Zoonoses Flashcards
what is 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
- Malaria
- Schistosomiasis (Snail fever)
- Oncoceriasis (River Blindness)
- Elephantiasis (Lymphatic Filariasis)
Are these zoonoses? if so why not?
Because 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
What are examples of Anthroponosis?
Influenza (virus affecting birds, pigs)
‘Strep throat’ (bacteria affecting dogs)
Leishmaniasis (parasite affecting dogs e.g.)
Chytridiomycosis (fungus affecting amphibians)
what can Zoonoses be?
Can be caused by virus, bacteria, parasites or fungi
Pathogens have developed strategies to ensure their own survival/propagation, how?
causing a chronic infection to survive
or have a non-human reservoir
List of zoonoses (partial) - bacteria
Salmonella
Campylobacter
Shigella
Anthrax
Brucella
E-coli (verotoxigenic)
Leptospirosis
Plague
Psittacosis (Ornitosis)
Q fever
Tularaemia
List of zoonoses (partial) - viruses
Rabies
Avian influenza
Crimean-Congo haemorrhagic fever (CCHF)
Ebola virus disease
Lassa Fever
Rift Valley fever
West Nile Fever
Yellow Fever
List of zoonoses (partial) - parasites
Cysticercosis
Echinococcosis
Toxoplasmosis
Trichinellosis
Visceral larva migrans (toxocara)
List of zoonoses (partial) - fungi
Dermatophytoses
Sporotrichosis
List of zoonoses (partial) - other (pirons)
BSE/CJDV
What are examples of ‘common’ zoonoses in the UK?
- Salmonella
- Campylobacter
- Toxoplasma
- (Psittacosis – Chlamydophila psittaci)
- (Q-fever - Coxiella Burnetti)
- Ringworm/dermatophytosis
what are some uncommon zoonoses?
• Now rarely seen in UK
Anthrax
Rabies
Bubonic plague
Tularaemia
Acute brucellosis
what are 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”
- Avian influenza
- Nipah virus
- Rabies
- Brucellosis
- Monkeypox (shown in picture)
how is rabies transmitted?
- Viral Infection (lyssavirus) transmitted from the bite of an infected animal
- Wide range of wild animal transmitters:
- Dogs (97%), bats
- Also monkeys, foxes, racoons, skunks, wolves, cats
• App. 55000 people, mainly children, die each year
What is the incubation period of rabies in humans?
• Incubation period in humans – 2 weeks to several months
How and what effects does rabies cause?
- Rabies virus travels to the 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 do you diagnose rabies?
• Diagnosis difficult
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
is rabies fatal?
• Always fatal if untreated (last death in UK May 2012)
what is the management 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
what is brucellosis?
- (Used to be) an occupational hazard of farmers, vets, slaughterhouse workers etc
- Organisms are excreted in milk, placenta and aborted foetus
how are humans infected with brucellosis?
a) During milking infected animals
b) During parturition
c) Handling carcasses of infected animals
d) Consumption of unpasteurized dairy products
Brucellosis - Risk of _____ in laboratory – warn lab!
spread
what are the features of brucellosis?
Now a rare disease in UK
Brucella - small, gram negative coccobacilli
3 species:
- Melitensis: most virulent
- Suis
- Abortus: least virulent
what is the incubation period of brucellosis?
• Incubation period 5-30 days (up to 6 months)
what are the different presentations of brucellosis?
Acute (now very rare in Scotland)
Subacute
Chronic
Subclinical (commonest)
what is the acute presentation of brucellosis?
lasts 1 - 3 weeks
High ‘undulant’ fever
Weakness, headaches
Drenching sweats
Splenomegaly
what is the sub-acute presentation of brucellosis?
lasts over 1 month
Fever and joint pains (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, Epididymo-orchitis, Rarely meningism, Splenomegaly
what is the sub-clinical presentation of brucellosis?
most common form
50% of exposed have positive serology
what is the treatment of 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 leptospirosis
- Was common in NE Scotland fish workers
- Due to L. icterohaemorrhagica
- Described in Fife miners – bitten by rats
- Flu like symptoms – then jaundice, and renal failure
- But now L. hardjo (cattle) is commonest form
- Fever, meningism – no jaundice
- 11% of dairy workers have positive serology
- Most have no history of illness
how is leptospirosis transmitted?
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?
Traditionally an occupational disease
Emerging:
Recreational (Borneo Eco Challenge 2000)
Unexplained emergence in Thailand; 30-40.000 cases at end of 1990s
Climate change/disaster associated outbreaks (Typhoon in The Phillippines 2009, Hurricane in Costa Rica 2017)
how are humans incidental hosts of leptospirosis?
Direct contact with the animal
Contact with environment (water) contaminated with their urine
Incubation 2-30 days (10-14)
what are the symptoms of leptospirosis?
Undifferented fever; myalgia, headaches & abdominal pain
how common is severe disease in leptospirosis?
Severe disease in 5-15%
how do you diagnose leptospirosis?
Think of it!
Fever in a cattle farmer, Exposure to water or rats, The farmer with protracted flu-symptoms is more likely to have leptospirosis than brucellosis
- 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
what is the treatment of leptospirosis?
• Early treatment:
- Lack of evidence that antibiotics are effective, but most effective during early phase of disease
- Doxycycline for mild disease, IV penicillin for severe
0 Steroids do not help
- Prompt dialysis
- Mechanical ventilation
what is lyme borrelios? (lyme disease)
- Clustering of childhood arthritis in Old Lyme, Connecticut, USA in 1977
- Burgdorfer found cause in 1982 – hence Borrelia burgdorferi
- Spirochaete found in wild deer
- Transmitted by tick, Ixodes ricinus
- Commonest in summer months
what is the vector of lyme disease?
tick
What is seen in 80-90% of cases of lyme disease?
Erythema Migrans (EM)
- Clinical diagnosis
- 3-90 days after the bite (7-30)
- Single or multiple lesions
what is ACRODERMATITIS CHRONICA ATROFICANS (ACA)?
- European (B. Afzelii)
- Elderly people
- Extensor surfaces of distal extremities
- Bluish-red discoloration - progresses over months to years to atrophic phase
- Peripheral neuropathy common
a skin rash indicative of the third or late stage of European Lyme borreliosis
what is LYMPHOCYTOMA?
- Bluish solitary painless nodule
- Earlobe or areola
- Children > Adults
App 15% of patients develop NB, what is it? (neuroborreliosis)
• Triad of facial nerve palsy, radicular pain & lymphocytic meningitis
- Radicular pain (70-85%), migratory, worse at night
- Cranial neuropathy (app 50%) - facial palsy
- Onset of symptoms 2-6 (1-12) weeks after bite
- Preceded by EM in 30-50%
what effects does lyme borreliosis in the usa?
• Cardiac disorders more common (8 – 10%)
- Carditis (peri-myocarditis)
- Heart block
• Arthritis more common - Large joints, often knees
what is the diagnosis of lyme disease?
- EM a clinical diagnosis - no lab needed
- ACA and Lymphocytoma clinical & high serology titres
- Arthritis - very high serology titres from synovial fluid. PCR
- NB, clinical + laboratory findings:
- Neuro symptoms consistent with LNB (Lyme Neuroborreliosis) & other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytic
- Paired blood and CSF serolgoy
what si the treatment of lyme?
- Oral Doxycycline or Amoxicillin, or IV Ceftriaxone
- Most manifestations treat for 21 days (28 in arthritis or ACA)
