Zoonoses

Question 1

What are zoonoses?

Answer 1

Infections that can spread from animals to humans, with the animal being the source of the infection.
Infections that depend on the human host for part of their life cycle such as malaria and schistosomiasis are not classified as zoonoses

Question 2

What are anthroponoses?

Answer 2

Infections where humans infect animals

Question 3

What are the features of monkeypox?

Answer 3

Endemic in central and west Africa

Characterised by a vesicular rash

Question 4

What are the features of rabies?

Answer 4

Spread from the bite of an infected animal (usually dogs)
Incubation period in humans varies from two weeks to several months
Can spread to the brain and cause an acute encephalitis

Question 5

What are the symptoms of a rabies encephalitis?

Answer 5

Malaise, headache & fever
Progression to mania, lethargy & coma
Over production of saliva & tears
 Unable to swallow & ‘hydrophobia’
Death by respiratory failure

Question 6

How is rabies diagnosed?

Answer 6

PCR of saliva or CSF most useful tests

Diagnosis often confirmed post mortem

Question 7

How is rabies treated?

Answer 7

Always fatal if untreated
Post-exposure prophylaxis given ASAP following bite by infiltrating human rabies immunoglobulin (HRIG) around the bite
Prophylaxis followed by four doses of rabies vaccine given over fourteen days

Question 8

How is brucellosis transmitted?

Answer 8

Infectious product excreted in milk, placenta and aborted fetus
Humans most commonly infected by:
-Milking infected animals
-During parturition (birthing)
-Handling carcasses of infected animals
-Consuming unpasteurized dairy products

Question 9

What are the characteristics of the brucellosis bacteria?

Answer 9

Gram negative coccobacilli

Incubation period of 5-30 days but can be up to 6 months

Question 10

What are the characteristics of the acute brucellosis presentation?

Answer 10

Lasts 1-3 weeks
High, undulant fever
Weakness
Headaches
Drenching sweats
Splenomegaly

Question 11

What are the characteristics of the sub-acute brucellosis presentation?

Answer 11

Lasts over one month
Fever
Joint pain (knee, hip, back sacroiliac joints)

Question 12

What are the characteristics of the chronic brucellosis presentation?

Answer 12

Lasts for months or years
Flu-like symptoms
Malaise
Depression
Chronic arthritis
Endocarditis
Epididymo-orchitis 
Rarely meningism
Splenomegaly

Question 13

What are the characteristics of the subclinical brucellosis presentation?

Answer 13

Most common presentation

50% have positive serology

Question 14

How is brucellosis treated?

Answer 14

Long acting doxycycline for 2-3 months
Additional rifampicin and IM gentamicin for first few weeks
Cotrimoxazole added for 2 weeks if CNS disease present

Question 15

What are the characteristics of leptospirosis icterohaemorrhagia?

Answer 15

Common in fish working populations

Symptoms start as flu-like before developing jaundice and renal failure

Question 16

What are the characteristics of leptospirosis hardjo?

Answer 16

Found in cattle
Symptoms of fever and meningism with no jaundice
Anyone recreationally/occupationally involved with water at risk
Patients with unclear/lymphocytic meningism should be checked

Question 17

What are the characteristics of leptospirosis bacteria?

Answer 17

Thin, highly mobile spirochaetes

Can survive in environment for months

Question 18

When is incidence of leptospirosis disease increased?

Answer 18

Occupational disease
Recreational disease
Emerging increase in natural disasters
Unexplained increase in Thailand

Question 19

What are the symptoms of leptospirosis infection?

Answer 19

A mild infection causes an undifferentiated fever, myalgia, headaches and abdominal pain.
Severe disease develops in 5-15% of cases and can cause Weikl’s disease (characteristic triad of jaundice, AKI and bleeding) or a pulmonary haemorrhage

Question 20

How is leptospirosis diagnosed?

Answer 20

Mainly based on a typical history
Diagnostic tests are not great but microscopic agglutination test, ELISA serology and PCR can be somewhat helpful. Cultures take at least a week and require special media

Question 21

How is leptospirosis treated?

Answer 21

Optimal when started early
Antibiotics only helpful in the early stage of the disease. Doxycycline can be used in mild disease and IV penicillin in severe disease
Dialysis and ventilation may be required in severe disease

Question 22

What is lyme borrelios and how is it transmitted to humans?

Answer 22

Spirochaete found in deer
Transmitted to humans via vector- ixodes genus of tick
Most common in the summer months

Question 23

How does Lymes disease present?

Answer 23

80-90% of cases present with erythema migrans (ring of rash)
Can be a single or multiple lesions
Most commonly presents 3-90 days after the bite
In cases of Lymes patients will often be unaware of having been bitten so it is more useful to ask if they’ve been in high risk areas (Highlands and SE England) than if they’ve been bitten.

Question 24

What are the possible complications of Lymes disease?

Answer 24

Acrodermatitis chronica atroficans- most common in elderly, causes bluish-red discoloration of the extensor surfaces of distal extremities and peripheral neruopathy
Lymphocytoma- bluish solitary painless nodule, most common on earlobe or areola. Affects children more than adults
Neuroborreliosis- triad of peripheral facial nerve palsy, radicular pain + lymphocytic meningitis. Symptoms begin 2-6 weeks after bite. Lumbar puncture will show high lymphocyte count

Question 25

What complications of Lymes are common in the US?

Answer 25

Cardiac complications

Arthritis

Question 26

How is Lymes disease diagnosed?

Answer 26

Clinically if EM present
High serology titres
Blood tests often give false negatives so are detrimental

Question 27

How is neuroborreliosis in Lymes diagnosed?

Answer 27

Clinical + laboratory
Requires:
-Neuro symptoms consistent with LNB & other causes excluded
-CSF pleocytosis (WBC in CSF), often lymphocytic
-Paired blood and CSF serology

Question 28

How is Lyme’s disease treated?

Answer 28

Oral doxycycline (first line), amoxicillin or IV ceftriaxone for 21 days in most cases
If associated arthritis or ACA then treat for 28 days