177. Q-fever (Zoon.).

Question 1

Q fever - Zoonosis Occurence Aetiology and Morphology?

Answer 1

Q-fever - ZOONOSIS

• Wide host range: mammals (Ru mainly), birds, humans
• History: 1935 Australia ʹ query fever

Occurrence: worldwide, Europe

Aetiology:

• Coxiella burnetii
• Coxiellaceae family - not rickettsia; Gram-negative
• Modified Ziehl-Neelsen (Stamp), Giemsa staining

Morphology:

• Small cell variant: inactive, good resistance in the environment (>1 year), outer membrane proteins
• Resembles the elementary body of chlamydia
• Resist dehydration: survive in environment for long time
• Large cell variant: phagolysosome, low pH; good resistance intracellular
• Metabolically active form
• Intracellularly resistant against lysosomal enzymes, pH in the lysosome
• Replication only in living cells (like Chlamydia): embyonated egg, tissue culture, laboratory animals
• Intracellular, obligate bacterium ʹ has own metabolism like other bacteria but needs nutrients from the host cells
• Virulence variants: virulent, avirulent (asymptomatic infections are common)

Question 2

Epidemiology?

Answer 2

Epidemiology

• Focal infection: rodents, birds, wild living animals, farm animals, ruminants ʹ maintaining host (mostly rodents/birds)
• Ticks (true vector ʹ can replicate and overwinter): passage in ticks increases virulence
• Spreading: Ticks, abortion (foetus, foetal membranes, foetal fluid), discharges (milk, faeces, urine, saliva etc.),
• dog (eating foetal membranes), dust

Question 3

Pathogenesis?

Answer 3

Pathogenesis

• Obligate IC bacterium
• Infection: cutaneous /PO/ aerosols:
• small cell variant
• transformation to large cell variant
• Septicaemia: lungs, liver,
• uterus, udder, lymphoid tissues
• Shedding: faeces, urine, milk, saliva
• Immuneresponse(not a good antigen) -> bacterium kicked out from blood circulation, but can replicate in the foetus & remain & remain in the udder & gut epithelium
• foetus & remain in the udder & gut epithelium (long lasting shedding with faeces & milk)
• Agent withdraws:
• Gut, udder: long carriage
• Foetus, foetal membranes: haemorrhagic-necrotic placentitis, abortion, stillbirth, non-viable
• newborns

Question 4

Pm lesions and diagnosis?

Answer 4

PM lesions (no PM lesions in cows)

• Foetal membranes: oedema, haemorrhages, necrosis of cotyledons, fibrin
• Foetus: enlarged parenchymal organs, liver ʹ serous hepatitis (histology), focal inflammation & necrosis

Diagnosis

• Epidemiology ʹ clinical signs ʹ PM lesions (haemorrhagic placentitis!)
• Detection of the agent: staining & microscope, IF, ELISA, PCR; isolation (not so easy to isolate from PM material,
• inoculate on tissue cultures/eggs/lab animals)
• Detection of antibodies: CFT, iIF, ELISA (abortion happens at end of pathogenesis, time for Abs to develop)

Question 5

Differential diagnosis, treatment , prevention eradication?

Answer 5

Differential diagnosis: abortions

Treatment: ABs ʹ tetracyclines (stop abortion wave, treatment of metritis, decrease of shedding)

Prevention

• Isolation of aborted animals shed bacterium after abortion)
• Disinfection
• Milk
• Diseased animals: boiled, to animals only (not for human consumption)
• Infected herd: pasteurised ʹ for human consumption

Vaccine:

• Netherlands: goats;
• Australia: sheep, rare use (prevent abortion, shedding & frequency of disease)

Eradication:

• small herds - selection;
• risk of reinfection is high b/c can survive in environment

Question 6

Public health?

Answer 6

Public health

• Zoonosis (only few bacteria necessary to infect humans)
• Apes: ID50: 1,7 bacterium (less than 2 bacteria can cause disease in a population)
• Biological warfare agent, bioterrorism
• Netherlands: 2200 cases (2009)
• Ljubljana Faculty (vet school): 36/66 seropositive students, 32 clinicalsigns
• Hungary: 2013 outbreak in sheep farm
• Infection from ruminants: PO/aerosols, occupational disease, milk, (ticks)
• Clinical signs: absent or mild; flu-like: fever, headache, myalgia, pneumonia, dry cough; chronic endocarditis, abortion,
• rash
• Diagnosis: anamnesis + clinical signs + serology
• Treatment: tetracyclines, rifampicin, fluoroquinolones
• Prevention: protecting clothes, masks (dust)
• Vaccination (not v good, can reduce number of cases, no need for regular vaccination ʹ rare outbreak)