Zoonoses Flashcards
What are zoonoses?
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
What are anthroponoses?
Infections where humans infect animals
What are the features of monkeypox?
Endemic in central and west Africa
Characterised by a vesicular rash
What are the features of rabies?
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
What are the symptoms of a rabies encephalitis?
Malaise, headache & fever Progression to mania, lethargy & coma Over production of saliva & tears Unable to swallow & ‘hydrophobia’ Death by respiratory failure
How is rabies diagnosed?
PCR of saliva or CSF most useful tests
Diagnosis often confirmed post mortem
How is rabies treated?
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
How is brucellosis transmitted?
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
What are the characteristics of the brucellosis bacteria?
Gram negative coccobacilli
Incubation period of 5-30 days but can be up to 6 months
What are the characteristics of the acute brucellosis presentation?
Lasts 1-3 weeks High, undulant fever Weakness Headaches Drenching sweats Splenomegaly
What are the characteristics of the sub-acute brucellosis presentation?
Lasts over one month
Fever
Joint pain (knee, hip, back sacroiliac joints)
What are the characteristics of the chronic brucellosis presentation?
Lasts for months or years Flu-like symptoms Malaise Depression Chronic arthritis Endocarditis Epididymo-orchitis Rarely meningism Splenomegaly
What are the characteristics of the subclinical brucellosis presentation?
Most common presentation
50% have positive serology
How is brucellosis treated?
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
What are the characteristics of leptospirosis icterohaemorrhagia?
Common in fish working populations
Symptoms start as flu-like before developing jaundice and renal failure
What are the characteristics of leptospirosis hardjo?
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
What are the characteristics of leptospirosis bacteria?
Thin, highly mobile spirochaetes
Can survive in environment for months
When is incidence of leptospirosis disease increased?
Occupational disease
Recreational disease
Emerging increase in natural disasters
Unexplained increase in Thailand
What are the symptoms of leptospirosis infection?
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
How is leptospirosis diagnosed?
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
How is leptospirosis treated?
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
What is lyme borrelios and how is it transmitted to humans?
Spirochaete found in deer
Transmitted to humans via vector- ixodes genus of tick
Most common in the summer months
How does Lymes disease present?
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.
What are the possible complications of Lymes disease?
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
What complications of Lymes are common in the US?
Cardiac complications
Arthritis
How is Lymes disease diagnosed?
Clinically if EM present
High serology titres
Blood tests often give false negatives so are detrimental
How is neuroborreliosis in Lymes diagnosed?
Clinical + laboratory
Requires:
-Neuro symptoms consistent with LNB & other causes excluded
-CSF pleocytosis (WBC in CSF), often lymphocytic
-Paired blood and CSF serology
How is Lyme’s disease treated?
Oral doxycycline (first line), amoxicillin or IV ceftriaxone for 21 days in most cases If associated arthritis or ACA then treat for 28 days
