Zoonoses Flashcards
What are zoonoses?
Infections that can pass between living animals and humans
Source of disease is the animal
WHO; infections that are naturally transmitted between vertebrate animals and humans
What is not a zoonose?
Malaria
Schistosomiasis
Oncoceriasis
Elephantitis
Because even though transmitted from animals, they depend on human host for part of their life cycle
What is anthroponosis?
‘Reverse zoonoses’
Humans infecting animals e.g. influenza, strep throat, leishmaniasis
What can cause zoonoses?
Viruses, bacteria, parasites, fungi
Pathogens have developed strategies to ensure their own survival
- causing a chronic infection to survive
- or have a non-human reservoir
What are some bacterial zoonoses?
- salmonella
- campylobacter
- shigella
- anthrax
- brucella
- E coli
- leptosporiasis
- plague
- psittacosis
- Q fever
- tularaemia
What are some viral zoonoses?
- rabies
- avian influenza
- crimean-congo haemorrhagic fever
- ebola virus disease
- lassa fever
- rift valley fever
- west nile fever
- yellow fever
What are some parasitic zoonoses?
- cysticercosis
- echinococcosis
- toxoplasmosis
- trichinellosis
- visceral larva migrans
What are some fungal zoonoses?
- dermatophytoses
- sporotrichosis
What are emerging zoonoses?
A zoonosis that is newly recognised or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range
i.e. avian influenza
Describe rabies infection
Viral infection transmitted from bite of infected animal
Wide range of animal transmitters, most commonly dogs 97%
incubation period humans 2 weeks to several months
Travels to brain via peripheral nerves
Causes acute encephalitis
What are symptoms of rabies?
Malaise, headache, fever
Progressing to mania, lethargy and coma
Over production saliva and tears
Unable to swallow and hydrophobia
Death by respiratory failure
Describe rabies diagnosis
Difficult
- PCR of saliva or CSF
- Often confirmed post mortem on brain biopsy
Always fatal if untreated
Describe rabies management
Immediately after bite give post-exposure prophylaxis
- human rabies Ig
- infiltrated round bite if possible
- +4 doses of rabies vaccine over 14 days
Describe brucellosis
Used to be occupational hazard of farmers, vets etc.
Organisms excreted in milk, placenta and aborted foetus
Humans are infected
a) during milking infected animals
b) during parturition
c) handling carcasses of infected animals
d) consumption unpasturised dairy products
NOW RARE IN UK
Describe brucella
Small, gram negative coccobacilli
3 species
- melitensis
- suis
- abortus
Incubation period up 5-30days
Describe symptoms of brucellosis
Acute lasts 1-3 weeks
- high ‘undulant’ fever
- weakness, headaches
- drenching sweats
- splenomegaly
Subacute over 1 month
- fever and joint pains
Chronic for months or years
- flu-like symptoms, malaise, depression, chronic arthritis
- endocarditis, epididymo-orchitis, rarely meningism, eplnomegaly
Subclinical is most common form
- 50% of exposed have positive serology
Management of brucellosis
Long acting doxycycline for 2-3 months + rifampicin or + intramuscular gentamicin for first week(s)
Relapses occur due to intracellular organism (5-10%)
Chronic form - difficult to free
Add cotrimoxazole for 2 weeks in CNS disease
Describe leptospirosis illness
Was due to L.icterohaemorrhagica
Flu-like symptoms - then jaundice and renal failure
But now L.hardjo (cattle) is most common form; 11% dairy workers have positive serology and most have no history of illness
Fever, meningism - no jaundice
Describe leptospirosis bacteria
Thin, highly mobile spirochaetes
One of the most widespread zoonosis
Many reservoir host
Survive in environment for weeks to months
Penetrate abraded skin or mucous membranes and cause systemic illness
Describe symptoms of leptospirosis
Undifferented fever, myalgia, headaches and abdo pain
Severe disease in 5-15%
- Weil’s disease (triad of jaundice, AKI, bleeding)
- pulmonary haemorrhage (PH)
- case fatality 5-40%, >50% in PH
Describe diagnosis of leptospirosis
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
Describe management of leptospirosis
Early treatment
- lack of evidence that antibiotics are effective
- doxycycline for mild disease, IV penicillin for severe
- steroids do not help
Prompt dialysis
Mechanical ventilation
Describe lyme borrelios
Spirochaete found in wild deer
Transmitted by tick (ixodes genus)
Commonest in summer months
Describe erythema migrans (EM)
Occurs in 80-90% of cases of lyme borrelios
3-90 days after bite
Single or multiple lesions
Describe acrodermatitis atroficans (ACA)
European, elderly people
Extensor surfaces of distal extremities
Bluish red discolouration; progresses over months to years to atrophic phase
Peripheral neuropathy common
Describe lymphocytoma
Bluish solitary painless nodule
Earlobe or areola
Children>adults
Describe neuroborreliosis (NB)
App 15% Lyme disease patients develop NB
Triad of facial nerve palsy, radicular pain an lymphocytic meningitis
- radicular pain; migratory, worse at night
- cranial neuropathy; facial palsy ~50%
Onset of symptoms 2-6 weeks after bite
Preceded by EM in 30-50%
How do you diagnose lyme disease?
EM a clinical diagnosis; no lab needed
ACA and lymphocytoma clinical and high serology titres
Arthritis; high serology titres from synovial fluid, PCR
NB, clinical + lab;
- neuro symptoms consistent with LNB and other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytotic
- paired blood and CSF serology
Treatment of lyme disease
Oral doxycycline or amoxicillin, or IV ceftriaxone
Most manifestations treat for 21 days (28 days in arthritis or ACA)
What are some manifestations of lyme disease?
- erythema migrans
- acrodermatitis chronica atroficans (ACA)
- lymphocytoma
- neuroborreliosis (NB)
- arthritis
