7. Zoonoses Flashcards

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1
Q

What is the definition of a Zoonose?

A

Infections (Bacterial, Viral, Parasite or Fungal) that are naturally transmitted between Vertebrate Animals and Humans (The Source of the disease being from the Animal)
Note - of the 1415 pathogens currently known to affect humans, 61% are Zoonotic

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2
Q

What are examples of diseases which are transmitted from animals to humans, which are not Zoonoses?

A
  1. Malaria (from a Mosquito)
  2. Schistosomiasis (from a Snail) - Snail Fever
  3. Oncoceriasis (from a Fly) - River Blindness
  4. Elephantiasis (from a Fly / Mosquito) - Lymphatic Filariasis
    Note - even though they are transmitted from the animal, they depend on the human host for part of their life-cycle
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3
Q
  1. What is an Anthroponosis?
  2. Give examples.
A
  1. “Reverse Zoonoses” - infections from humans which can effect animals
  2. a) Influenza (Virus affecting birds / pigs)
  3. b) “Strep Throat” (Bacteria affecting dogs)
  4. c) Leishmaniasis (Parasite affecting dogs)
  5. d) Chytridiomycosis (Fungus affecting amphibians)
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4
Q

What are the most common Bacterial Zoonoses?

A
  1. Salmonella (Common in the UK)
  2. Campylobacter (Common in the UK)
  3. Coxiella Burnetti (Q Fever) (Common in the UK)
  4. Chalmydophila Psittaci (Psittacosis / Ornitosis)
    (Common in the UK)
  5. Anthrax (Rare in the UK)
  6. Brucella (Rare in the UK)
  7. Leptospirosis
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5
Q

What are the most common Viral Zoonoses?

A
  1. Rabies (Emerging but Rare in the UK)
  2. Avian Influenza (Emerging)
  3. Ebola Virus Disease
  4. Yellow Fever
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6
Q

What are the most common Fungal Zoonoses?

A
  1. Dermatophytoses (Ringworm) (Common in the UK)
  2. Sporotrichosis
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7
Q

What are the most common Parasite Zoonoses?

A
  1. Toxoplasmosis (Common in the UK)
  2. Cysticercosis
  3. Echinococcosis
  4. Trichinellosis
  5. Visceral Larva Migrans (Toxocara)
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8
Q

How is Rabies transmitted?

A

From the bite of an infected animal, normally a dog (97%) or a bat

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9
Q

How does Rabies present?

A

The Rabies Virus travels to the Brain via the Peripheral Nerves (it can take up to 2 months) and so presents as an acute Encephalitis:
1. Malaise, Headache and Fever
2. Progression to Mania, Lethargy and Coma
3. Over-production of Saliva and Tears
4. Unable to swallow and Hydrophobia
5. Death by Respiratory Failure

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10
Q

How is Rabies diagnosed?

A

Diagnosis is difficult:
1. PCR of Saliva or CSF
2. Often confirmed post-mortem on brain biopsy

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11
Q

How is Rabies treated?

A

Immediately after the bite give post-exposure prophylaxis: Human Rabies Immunoglobulin infiltrated around the bite (if possible) + 4 doses of Rabies Vaccine over the next 14 days
Note - this is fatal if untreated

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12
Q

Where was Brucellosis an occupational hazzard?

A
  1. Farmers
  2. Vets
  3. Slaughterhouse Workers
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13
Q

How are humans infected with Brucellosis?

A
  1. During milking infected animals
  2. During parturition
  3. Handling carcasses of infected animals
  4. Consumption of unpasteurized dairy products
    Note - the organisms are excreted in milk, placenta, and aborted foetus
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14
Q

How does Brucellosis present?

A
  1. Actue (1-3 weeks):
  2. a) Fever + Drenching Sweats
  3. b) Weakness, Headaches
  4. c) Splenomegaly
  5. Subacute (>1 month): Fever and Joint pains
  6. Chronic (>months or years): Flu-like symptoms
  7. Subclinical (commonest): 50% exposed have positive serology
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15
Q

What is the treatment of Brucellosis?

A
  1. Long acting Doxycycline for 2-3 months
    • Rifampicin
    • Intramuscular Gentamycin for 1st weeks
  2. Cotrimoxazole for 2 weeks (in CNS disease)
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16
Q

What is the commonest form of Leptospirosis?

A

L. Hardjo (cattle) - 11% of dairy workers have a positive serology, though most have no history of the illness

17
Q

How does Leptospirosis present?

A
  1. Jaundice
  2. Liver Failure
  3. Renal Failure
18
Q

What is the treatment of Leptospirosis?

A
  1. Usually benign
  2. Penicillin as early as possible
19
Q

What is the main source of Toxoplasmosis?

A

Toxoplasma Gondii is found commonly in cats

20
Q

How is Toxoplasmosis transmitted into humans?

A
  1. From oocysts in cat faeces
  2. From trophozoites in under-cooked meats
21
Q

How does Toxoplasmosis infection present?

A
  1. Asymptomatic
  2. Acute: Pneumonia, Fever, Cough, Rash
  3. Chronic: Lymphadenopathy, Lymphcytosis, Atypical Mononuclear Cells on the Blood Film
  4. Chorio-Retinitis and Uveitis
  5. Congenital form: Hydrocephalus, Microphthalmos, Microcephaly, Convulsions, Calcification in Brain on X-Ray - usually fatal
22
Q

How is Toxoplasmosis diagnosed?

A

Serology:
1. Toxoplasma Dye Test
2. IgM antibodies

23
Q

How is Toxoplasmosis treated?

A
  1. Most don’t require treatment
  2. Sulphonamide and Pyrimethamine
  3. Tetracycline (occasionally)
24
Q

What is the cause of Lyme Disease?

A
  1. Borrelia Burgdorferi
  2. Spirochaete found in wild Deer
25
Q

How is Lyme Disease transmitted to humans?

A

Via Ticks

26
Q

What can Lyme Disease go on to form?

A
  1. Acrodermatitis Chronica Atroficans (ACA)
  2. Lymphocytoma
  3. Neuroborreliosis (NB)
27
Q

What is Acrodermatitis Chronica Atroficans (ACA)?
Note - this is caused by Lyme Disease

A

The Extensor Surfaces of the Distal Extremities (commonly of elderly) turn bluish red - and progress to atrophic disease
Peripheral Neuropathy common

28
Q

What is Lymphocytoma?
Note - this is caused by Lyme Disease

A

Bluish, solitary, painless nodule found in the earlobe or Aerola
Note - more common in children

29
Q

What is Neuroborreliosis (NB)?
Note - this is caused by Lyme Disease

A

Triad of:
1. Cranial Nerve Palsy (Normally Facial Nerve)
2. Radicular Pain (Migratory, worse at night)
3. Lymphocytic Meningitis

30
Q

How is Lyme Disease diagnosed?

A

Clinically:
1. Single / multiple lesions - red area which can then spread (Erythema Migrans)
2. ACA and Lymphocytoma
3. Arthritis - very high serology titres from Synovial Fluid