JC90 (Microbiology) - Fever in the traveller Flashcards
Factors that influence level of travel risks
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
List environmental and infection risk to travelers
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
Preventive measures against health risk during travels
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
Outline history taking for a returning traveler with illness
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)
Common pathogens associated with ingestion of raw/ uncooked food
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
Common pathogens associated with arthropod bites
Malaria
Dengue
Japanese encephalitis, Hemorrhagic fevers
Zika virus infection, chikungunya, rickettsioses
Relapsing fevers, babesiosis, trypanosomiasis, dirofilariasis
Common pathogens associated with blood/ body fluid exposure
e.g. sex, blood, body fluids, transfusion, surgery, IVDU, Tattoos, body piercing
Sexually-transmitted diseases e.g. syphillis
bloodborne viruses: HIV
hepatitis B/C
non-tuberculous mycobacterial
Common pathogens associated with fresh water contact
Leptospirosis (unculturable)
Schistosomiasis (Katayama fever), legionellosis (respiratory tract infection)
Common pathogens a/w contaminated soil exposure
Histoplasmosis, coccidioidomycoses, other endemic mycoses, cutaneous larva migrans, strongyloidiasis (helminth)
Common pathogens a/w rodents contact
Rodents Leptospirosis Plaque, rat-bite fever Hantavirus infections Hemorrhagic fevers (e.g. Lassa fever, Crimean-Congo)
Common pathogens a/w wild animal contact/ bites
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
Common pathogens a/w overseas hospitalization
antibiotic-resistant organism (colonization/ infection):
Bacteria: ESBL-, carbapenemase-producing Enterobacteriaceae
MRSA, VRE, multidrug-resistant Acinetobacter baumannii, Pseudomonas aeruginosa
Multi-resistant Candida auris
Outline physical exam for a returning traveler with illness
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 **
First-line investigations for returning traveler with illness
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
4 key questions for formulating differential diagnosis of sickness after travel?
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
Framework for management of infectious disease emergency (returning traveler)
- Must exclude Hemorrhic signs: meningococcal, Gram-ve bacteraemia, viral hemorrhagic fever
- Exclude malaria: serial thick smears to confirm malaria + empirical therapy if end-organ damage
Malaria
- Etiology/ vector
- Transmission
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)
Malaria
- Incubation period
- Symptoms and signs
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
Falciparum malaria infection infectious emergency, deadly
- Presentation
Dead in a day!
Impaired consciousness
Shock
Renal impairment, acidosis, hypoglycaemia
Severe malarial anaemia and jaundice
Significant bleeding
Pulmonary oedema
Hyperparasitaemia (P. falciparum, >10%)
Malaria
Diagnostic tests (3)
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
Blood smear for malaria
How many smears?
Cause of false negative smear?
At least 3 smears over 48 hours
one negative blood smear does not exclude malaria
False negative smear: received prophylaxis or partial treatment
Falciparum malaria
- Endemic areas
- Treatment options
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)
Falciparum malaria
- Preventive measures: exposure and chemoprophylaxis
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
Dengue
- causative pathogen
- Transmission/ vector
- Incubation period
- Superimposed infections
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)
Dengue
Definitive diagnosis methods
Treatment options
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
Subclinical infection of Dengue
Presentation
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
Severe dengue infection
Presentation and complications
- Dengue haemorrhagic fever (DHF)
- Dengue shock syndrome (DSS)
Presentation: severe bleeding tendency:
Epistaxis, petechiae, oozing at intravenous drip sites, purpura, gastrointestinal
bleeding, internal bleeding
Enteric fever
Causative pathogens
Transmission
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)
Enteric fever
Presentation
Complications
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
Enteric fever
First-line and diagnostic Investigations
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)
Enteric fever
Treatment options
Prophylaxis options
3rd-generation cephalosporins (ceftriaxone,cefotaxime)
Fluoroquiniolones (resistance increasing)
Azithromycin
Prevention:
Ensure food and water hygiene
Vaccines
Traveler’s diarrhea
Causative pathogen
Mainly bacterial:
o Especially enterotoxigenic E. coli (ETEC)
o Other enteric pathogens (e.g. Campylobacter jejuni, Salmonella, Shigella)
Norovirus (think cruise ship outbreak)
Traveler’s diarrhea
Risk factors
Incubation period
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
Traveler’s diarrhea
Management options
Prevention options
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
Amoebiasis
2 clinical entities and various presentations
Complications
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
Extra-intestinal amoebic liver abscess
- Typical presentation (with or without diarrhea or dysentery?)
- Treatment
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)
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
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?
Malaria
Investigation for malaria: 3 blood smears Antigen test against plasmodial antigens PCR for plasmodium spp. Parasitaemia level in blood
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?
Entamoeba histolytica (metronidazole + luminal agent (e.g. diloxanide furoate))
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
Enteric fever
Exclude other causes as appropriate (remember malaria and other infections (e.g. dengue) can present with diarrhea)
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?
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)
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
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
