Zoonoses Flashcards
Definition of zoonoses
Infections that can pass between living animals and humans, where the source of the disease is from the animal
WHO definition of zoonoses
Infections that are naturally transmitted between vertebrae animals and humans
Definition of anthropnonosis
‘Reverse zoonoses’ in that humans are infecting the animals
Examples of anthropnonosis
Influenza affecting birds and pigs
Strep throat affecting dogs
Leishmaniasis affecting dogs
Definition of emerging zoonoses
A zoonosis that is newly recognised or newly evolved, or that has previously occurred but shows an increase in incidence or expansion in geographical host or vector range
Zoonoses can be caused by…
Virus
bacteria
fungus
parasite
Zoonoses pathogens developed strategies to ensure own survival/propagation including…..
Causing a chronic infection to survive
OR
Have a non-human reservoir
Examples of bacterial zoonoses
Salmonella Campylobacter Shigella Brucella E. coli (verotoxigenic) Plague Leptospirosis
Examples of viral zoonoses
Rabies Avian influenza Ebola Yellow fever West nile fever
Examples of parasitic zoonoses
Toxoplasmosis
Trichinellosis
Echinococccosis
Examples of fungal zoonoses
Dermatophystoses (Ringworm)
Sporotrichosis
What virus causes rabies?
Lyssavirus
How to catch the virus of rabies
From the bite of an infected animal
Incubation period of rabies
2 weeks to several months
Pathology of rabies once infected
Travels to brain via peripheral nerves - so where you are bitten is important
When it reaches the CNS it is 100% fatal
Causes an acute encephalitis
Presentation of rabies (once got an acute encephalitis)
Malaise Headache Fever Progressing to mania, lethargy and coma Over production of saliva and tears Unable to swallow and 'hydrophobia' Death by respiratory failure
Investigations for rabies (difficult)
PCR of saliva or CSF
Immediately after the bite, what is given?
Post exposure prophylaxis
- human rabies immunoglobulin (HRIG)
- Infiltrated around bite (if possible)
- 4 doses if rabies vaccine over 14 days
Post exposure prophylaxis of rabies
Human rabies immunoglobulin (HRIG)
Infiltrated around bite (if possible)
+ 4 doses of rabies vaccine over 14 days
What is brucellosis?
Small, gram -ve coccobacilli
Brucellosis is now a rare disease in the UK, but used to be an occupational hazard of…
Farmers
Vets
Slaughterhouse workers
Where are brucellosis organisms excreted?
Milk
Placenta
Aborted foetus
How do humans get infected by brucellosis?
During milking infected animals
During parturition
Handling carcasses of infected animals
Consumption of unpasteurised dairy products
3 species of brucellosis
Melitensis
Suis
Abortus
Most virulent species of brucellosis
Melitensis
Incubation period of brucellosis
5 - 30 days (up to 6 months)
Symptoms of brucellosis
Acute (1-3 weeks) - high undulant fever - weakness - headaches - drenching sweatings - splenomegaly Subacute (>1 month) - fever - joint pains (knee, hip, back) Chronic (months to years) - flu like symptoms - malaise - depression - endocarditis - chronic arthritis - rarely meningitis - epididymo-orchitis - splenomegaly Subclinical (commonest) - 50% of exposed have +ve serology
Treatment of brucellosis infection
Long acting doxycycline for 2-3 months + rifampicin or IM gentamycin for first week(s)
Add cotriomoxazole for 2 weeks in CNS disease
Types of leptospirosis
L. icterogaemorrhagica
L. hardjo
Where is L. icterogaemorrhagica found?
Fish
Rats
Symptoms of L. icterogaemorrhagica
Flu like symptoms
then
jaundice
renal failure
Where is L. hardjio found?
Cattle
Symptoms of L. hardjio
Fever
Meningism
NO JAUNDICE
most have no history of illness
Life cycle of leptospirosis
- thin highly mobile spirochoetes, mainly resevior host. survive in environment for weeks to months
- penetrate abraded skin or mucous membranes and cause systemic illness.
Humans are incidental hosts
What contact of leptospirosis leads a human to catch it?
Direct contact with animal
Contact with environment (water) contaminated with their urine
Incubation period of leptospirosis
2-30 days (10-14)
Symptoms of leptospirosis
Undifferentiated fever Myalgia Headaches Abdominal pain Severe disease 5-15% - weil's disease - pulmonary haemorrhage - fatality in 5-40%
Weil’s disease is a triad of….
- Jaundice
- AKI
- Bleeding
Investigations of leptospirosis
Microscopic agglutination test (MAT)
ELISA serology
PCR
Culture - take at least 1 week on special media
Treatment of leptospirosis
Early treatment - doxycycline for mild disease - IV penicillin for severe Prompt dialysis Mechanical ventilation
What is lyme borrelios and where is it found?
Spirochaete
Found in wild deer
What is lyme ricinius transmitted by?
Ticks
The vector for lyme borrelios thrives in what environment?
Active > 4C
Humidity
What time of the year is lyme borrelios most common?
Summer months
Presentation of lyme borrelios
Erythra migrans - 3-90 days after the bite ACA (acrodermatitis chronica atroficans) - elderly - blue-reddish discolouration - extensor surfaces of distal extremities - peripheral neuropathy common Lymphocytoma Neuroborreliosis (15%) - traid of facial nerve palsy, radicular pain, lymphocytic meningitis - 2-6 weeks after the bite Cardiac disorders Arthritis (large joints, often knees)
Investigations of lyme
EM clinical diagnosis
High serology titres and ACA + lymphocytoma clinical
Arthritis - very high serology titres from synovial fluid - PCR
Treatment of lyme
Oral doxycycline or amoxicillin OR
IV ceftrixazone
Most manifestations treat for 21 days (28 days in arthritis or ACA)
