L14: Travel infection Flashcards
Why do we need to considered travel infection?
Increasing global travel–> easy due to transport
Access to more ‘exotic’ destinations–> infections that weren’t prevalent becoming prevalent
Travelling with co-morbidities–> immunosupressed etc–> exposed to infections, present in different ways
War and natural disaster help increase infection in populations
Migration of populations–> spread between populations
Emerging infections–> new ones
When looking at the infection model what are the most important things to consider with travel infections?
As well as normal person factors
Consider time–> determine incubation period
–> calendar time–> when they went, time of exposure
–> relative time–> time since travelling
Place–> where they have been
–> recent place and over last 6 months-year
As well as normal infections, what additional infections are people exposed to when they go abroad?
Bacterial usually transmitted via a vector
–> Rickettsia and Spirochaete
Parasites
–> Protozoa (malaria)
–> Helminths (worms)–> present later on through BV
What are rickettsia?
Small intracellular bacteria
Tics, lice, fleas mites etc…
Usually transmitted from animal to human
What is a vector?
Something acts as a vehicle to artificially carry foreign genetic material into another cell
What is a Spirochaete?
Spiral shaped bacteria Example: leptiospira Carried in urine of infected animal Released into fresh water Enter human through mucous membrane
What are protozoa?
Single celled infections
Malaria
Why is it important to ask about travel history?
Recognise imported disease–> rare/unknown in the UK
–> Don’t ask, don’t think, may misdiagnose something serious
Different strains of the same pathogen in different countries–> maybe antigenically different, resistant to different antibiotics, impacts on protection and detection
Infection prevention–> some infections highly contagious
- -> on ward safety
- -> in the lab–> handling samples safely
What questions do you need to ask to determine incubation period and attempt to identify species of bacteria?
Where? –> where did they go?
When?–> how long ago? –> Incubation period
What?–> What are the signs and symptoms?
How?–> How did they acquire it?
How can incubation period help determine type of infection?
<10 days–> Virus, bacteria of certain types and some parasites
10-21 days–> Virus unlikely, Bacteria and parasites more likely
> 21 days–> Unusual types of bacteria, some parasites
How can the signs/symptoms help determine infection?
Differentiate where the infection is Resp--> likely present with SoB, cough GI--> Diarrhoea (blood in, fever) Skin--> rash--> localised or systemic Jaundice--> Liver affected--> Hep A and E CNS--> headache, meningism Haematological--> Lymphadenopathy, splenomegaly, haemorrhage Eosinophils raised in some infections
What are some of the different methods of acquiring an infection?
Food/water Insect/ tick bite Swimming Sexual contact Animal contact (bite safari) Recreational activities
What are some specific risk factors for certain infections?
Animal bite--> rabies Rodents--> Leptospirosis Mosquito/ insect bite--> Malaria, dengue Tick bite--> Rickettsia Dead/ slaughtered animals--> Anthrax, Ebola Farms--> Q-fever Game parks--> RIckettsia Fresh water--> Schistosomiasis, leptospirosis Caves--> histoplasmosis Unpasteurised dairy--> Brucellosis Shellfish--> Vibrios Under/ uncooked meat/fish--> Salmonella
What other aspects of the travel history would you also want to know?
Anyone unwell on trip/ after trip?
Did they take preventative measures? Vaccinations, prophylactics, etc
Exposure to healthcare whilst abroad? May have been exposed to severe infections
What examinations would you want to carry out?
Temp--> determine if fever present BP--> Reduced, increased HR-- tachycardic (inline with fever), brachycardic O2 saturation Look for skin marks--> bite marks etc
What investigation would you want to carry out?
Blood test–> FBC
Biochemistry –> urea, creatine, bilirubin, ALT, ALP, CRP
Blood film–> look at cells present, morphology of cells
What is malaria?
Parasitic infection
Transmitted from human to human via a vector
How common is malaria?
Commonest imported infection to the UK
250million cases and 1 million deaths per year (under estimation)
UK–> 1500 cases per year (11 deaths)
How many different types of Malaria are there? Which are the most common?
5 main species of Plasmodium
- ->Falciparum
- -> Vivax
Which countries are most at risk of Malaria?
Around the equator Subsaharen South Africa Parts of south and central America Indian subcontinent Parts of Indonesia and Australia
What are the symptoms of Malaria?
Often vague--> often missed Headache- central Chills and sweating Dry cough Enlarged spleen Nausea and vomiting Back pain Fatigue and pain in muscles Systemic fever--> usually only symptom
What is the incubation period for malaria?
Minimum of a week
P. Falciparum presents within 4 weeks
P. Vivax/Ovale–> Up to a year (dormant in the liver for a period of time)
Must check travel history up to at least 6 months
What are the signs of severe Falciparum malaria?
CVS–> Tachycardia, hypotension, arrhythmias
Respiratory–> Adult respiratory distress syndrome
GIT–> Diarrhoae, Deranged LFTs, Bilirubin
Renal–> acute renal injury
CNS–> confusion, fits, cerebral malaria
Blood–> Low/normal WCC, thrombocytopenia, DIC
Metabolic–> Metabolic acidosis, hypoglycaemia
Secondary infection
What is the life cycle of a mosquito parasite?
- Life cycle within the mosquito and within the human
- Transmitted to human into liver- exo-erythrocytic
- Infects liver cell matures to Schizoit
- Releases loads of meroziotes
- Burst out of liver cell
- Enter blood stream infect erythrocytes
- Rupture erythrocytes releasing more into blood stream etc…
- Some RBC develop into gametocytes which are taken up by new mosquite and injected into new human
Why is it so hard to manage malaria?
Complex lifecycle
Difficult to determine which part of cycle to target
How do you diagnose malaria?
ID physician required
3x blood film (doesn’t always present on first 2)
FBC, U and E, LFTs, glucose, coagulation
Parasites make RBC sticky–> microocclusion–> affect kidneys and brain
CT scan maybe necessary
Chest x-ray
How is Malaria treated?
Depends on the species
P. falciparum –> Artesunate (best) or Quinine + doxycycline (antibiotic) (more side effects with this one)
P. Vivax, ovale, malariae–> Chloroquine, dormant hypnozoites (liver)–> recur months- years later, give additional primaquine
How can Malaria be prevented?
ABC
Assess risk–> knowledge of at risk areas, regular/returning travellers
Bite prevention–> Repellant, adequate clothing, nets, chemoprophylaxis before travel, and regular returning travellers
Chemoprophylaxis–> specific to region, start before and continue after return
Where is typhoid and paratyphoid (enteric fever) mainly seen? How common is it?
Mainly Asia (Africa and S America)--> poor sanitation 21 million cases/year, mainly in children UK travel related--> 500 cases/year
What is the mechanism of action of enteric fever?
Feacal-oral transmission from contaminated food/water
Can be a carrier without symptoms
What is the most common species of typhoid and paratyphoid?
Salmonella typhi and salmonella paratyphi (A, B and C)
Enterobacteriaceae aerobic gram negative bacillus
How does Salmonella typhi and paratyphoid cause illness?
Low infectious dose
Survives gastric acid
Fimbriae adhere to epithelium over ileal lymphoid tissue (Peyer’s patch)–> RE system/ blood
Reside within macrophages (liver/ bone marrow/ spleen)–> hide from the immune system
What are the signs and symptoms of enteric fever?
Systemic disease (bacteraemia/sepsis) Fever Headache Abdominal discomfort Dry cough Relative bradycardia (compared to when you have a fever)
What is the incubation period of enteric fever?
7-14 days
What complications are associated with enteric fever?
Intestinal haemorrhage and perforation Seeding 10% mortality Chronic carrier state 1-5% Paratyphoid (milder)
What would you expect to fund upon investigation of possible enteric fever? What would you expect in a blood culture?
Moderate anaemia
Lymphopenia
Mild raised LFTs (transaminase and bilirubin)
Culture: typhoid positive
What is the treatment for enteric fever?
Multidrug resistance
Fluroquinone–> may work
Usually treated with IV ceftriaxone (cephalosporin) (cell wall synthesis- B lactam) or azithromycin (macrolide) (protein synthesis) for 7-14 days
How is enteric fever prevented?
Food and water hygiene precautions
Typhoid vaccine–> high risk travel, laboratory personnel
–> capsular polysaccharide antigen or live attenuated vaccine
What are non-typhoidal salmonella infections?
Food poisoning salmonellas
Widespread distribution
Causes: Diarrhoea, fever, vomitting, abdominal pain
Generally self limiting
Bacteriaemia and deep-seated infections occur if immunocompromised
What is dengue fever?
Common arbovirus (virus transmitted by arthopod (exoskeleton body))
100million cases per year
25000 deaths per year
4 different serotypes
Found in different sub and tropical regions
How does dengue fever present? What is the incubation period? How is it treated?
First presentation widespread rash but ranges from asymptomatic to non-specific febrile illness (back pain, headache behind eyes and abrupt fever)
Last 1-5 days
Improves 3-4 days after rash
Supportive treatment- no specific
How is Dengue fever investigated?
Nothing on blood culture Stool/ urine secretion negative CXR- negative Dengue PCR +ve Dengue serology IgM +ve --> IgG indicate chronic infection
What happens when you get re-infected with dengue?
Different serotype
Antibody dependent enhancement
–> Dengue haemorrhagic fever
–> Dengue shock syndrome
Female visited family in Benin, multiple bite and spots on back, reported something ‘fell out’, no other symptoms or fever and blood tests were normal what is she likely to have?
Myiasis
Fly larva (tumbu, bot fly)
Cover with vaseline–> starve of O2–> maggots come to surface–> pull out
What are the most common types of emerging diseases?
Usually viruses–> mutate quickly
Respiratory infections–> spread easily between people
What are some common respiratory infections that have causes pandemics?
Influenza A
Coronavirus–> SARS, MERS-CoV, COVID-19
Why is influenza A still around today?
Influenza virus–> shift in antigens every decade–> New glycoprotiens enveloped or virus mixes with animal viruses to form a new virus–> humans dont have the antibodies to deal with it –> pandemic
Every year get ‘drift’ in antigens meaning a new vaccination is needed every year
Where does COVID-19 likely come from?
Bats primary source (intermediate/ vector for transmission to humans?)
Spread by respiratory droplets from human to human
Incubation period 14 days from exposure
What is Ebola?
Filovirus
Flu like illness with vomiting, diarrhoea, headaches, confusion and rash
Internal/external bleeding at days 5-7
Spread by direct contact with body fluids
High case fatality rate- >50%
What is Zika virus?
Arbovirus (flavivirus SS enveloped RNA viruses)
Isolated in Rhesus monkey
20% symptoms–> Like dengue fever
Causes congenital microcephaly, foetal loss
Sexually transmitted
No treatment and no vaccines
