29 Multisystem Zoonoses Flashcards
Zoonoses are animal diseases, which can incidentally infect humans. Most are poorly transmitted between humans
Which VHF belong to these classes?
Arenavirus
Bunyavirus
Filovirus
Arenavirus - Lymphocytic choriomeningitis Lassa Machupo Junin
Bunyavirus -
Hanta
Filovirus -
Marburg
Ebola
Q fever caused by Coxiella Burnetti. Called this as unknown agent, and named “query fever”
Coxiella burnetti is a rickettsia - gram neg, non-spore forming bacteria
How does it differ from other rickettsiae?
No transmitted by arthropods
resistant to dessication/ heat/ sunlight, so stable enough to exist in dust, and infect via inhalation
main site of action is the lung, rather than vascular endothelium. So does not cause rash
Who is at risk of Q fever infection?
Exposure to domestic/ wild animals - cattle/ sheep/ goats
vets/ farmers/ abattoir workers
unpasteurised milk
What is life cycle of Q fever in human?
Inhaled - exposure to milk/ urine/ faeces
multiplies in terminal airways of lungs
3 weeks later presents with fever, headache, and features of atypical pneumonia
Can resolve spontaneously within 2 weeks.
Can become chronic - spread to liver causing hepatitis, or spread to heart causing IE
How to diagnose Q fever?
Serology - may need to check initial and convalescent samples
PCR
Does not grow in blood cultures
What is treatment of Q fever?
How to prevent?
Doxycycline or co-trimoxazole
Pasteurise milk
Vaccine available Australia
Anthrax caused by Bacillus anthracis. Gram-positive rod, which is spore forming, and can survive for years in the soil
Who is infected by anthrax?
Primarily herbivores who are exposed to infected soil
They secrete bacilli in faeces/ urine saliva
Humans infected with direct contact with infected animals, or by direct contact with spores in animal products
What are two clinical pictures of anthrax infection?
Cutaneous - eschar forms. Can then spread to lymph nodes, and cause septicaemia in 10% cases
Pulmonary - if inhaled. LEads to pulmonary oedema, mediastinal haemorrhage . Spreads to bloodstream cusing septicaemia and death. Cannot be spread person-person
How to diagnose cutaneous anthrax?
What is treatment?
film from skin lesion - gram positive bacilli
PCR of lesion
- Ciprofloxacin
- 20% fatality if untreated
- anthrax anti-toxin if septic
- cipro can be given as post-exposure prophylaxis e.g in bioterrorism
- vaccine available
Yersinia pestis causes plague. Infects rodents (rats/ squirrels/ gerbils), and spread to humans by fleas.
Bacteria causes blood to clot in gut of flea, and eventually blocks gut lumen. So flea regurgitates infected material as it attempts to feed on human
What is structure of yersinia pestis?
How does it spread between humans?
Gram-negative rod
antiphayocytic capsule prevents phagocytosis
Usually not transmitted person-person. If high replication in lung and bronchopneumonia “pneumonic plague”, it can then be transmitted between humans
How does bubonic plague occur?
Infecting bacteria multiply at site of entry, spread to lypmh nodes which become necrotic
bacteria then spread to blood causing septicaemia, haemorrhagic illness, with multisystem involvement - spleen/ liver/ lungs/ CNS
bubonic plague has no person-person transmission
Plague has 50% mortality if bubonic, and 100% if pulmonary.
How to diagnose?
Gram stain - lymph node biopsy (bubonic) or sputum (pneumonic)
What is treatment of plague?
Streptomycin or
doxycycline or
ciprofloxacin
How to prevent plague?
quarantine ships at ports
rodent control
isolate patients with plague
doxycycline prophlyaxis during outbreaks
vaccination of military or certain groups in endemic areas
Franscisella tularanesis causes tularaemia.
What is gram stain?
How is it transmitted?
Gram negative rod
transmitted from rodents by ticks/ mites/ lice/ flies. Usually contact of human with infected carcass
Seen in USA/ Europe. Species in USA causes more severe disease
What are symptoms of tularaemia?
Multiplies at site of entry of vector bite, and forms skin ulcer after 3-5 days. Can form rash
If inhaled - causes pneumonia , most serious manifestation
lives intracellularly in macrophages, and moves to lymph nodes - which become painful and swollen
moves to bloodstream - febrile illness
How is tularaemia diagnosed?
IFA of tissue
serology
What is treatment of tularaemia?
Vaccine exists for high risk groups e.g fur trapper. But is not 100% effective
Streptomycin is primary treatment or
doxycycline or
gentamicin
Pasteurella multocida is part of normal flora of cats/ dogs. Transmitted by bite/ scratch. Worldwide distribution
What is gram stain?
Gram negative rod
What clinical infection does pasteurella cause?
after bite/ scratch - local multiplication causes cellulitis and lymphadenitis (also risk of anaerobe co-infection)
can become systemic and cause pneumonia
What is treatment of pasteurella infection?
Co-amoxiclav
add metronidazole if concerned about anaerobe co-infection
need to clean wound first
Leptospira interrogans is spirochete which causes leptospirosis. Have two flagella.
Many different species with many serotypes
Which animals are infected by it?
Rats/ mice/ voles
Can infect any mammal including dogs/ humans
How are humans infected by leptospirosis?
Contaminated water/ food - usually rat urine
enter via breaks in skin or mucosa
at risk - swimmer, miners, farmer, sewage worker
bacteria present in human urine, but person-person transmission rare
What are clinical features of leptospirosis?
fever and influenza type illness, which resolves spontaneously in 90% cases
can cause - hepatitis jaundice AKI aseptic meningitis
Weil’s disease - renal/ liver failure
severe cases due to damage to endothelium
How to diagnose leptospirosis?
Clinical history of water exposure
serology
What is treatment of leptospirosis?
Mild disease -
Doxycycline or
penicillin
Severe -
ceftriaxone
What is cause of rat bite fever?
spirillum minus - gram neg spiral
streptobacillus moniliformis
both found in oropharyngeal flora of 50% healthy rats worldwide
What are symptoms of rat bite fever?
incubates 7-10 days
fever headache myalgia local lesion and also maculopapular rash lymphadenopathy
Complications -
pneumonia
IE
fever may be recurrent if untreated
mortality 10% if untreated
How to diagnose rat bite fever?
How to treat rat bite fever?
Culture from wound site/ lymph node/ blood
streptomycin or
penicillin or
ceftriaxone
What is structure of bacteria which cause brucellosis?
Gram neg coccobacilli, adapted for itnracellular replication
Four species - B abortus B melitensis B suis B canis
How are humans infected with brucella?
Consumption unpasteurised milk/ cheese
direct contact with infected animal - farmer/ vet/ abbatoir. Enters via abrasions in skin, or inhaled
Animals includes - cows/ goats/ sheep/ pigs/ dogs. Varies by country
no person-person spread
What are clinical features of brucellosis?
Incubation period 2-6 weeks
Infects reticuloendothelial system - liver, spleen, bone marrow, lymphoid tissue. Bacteria survive for long time, and multiply, causing granulomatous reaction
can often be subclinical
fever - undulant
fatigue
night sweats
Rarer events - hepatitis osteomyelitis IE meningitis
long term sequale after >1 year -
fatigue
aches/ pains
anxiety/ depression
How to diagnose brucellosis?
blood culture - although rare to isolate
biopsy lymph node/ bone marrow
serology - observe rising titre. Although weaker antibody response as intracellular bacteria
What is treatment of brucellosis?
doxycycline + streptomycin for 6 weeks
brucella destroyed by pasteurisation
Echinococcus are tapeworms of dogs. Eggs laid by worm are passed in faeces. Can be swallowed by sheep or humans, eggs hatch and release larvae which penetrate small intestine, and enter blood vessel. Larvae then move to liver or lung. Then grow slowly into large thick-walled fluid filled hydatid cysts
What two clinical pictures can they cause?
Echinococcus granulosus (cystic hydatid) - makes large cyst in liver
Echinococcus multilocularis (alveolar hydatid) - makes multilocular mass in liver, can spread to lung/ brain
What is treatment of hydatid disease (cystic)?
If dead cysts - no need to aspirate
Aspirate cyst
Albendazole + praziquantel
If aspirate and fluid leaks, can cause severe anaphylactic reaction
What is treatment of hydatid disease (alveolar)?
Surgically remove - can spread in liver and resemble HCC. May be inoperable
albendazole - may need lifelong therapy if inoperable
What are symptoms of hydatid disease?
Fever abdominal bloating diarrhoea anaemia cough
Symptoms may only occur 5-15 years after initial exposure
Trichinella spiralis is transmitted in undercooked pork. Natural life cycle involves various mammals.
How are humans infected?
Undercooked meat (pork/ game/ horse) containing encysted infected larval stages.
Larvae multiply rapidly into adults in small intestine, then invade mucosa. Then spreads around blood stream to various organs
What are symptoms of trichinella infection?
CNS - seizures
myocardium - heart failure
fever
arthralgia
eosinophilia
periorbital oedema
How to diagnose trichinella infection?
what is treatment?
Muscle biopsy
serology
benzimidazoles + steroids
38 year old welsh farmer presents 6 week history of fever, weight loss.
Blood culture neg x3
TTE - vegatite lesion
what is most likely cause?
Bartonella quintana Chlamydia psitacci Coxiella burnetti Kingella Streptococcus oralis
Coxiella burnetti
exposure to sheep/ cattle
kingella/ streptococcus are easily culturable, so would be positive.
bartonella quintana does not cause IE. Bartonella henselae can cause IE
Chlamydia does not cause IE
