Zoonoses Flashcards
What are zoonoses?
Infections that can pass between living animals and humans
Source of the disease is from the animal
What is the WHO definition of zoonoses?
Infections that are naturally transmitted between vertebrate animals and humans
Give examples of infections transmitted by animals but which are not zoonoses, why are these not zoonoses?
Malaria
Schistosomiasis
Oncoceriasis
Elephantitis
Even though these are transmitted from animals, they depend on the human host for part of their life cycle
What is anthroponosis?
‘reverse zoonosis’ - infections in humans that can infect animals
Give examples of anthoponoses
Influenza
Strep throat
Leishmaniasis
Chytridiomycosis
What percentage of the 1415 pathogens currently known to affect humans are zoonotic?
61%
Pathogen types which can cause zoonoses
Viruses
Bacteria
Parasites
Fungi
Examples of bacterial zoonoses
Salmonella Campylobacter Shigella Anthrax Brucella E. coli Leptospirosis Plague Psittacosis Q fever Tularaemia
Examples of viral zoonoses
Rabies Avian influenza Crimean-Congo Haemorrhagic fever Ebola virus disease Lassa fever Rift valley fever West Nile fever Yellow fever
Examples of parasitic zoonoses
Cysticercosis Echinococcosis Toxoplasmosis Trichinellosis Visceral larva migrans
Examples of fungal zoonoses
Dermatophytoses
Sporotrichosis
Examples of prion zoonoses
BSE
CJD V
Common zoonoses in the UK
Salmonella Campylobacter Toxoplasma Psittacosis Q fever Ringworm
Uncommon zoonoses in the UK
Anthrax Rabies Bubonic plague Tularaemia Acute brucellosis
What is an emerging zoonosis?
A zoonosis that is newly recognised or newly evolved, or one that had occurred previously but shows an increase in incidence or expansion in geographical, host or vector range
Examples of emerging zoonoses
Avian influenza Nipah virus Rabies Brucellosis Monkeypox
How is rabies transmitted?
Lyssavirus transmitted from the bite of an infected animal, most commonly dogs (97%) and bats, although there is a wide range of animal transmitters
Deaths caused per year by rabies
Approximately 55,000
Incubation period of rabies in humans
Ranges from 2 weeks to several months
How does the rabies virus work?
Travels to the brain via peripheral nerves and causes acute encephalitis
Clinical features of rabies
Malaise, headache, fever Progression to mania, lethargy and coma Over-production of saliva and tears Inability to swallow Hydrophobia Death due to respiratory failure
What post-exposure prophylaxis should be given immediately after a bite from an animal with rabies?
Human rabies immunoglobulin
Infiltrated around the bite if possible
4 doses of rabies vaccine over 14 days
How are humans infected by brucellosis?
During milking infected animals
During parturition
Handling carcasses of infected animals
Consumption of unpasteurised dairy products
What species of brucella is the most virulent in humans?
Melitensis
Clinical features of brucellosis
Incubation period of 5-30 days
Can be acute, subacute, chronic or subclinical
Acute presentation of brucellosis
Lasts 1-3 weeks High undulant fever Weakness Headaches Drenching sweats Splenomegaly
Subacute presentation of brucellosis
Lasts over 1 month
Fever
Joint pains
Chronic presentation of brucellosis
Lasts months or years Flu-like symptoms Malaise Depression Chronic arthritis Endocarditis Epididymo-orchitis Meningism, splenomegaly rarely
Subclinical presentation of brucellosis
Most common form
50% of exposed will have positive serology
Treatment of brucellosis
Long acting doxycycline for 2-3 months
Rifampicin or IM gentamicin for the first week
Add co-trimoxazole for 2 weeks in CNS disease
Causative organism of leptospirosis
L. Icterohaemorrhagica (rats) L. Hardjo (cattle) L. Canicola (dogs) L. Pomona (pigs) L. Australis (hedgehogs) L. Grippotyphosa (voles)
Presentation of leptospirosis
Flu like symptoms followed by jaundice and renal failure
What is the commonest causative organism of leptospirosis?
L. Hardjo
Treatment of leptospirosis
Penicillin as early as possible
What leptospirosis infection is usually benign and self-limiting?
L. Hardjo
Cause of toxoplasmosis
Intracellular protozoan parasite - toxoplasma gondii
Main source of toxoplasmosis
Cats
30-80% of domestic adult cats show evidence of past exposure
How do humans acquire toxoplasmosis infection?
From oocysts in cat faeces or from trophozoites in undercooked meats
Clinical features of acute form of toxoplasmosis infection
Pneumonia
Fever
Cough
Rash
Clinical features of chronic form of toxoplasmosis infection
Lymphadenopathy
Lymphocytosis
Atypical mononuclear cells on blood film
Chorio-retinitis and uveitis
Clinical features of congenital form of toxoplasmosis infection
Hydrocephalus Micro-ophthalmos Microcephaly Convulsions Calcification in brain on x-ray Usually fatal
Diagnosis of toxoplasmosis infection
Serological
Toxoplasma dye test, positive within 1 month of infection and remains positive for life
IgM antibodies - indicate acute infection
Treatment of toxoplasmosis infection
Most will not require treatment
Sulphonamide and pyrimethamine
Folate antagonists
Occasionally tetracycline
How is Lyme disease transmitted?
By ticks - ixodes recinus
Species of ixodes genus responsible for Lyme disease
I. ricinus
I. scapularis/pacificus
I. persulcatus
Pathogen responsible for Lyme disease
Borrelia Burgdorferi
In what percentage of cases of Lyme disease doe erythema migrans occur?
80-90% of cases
7-30 days after the bite
What patients are most affected by acrodermatitis chronica atroficans as a result of Lyme disease?
Elderly
What patients are most affected by lymphocytoma as a result of Lyme disease?
Children
How does acrodermatitis chronica atroficans present?
Bluish-red discolouration of the extensor surfaces of the distal extremities, progression over months to years
Peripheral neuropathy common
How does lymphocytoma present?
Bluish, solitary, painless nodules on earlobe or areola
What percentage of patients with Lyme disease will develop neuroborreliosis?
approximately 15%
How does neuroborreliosis present?
Triad of facial nerve palsy, radicular pain and lymphocytic meningitis
Onset of symptoms 2-6 weeks (can range from 1-12 weeks) after the bite
Preceded by erythema migrans in 30-50%
Conditions more common in individuals with Lyme Borreliosis
Cardiac disorders
Carditis
Heart block
Arthritis
How are erythema migrans, acrodermatitis chronica atroficans, lymphocytoma and arthritis diagnosed?
EM - clinical, no labs
ACA and lymphocytoma - clinical and high serology titres
Arthritis - very high serology titres from synovial fluid
Clinical and laboratory findings in Lyme disease
Neuro symptoms consistent with neuroborreliosis
CSF pleocytosis, often lymphocytic
Blood and intrathecal Bb-specific antibody production
Management of erythema migrans
Doxycycline, amoxicillin or cefuroxime axetil recommended for two weeks
Management of acrodermatitis chronica atroficans
PcV 2g TDS
or
doxycycline 200mg OD for 3 weeks
Management of Lyme neuroborreliosis
Doxycycline 200mg OD-BD
10-14 days
or
Ceftriaxone 2g OD for 14 days
