Zoonoses Flashcards
What is zoonoses?
- Infections that can pass between living animals and humans
- The source of the disease is from the animal
- Infections that are naturally transmitted between vertebrae animals and humans
Why are malaria, snail fever, river blindness and lymphatic filariasis not considered zoonoses?
Even though transmitted from animals, they depend on the human host for part of their life-cycle
What is anthroponosis?
‘Reverse zoonoses’ in that humans are infecting animals
Give examples of anthoponosis.
- Influenza (virus affecting birds, pigs)
- ‘Strep throat’ (bacteria affecting dogs)
- Leishmaniasis (parasite affecting dogs e.g.)
- Chytridiomycosis (fungus affecting amphibians)
What can cause zoonoses?
- Virus
- Bacteria
- Fungus
- Parasites
What strategies have pathogens developed to ensure their own survival/propagation?
- Causing a chronic infection to survive
- Have a non-human reservoir
Give examples of bacteria zoonoses.
- Salmonella
- Campylobacter
- Shigella
- Anthrax
- Brucella
- E-coli (verotoxigenic)
- Leptospirosis
- Plague
- Psittacosis (Ornitosis)
- Q fever
- Tularaemia
Give examples of virus zoonoses.
- Rabies
- Avian influenza
- Crimean-Congo haemorrhagic fever (CCHF)
- Ebola virus disease
- Lassa Fever
- Rift Valley fever
- West Nile Fever
- Yellow Fever
Give examples of parasite zoonoses.
- Cysticercosis
- Echinococcosis
- Toxoplasmosis
- Trichinellosis
- Visceral larva migrans (toxocara)
Give examples of fungi zoonoses.
- Dermatophytoses
- Sporotrichosis
Give examples of prion zoonoses
BSE/CJDv
What are common zoonoses in the UK?
- Salmonella
- Campylobacter
- Toxoplasma
- (Psittacosis: Chlamydophila psittaci)
- (Q-fever: Coxiella Burnetti)
- Ringworm/dermatophytosis
What zoonoses are now rarely seen in the 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
Give examples of emerging zoonoses.
- Avian influenza
- Nipah virus
- Rabies
- Brucellosis
- Monkeypox
What is rabies
Viral Infection (lyssavirus) transmitted from the bite of an infected animal
What animal can transmit rabies?
Wide range of wild animal transmitters:
- Dogs (97%), bats
- Also monkeys, foxes, racoons, skunks, wolves, cats
How many people die from rabies per year?
App. 55000 people, mainly children, die each year
What is the incubation period for rabies?
2 weeks to several months
What happens once the rabies virus enters the body?
It travels to the brain via the peripheral nerves and 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?
- Diagnosis is difficult
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
How should rabies be treated?
It is always fatal if left untreated so 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
How is brucellosis transmitted?
Organisms are excreted in milk, placenta and aborted foetus
How are humans infected with brucellosis?
- During milking infected animals
- During parturition
- Handling carcasses of infected animals
- Consumption of unpasteurized dairy products
What organism is responsible for brucellosis?
Brucella, a small gram negative coccobacilli
What are the 3 species of brucella?
- Melitensis
- Suis
- Abortus
What are the features of the melitensis species of brucella?
- Most virulent in man
- Goat, sheep and camel host
- Found in the Mediterranean, S. America, China, India and the Middle East
What are the features of the suis species of brucella?
- Pig host
- Found in N. America, S. America and SE Asia
What are the features of the abortus species of brucella?
- Least virulent in man
- Cattle and buffalo host
- Found worldwide
What is the incubation period for brucellosis?
5-30 days (up to 6 months)
What is the acute 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 pain (knee, hip, back SI joints)
What is the chronic presentation of brucellosis?
Lasts for months or years
- Flu-like symptoms
- Malaise
- Depression
- Chronic arthritis
- Endocarditis
- Epidiymo-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 organism causes leptospirosis?
- L. icterohaemorrhagica from rats
- L. hardjo from cattle
What is another name for leptospirosis?
Rat fever
How does L.hardjo infection present?
- Fever
- Meningism
- NO JAUNDICE
How does L. icterohaemorrhagica infection present?
Flu-like symptoms then jaundice and renal failure
What are the featres of leptospira?
Thin, highly mobile spirochaetes -One of the most widespread Zoonosis -Many reservoir host -Survive in the environment for weeks to months -Penetrate abraded skin or mucous membranes and cause systemic illness-
How is the epidemiology of leptospirosis changing?
- Used to be an occupation disease
- Now outbreaks associated with recreational challenges. unexplained emergences and disaster associated outbreaks
How do humans contact leptospirosis?
- Humans are incidental hosts
- Direct contact with the animal
- Contact with environment (water) contaminated with their urine
What is the incubation period for leptospirosis?
2-30 days (10-14)
What are the symptoms of leptospirosis infection?
- Undifferented fever
- Myalgia
- Headaches
- Abdominal pain
What symptoms can occur in severe leptospirosis?
- Weil’s disease (Triad of jaundice, AKI, bleeding)
- Pulmonary haemorrhage (PH)
- Case fatality 5-40%, >50% in PH
How is leptospirosis diagnosed?
- Microscopic agglutination test (MAT) requires paired sera – not useful in clinical context
- ELISA serology - suboptimal
- PCR?
- Culture – take at least one week on special media
-Think of the diagnosis in contect of the patient’s history
What is the treatment for leptospirosis?
Early treatment
- Doxycline for mild disease
- IV penicillin for severe disease
- Prompt dialysis
- Mechanical ventilation
How is Lyme borrelios transmitted?
Tick (Ixodes ricinus in Europe)
When is Lyme disease most common?
Summer months ( ticks active >4C and in humid conditions)
What organism is responsible for Lyme disease in Europe?
Borrelia burgdoferi
What is erythema migrans?
- A rash associated which can provide the clinical diagnosis of Lyme disease
- Single or multiple lesions
- Occur in 80-90% of cases
- Appears 3-90 days after the bite (7-30)
What is acrodermatitis chronic atroficans?
- A late manifestation of Lyme disease
- Occurs in elderly people
- Bluish-red discolouration of the extensor surfaces of distal extremities which progresses over monthe to years to atrophic phase
- Peripheral neuropathy is common
What is lymphocytoma?
- A bluish solitary painless nodule that usually occurs on the earlobes or areola
- More common in children
- Can occur in Lyme disease
What is neuroborreliosis?
- A triad of facial nerve palsy, radicular pain (migratory and worse at night) and lymphocytic meningitis
- Onset 2-6 (1-2) weeks after tick bite (Lyme’s)
- Often preceded by EM
What symptoms of Lyme disease are more common in the USA?
Cardiac disorders
- Carditis (peri-myocarditis)
- Heart block
Arthritis
-Large joints, often knees
How is Lyme disease diagnosed?
- EM by clinical observation
- ACA and lymphocytoma: high serology titres
- Arthritis: very high serology titres of synovial fluid and PCR
- Neuro symptoms consistent with LNB & other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytic
- Paired blood and CSF serolgoy
What is the treatment for Lyme disease?
- Oral Doxycycline or Amoxicillin, or IV Ceftriaxone
- Most manifestations treat for 21 days (28 in arthritis or ACA)
