Zoonoses

Question 1

what are zoonoses?

Answer 1

infections that can pass between living animals and humans. the source is the animal

Question 2

give examples of infections that are NOT zoonoses. why are they not?

Answer 2

• Malaria
• Schistosomiasis (snail fever)
• Onchoceriasis (river blindness)
• Elephantiasis (lymphatic filariasis)
Although these infections are transmitted from animals they depend on the human host for part of
their life-cycle therefore they are NOT zoonoses.

Question 3

what are anthroponosis?

Answer 3

reverse zoonoses in that humans infect animals

Question 4

give examples of anthroponosis’

Answer 4

• Influenza (virus affecting birds, pigs)
• Strep throat (bacteria affecting dogs)
• Leishmaniasis (parasite affecting dogs)
• Chytridiomycosis (fungus affecting amphibians)

Question 5

give examples of bacterial zoonoses

Answer 5

salmonella
campylobacter
shigella
anthrax
brucella
e. coli (verotoxigenic)
leptospirosis
plaque
psittacosis (omitosis)
q fever
tularaemia

Question 6

give examples of viral zoonoses

Answer 6

rabies
avian flu
crimea-congo haemorrhagic fever
ebola
lassa fever
rift valley fever
west nile fever
yellow fever

Question 7

give examples of parasite zoonoses

Answer 7

cystercosis
echinococcosis
toxoplasmosis
trichhinellosis
viscercal larva migrans (toxocara)

Question 8

give examples of fungal zoonoses

Answer 8

dermatophytosis

sporotrichosis

Question 9

give examples of piron zoonoses

Answer 9

BSE

CJD

Question 10

what are emerging zoonoses?

Answer 10

This is 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.

Question 11

give examples of emerging zoonoses

Answer 11

avain flu
nipha virus
rabies
brucellosis
monkeypox

Question 12

discuss a rabies infection

Answer 12

This is a viral infection (lyssavirus) transmitted from the bite of an infected animal. There is a wide range of wild animal transmitters: dogs account for 97% then bats, also monkeys, foxes, racoons, skunks, wolves and cats. Around 55,000 people, mainly children, die each year from rabies. The incubation period in humans is around 2 weeks to several months. Rabies virus travels to the brain via the peripheral nerves, causing an acute encephalitis.

Question 13

sequelae of rabies

Answer 13

• Malaise, headache and fever
• Progressing to mania, lethargy and coma
• Over production of saliva and tears
• Unable to swallow and hydrophobia
• Death by respiratory failure

Question 14

post bite prophylaxis for rabies

Answer 14

human rabies immunoglobulin
infiltrated round bite if possible
+4 doses of rabies vaccine over 14 days

Question 15

discuss the effects of brucellosis

Answer 15

This used to be an occupational hazard of farmers, vets and slaughterhouse workers etc. the organisms are excreted in milk, placenta and aborted foetus. Humans are infected:
• During milking infected animals
• During parturition
• Handling carcasses of infected animals
• Consumption of unpasteurised dairy products
Brucellosis is now a rare disease in the UK. Brucella is a small gram negative coccobacilli.

Question 16

incubation period for brucella

Answer 16

5-30 days up to 6 months

Question 17

acute presentation of brucellosis

Answer 17

a. Lasts 1-3 months
b. High “undulant” fever
c. Weakness, headaches
d. Drenching sweats
e. Splenomegaly
f. Very rare in Scotland

Question 18

subacute presentation of brucellosis

Answer 18

> 1 month

fever and joint pains esp knee, hip, back SI joints

Question 19

chronic presentation of brucellosis

Answer 19

months - years
flu like symptoms, malaise, depression, chronic arthritis, endocarditis, epididymo-orchitis
rarely meningism and splenomegaly

Question 20

subclinical presentation of brucellosis

Answer 20

most common form

50% of exposed have positive serology

Question 21

treatment of brucellosis

Answer 21

Treat using long acting doxycycline for 2-3 months + rifampicin or + IM gentamycin for first week(s). relapses occur due to intracellular organism. The chronic form of brucellosis is difficult to treat. In cases of CNS disease add cotrimoxazole for two weeks.

Question 22

discuss leptospirosis

Answer 22

• Was common in NE Scotland fish workers
o Due to L. icterohaemorrhagica
o Described in Fife miners – bitten by rats
o Flu like symptoms then jaundice and renal failure
• But now L. hardjo (cattle) is commonest form
o Fever, meningism – no jaundice
o 11% of dairy workers have positive serology
o Most have no history of illness
• Thin, highly mobile spirochetes
• One of the widest spread zoonosis
• May reservoir host
• Survive in the environment for weeks to months
• Penetrate abraded skin or mucous membranes and cause systemic illness
• Epidemiology
o Traditionally an occupational disease
o Recreational – Borneo Eco Challenge 2000
o Unexplained emergence in Thailand 30-40,000 case at end of 1990s
o Climate change/disaster are associated with outbreaks (typhoon in the Philippines in
2009, Hurricane in Costa Rica 2017)
• Humans are incidental hosts
o Direct contact with the animal
o Contact with the environment (water) contaminated with their urine
o Incubation 2-30 days (10-14)
• Undifferentiated fever, myalgia, headaches, and abdominal pain
• Severe disease in 5-15%
o Weil’s disease (triad of jaundice, AKI, bleeding)
o Pulmonary haemorrhage
o Cause fatality in 5-40%, > 50% of those with PH

Question 23

diagnosis of leptospirosis

Answer 23

think if: fever in cattle farmer, exposure to water or rats, farmer with flu more likely leptospirosis than brucellosis
microscopic agglutination test required paired sera
ELISA serology
PCR
Culture

Question 24

treatment of leptospirosis

Answer 24

Early
§ Lack of evidence for antibiotics but most effective during early phase
§ Doxycycline for mild
§ IV penicillin for severe
§ Steroids do not help
o Prompt dialysis
o Mechanical ventilation

Question 25

discuss lyme borrelios

Answer 25

• Clustering of childhood arthritis in Old Lyme, Connecticut, USA in 1977
• Burgdorferi found cause in 1982 – hence Borrelia burgdorferi
• Spirochete found in wild deer
• Transmitted by tick, ixodes Ricinus
• Commonest in summer months
• Vector
o Ixodes genus (i. richinus Europe, i. scapularis ipacificus North America, i. persulcatus
Asia)
o Active in > 4°C, humidity
• Erythema migrans
o 80-90% of cases
o Clinical diagnosis
o 3-90 days after the bite (7-30)
o Single or multiple lesions
• Acrodermatitis Chronica Atroficans (ACA)
o European (B. Afzelli)
o Elderly people
o Extensor surfaces of distal extremities
o Bluish-red discolouration – progresses over months to years to atrophic phase
o Peripheral neuropathy common
• Lymphocyte
o Bluish solitary painless nodule
o Earlobe or areola
o Children > adults
• Neuroborreliosis
o Approx. 15% of patients develop NB
o Triad of:
§ Facial nerve palsy
§ Radicular pain – 70-85% migratory, worse at night
§ Lymphocytic mengitis
o Onset of symptoms 2-6 (!-12) weeks after bite
o Preceded by EM in 30-50%
• Lyme Borreliosis – USA
o Cardiac disorders more common (8-10%)
§ Carditis (peri-myocarditis)
§ Heart block
o Arthritis more common
§ Large joints, often knees

Question 26

diagnosis of lyme disease

Answer 26

o EM is a clinical diagnosis
o ACA and lymphocytoma clinical and high serology titres
o Arthritis – very high serology titres from synovial fluid. PCR
o Clinical and laboratory findings
§ Neuro symptoms consistent with LNB and other causes excluded
§ CSF pleocytosis (WBC in CSF), often lymphocytic
§ Paired blood and CSF serology

Question 27

treatment of lyme disease

Answer 27

o Oral doxycycline or amoxicillin, or IV ceftriaxone

o Most manifestations treat for 21 days, 28 das in arthritis or ACA