Zoonoses

Question 1

Define the term zoonosis

Answer 1

• 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
• Can be caused by virus, bacteria, parasites or fungi​
• Pathogens have developed strategies to ensure their own survival/propagation​
○ causing a chronic infection to survive​
○ or have a non-human reservoir

Question 2

Give examples of zoonoses

Answer 2

○ Salmonella
○ Campylobacter
○ Toxoplasma
○ (Psittacosis – Chlamydophila psittaci)
○ (Q-fever - Coxiella Burnetti)
○ Ringworm/ dermatophytosis
○ Anthrax
○ Rabies
○ Bubonic plague
○ Tularaemia
○ Acute brucellosis

Question 3

What is the epidemiology of these disease?

Answer 3

• It is likely that most modern infectious diseases originated in animal
• Of the 1415 pathogens currently known to affect humans, 61% are zoonotic

Question 4

What is Rabies?

Answer 4

○ 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​
○ Incubation period in humans – 2 weeks to several months​
○ Rabies virus travels to the brain via peripheral nerve

Question 5

What are the symptomsof Rabies?

Answer 5

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

Question 6

Why is the diagnosis of Rabies difficult?

Answer 6

• PCR of saliva or CSF​

- Often confirmed post mortem on brain biopsy​

Question 7

True or false: Rabies is always fatal if untreated?

Answer 7

True

Question 8

What is the treatment for Rabies?

Answer 8

○ 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

Question 9

What is Brucellosis?

Answer 9

○ (Used to be) an occupational hazard of​ farmers, vets, slaughterhouse workers etc​
○ Organisms are excreted in milk, placenta and aborted foetus​
○ Brucella - small, gram negative coccobacilli​
○ Three species
- Melitensis
- Suis
- Abortus
○ Incubation period 5-30 days (up to 6 months)​

Question 10

What is the aetiology of Brucellosis?

Answer 10

• Milking infected animals​
• During parturition​
• Handling carcasses of infected animals​
• Consumption of unpasteurized dairy products​

Question 11

What are the acute symptoms​ of brucellosis?

Answer 11

□ Lasts 1-3 weeks
□ High ‘undulant’ fever​
□ Weakness, headaches​
□ Drenching sweats​
□ Splenomegaly​

Question 12

What are the subacute symptoms​ of brucellosis?

Answer 12

□ Lasts over 1 month

□ Fever and joint pains (knee, hip, back SI joints)

Question 13

What are the chronic symptoms​ of brucellosis?

Answer 13

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

Question 14

What are the subclinical symptoms​ of brucellosis?

Answer 14

□ commonest

□ 50% of exposed have positive

Question 15

What is the management of brucellosis?

Answer 15

• 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

Question 16

What is Leptospirosis

Answer 16

○ Was common in NE Scotland fish workers
○ Thin, highly mobile spirochetes​
○ 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

Question 17

What are the organisms that cause Leptospirosis and what do they do?

Answer 17

○ 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​

Question 18

How is Leptospirosis transfered?

Answer 18

○ Humans are incidental hosts​

• Direct contact with the animal​
• Contact with environment (water) contaminated with their urine​
• Incubation 2-30 days (10-14)​

Question 19

What are the genral features of Leptospirosis?

Answer 19

Undifferentiated fever; myalgia, headaches & abdominal pain

Question 20

What happens in severe Leptosirosis?

Answer 20

• Well’s disease (triad of jaundice, AKI, bleeding)
• pulmonary haemorrhage
• Case fatalty 5-40%, >50% in PH​

Question 21

How is Leptosirosis diagnosed?

Answer 21

• Think of it
• 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​

Question 22

How is Leptosirosis managed?

Answer 22

• 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​
  □ Steroids do not help​
• Prompt dialysis​
• Mechanical ventilation

Question 23

What is Lyme Borrelosis?

Answer 23

○ Spirochete found in wild deer​
○ Transmitted by tick, Ixodes Ricinus​
○ Commonest in summer months

Question 24

What is Erythema Migrans?

Answer 24

• an expanding rash often seen in the early stage of Lyme disease
• 80-90% of cases​
• Clinical diagnosis​
• 3-90days after the bite​ (7-30)​
• Single or multiple lesions​

Question 25

What is Acrodermatitis chronica atroficans?

Answer 25

• A skin rash indicative of the third or late stage of European Lyme borreliosis
• European (B. Afzelii)​
• Elderly people​
• Extensor surfaces of distal extremities​
• Bluish-red discoloration: progresses over months to years to atrophic phase​
• Peripheral neuropathy common

Question 26

What is Lymhocytoma?

Answer 26

• Indicative of stage 2 Lyme’s
• Bluish solitary painless nodule​
• Earlobe or areola​
• Children > Adults​

Question 27

What is Neuroborreliosis

Answer 27

• A neurological manifestation of Lyme disease
• 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 28

How is Lyme borrialis diagnosed?

Answer 28

• 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 & other causes excluded​
  □ CSF pleocytosis (WBC in CSF), often lymphocytic​
  □ Paired blood and CSF serology​

Question 29

What is the treatment for Lyme’s disease

Answer 29

• Oral Doxycycline or Amoxicillin, or IV Ceftriaxone​

- Most manifestations treat for 21 days (28 in arthritis or ACA)​