Zoonosis Flashcards
What is zoonosis?
Infectious disease transmitted naturally between humans and animals wild or domestic
Zoonotic in animal reservoirs and transmits to humans with little onward spread
Describe zoonotic spread to humans
Now established human transmission with no/ little ongoing zoonotic transmission - HIV
Both typically cause stably endemic disease with localised outbreaks
Efficient transmission once transmitted from host - typically rapidly spreading sizeable outbreaks
How are zoonotic diseases transmitted?
Airborne
Vectors - infected agents from animals
Close proximity to animals - faecal/ oral transfer
Food-borne
Direct contact from animals - bites from infected animals
What is needed for spill over from zoonotic pool to human infection?
Ecological contact
Phylogenetic distance
Viral traits
What are risks for zoonosis?
Human living environments
Natural ecosystems
Food and agriculture
All can cause disease emergence, re-emergence and persistence
Can reservoir be predicted?
Largely found to be host neutral
Bats and rodents carried no higher prediction than for their size of groups
Largely predictable without need for invoking special ecology or immunological relationships
What are common UK zoonosis?
Salmonella
Campylobacter
Toxoplasma
Ringworm/ dermatophytosis
What are uncommon UK zoonosis?
Anthrax, rabies, bubonic plaque, tularaemia and acute brucellosis
What is not zoonosis?
Malaria
Schistosomiasis
Onchocerciasis
Elephantiasis
Because they are transmitted from animals by depend on human host as part of their life cycle - not an accidental spill over
What is anthroponosis?
Reverse zoonosis in that humans are infecting animals
Ex. influenza, step throat, leishmaniasis and chytridiomycosis
What are some complex interacting reasons for pathogen emergence?
Changing land use
Human population growth
Globalisation and air travel
Changing human behaviours - travel, meat eating, exotic pets and closer interaction to wildlife
Describe the connection of food security and zoonosis
Increasing global meat consumption and production
Intensification of livestock production
Substandard animal welfare
Inadequate disease surveillance
Improper preparation or slaughter
Incomplete understanding of pathogen lifecycles
What is Lyme disease?
Spirochete found in wild dear
Transmitted by tick - lxodes ricinus
Commonest in summer months
Borrelia Burgdorferi
What is the Lyme vector?
Lxodes genus - ricinus (Europe), scapilaris and persulcatus
What is erythema migrans?
Classic presentation mark of Lyme disease
3-90 days after the bite
Mainly single lesion but can have multiple
What are some Lyme disease symptoms?
Fever, chills, fatigue, fatigue and erythema migrans
Later - facial palsy, irregular heartbeat and dizziness
Describe neuroborreliosis
Triad of facial nerve palsy, radicular pain and lymphocytic meningitis
Onset of symptoms 2-6 weeks after bite
Preceded by EM in 30-50%
How is Lyme disease diagnosed?
If erythema migrans rash present - offer antibiotics
If not then offer ELISA test
Positive then offer immunoblot test
If positive then offer antibiotics and negative then alternative diagnosis
What is the treatment for Lyme disease?
First line is Doxycycline
Then amoxicillin if child
Neuro Lyme - Ceftriaxone
Describe Leptospirosis
Spirochete
One of the most widespread zoonosis
Many reservoir hosts
Survive in the environment for weeks to months
Penetrate abraded skin or mucous membranes to cause systemic illness
What are the symptoms of leptospirosis?
Undifferentiated fever, myalgia, headaches and abdominal pain
Severe disease - Weil’s disease and pulmonary haemorrhage
How is leptospirosis spread?
Human is incidental host - direct contact with animal
Contact with environment contaminated with their urine
Incubation is 20-30 days
What are the investigations for leptospirosis?
Clinical suspicion
Serology - IgM and IgG
Microscopic agglutination test
What is the treatment for leptospirosis?
Doxycycline
Amoxicillin or azithromycin as second line
Severe disease - ceftriaxone
Describe rabies
Viral infection transmitted from bite of an infected animal
Wide range of wild animal transmitters - dogs, bats, monkeys, foxes, racoons…
Incubation is 1-3 months but may be years
Describe the pathogenesis of rabies
Virus enters tissue from saliva of biting animal
Virus replicates in muscle near bite
Virus moves up peripheral nervous system to CNS in spinal cord
Virus reaches brain and causes fatal encephalitis
Enters salivary glands and other organs
What are the symptoms of rabies?
Furious - hydrophobia, insomnia, confusion, agitation and coma
Paralytic - ascending flaccid paralysis, fever, confusion and coma
What is the investigations for rabies?
PCR of skin biopsy and saliva
Often post mortem confirmation - brain biopsy
What is the treatment for rabies?
Nil effective
Milwaukee protocol
What is the post-exposure treatment for rabies?
Fully immunised - 2 doses on day 0 and 3-7
Not immunised and immunocompetent - HCG and 4 doses
Not immunised and immunocompromised - HRIG and 5 doses
Describe Ebola
Filovirus
West and central Africa
5 species
Numerous outbreaks
Most recent was 2014-16
How is Ebola transmitted?
Animal to animal transfer - bats are host
Spill over event
Human to human transmission
Survivor - has tiredness and muscle aches
What are the symptoms of Ebola?
Dry - fever, fatigue and aches + pains
Wet - vomiting, diarrhoea and haemorrhage
What is the incubation period for Ebola?
2-21 days
Average - 8-10 days
What are the investigations for Ebola?
PCR
Serology - IgM and IgG
What is the treatment and vaccination for Ebola?
INMAZEB - 3 monoclonal antibodies
EBANGA - 1 monoclonal antibody
Vaccine - Ervebo - 1 dose during outbreak. Zabdeno and Mvabea - 2 doses of each
What type of infection can zoonosis be?
Bacterial, viral, fungal and priron
