Zoonoses Flashcards
What is zoonoses?
Infections that are naturally transmitted between vertebrate animals and humans (source is the animal)
Are diseases that are transmitted from animals but depend on human host for part of their life cycle zoonoses?
No, such as
- Malaria
- Schistosomiasis (Snail fever)
- Oncoceriasis (river blindness)
- Elephantiasis (lymphatic filariasis)
What is antroponosis?
Infections that are naturally transmitted between humans and animals (source is the human)
What are some examples of antrhoponosis?
- Influenza (virus affecting birds, pigs)
- Strep throat (bacteria affecting dogs)
- Leishmaniasis (parasite affecting dogs)
- Chytridiomycosis (fungus affecting amphibians)
What are some methods pathogens have developed to ensure their survival?
- Causing a chronic infection to survive
- Or having a non-human reservoir
What are some common zoonoses in the UK?
- Salmonella
- Campylobacter
- Toxoplasma
- (Psittacosis – Chlamydophila psittaci)
- (Q-fever - Coxiella Burnetti)
- Ringworm/dermatophytosis
What are some uncomon zoonoses in the UK?
- Anthrax
- Rabies
- Bubonic plague
- Tularaemia
- Acute brucellosis
What is the definition of emerging zoonoses?
A zoonosis that is newly recognized or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range
What are some examples of emerging zoonoses?
- Avian influenza
- Nipah virus
- Rabies
- Brucellosis
- Monkeypox
What viral infection causes rabies?
Lyssavirus
How is rabies transmitted?
Wide range of wild animal transmitters (bite):
- Dogs (97%), bats
- Also monkeys, foxes, racoons, skunks, wolves, cats
What is the presentation of rabies?
- Travels to brain via peripheral nerves
- Causes an acute encephalitis
- Malaise, headache & fever
- Progressing to mania, lethargy & coma
- Over production of saliva & tears
- Unable to swallow & ‘hydrophobia’
- Death by respiratory failure
How is rabies diagnosed?
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
What is the prognosis of rabies if untreated?
Always fatal
What is the treatment for rabies?
- Human rabies immunoglobulin (HRIG)
- Infiltrated round the bite (if possible)
- +4 doses of rabies vaccine over 14 days
How do humans get infected by brucellosis?
- During milking infected animals
- During parturition
- Handling carcasses of infected animals
- Consumption of unpasteurised dairy products
Where are brucellosis organisms excreted?
Organisms are excreted in milk, placenta and aborted foetus
What bacteria is responsible for brucellosis?
Bacteria responsible is Brucella, small gram negative coccobacilli
What are the 3 species of brucella from most virulent to least?
1) Melitensis
2) Suis
3) Abortus
What is the presentation of brucellosis?
- Acute (now very rare in Scotland)
- Lasts 1-3 weeks
- High ‘undulant’ fever
- Weakness, headaches
- Drenching sweats
- Splenomegaly
- Subacute
- Lasts over 1 month
- Fever and joint pains (knee, hip, back SI joints)
- Chronic
- Lasts for months or years
- Flu like symptoms, malaise, depression, chronic arthritis
- Endocarditis, epididymo-orchitis, rarely menignism, plenomegaly
- Subclinical (commonest)
What is the treatment for brucellosis?
- Long acting doxycycline for 2-3 months and rifampicin or +intramuscular gentamycin for first week
- Relapses occur due to intracellular organism (5-10%)
- Chronic form is difficult to treat
- Add cotrimoxazole for 2 weeks in CNS disease
What causes leptospirosis?
Thin, highly mobile spirochaetes
How is leptospirosis transmitted to humans?
Penetrate abraded skin or mucous membranes and cause systemic illness
Traditionally an occupational disease, 10% of dairy farmers have
How transmitted to humans:
- Direct contact with infected animal
What are the main species of leptospriosis?
- L. Hardjo (most common)
- From cattle
- Fever, meningism – no jaundice
- L. Icterohaemorrhagica
- From rats
- Flu like symptoms, then jaundice and renal failure
