Zoonoses Flashcards
Define the term zoonosis
• 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
Give examples of zoonoses
○ Salmonella ○ Campylobacter ○ Toxoplasma ○ (Psittacosis – Chlamydophila psittaci) ○ (Q-fever - Coxiella Burnetti) ○ Ringworm/ dermatophytosis ○ Anthrax ○ Rabies ○ Bubonic plague ○ Tularaemia ○ Acute brucellosis
What is the epidemiology of these disease?
- It is likely that most modern infectious diseases originated in animal
- Of the 1415 pathogens currently known to affect humans, 61% are zoonotic
What is Rabies?
○ 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
What are the symptomsof Rabies?
- Malaise, headache & fever
- Progressing to mania, lethargy & coma
- Over production of saliva & tears
- Unable to swallow & ‘hydrophobia’
- Death by respiratory failure
Why is the diagnosis of Rabies difficult?
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
True or false: Rabies is always fatal if untreated?
True
What is the treatment for Rabies?
○ 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
What is Brucellosis?
○ (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)
What is the aetiology of Brucellosis?
- Milking infected animals
- During parturition
- Handling carcasses of infected animals
- Consumption of unpasteurized dairy products
What are the acute symptoms of brucellosis?
□ Lasts 1-3 weeks □ High ‘undulant’ fever □ Weakness, headaches □ Drenching sweats □ Splenomegaly
What are the subacute symptoms of brucellosis?
□ Lasts over 1 month
□ Fever and joint pains (knee, hip, back SI joints)
What are the chronic symptoms of brucellosis?
□ Lasts for months or even years □ Flu-like symptoms □ Malaise □ Depression □ Chronic arthritis □ Endocarditis □ Epididymo-orchitis □ Rarely meningism □ Splenomegaly
What are the subclinical symptoms of brucellosis?
□ commonest
□ 50% of exposed have positive
What is the management of brucellosis?
- 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
What is Leptospirosis
○ 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
What are the organisms that cause Leptospirosis and what do they do?
○ 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
How is Leptospirosis transfered?
○ Humans are incidental hosts
- Direct contact with the animal
- Contact with environment (water) contaminated with their urine
- Incubation 2-30 days (10-14)
What are the genral features of Leptospirosis?
Undifferentiated fever; myalgia, headaches & abdominal pain
What happens in severe Leptosirosis?
- Well’s disease (triad of jaundice, AKI, bleeding)
- pulmonary haemorrhage
- Case fatalty 5-40%, >50% in PH
How is Leptosirosis diagnosed?
- 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
How is Leptosirosis managed?
- 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
What is Lyme Borrelosis?
○ Spirochete found in wild deer
○ Transmitted by tick, Ixodes Ricinus
○ Commonest in summer months
What is Erythema Migrans?
- 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
