Microbiology - Healthy & Unhealthy Communities Flashcards
Key factors determining the travel-related risk
Mode of transportation
Destination (local infection epidemiology)
Season of travel
Duration of travel
Standards of accom, food hygiene and sanitation
Behaviour of the traveller/ purpose of travel
Underlying health of traveller
Why is the epidemiology of infectious diseases of importance to travellers
Outbreaks of known or newly emerging infectious diseases are often predictable – decision on need for certain vaccine or antimalarial prophylaxis
Risky behaviour of travellers
Going outdoors in the evenings in an malaria-endemic area without taking precautions
Swimming in Schistosoma infested lakes
Exposure to insects, rodents, bats and other animals
Contaminated food/ water is a major risk
Unprotected sexual intercourse
Epidemiology of gastroenteritis
Worldwide in endemic areas, 1.5 million children die yearly due to infectious gastroenteritis
Viral gastroenteritis accounts for ~68% of all gastroenteritis episodes in travellers
Causative agents of gastroenteritis
Rotavirus
Norovirus
Astrovirus
Causes of bacterial gastroenteritis
Campylobacter jejuni (Enterotoxigenic) E. coli Salmonella Shigella Vibrio cholerae
GE presentation
Anorexia Nausea Vomiting Diarrhoea Abdominal discomfort
GE dx
Clinical evaluation
Stool testing
GE treatment
Oral or IV rehydration
Abx in select bacterial cases and if bacteraemia
Where is infectious hepatitis prevalent
In areas of developing countries with poor sanitation, crowding and lack of access to clean water
Enterically (food and waterborne) transmitted viral pathogens
Hep E
Hep A
Transmission of Hep E
Faeces (drinking contaminated water or eating contaminated food)
Outbreaks of Hep E
Seasonal, often associated with monsoon period
Incubation of Hep E
3-7 weeks
Attack rate of Hep E
1 in 2
Mortality of Hep E
<1% but 15-25% in antenatal women
Severity of Hep E
Increases with age
Vaccine for Hep E
Developed – in use in China, Nepal
Prevention and control measures for Travellers to Hep E endemic regions
Avoid drinking water (and beverages with ice) of unknown purity
Uncooked shellfish
Uncooked fruit/ vegetables not peeled or prepared by traveller
Hep A infection characteristics
Acute, self-limiting infection of the liver
Infection may be asymptomatic in children
Adults symptomatic
Rarely, fulminant hepatitis can ensue
How many serotypes are there of Hep A
Only one
How many genotypes of Hep A are there
Multiple genotypes have been identified incl 4 human genotypes
What type of virus is Hep A
A single-stranded, +ve sense, linear RNA virus of 7.5 kb in length
General Hep A prevention
Good hygiene
Hep A - pre-expsoure
Active immunisation vaccine (killed whole virus)
Travellers to intermediate and high-risk areas
Individuals at risk due to sexual behaviour, parenatal drug abuse
Hep A - post-exposure
Vaccine (within 7 days) Immunoglobulin HNIG (within 14 days of onset of disease in primary case)
Hep A vaccine
Prepared from formaldehyde inactivated Hep A virus grown in human diploid cells
2 types of vaccine – single and combined
Single component Hep A vaccine
Havrix
Epaxalm Avaxim
Vaqta Paediatric
Combined Hep A vaccine
Hep B vaccine (Twinrix) or thyroid vaccine (Hepatyrix)
Arthropod
Mosquitoes and ticks
Mosquito-borne parasitic infection
Malaria
Mosquito associated viral infections
Dengue types 1, 2, 3, 4 Japanese encephalitis Murray valley encephalitis St Louis encephalitis West Nile virus Zika virus Yellow fever Chikungunya virus
Transmission of Dengue fever
Transmitted to people by bite of Aedes mosquito that is infected w/ dengue virus
Symptoms of Dengue fever
High fever Severe headache Severe pain behind eyes Joint pain Muscle and bone pain Rash Mild bleeding (e.g. nose or gums bleed, easy bruising)
Dengue haemorrhage fever
Characterized by a fever that lasts from 2-7 days, w/ general signs and symptoms consistent w/ dengue fever
When the fever declines, symptoms incl persistent vomiting, severe abdominal pain and dyspnoea may develop
When does haemorrhage occur in dengue haemorrhage fever
Haemorrhage follows leading to failure of the circulatory system and shock, leading to death if circulatory failure is not corrected
Tick-borne infections
Tick-borne encephalitis (Central European, Far Eastern, Siberian) Kyasanur Forest disease (Alkhumra) Louping ill Omsk haemorrhagic fever Powosan Crimean-Congo haemorrhagic fever
What does Crimean-congo haemorrhagic fever causes
Causes severe viral haemorrhagic fever outbreaks
Case fatality of CCHF
10-40%
Incubation period of CCHF
1 - 3 days
Symptoms of CCHF
Fever, myalgia, neck stiffness, backache, headache, photophobia
Nausea, vomiting, diarrhoea, abdominal pain, mood swings, confusion
Complications of CCHF
Bleeding into the skin, mucosa, internal organs
Liver failure, kidney failure
VHFs
Viral haemorrhagic fevers (VHFs) refer to group of epidemic prone diseases that are caused by several distinct families of viruses
Characteristic of VHFs
The overall vascular system is damaged and the body’s ability to regulate itself is weakened
Symptoms can often be accompanied with life-threatening bleeding
VHFs found in Africa
Marburg and Ebola haemorrhagic fevers Crimean-Congo haemorrhagic fever (CCHF) Rift Valley fever (RVF) Lassa fever Yellow fever
TB
A severe infectious disease caused by various strains of mycobacteria, most commonly Mycobacterium tuberculosis
Infection of TB
People are infected w. TB by inhaling airborne droplets produced by infectious TB carriers
Latent TB infection (LTBI) carriers are asymptomatic and not infectious
BCG vaccine and TB
Provides partial protection
Treatment for TB
Standard treatment of TB consists of a six-month regimen of 4 first-line drugs (isoniazid, rifampicin, ethambutol and pyrazinamide)
Case fatality of MERS-CoV
35.5.%
Transmission of MERS-CoV
Human-to-human
Symptoms of MERS-CoV
Symptoms icl fever, cough and SOB
Pneumonia is common, but not always present
GI symptoms incl diarrhoea, have also been reported
Rabies
Vaccine-preventable viral disease which occurs in more than 150 countries
Main source of human rabies death
Dogs, contributing up to 99% of all rabies transmissions to humans, however any mammal can transmit rabies
Mx of suspected rabies
Immediate, thorough wound washing with soap and water after contact with a suspect rabid animal is crucial followed by post-exposure prophylaxis (rabies vaccine and RIG)
Monkey pox
Rare viral zoonotic disease that occurs primarily in remote parts of central and west Africa, near tropical rainforests
Monkeypox trasmission
Mostly transmitted from various wild animals such as rodents and primates, but has limited secondary spread through human-to-human transmission
Treatment of smallpox
No spp treatment or vaccine available although prior smallpox vaccination was highly effective in preventing monkeypox as well
Malaria
Life-threatening illness caused by infection of red blood cells by Plasmodium parasites.
Notfiable disease
Who should immediate admission arranged for of those with suspected malaria
People with suspected severe or complicated malaria
People with suspected falciparum malaria
Pregnant women
Children
People who are older than 65 years of age.
Human malaria parasites
P. falciparum (malignant tertian) P. vivax (benign tertian) P. malariae P. ovale P. knowlesi
Malaria epidemiology
Restricted to areas mosquitoes can breed: tropics between 60 degrees N and 40 degrees S. 90% of cases occur in Africa, 7% in South-East Asia and 2% in Eastern Mediterranean region
Presentation of malaria
Fever (most common), general malaise, headache, myalgia & arthralgia, confusion and vomiting or diarrhoea
Splenomegalogy and malaria
Experienced by many older children and adults
Occurs as erythrocytes burst due to osmotic fragility caused by parasitic infection
P. vivax - malaria
Develops into chronic febrile illness with severe mortality, causes malaria with pronounced anaemia and respiratory illness
P. ovale and P. malariae
Usually self-limiting but can recur as they often form hypnozoites that can represent with anaemia even years after original infection (decades)
Most dangerous Plasmodium infection
P. falciparum malaria is frequently fatal during first 2 weeks because of a variety of complications.
Ix for malaria
Travel hx paramount
Examine the patient looking for signs of severe malaria such as impaired consciousness, confusion, hypotension, respiratory distress or jaundice
Dx of malaria
Only possible with microscopy of thick and thin blood films or an antigen detection test
If the first blood films are -ve, further blood testing must be arranged 12 to 24 hours later and again after a further 24 hours to rule out infection.
Hypnozoites
Dormant parasites which persist in the liver after treatment
Drug of choice for malaria
IV artesunate, but this can cause haemolysis and follow-up blood tests are required.
2nd drug of choice for severe/ complicated malaria
IV quinine
Requires cardiac monitoring and regular BMs as there are risks of arrhythmias and hypoglycaemia
ACT
Artemisinin combination therapy
May be used to treat uncomplicated malaria and is the preferred treatment for mixed infection as it can help avoid development of drug resistance
Chlorquine for malaria
May be used to treat uncomplicated P. malariae, P. ovale and P. knowlesi and most cases of P. vivax malaria but use depends upon patterns of resistance and tolerance.
Primaquine for malaria
Used to prevent relapse of benign malrias as it eradicates hypnozoites (P Vivax and P. Ovale)
Poor prognostic factors of malaria
High levels of parasitaemia Peripheral P. falciparum blood schizonts Pigment deposits in leucocytes Metabolic acidosis Older age Coma Renal impairment (organ dysfunction)
Drugs used for malaria
Artesunate Quinine ACT Chloroquine Primaquine
