Zoonoses Flashcards
WHO definition of zoonoses
-Infections that are naturally transmitted between vertebrate animals and humans
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 - Incubation period in humans – 2 weeks to several months
- Rabies virus travels to the brain via peripheral nerves
Rabies presentation
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
Rabies diagnosis
- PCR of saliva or CSF
- often diagnosed post mortem on brain biopsy
Rabies prognosis
- 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
Rabies treatment
- wound cleansing
- multiple-dose immunisation protocol
- rabies immunoglobulin
Brucellosis exposure
- (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
Brucellosis
-small gram negative coccobacilli
Brucellosis presentation
- Incubation period 5-30 days (up to 6 months)
- Symptoms
- Acute (now very rare in Scotland)
- Subacute
- Chronic
- Subclinical (commonest)
Brucellosis acute presentation
- lasts 1 - 3 weeks
- high ‘undulant’ fever
- weakness, headaches
- drenching sweats
- splenomegaly
Brucellosis subacute presentation
- lasts over 1 month
- fever and joint pains (knee, hip, back SI joints)
Brucellosis chronic presentation
- lasts for months or years
- flu-like symptoms
- malaise
- depression
- chronic arthritis
- endocarditis
- epididymo-orchitis
- rarely meningism
- splenomegaly
Subclinical brucellosis
- most common form
- 50% of exposed have positive serology
Brucellosis treatment
- 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
Leptospirosis
-the infection is caused by motile spirochetes from the genus leptospira and is maintained in nature by chronic renal infection of carrier animals
Leptospirosis is associated with:
- occupational exposure (eg cattle farmer)
- water sports
- flooding
Leptospirosis presentation
- high remittent fever
- headache
- myalgia
- conjunctival suffusion
- muscle tenderness
Leptospirosis investigations
- blood culture
- ELISA serology
- PCR
- microscopic agglutination test (MAT)
Leptospirosis treatment
- early treatment
- doxycycline for mild disease
- IV penicillin for severe
- steroids do not help - prompt dialysis
- mechanical ventilation
Lyme borrelios
- spirochaete found in wild deer
- transmitted by tick, Ixodes ricinus
- causes Lyme disease
Erythema migrans
- pathogonomic feature of Lyme disease
- usually develops within 1 - 2 weeks at the site of the tick bite
Acrodermatitis chronica atrophicans
- skin rash indicative of late stage of Lyme borreliosis
- chronically progressive course
- finally leads to a widespread atrophy of the skin
- peripheral neuropathy common
Borrelial lymphocytoma
- bluish solitary painless nodule
- earlobe or areola
Neuroborreliosis
- 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%
Lyme disease diagnosis
- Lyme specific IgM and IgG
- PCR
- EM - clinical diagnosis
- arthritis - very high serology titres from synovial fluid
Lyme disease treatment
- oral doxycycline or amoxicillin
- if central nervous system manifestations - intravenous ceftriaxome
- most manifestations treat for 21 days
- 28 days in arthritis or ACA
