zoonoses - optional Flashcards
define zoonoses
infections that can pass between living animals and humans
the source of disease is from the animal
4 examples of diseases that aren’t zoonoses and why
malaria
schistosomiasis
oncoceriasis
elephantiasis
even though they are transmitted from animals they depend on the human host for part of their life-cycle
define anthroponosis
reverse zoonoses
humans are infecting animals
4 examples of anthroponosis
influenza - virus; birds, pigs
strep throat - bacteria; dogs
leishmaniasis - parasite; dogs
chytridomycosis - fungus; amphibians
what organisms can cause zoonoses
virus
bacteria
parasites
fungi
strategies developed by pathogens to ensure their own survival
causing a chronic infection to survive
non-human reservoir
examples of bacterial zoonoses
Salmonella Campylobacter Shigella Anthrax Brucella E-coli (verotoxigenic) Leptospirosis Plague Psittacosis (Ornitosis) Q fever Tularaemia
examples of viral zoonoses
Avian influenza Crimean-Congo haemorrhagic fever (CCHF) Ebola virus disease Lassa Fever Rift Valley fever West Nile Fever Yellow Fever
examples of parasitic zoonoses
Cysticercosis Echinococcosis Toxoplasmosis Trichinellosis Visceral larva migrans (toxocara)
2 examples of fungal zoonoses
Dermatophytoses
Sporotrichosis
example of prion zoonoses
BSE/CJDV
what are the 6 commonest zoonoses in the UK
salmonella campylobacter toxoplasma psittacosis Q fever ringworm/dermatophytosis
5 uncommon zoonoses in the UK
anthrax rabies bubonic plague tularaemia acute brucellosis
what is an emerging zoonoses
zoonosis that is newly recognized or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range
5 examples of emerging zoonoses
avian influenza nipah virus rabies brucellosis monkeypox
how is rabies transmitted
viral infection
bite of an infected animals
97% dogs, bats, monkeys, foxes, racoons, skunks, wolves, cats
mortality of rabies
~550 000 (mainly children) die p/a
incubation period of rabies in humans
2wks up to several mths
how does rabies get to the brain
travels via peripheral nerves
clinical features of rabies
causes an acute encephalitis
malaise, headache, fever progresses to mania, lethargy and coma over production of saliva and tears unable to swallow and hydrophobia death by respiratory failure
diagnosis of rabies
difficult
PCR of saliva or CSF
often confirmed post-mortem on brain biopsy
prognosis of rabies
always fatal if untreated
treatment of rabies
post-exposure prophylaxis immediately after the bite
- human rabies immunoglobulin (HRIG)
- infiltrated around the bite if possible
- 4 doses of rabies vaccine over 4 days
who was at main risk of brucellosis
used to be occupational hazard of farmers, vets, slaughterhouse workers etc
where are brucellosis organisms excreted
in milk, placenta and aborted foetus
when are humans infected with brucellosis
during milking of infected animals
during parturition
handling carcasses of infected animals
consumption of unpasteurised dairy products
what organism causes brucellosis
brucella
small, gram -ve coccobacilli
3 species of brucella
melitensis
suis
abortus
which species of brucella is most and least virulent
most - melitensis
least - abortus
animal hosts of brucella species
melitensis - goats, sheep, camels
suis - pigs
abortus - cattle, buffalo
geographic area of brucella species
melitensis - Mediterranean, S america, China, India, middle east
suis - N and S america, SE asia
abortus - worldwide
incubation period of brucellosis
5-30 days
up to 6mths
symptoms of brucellosis
acute - now very rare in scotland
subacute
chronic
subclinical - commonest
acute presentation of brucellosis
lasts 1-3wks
high ‘undulant’ fever
weakness, headaches, drenching sweats
splenomegaly
subacute presentation of brucellosis
lasts >1mth
fever and joint pains - knee, hip, back SI joints
chronic presentation of brucellosis
lasts for mths-yrs flu-like symptoms malaise depression chronic arthritis endocarditis epididymo-orchitis rarely meningism splenomegaly
subclinical presentation of brucellosis
most common form
50% of exposed have +ve serology
treatment of brucellosis
long acting doxycycline for 2-3mths
+ rifampicin
or + IM gentamycin for first wk
chronic form is difficult to treat
add co-trimoxazole for 2wks in CNS disease
relapse in brucellosis
occurs due to intracellular organism (5-10%)
who gets leptospirosis
was common in NE scotland fish workers
Fife miners - rat bites
11% of dairy workers have +ve serology
most have no hx of illness
leptospirosis causative organism
L. iceterohaemorrhagica
now L. hardjo (cattle) is commonest form
thin, highly mobile spirochaetes
clinical presentation of leptospirosis
L. iceterohaemorrhagica: flu like symptoms
then jaundice and renal failure
L. hardjo:
fever, meningism, no jaundice
leptospirosis reservoir
many reservoir hosts - mammals
survive in the environment for wks-mths
how does leptospirosis enter the body
penetrate abraded skin or mucous membranes and cause systemic illness
leptospirosis risk factors
planting, weeding, harvesting
hunting, gutting, skinning, butchering
canoeing, bathing, swimming
fishing, clamming
changing epidemiology of leptospirosis
traditionally an occupational disease
emerging:
recreational - borneo eco challenge 2000
unexplained emergence in Thailand - late 1990s
climate change/disaster associated outbreaks - phillipines typhoon 2009, costa rican hurricane 2017
human hosts and leptospirosis
humans are incidental hosts
- direct contact w/ the animal
- contact w/ environment (water) contaminated w/ their urine
- incubation 2-30 days (10-14)
symptoms of leptospirosis
undifferentiated fever, myalgia, headaches, abdo pain
leptospirosis - severe disease
occurs in 5-15%
Weil’s disease: triad of jaundice, AKI, bleeding
pulmonary haemorrhage (PH)
case fatality 5-40%, >50% in PH
diagnosis of leptospirosis
think is it likely?
- fever in cattle farmer
- exposure to water or rats
- farmer w/ protracted flu-symptoms is more likely to have leptospirosis than brucellosis
microscopic anticoagulation test - not useful in clinical context
ELISA serology - suboptimal
PCR
culture - at least 1/wk on special media
treatment of leptospirosis
early treatment
- abx are most effective during early phase of disease
doxycycline for mild disease, IV penicillin for severe
steroids don’t help
prompt dialysis
mechanical ventilation
how is Lyme borrelios transmitted
spirochaete found in wild deer
transmitted by tick (Ixodes ricinus)
commonest in summer mths
vector of Lyme borrelios
Ixodes genus ticks
I. ricinus - europe
I. scapularis/pacificus - N america
I. persulcatus - Asia
active >4C, humidity
causative organism of Lyme borrelios
borrelia burgdorferi
erythema migrans (EM) in Lyme borrelios
80-90% of cases
clinical diagnosis
3-90 days after the bite (7-30)
single or multiple lesions
acrodermatitis chronica atroficans (ACA) in Lyme borrelios
european (B. afzelii) elderly people extensor surfaces of distal extermities bluish-red discolouration - progresses over mths-yrs to atrophic phase peripheral neuropathy common
lymphocytoma in Lyme borrelios
bluish solitary painless nodule
earlobe or areola
children > adults
what 5 of Lyme borrelios pts develop neuroborreliosis (NB)
~15%
symptoms of NB
triad of facial nerve palsy, radicular pain and lymphocytic meningitis
- radicular pain (70-85%), migratory, worse at night
- cranial neuropathy (~50%)
onset of symptoms 2-6 (1-12) wks after bite
preceded by EM in 30-50%
lyme borreliosis - USA
cardiac disorders more common (8-10%)
- carditis (peri-myocarditis)
heart block
arthritis more common
- large joints, often knees
diagnosis of Lyme borrelios
EM is a clinical diagnosis - no lab needed
ACA and lymphocytoma clinical and high serology titres
arthritis - very high serology titres from synovial fluid. PCR
- clinical + lab findings
- neuro symptoms consistent w/ LNB and other causes excluded
- CSF pleocytosis (WBC in CSF), often lymphocytic
- paired blood + CSF serology
Lyme treatment
oral doxycycline or amoxicillin or IV ceftriaxone
most manifestations treat for 21 days (28 in arthritis or ACA)
