Zoonoses

Question 1

WHO definition of zoonoses

Answer 1

-Infections that are naturally transmitted between vertebrate animals and humans

Question 2

Rabies

Answer 2

• 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
• Incubation period in humans – 2 weeks to several months
• Rabies virus travels to the brain via peripheral nerves

Question 3

Rabies presentation

Answer 3

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

Question 4

Rabies diagnosis

Answer 4

• PCR of saliva or CSF

- often diagnosed post mortem on brain biopsy

Question 5

Rabies prognosis

Answer 5

• almost always fatal following onset of clinical signs
• disease is rapidly progressive with death occurring within 2 weeks in most cases
• always fatal if untreated

Question 6

Rabies treatment

Answer 6

• wound cleansing
• multiple-dose immunisation protocol
• rabies immunoglobulin

Question 7

Brucellosis exposure

Answer 7

• (Used to be) an occupational hazard of farmers, vets, slaughterhouse workers etc
• Organisms are excreted in milk, placenta and aborted foetus
• Humans infected
  - During milking infected animals
  - During parturition
  - Handling carcasses of infected animals
  - Consumption of unpasteurized dairy products

Question 8

Brucellosis

Answer 8

-small gram negative coccobacilli

Question 9

Brucellosis presentation

Answer 9

• Incubation period 5-30 days (up to 6 months)
• Symptoms
  - Acute (now very rare in Scotland)
  - Subacute
  - Chronic
  - Subclinical (commonest)

Question 10

Brucellosis acute presentation

Answer 10

• lasts 1 - 3 weeks
• high ‘undulant’ fever
• weakness, headaches
• drenching sweats
• splenomegaly

Question 11

Brucellosis subacute presentation

Answer 11

• lasts over 1 month

- fever and joint pains (knee, hip, back SI joints)

Question 12

Brucellosis chronic presentation

Answer 12

• lasts for months or years
• flu-like symptoms
• malaise
• depression
• chronic arthritis
• endocarditis
• epididymo-orchitis
• rarely meningism
• splenomegaly

Question 13

Subclinical brucellosis

Answer 13

• most common form

- 50% of exposed have positive serology

Question 14

Brucellosis treatment

Answer 14

• Long acting Doxycycline for 2-3 months + Rifampicin or intramuscular gentamycin for first week
• Relapses occur due to intracellular organism (5-10%)
• Chronic form – difficult to treat
• Add Cotrimoxazole for 2 weeks in CNS disease

Question 15

Leptospirosis

Answer 15

-the infection is caused by motile spirochetes from the genus leptospira and is maintained in nature by chronic renal infection of carrier animals

Question 16

Leptospirosis is associated with:

Answer 16

• occupational exposure (eg cattle farmer)
• water sports
• flooding

Question 17

Leptospirosis presentation

Answer 17

• high remittent fever
• headache
• myalgia
• conjunctival suffusion
• muscle tenderness

Question 18

Leptospirosis investigations

Answer 18

• blood culture
• ELISA serology
• PCR
• microscopic agglutination test (MAT)

Question 19

Leptospirosis treatment

Answer 19

• early treatment
  - doxycycline for mild disease
  - IV penicillin for severe
  - steroids do not help
• prompt dialysis
• mechanical ventilation

Question 20

Lyme borrelios

Answer 20

• spirochaete found in wild deer
• transmitted by tick, Ixodes ricinus
• causes Lyme disease

Question 21

Erythema migrans

Answer 21

• pathogonomic feature of Lyme disease

- usually develops within 1 - 2 weeks at the site of the tick bite

Question 22

Acrodermatitis chronica atrophicans

Answer 22

• skin rash indicative of late stage of Lyme borreliosis
• chronically progressive course
• finally leads to a widespread atrophy of the skin
• peripheral neuropathy common

Question 23

Borrelial lymphocytoma

Answer 23

• bluish solitary painless nodule

- earlobe or areola

Question 24

Neuroborreliosis

Answer 24

• App 15% of patients develop NB
• 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%

Question 25

Lyme disease diagnosis

Answer 25

• Lyme specific IgM and IgG
• PCR
• EM - clinical diagnosis
• arthritis - very high serology titres from synovial fluid

Question 26

Lyme disease treatment

Answer 26

• oral doxycycline or amoxicillin
• if central nervous system manifestations - intravenous ceftriaxome
• most manifestations treat for 21 days
• 28 days in arthritis or ACA