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
What is the presentation of leptospirosis?
- L. Hardjo (most common)
- From cattle
- Fever, meningism – no jaundice
- L. Icterohaemorrhagica
- From rats
- Flu like symptoms, then jaundice and renal failure
- General
- Undifferented fever
- Myalgia
- Headaches
- Abdominal pain
Leptospirosis can lead to severe disease in 5-15%, what are examples?
- Weil’s disease (triad of jaundice, AKI and bleeding)
- Pulmonary haemorrhage (PH)
How is leptospirosis diagnosed?
- Microscopic agglutination test (MAT), but requires paired sera so not useful in clinical context
- ELISA serology, is suboptimal
- PCR?
- Culture, takes at least 1 week on special media
What is the treatment for leptospirosis?
- Early treatment important
- Lack of evidence antibiotics are effective but most effective during early phase of disease
- Doxycycline for mild disease
- IV penicillin for severe disease
- Steroids do not help
- Prompt dialysis
- Mechanical ventilation
What causes lyme borrelios?
Borrelia burgdorferi is the cause, found in wild deer
What is lyme borrelios transmitted by?
Transmitted by ticks (Ixodes ricinus), which is the vector:
- I. Ricinus (Europe)
- I. Scapularis/pacificus (N. America)
- I. Persulcatus (Asia)
- Active when >4oC and humid
What is the presentation of lyme borrelios?
- Erythema migrans (EM)
- 80-90% of cases)
- Single or multiple lesions
- Acrodermatitis chronica atroficans (ACA)
- Affects extensor surfaces of distal extremities
- Bluish-red decolourisation
- Peripheral neuropathy common
- Lymphocytoma
- Bluish solitary painless nodule
- Earlobe or areola
- Children > adults
- Neuroborreliosis (NB)
- Triad of facial nerve palsy, radicular pain and lymphocytic meningitis
- Preceded by EM in 30-50% of cases
- Cardiac disorders
- Carditis
- Heart block
- Arthritis
How is lyme borrelios diagnosed?
- EM is a clinical diagnosis, no lab needed
- ACA and lymphocytoma clinical and high serology titres
- Arthritis very high serology titres from synovial fluid, PCR
- Usually clinical and lab findings
- Neuro symptoms consistent with LNB and other causes excluded
- CSF pleocytosis (WBC in CSF)
- Paired blood and CSF serology
What does EM stand for?
Erythema migrans
What does ACA stand for?
Acrodermatitis chronica atroficans
What is the treatment for lyme borrelios?
- Oral doxycycline or amoxicillin or IV ceftriaxone
