7. Zoonoses

Question 1

What is the definition of a Zoonose?

Answer 1

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

Question 2

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

Answer 2

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

Question 3

1. What is an Anthroponosis?

2. Give examples.

Answer 3

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)

Question 4

What are the most common Bacterial Zoonoses?

Answer 4

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

Question 5

What are the most common Viral Zoonoses?

Answer 5

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

Question 6

What are the most common Fungal Zoonoses?

Answer 6

1. Dermatophytoses (Ringworm) (Common in the UK)

2. Sporotrichosis

Question 7

What are the most common Parasite Zoonoses?

Answer 7

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

Question 8

How is Rabies transmitted?

Answer 8

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

Question 9

How does Rabies present?

Answer 9

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

Question 10

How is Rabies diagnosed?

Answer 10

Diagnosis is difficult:

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

Question 11

How is Rabies treated?

Answer 11

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

Question 12

Where was Brucellosis an occupational hazzard?

Answer 12

1. Farmers
2. Vets
3. Slaughterhouse Workers

Question 13

How are humans infected with Brucellosis?

Answer 13

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

Question 14

How does Brucellosis present?

Answer 14

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

Question 15

What is the treatment of Brucellosis?

Answer 15

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

Question 16

What is the commonest form of Leptospirosis?

Answer 16

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

Question 17

How does Leptospirosis present?

Answer 17

1. Jaundice
2. Liver Failure
3. Renal Failure

Question 18

What is the treatment of Leptospirosis?

Answer 18

1. Usually benign

2. Penicillin as early as possible

Question 19

What is the main source of Toxoplasmosis?

Answer 19

Toxoplasma Gondii is found commonly in cats

Question 20

How is Toxoplasmosis transmitted into humans?

Answer 20

1. From oocysts in cat faeces

2. From trophozoites in under-cooked meats

Question 21

How does Toxoplasmosis infection present?

Answer 21

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

Question 22

How is Toxoplasmosis diagnosed?

Answer 22

Serology:

1. Toxoplasma Dye Test
2. IgM antibodies

Question 23

How is Toxoplasmosis treated?

Answer 23

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

Question 24

What is the cause of Lyme Disease?

Answer 24

1. Borrelia Burgdorferi

2. Spirochaete found in wild Deer

Question 25

How is Lyme Disease transmitted to humans?

Answer 25

Via Ticks

Question 26

What can Lyme Disease go on to form?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

How is Lyme Disease diagnosed?

Answer 30

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