Zoonoses Flashcards
What is zoonoses?
Infections that are naturally transmitted between vertebrate animals and humans
What is not a zoonose? And why?
Malaria Schistosomiasis (Snail fever) Oncoceriasis (River Blindness) Elephantiasis (Lymphatic Filariasis) - Because even though transmitted from animals, they depend on the human host for part of their life-cycle
What is a anthroponosis? Give some examples.
‘Reverse zoonoses’ in that humans are infecting animals - Influenza (virus affecting birds, pigs) - ‘Strep throat’ (bacteria affecting dogs)
Of the current pathogens affecting humans, what percentage are zoonotic?
It is likely that most modern infectious diseases originated in animal Of the 1415 pathogens currently known to affect humans, 61% are zoonotic
What can cause zoonoses?
Can be caused by virus, bacteria, parasites or fungi - Where pathogens have developed strategies to ensure their own survival
What are common zoonoses in the UK?
Salmonella Campylobacter Toxoplasma (Psittacosis – Chlamydophila psittaci) (Q-fever - Coxiella Burnetti) Ringworm/dermatophytosis
What are some emerging zoonoses in the UK?
- Avian influenza
- Nipah virus
- Rabies
What is rabies infection?
Viral Infection (lyssavirus) transmitted from the bite of an infected animal
What animals transmit it?
Dogs (97%), bats
How many people die from rabies each year?
App. 55000 people, mainly children, die each year
What is the incubation period of rabies?
2 weeks to several months
What is the transmission of Rabies in the body and what effect does this have?
Travels to the brain via the peripheral nerves
It causes an acute encephalitis: malaise, headache and fever
- Progresses to mania, lethargy and coma
- Over production of tears and saliva
- Unable to swallow
- Death by resp failure
How is diagnosis of Rabies carried out?
PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
What is the prognosis of rabies?
•Always fatal if untreated (last death in UK May 2012)
What is the immediate treatment of rabies?
Immediately after bite give post-exposure prophylaxis
- human rabies immunoglobulin (HRIG)
- infiltrated round the bite (if possible)
- +4 doses of rabies vaccine over 14 days
Outline brucellosis.
- (Used to be) an occupational hazard of farmers, vets, slaughterhouse workers
- Organisms are excreted in milk, placenta and aborted foetus
Humans infected when: during partirition, handling carcasses of dead animals, during milking of infected animals
How common is brucellosis?
v rare
What is the incubation period of brucellosis?
•5-30 days (up to 6 months)
What are the symptoms of brucellosis?
- Acute (now very rare in Scotland)
- Subacute
- Chronic
- Subclinical (commonest)
How do we treat brucellosis?
- Long acting Doxycycline for 2-3 months + Rifampicin, or + intramuscular gentamycin for first week(s)
- Relapses occur due to intracellular organism (5-10%)
- Chronic form – difficult to treat
Outline leptospirosis.
Infection that was common in NE scotland fish workers.
Infection associated with rats but now more commonly cattle.
In severe cases aka weil’s disease!!
What are the symptoms of leptospirosis?
Flu like symptoms – then jaundice, and renal failure
Undifferented fever; myalgia, headaches & abdominal pain
What is the mode of transmission of leptospirosis?
Animal urine
How does leptospirosis access the body?
Penetrate abraded skin or
mucous membranes and
cause systemic illness
How do human’s host leptospirosis?
Humans are incidental hosts
- Direct contact with the animal
- Contact with environment (water) contaminated with their urine
- Incubation 2-30 days (10-14)
How can we diagnose leptospirosis?
Think of it!
- Microscopic agglutination test (MAT) requires paired sera – not useful in clinical context
- ELISA serology - suboptimal
- Culture – take at least one week on special media
How can we treat leptospirosis?
–Lack of evidence that antibiotics are effective, but most effective during early phase of disease
–Doxycycline for mild disease, IV penicillin for severe
–Steroids do not help
**Prompt dialysis is necessary**
What is the vector for lyme borrelios (lyme’s disease)?
the little buggars - ticks [Ixodes genus]
When is lyme borrelios most common?
Summer months
What is the features of lymes?
Red circular rash around the site of bite. Rash may migrate along dermatome.
If a patient presents one day after tick bite with a rash, is it lyme’s?
No, lymes rash will only present 3-90 days after the bite.
How is lyme’s diagnosed?
Clinical diagnosis – no lab needed
NB, clinical + laboratory findings
- Neuro symptoms consistent with LNB & other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytic
- Paired blood and CSF serolgoy
How is lyme’s disease treated?
- Oral Doxycycline or Amoxicillin, or IV Ceftriaxone
- Most manifestations treat for 21 days (28 in arthritis or ACA)
