. (LO1)
If identified promptly, appropriate treatment is given and no organ dysfunction has occurred, most people make a rapid and complete recovery
If treated inappropriately or delayed, severe or fatal malaria can develop.
Untreated malaria is fatal in most cases.
Describe how we can prevent malaria. (LO1)
- Travel clinic or GP before travelling.
- Take antimalarial medication as prescribed - start a few days or weeks before travelling and stop a few weeks after you return.
- Use insect repellent on skin - 50% DEET based.
- Mosquito nets treated with insecticide around beds.
- Long-sleeved clothing and trousers in the evening, when mosquitos are most active.
- Antimalarial medicine may be prescribed even if you are travelling to a low-risk area.
Describe the investigations for malaria. (LO1)
- Lateral flow devices: detect antigen without need for a lab.
- Molecular assays: detect malarial DNA/RNA and are much more sensitive. Available in reference labs.
- Antibody testing - if persisting for several years.
- Thick and thin blood films: detects parasitised red blood cells.
NOTE: one single negative blood film doesn’t exclude any species of malaria. Further blood films need to be done 24 and 48 hours in continuum.
NOTE: P. falciparum schizont stage (late) may be sequestered in deep tissues, so parasites may be deceptively scarce in, or even absent from peripheral blood.
List some hospital investigations for malaria. (LO1)
- Polymerase chain reaction (PCR) blood.
- FBC - may show thrombocytopaenia, anaemia, variable white cell count.
- Clotting profile.
- Serum LFTs - may show elevated bilirubin or elevated aminotransferases.
- U+Es - usually normal or mildly impaired, renal failure may be present in severe infection.
- Urinalysis - may show trace to moderate proteins, urobilinogen and conjugated bilirubin may be present.
- Arterial blood gas.
List the types of arthropod infections. (LO2)
- Mosquito-borne parasitic infections.
- Mosquito-associated viral infections.
- Tick-borne infections.
Give an example of a mosquito-borne parasitic infection. (LO2)
Malaria.
List some examples of mosquito-associated viral infections. (LO2)
- Dengue - types 1, 2, 3, 4.
- Japanese encephalitis.
- Murray Valley encephalitis.
- St Louis encephalitis.
- West Nile virus.
- Zika virus.
- Yellow fever.
- Chikungunya virus.
List some examples of tick-borne infections. (LO2)
- Encephalitis.
- Kyasanur Forest disease (Alkhumra).
- Loupill ill.
- Omsk haemorrhagic fever.
- Powasan.
- Crimean-Congo haemorrhagic fever.
List the prevention measures against arthropod associated travel infections. (LO2)
Arthropod avoidance:
- Repellent spray.
- Bed nets.
- Avoid monsoon season.
- Travel to colder, dryer areas.
- Stay inside at night.
Chemoprophylaxis:
- Malaria.
- Vaccines.
Describe the epidemiology of dengue fever. (LO2)
- ~400 million infections annually - 25% symptomatic.
- <10% mortality.
Prevalent in:
- South-east Asia.
- Africa.
- Australia.
- Pacific islands.
- South America.
Which micro-organism is responsible for dengue fever? How is it transmitted? (LO2)
- Micro-organism: Dengue virus (DENV) from the Flavivirus genus.
- Transmission: bite from an infected Aedes mosquito.
Describe the clinical presentation of dengue fever. (LO2)
- Fever - 2-7 days.
- Headache.
- Pain behind the eyes.
- Arthralgia.
- Myalgia.
- Bone pain.
- Mild bleeding: nose, gums.
- Rash.
Can lead to haemorrhage.
Describe the investigations for dengue fever. (LO2)
- Seroconversion of IgM or IgG.
- Isolation of the virus.
- Detection of RNA by PCR in the blood or CSF.
- ELISA kits - NS1 antigen.
Describe the management for dengue fever. (LO2)
- Paracetamol/NSAIDs.
- Fluids.
- Rest.
- No vaccine or specific treatment.
Describe the epidemiology of malaria. (LO2)
- 212 million cases worldwide (2015).
- 62% mortality.
- Fluctuates with seasonal shift.
Prevalent in:
- Africa.
- South Asia.
- South America.
Which micro-organism is responsible for malaria? How is it transmitted? (LO2)
- Micro-organism: Protozoa of the Plasmodium genus.
- 4 types can cause disease in humans: P falciparum, P vivax, P ovale and P malariae.
- Transmission: bite from an infected Anopheles mosquito.
Describe the clinical presentation of malaria. (LO2)
- Fever.
- Headache.
- Vomiting.
- Muscle pain.
- Diarrhoea.
Extreme:
- Cerebral malaria.
- Liver and kidney failure.
- Pulmonary oedema.
What are the risk factors for more severe malaria? (LO2)
- Pregnancy.
- <5 years old.
Describe the diagnosis of malaria. (LO2)
- Thick and thin blood film.
- Liver function tests (LFT).
What is the management for malaria? (LO2)
- Prophylaxis (tablets).
List some common viral haemorrhagic fevers (VHFs). (LO2)
- Dengue haemorrhagic fever.
- Crimean-Congo haemorrhagic fever.
- Ebola.
- Marburg.
- Rift Valley fever (RVF).
- Lassa fever.
- Yellow fever.
- All of these can lead to bleeding.
Describe the clinical presentation of dengue haemorrhagic fever. (LO2)
- Fever - 2-7 days.
- Fever declines - persisting vomiting, abdominal pain, dyspnoea.
- Haemorrhage = circulatory failure, shock and death.
Describe the investigations for dengue haemorrhagic fever. (LO2)
- Seroconversion of IgM or IgG.
- Isolation of the virus.
- Detection of RNA by PCR in blood or CSF.
- ELISA kits - NS1 antigen.
Describe the epidemiology of Crimean-Congo haemorrhagic fever. (LO2)
- Mortality 10-40%: 30%.
Prevalent in:
- Africa.
- Asia.
- Eastern Europe.
Which micro-organism is responsible for Crimean-Congo haemorrhagic fever? How is it transmitted? How long is the incubation time? (LO2)
- Micro-organism: Nairovirus.
- Transmission: bite from an infected Ixodes tick or inoculation with body fluids of an infected person.
- Incubation: 1-3 days.
List the clinical presentations of Crimean-Congo haemorrhagic fever. (LO2)
- Fever.
- Myalgia.
- Stiff neck.
- Backache.
- Headache.
- Photophobia.
- Nausea.
- Diarrhoea.
- Abdominal pain.
- Mood swings.
- Confusion.
- Bleeding into the skin mucosa and internal organs.
- Liver and kidney failure.
Describe the investigations for Crimean-Congo haemorrhagic fever. (LO2)
- Examination.
- Liver function tests (LFTs).
- Bloods.
- Throat swab.
- Urinalysis.
Describe the management for Crimean-Congo haemorrhagic fever. (LO2)
- Isolation.
- Fluids.
- Paracetamol/NSAIDs.
Describe the epidemiology of Ebola. (LO2)
- Prevalent in Central Africa.
- Mortality is 25-90%.
Which micro-organism is responsible for Ebola? How is it transmitted? How long is the incubation time? (LO2)
- Micro-organism: Ebola virus.
- Transmission: Inoculation with bodily fluids from infected primates or people.
- Reservoir: Fruit bats.
- Incubation: 8-10 days.
List the clinical features of Ebola. (LO2)
- Fever.
- Malaise.
- Myalgia.
- Sore throat.
- Headache.
- Vomiting.
- Hiccups.
- Maculopapular rash (day 5-7).
- Haemorrhage.
- Diarrhoea.
- Kidney and liver failure.
Describe the investigations for Ebola. (LO2)
- Full blood count (FBC).
- Blood culture.
- Throat swab.
- Pleural fluid sample.
List the most common symptoms between most viral haemorrhagic fevers (VHFs). (LO2)
- Fever.
- Malaise.
- Body pains.
- Sore throat.
- Headache.
- Vomiting and diarrhoea.
- Abdominal pain.
- Haemorrhage.
- Shock.
List the most common clinical findings upon examination for viral haemorrhagic fevers (VHFs). (LO2)
- Conjunctivitis.
- Throat infection.
- Erythematous/petechial rash.
- Bleeding.
- Lymphadenopathy.
- Bradycardia.