MICRO: Zoonoses Flashcards
What are zoonoses? What % of infections are made up by these?
Diseases that pass between people and animals
More than 70% of emerging human infectious diseases come from animals
- Examples of new emerging infectious diseases
- VHF (viral haemorrhagic fevers)
- Respiratory diseases (MERS)
- Novel influenza viruses (pH1N1)
How are zoonoses transmitted?
- Everyday contact with animals – scratches and bites*
- By-products (faeces/urine) – contaminated soil, litter
- Foodstuffs – carcass processing, milk and milking, raw/undercooked meats
*NB: less traditional pets must be considered e.g. reptiles, rodents, chickens.
What are the two levels of classifying zoonoses?
- Farm/Wild vs Companion
- UK vs Tropical
Farm/wild animals
- Cattle
- Poultry
- Goats
- Pigs
Companion animals
- Cats/dogs (ticks, mice/rodents)
- Reptiles/amphibians
- Fish
Give examples of zoonoses according to this classification.
NOTE: conditions that are native to the UK can also happen in other places, but it doesn’t tend to work the other way around (e.g. cases of Brucella likely to be due to a recent travel history and not likely to have been picked up in the UK)
What is the most common cause of gastroenteritis and how is it transmitted?
Cause: Campylobacter
Reservoir = poultry, cattle
Transmission = contaminated food; often, cross-contamination.
What are the clinical features of campylobacter infection? How is it investigated and managed?
-
Investigations
- Stool culture
-
Management
- Supportive
Which strains of salmonella infect humans? What is its reservoir?
There are >200 strains of salmonella but only typhi and parathyphi can infect humans
Reservoir: poultry, reptiles/amphibians
How is salmonella transmitted? What are its clinical features?
Transmission:
- Contaminated food
- Poor hand hygiene
Clinical presentation
- Diarrhoea
- Vomiting
- Fever
How is salmonella investigated? What is the management?
Investigations
- Stool culture
Management
- Supportive
- Ciprofloxacin or Azithromycin
Which zoonotic infection is a curved, gram-ve rod and has a reservoir of kittens >cats?
Bartonella henselae
Transmitted by scratches, bites, licks of open wounds, fleas.
What diseases are caused by bartonella henselae? Which patients are affected by each?
- Cat Scratch Disease - affects immunocompetent and can present similarly to TB/lymphoma
- Bacillary angiomatosis - affects immunocompromised i.e. HIV
What are the clinical features of cat scratch disease?
Presentation
- Macule at site of inoculation
- Becomes pustular
- Regional adenopathy
- Systemic symptoms (fever, night sweats, weight loss) i.e. like TB/lymphoma
What are the clinical features of bacillary angiomatosis?
CAN BE FATAL AT PRESENTATION
- Skin papules
- Disseminated multi-organ and vasculature involvement
- Leads to bursting of blood vessels in various organs and tissues –> can cause long term sequelae
What investigations would you do for cat scratch disease vs bacillary angiomatosis? What is the management of each? (NB: don’t need to learn managements in this lecture)
CSD:
- Ix: serology
- Mx: erythromycin, doxycycline
BA:
- Ix: histopathology. serology
- Mx: erythromycin, doxycycline, rifampicin.
What is the reservoir of toxoplasmosis and how is it transmitted?
Reservoir = cats, sheep
Transmission:
- Infected meat
- Faecal contamination
- NB: Toxoplasmosis actually affects mice cognition and participation in risky activities which makes them more likely to be caught by a cat and ingested so that the life cycle can complete. Cats can then pass it onto humans.*
- Toxoplasmosis is actually present disproportionately more in those with schizophrenia so perhaps it may be linked to its development. This is especially dangerous in pregnant women as it can affect the foetus,*
What is the clinical presentation of toxoplasmosis?
Clinical presentation:
- Fever + adenopathy
- Still-birth
- Progressive
- visual loss
- hearing loss
- motor loss
- cognitive loss
- Seizures
- Neuropathies (immunocompromised)
What are the investigations and management of toxocplasmosis in pregnancy?
- Serology - Sabin Feldman Dye test (serum incubated with methylene blue dye to stain blue if no anti-toxo antibodies are present and so toxo remains intact)
- Toxoplasmosis PCR +ve in mother, -ve in baby –> Spiramycin (3-week course, 2-3g/day)
- I.E. no vertical transmission
- Spiramycin prevents vertical transmission
- Toxoplasmosis PCR +ve in mother, +ve in baby–> Pyrimethamine + Sulfadiazine
- Treat baby for up to 1 year after delivery (if no termination)
- Adjunct: Prednisolone
What zoonotic infections are transmitted through unpasterurised milk? What are other transmission types and what is the reservoir for this?
Reservoir = cattle, goats
Transmission:
- Unpasteurised milk/cheese
- Mucosal splash
- Undercooked meat
- Aerosolization/inhalation
How does Brucellosis present?
Presentation:
- FLAWS (over a period of months)
- Back pain
- Orchitis (may lodge in testes)
- Focal abscesses (psoas, liver, etc.)
What investigations can be done for brucellosis? What is the management?
- 1st: Blood/pus culture (in Castaneda medium) – must tell the lab that this is ?brucella
- 2nd: Serology
Management: 6 weeks of
- Doxycycline; and
- Gentamycin or rifampicin
What is the pathogen causing Q fever? What is its reservoir and mode of transmission?
Cause: Coxiella burnetti
Reservoir = cattle, goats, (sheep)
Transmission:
- Aerosolisation/inhalation of secretions, waste, or milk of infected animals
- Unpasteurised milk
NB: most of goat products in UK come from the Netherlands. Common practice used to be that goat faeces and urine were not cleaned up but rather hay was piled on top; when it started to smell windows/doors were opened and this created the ideal environment for Q fever and >100,000 cases were reported there.
What is the clinical presentation of Q fever?
Clinical presentation:
- Fever
- ‘Flu-like’ illness
- Pneumonia
- Hepatitis
- Endocarditis
- Focal abscesses (para-vertebral/discitis, etc.)
What investigations and management are used for Q fever?
Investigations:
- Serology
Management:
- Doxycycline
- (Hydroxychloroquine)
What causes rabies? What are the reservoirs and modes of transmission?
Lyssa virus
Reservoir = dogs, cats, bats
Transmission:
- Bites, scratches
- Contact with infected fluid
