Zoonoses Flashcards
What is a zoonosis?
Infections that can pass between living animals and humans - the source of the disease is from the animal
WHO - infections that are naturally transmitted between vertebrate animals and humans
MUST NOT rely on humans for any part of their life cycle e.g. like malaria
How many known pathogens are zoonotic?
61% of the known 1415
What are the common zoonoses in the UK?
Salmonella Campylobacter Toxoplasma Psittacosis (chlamydia psittaci) Q-fever (coxiella burnetti) Ringworm/dermatophytosis
What are some emerging zoonoses?
Avian flu Nipah virus Rabies Brucellosis Monkeypox
What animals transmit Rabies, what is the incubation period, and how does it present?
97% dogs, otherwise bats, sometimes a few others
Incubation period 2 weeks to several months
Travels to brain via peripheral nerves
Presents as acute encephalitis
- malaise, headache and fever
- progressing to mania, lethargy and coma
- saliva/tear over-production
- unable to swallow and hydrophobia
- death by respiratory failure
How is rabies diagnosed and treated?
PCR of saliva/CSF
- often confirmed post-mortem on brain biopsy
Immediately after bite give post-exposure prophylaxis
- human rabies immunoglobulin
- infiltrated round the bite
- +4 doses of rabies vaccine over 14 days
Always fatal if untreated
How is brucellosis transmitted?
Cattle/sheep/goats/pigs
- organisms excreted in milk, placenta and aborted foetus
Humans infected
- during milking affected animals
- during parturition (giving birth)
- handling of carcasses of infected animals
- consumption of unpasteurised dairy products
Rare in UK
What is the incubation of brucellosis and how does it present?
5-30 days usually - but up to 6 months
Presents acutely, subacutely, chronically
Acute (1-3 weeks)
- high undulant fever
- weakness
- headaches
- sweats
Subacute (1 month+)
- fever and joint pains
Chronic (months/years)
- flu-like
- chronic arthritis
- endocarditis
Subclinical - most common
- 50% of exposed have positive serology
How is brucellosis treated?
Long-acting doxycycline for 2-3 months
With rifampicin or intramuscular gentamycin
Add cotrimoxazole if CNS disease
What is the presentation of leptospirosis?
Flu-like symptoms, then jaundice and renal failure - old forms
New (more common) form - fever, meningism, no jaundice
11% of dairy workers have positive serology but most have no history of illness
How is leptospirosis diagnosed?
Risk factors
- fever in cattle farmer - more likely than brucellosis
- exposure to water/rats
Microscopic Agglutination Test - not useful
ELISA serology - suboptimal
PCR?
Culture
How is leptospirosis treated?
Must treat early
- antibiotics not particularly effective, but most effective if given early
- doxycycline for mild or IV penicillin for severe
Prompt dialysis
Mechanical ventilation
How is Lyme disease transmitted (vector and pathogen), and how does it present (initially)?
Tick bite (Ixodes ricinus) containing borrelia burgdorferi
Erythema migrans in 80-90% of cases - 3-90 days after the bite
- be aware of acrodermatitis chronic atrophicans caused by borellia afzelii
May see lymphocytoma
What are some complications/other presentations of Lyme disease?
Neuroborreliosis
- triad: nerve palsy, radicular pain, lymphocytic meningitis
- onset usually 2-6 weeks after bite
- preceded by EM in ~50%
Arthritis - large joints (knees)
Cardiac disorders - carditis, heart block
Which investigations can diagnose each presentation of Lyme?
Erythema migrans and possible exposure to tick - clinical diagnosis
ACA and lymphocytoma clinical and high serology titres
- neuroborreliosis clinical and CSF+Blood serology
Arthritis will have high serology from synovial fluid, and positive PCR
