Zoonoses Flashcards
What are zoonoses?
Infections that can pass between living animals and humans
The source of the disease is from the animal
•WHO definition: Infections that are naturally transmitted between vertebrate animals and humans
Why aren’t the likes of malaria and schistosomiasis zoonoses?
Because they depend on the human host for part of their life cycle
What is the word for reverse zoonoses?
Anthroponosis - humans are infecting animals
Give examples of anthroponosis
Influenza
Strep throat
Leishmaniasis
Chytridiomycosis
What percentage of the 1415 pathogens that infect humans are zoonotic?
61%
What strategies can zoonoses use to ensure their own survival/propagation?
Can cause a chronic infection to survive
Non-human reservoir
Give three examples of bacterial zoonoses
Salmonella
Campylobacter
Anthrax
Give three examples of viral zoonoses
Rabies
Avian influenza
Ebola virus disease
Give three examples of parasitical zoonoses
Toxoplasmosis
Cysticercosis
Echinococcosis
Give examples of fungal zoonoses?
Dermatophytoses
Sporotrichosis
What are the common Zoonoses in the UK
- Salmonella
- Campylobacter
- Toxoplasma
- (Psittacosis – Chlamydophila psittaci)
- (Q-fever - Coxiella Burnetti)
- Ringworm/dermatophytosis
Uncommon zoonoses include
•Now rarely seen in UK
Anthrax
Rabies
Bubonic plague
Tularaemia
Acute brucellosis
What is an 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
So it is newly recognised, or newly evolved, or has recently increased incidence or expansion in geographical host or vector range
What are examples of emerging zoonoses?
- Avian influenza
- Nipah virus
- Rabies
- Brucellosis
- Monkeypox
What is the most likely transmitter of rabies?
–Dogs (97%), bats
–Also monkeys, foxes, racoons, skunks, wolves, cats
How many people die each year from rabies?
•App. 55000 people, mainly children, die each year
What is the incubation period of rabies?
2 weeks to several months
How does the rabies virus travel to the brain?
Travels to the brain via peripheral nerves
What are the clinical features of rabies?
•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 do you diagnose rabies?
•Diagnosis difficult
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
What is the prognosis of rabies?
Always fatal if untreated
What is post exposure prophylaxis 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
Who is more exposed to brucellosis?
Used to be an occupational hazard of farmers, vets, slaughterhouses workers etc
Where are brucellosis organisms excreted?
Excreted in milk, placenta and aborted foetus
Humans are infected:
During milking infected animals
During parturition
Handling carcasses of infected animals
Consumption of unpasteurized dairy products
What type of bacteria are brucella?
Small gram negative coccobacilli
Examples include melitensis, suis, abortus
What is the incubation period for brucellosis?
5-30 days (up to 6 months)
What is the actue presentation of brucellosis?
Lasts 1-3 weeks
High ‘undulant’ fever
Weakness, headaches
Drenching sweats
Splenomegaly
What is the subacute presentation of brucellosis?
Lasts over 1 month
Fever and joint pains (knee, hip, back SI joints)
What is chronic presentation of brucellosis?
Lasts for months or years
Flu-like symptoms. Malaise. Depression. Chronic arthritis
Endocarditis. Epididymo-orchitis. Rarely meningism. Splenomegaly
What is the subclinical presentation of brucellosis?
Most common form - 50% of exposed have positive serology
What is the treatment for 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•
- Add Cotrimoxazole for 2 weeks in CNS disease
What is the hostorical cause of leptospirosis?
Due to L icterohaemorrhagica historically
Common in NE scotland amongst fish workers - also described in mine workers who were bitten by rats
Now L. hardjo is the commonest form (cattle - dairy workers commonly have positive serology)
What are the symptoms of L.Icterhaemorrhagica and L.Hardjo?
L. Icterhaemorrhagica = flu like symptoms - then jaundice and renal failure
L. Hardjo - fever, meningism and no jaundice
What type of organism is leptospirosis?
Thin highly mobile spirochaetes
One of the most widespread Zoonosis
Many reservoir host, survive in the environment for weeks to months
How does leptospirosis enter the body?
Penetrates abraded skin or mucous membranes and cause systemic illness
Direct contact with the animal
Contact with environment (water) contaminated with their urine
Incubation 2-30 days (10-14)
What are the signs and symptoms of leptospirosis?
Undifferentiated fever, myalgia, headaches and abdominal pain
Severe disease in 5-15 %:
Weil’s disease (triad of jaundice, AKI and bleeding)
Pulmonary haemorrhage
Case fatality 5-40%, over 50% in pulmonary haemorrhage
A farmer with protracted flu-like symptoms is more likely to have?
Brucellosis or leptospirosis?
The farmer with protracted flu-symptoms is more likely to have leptospirosis than brucellosis
What is the mode of transmission for Lyme Borellios?
Spirochaete found in wild deer
Transmitted by tick, Ixodes ricinus (europe)
The Ixodes genus is the vector
What are the signs and symptoms of lymes?
Erythema migrans
80-90% of cases, 3-90 days after the bite
Single or multiple lesions
Acrodematitis chronica atroficans - extensor surfaces of distal extremities, bluish red discolouration - progresses over months to years to atrophic phase, peripheral neuropathy is common
Lymphocytoma - bluish solitary painless nodule, earlobe or aerola, more common in children than adults
Neuroborelliosis (NB)
15% of patients develop this
Triad of facial nerve palsy, radicular pain (migratory and worse at night) and lymphocytic meningitis
Onset of symptoms 2-6 weeks after bits
Preceeded by EM
Lyme borreliosis - USA
cardiac disorders are more common (carditis and heart block)
Arthritis is more common (large joints, often knees)
What is the diagnosis of Lymes disease?
EM = clinical diagnosis
Acrodermatitis chronica atroficans = clinical and high serology titres
Arthritis = very high serolgy titres from synovial fluid - PCR
NB - clinical and laboratory findings
- Neuro symptoms consistent with LNB & other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytic
- Paired blood and CSF serolgoy
ELISA if Lymes disease is suspected but there is no Eryhtema migrans
Immunoblot test if there is positive ELISA or symptoms remain after 12 weeks even if there is a negative ELISA
What is the treatment for LYMES?
Oral doxycycline or amoxicillin or IV ceftriaxone
Most manifestations treat for 21 days (28 in arthritis or ACA)
Treatment of Neuroborriellosis is with parenteral beta lactam antibiotics for 2-4 weeks, cephalosporins may be superior to penicillin in this situation.
