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MBBS IV - Junior Clerkship WCS > JC90 (Microbiology) - Fever in the traveller > Flashcards

JC90 (Microbiology) - Fever in the traveller Flashcards

1
Q

Factors that influence level of travel risks

A

 Destination of travel, standards of accommodation and food hygiene
 Season of travel
 Duration of stay

 Exposure: purpose and nature of travel, behaviour of the traveler (e.g. sex tourism)

 Pre-existing health of the traveler, e.g. children, infants, the elderly, pregnant women, persons with disabilities, persons with chronic medical illnesses

 Pre-travel preparations

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2
Q

List environmental and infection risk to travelers

A

Environmental risks, e.g.:
 Accidents, motion sickness, travel by air
 Altitude
 Heat stroke and heat exhaustion, humidity, exposure to cold
 Ultraviolet radiation from the sun, foodborne and waterborne health risks (e.g. drowning)
 Animals, insects

Infections, e.g.:
 Foodborne and waterborne diseases
 Vector borne diseases, zoonoses
 Sexually-transmitted diseases, bloodborne infections
 Airborne diseases
 Diseases transmitted from soil and water

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3
Q

Preventive measures against health risk during travels

A

Medical counselling before travel:

  • Assess health risks associated with travel
  • vaccinations, antimicrobial prophylaxis; usual medications

Precautions during travel:

  • Education and counselling on prevention of foodborne, waterborne, vectorborne diseases and other health risks
  • Medical kit

Follow-up after travel if

  • chronic disease
  • Illness after return
  • exposed to serious infectious disease
  • > 3 months in a developing country
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4
Q

Outline history taking for a returning traveler with illness

A

Present illness:

  • Onset, incubation period
  • Duration
  • Symptomatology
  • Fever pattern

Travel history:
- dates and destinations

Contact history:

  • Sexual exposure, sexual history
  • Needle and blood exposure: drugs, tattoos, piercings, injections..etc
  • Animal/ arthropod contacts
  • Exposure to unclean water
  • Food and drink exposure (swimming, walking, rafting)

Prophylactic measures (antibiotics, insect repellants)

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5
Q

Common pathogens associated with ingestion of raw/ uncooked food

A

Enteric infections (foodborne, waterborne infections):
 Traveller’s diarrhea
 Dysentery (bacillary Shigella, amoebic infection)
 Hepatitis A, E
 Enteric fever (incl. typhoid salmonellosis)
 Cholera (Vibrio)
 Giardiasis (parasite)

 Others: EHEC, campylobacteriosis, brucellosis, listerosis,
toxoplasmosis, protozoal and helminth infections (amoebiasis),
Norovirus

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6
Q

Common pathogens associated with arthropod bites

A

 Malaria
 Dengue
 Japanese encephalitis, Hemorrhagic fevers
 Zika virus infection, chikungunya, rickettsioses
 Relapsing fevers, babesiosis, trypanosomiasis, dirofilariasis

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7
Q

Common pathogens associated with blood/ body fluid exposure

e.g. sex, blood, body fluids, transfusion, surgery, IVDU, Tattoos, body piercing

A

Sexually-transmitted diseases e.g. syphillis
bloodborne viruses: HIV
hepatitis B/C
non-tuberculous mycobacterial

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8
Q

Common pathogens associated with fresh water contact

A

 Leptospirosis (unculturable)

 Schistosomiasis (Katayama fever), legionellosis (respiratory tract infection)

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9
Q

Common pathogens a/w contaminated soil exposure

A

Histoplasmosis, coccidioidomycoses, other endemic mycoses, cutaneous larva migrans, strongyloidiasis (helminth)

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10
Q

Common pathogens a/w rodents contact

A 
Rodents 
 Leptospirosis
 Plaque, rat-bite fever
 Hantavirus infections
 Hemorrhagic fevers
(e.g. Lassa fever, Crimean-Congo)
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11
Q

Common pathogens a/w wild animal contact/ bites

A

 MERS-CoV infection (travel history to Middle East, contact history with camels)
 Herpes B virus infection, Q fever, brucellosis, tularaemia, anthrax, psittacosis, avian influenza
 Bite wound infections
 Rabies, bat rabies

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12
Q

Common pathogens a/w overseas hospitalization

A

antibiotic-resistant organism (colonization/ infection):

Bacteria: ESBL-, carbapenemase-producing Enterobacteriaceae
MRSA, VRE, multidrug-resistant Acinetobacter baumannii, Pseudomonas aeruginosa

Multi-resistant Candida auris

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13
Q

Outline physical exam for a returning traveler with illness

A

General:
o Skin lesions (rash, eschar, bite marks, needle marks)
o Jaundice
o Bleeding tendencies (gum, ecchymosis)

Systemic, e.g. lymphadenopathy, organomegaly, localizing signs

** Must perform head-to-toe examination with absolute exposure **

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14
Q

First-line investigations for returning traveler with illness

A

Haematological: cell counts, differential, coagulation studies

Biochemistry: liver, kidney, creatine kinase

Radiological imaging: X-ray, CT (e.g. abdomen, brain), MRI (as indicated)

Microbiological:
o Microscopy (e.g. parasites): blood film, stool
o Culture: blood, stool, urine, tissues, sputum
o Serology (Ab response may not be positive in acute stage)

Tissue biopsy: microbiology, histopathology

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15
Q

4 key questions for formulating differential diagnosis of sickness after travel?

A

4 key questions:
 Based on geographical areas visited: any epidemic or pandemics, any local outbreaks, any antibiotic resistance

 Based on the time of travel (incubation periods)?

 What activities, exposures, host factors, clinical and laboratory findings?

 What is/are treatable, transmissible, or both?
o Ebola: put to isolation ward
o Malaria is treatable

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16
Q

Framework for management of infectious disease emergency (returning traveler)

A
  1. Must exclude Hemorrhic signs: meningococcal, Gram-ve bacteraemia, viral hemorrhagic fever
  2. Exclude malaria: serial thick smears to confirm malaria + empirical therapy if end-organ damage
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17
Q

Malaria

  • Etiology/ vector
  • Transmission
A

5 Plasmodium species (= blood protozoa, parasite):
 P. vivax (commonest)
 P. falciparum (commonest): most fulminant form of disease (= medical emergency, rapidly fatal
 P. malariae
 P. ovale
 P. knowlesi (only in some Southeast Asian countries)

Transmission:
From person-to-person via:
 Bites of female Anopheles mosquitoes*;
 Blood transfusion (occasionally)

18
Q

Malaria

  • Incubation period
  • Symptoms and signs
A

Incubation: Unexplained fever that starts after the 7th day of visit in
an endemic area

S/S with highest frequency of presentation:

  • Fever
  • Rigor/ Shivering
  • Headache
  • Vomiting
  • Arthralgia/ myalgia
  • Diarrhea
19
Q

Falciparum malaria infection infectious emergency, deadly

  • Presentation
A

Dead in a day!

 Impaired consciousness
 Shock

 Renal impairment, acidosis, hypoglycaemia

 Severe malarial anaemia and jaundice

 Significant bleeding

 Pulmonary oedema

 Hyperparasitaemia (P. falciparum, >10%)

20
Q

Malaria

Diagnostic tests (3)

A

Demonstrate Plasmodium in stained blood smear

  • Must have >3 smears
  • Peripheral blood or marrow blood in thick and thin films
  • Measure parasitaemia

Plasmodial antigens test with immunochromatographic kits (rapid)

PCR for Plasmodium spp. in blood

21
Q

Blood smear for malaria

How many smears?
Cause of false negative smear?

A

At least 3 smears over 48 hours

one negative blood smear does not exclude malaria

False negative smear: received prophylaxis or partial treatment

22
Q

Falciparum malaria

  • Endemic areas
  • Treatment options
A

Endemic and resistant in Central Africa and SE asia

Treatment options:
Severe/ falciparum malaria:
 Artemisinin-based therapy (e.g. iv artesunate)
 Quinine

Other options:
 Atovaquone-proguanil
 Quinine + doxycycline
 (Mefloquine)

23
Q

Falciparum malaria

  • Preventive measures: exposure and chemoprophylaxis
A

Chemoprophylaxis: start up to 3 weeks before and end up to 4 weeks after travel
 Atovaquone-proguanil (Malarone®)
 Doxycycline
 (Mefloquine)

Exposure:
o Long-sleeve shirts, bednets
o Proper use of insect repellents, e.g. DEET

24
Q

Dengue

  • causative pathogen
  • Transmission/ vector
  • Incubation period
  • Superimposed infections
A

4 types of dengue viruses

Vectors (present in HK):
 Aedes aegypti
 Other Aedes species (e.g. Aedes albopictus)

Incubation period: 4-7 days

May superimpose other arbovirus infections (e.g. chikungunya, Zika
virus)

25
Q

Dengue

Definitive diagnosis methods
Treatment options

A

Virus detection (first 5 days):
o Serum for RT-PCR
o Serum for virus isolation

Dengue serology
o NS1 antigen detection
o Antibody testing (IgM)

Tx: Supportive:
 Symptomatic treatments
 Transfusion if necessary in severe cases

26
Q

Subclinical infection of Dengue

Presentation

A

Asymptomatic/ subclinical infection

Phase 1:

  • Sudden high fever (≥39°C), chilliness, prostration
  • Frontal/ retro-orbital headache, backache, muscle, joint pain
  • Transient generalized macular rash in the first 24h
  • Facial flushing, eyelid puffiness, conjunctival congestion, pain on moving eyeballs

Phase 2:

  • Fever subsides within 3-4 days
  • generalized morbilliform rash sparing palms and soles lasting for 1-5 days
27
Q

Severe dengue infection

Presentation and complications

A
  1. Dengue haemorrhagic fever (DHF)
  2. Dengue shock syndrome (DSS)

Presentation: severe bleeding tendency:
Epistaxis, petechiae, oozing at intravenous drip sites, purpura, gastrointestinal
bleeding, internal bleeding

28
Q

Enteric fever

Causative pathogens
Transmission

A

 Typhoid fever: Salmonella enterica serotype Typhi
 Paratyphoid fever: Salmonella enterica serotype Paratyphi A, B, C
Others: Yersinia enterocolitica, Brucella, Campylobacter fetus

Transmission: faecal-oral route (contaminated water, food)

29
Q

Enteric fever

Presentation
Complications

A

Symptomatology:
Persistent fever, diarrhea but not dysentry
 Relative bradycardia, rose spots

Complications (generally preventable by early and appropriate treatment):
 Intestinal perforation, intestinal haemorrhage, coma
 Disseminated intravascular coagulation

30
Q

Enteric fever

First-line and diagnostic Investigations

A

 Blood culture: positive in ~90% of early cases

 Stool culture: usually lower yield

 Serology:
A. Paired sera: rising antibody titre
B. The Widal’s test (for negative culture)

31
Q

Enteric fever

Treatment options
Prophylaxis options

A

 3rd-generation cephalosporins (ceftriaxone,cefotaxime)

 Fluoroquiniolones (resistance increasing)

 Azithromycin

Prevention:
 Ensure food and water hygiene
 Vaccines

32
Q

Traveler’s diarrhea

Causative pathogen

A

Mainly bacterial:
o Especially enterotoxigenic E. coli (ETEC)
o Other enteric pathogens (e.g. Campylobacter jejuni, Salmonella, Shigella)

Norovirus (think cruise ship outbreak)

33
Q

Traveler’s diarrhea

Risk factors
Incubation period

A

30-50% travellers from industrialized to developing countries

Risk depends on:
o Destination
o Country of origin
o Travel behaviour: accommodation, food, standard of hygiene, food habits,
etc.
At-risk populations:
o Hypo-/ achlorhydria
o Extremes of age
o Immunosuppressed: HIV/AIDS, steroids, transplant recipients, etc.

Incubation:
 90% in the first 2 weeks
 Mean duration: 3-4 days

34
Q

Traveler’s diarrhea

Management options
Prevention options

A

Mx:
 Fluid and electrolyte replacement: oral rehydration solution
 Symptomatic treatment: loperamide for watery diarrhea ONLY
 Empirical antimicrobial therapy: E.g. bismuth subsalicylate, rifaximin,
ciprofloxacin, azithromycin

Prevention: 
 Pre-travel counselling and education
 Behavioural modification/precautions
 Vaccination for Cholera 
 Pharmacological (antimicrobial) prophylaxis e.g. bismuth subsalicylate, rifaximin
35
Q

Amoebiasis

2 clinical entities and various presentations
Complications

A

Intestinal disease:
 Asymptomatic infection
 Symptomatic non-invasive infection: abdominal pain, diarrhoea
 Amoebic colitis with dysentery

Extraintestinal disease:
 Commonest = amoebic liver abscess in right lobe of liver (79-95%)
 Other abscesses: pleuropulmonary abscess, pericardial abscess, brain abscess

Complications: perforation of colon, toxic megacolon, amoeboma (amoebic granuloma), perianal ulceration

36
Q

Extra-intestinal amoebic liver abscess

  • Typical presentation (with or without diarrhea or dysentery?)
  • Treatment
A

amoebic liver abscess: rarely presents with dysentry and diarrhea
o 20% have history of dysentery
o 10% have diarrhea/ dysentery at the time of diagnosis

Treatment: metronidazole + diloxanide furoate (or another suitable luminal agent)

37
Q

Case scenario

A

 HT, obstructive sleep apnoea, gout

 Been to Africa for 3 years, previously to South Africa; travelled to Central African Republic twice in recent year

 12.8.2016: fever + chills: seen by GP, given oral cefuroxime axetil + doxycycline
 14.8.2016: admitted
o Low WBC, lymphopenia, low platelets
o Renal impairment, elevated liver enzymes

37
Q

Case scenario

 HT, obstructive sleep apnoea, gout

 Been to Africa for 3 years, previously to South Africa; travelled to Central African Republic twice in recent year

 12.8.2016: fever + chills: seen by GP, given oral cefuroxime axetil + doxycycline

 14.8.2016: admitted
o Low WBC, lymphopenia, low platelets
o Renal impairment, elevated liver enzymes

What is the most likely infectious disease and immediate investigation?

A

Malaria

Investigation for malaria: 
3 blood smears 
Antigen test against plasmodial antigens 
PCR for plasmodium spp. 
Parasitaemia level in blood
38
Q 
Patient 5 (M/66):
 Travelled to India for 2 months (Oct to Nov, 2004), returned 3 weeks ago
 Had on and off diarrhea while in India, treated by local doctors
 Admitted 10.12.2004 for fever, chills, rigor, abdominal pain, watery diarrhea
 Deranged liver function

What pathogen can cause relapse of diarrhea and affect the liver?

A

Entamoeba histolytica (metronidazole + luminal agent (e.g. diloxanide furoate))

39
Q

Patient 4 (M/23, Scottish, good past health):
 DOA 9.4.2011
 Traveled to Nepal
 Fever and chills
 Diarrhea: 5 bowel motions in the past 1 day, loose stool: no blood/ mucus (not dysentry)
 Mosquito bites ++, been to forestry areas
 2 persons in the hotel and some friends had fever + diarrhea

Most likely Dx

A

Enteric fever

Exclude other causes as appropriate (remember malaria and other infections (e.g. dengue) can present with diarrhea)

40
Q

Patient 3 (F/27 recently unemployed):
 Travelled to Cambodia for 2 weeks
 Developed fever 2 weeks after returning to HK (longer incubation period)
 Noted to have diarrhoea after admission
 Pulse-temperature deficit
 Mild hepatospleomegaly
 CBP normal; lymphopenia (ALC = 0.6), deranged liver fuction ALT 125, ALT…
 Macule at flank

Most likely pathogen?

A

Approach:
o If there is no rash: exclude malaria and other causes
o But the skin is pathognomonic (rose spot: typhoid and paratyphoid)
o Blood and stool culture
o Serology (with paired sera)

41
Q

Patient 2 (F/24 French):
 Working in HK for 1 year
 Admitted Jan 13
 Fever and chills for ~1 week (onset ~Jan 7):
o Daily fever
o Peak 38-38.5oC
o Malaise, decreased appetite, no skin rash

 Seen by private doctor: fever did not respond to antibiotics
 Traveled to Thailand almost exclusively to rural areas: countless mosquitoes bites, no prophylaxis of malaria

 Diffuse general maculopapular rash blanchable

Most likely causative pathogen

A

Diffuse general maculopapular rash blanchable
o Not that of meningococcaemia: hemorrhagic, petechial, localized, nonblanchable

Syndrome: fever + rash (think Dengue), Rash is not typical of malaria

 Serology: dengue IGM positive
 RT-PCR: dengue type 2

MBBS IV - Junior Clerkship WCS (131 decks)

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