113. Listeriosis (Zoon.).

Question 1

Occurrence?

Answer 1

Occurrence:

• worldwide,
• sporadic (some years more frequent than others),
• moderate/colder climate (NOT tropical)

Question 2

Aetiology?

Answer 2

Aetiology

• Gr +ve, non-spore forming bacteria
• (bacterium attach to each other ʹ contains mycolic acid and lipoids in cell wall),
• facultative pathogen
• Listeria monocytogenes, L. ivanovii
• both agents cause exactly the same disease (do not need to differentiate)
• Habitat: soil, gut, water, silage, food
• Replication: 0-42oC (optimal ~35-36oC) ʹ
• wide temp range where the bacteria can replicate (can replicate in the environment as well! ʹ influences pathogenesis)
• Culture (blood agar ʹ can see haemolysis), selective enrichment ʹ inoculate & put media into the fridge where the normal bacteria cannot grow but listeria can! (cold enrichment: 4-6c,U-tube)
• Antigen structure (16 serotypes: 1/2a, 4b most frequent, ͙͘Ϳ
• composite antigen structure,
• composition of antigens allows us to differentiate the serotypes
• majority belong to 1a serotype
• Virulence factors:
• Phospholipase
• Haemolysin/listeriolysin: causing haemolysis ʹ diameter of haemolytic zone correlates with virulence strains),
• Lipids in the cell wall: bacteria form clusters due to incr lipid content. increase resistance of the bacterium & prevent phagocytosis)
• Phospholipase & haemolysin: Anti-phagocytic effect (preventing digestion of bacterium) so that listeria
• can survive intra-cellularly
• Resistance quite good: environment, part of bacteria can survive pasteurisation (can even replicate in the
• environment as well as survive if between 0-42c)
• Disinfection can inactivate bacteria

Question 3

Epidemiology?

Answer 3

Epidemiology

• Occurrence of the agent: soil, environment water, gut; silage; puddles, pools
• From the soil ʹ can infect & replicate in the silage (important form of animal infection)
• Predisposing factors: (facultative pathogenic
• overcrowding; pregnancy, farrowing (lambing); nutritional problems (Se deficiency, mycotoxins, silage
• feeding); parasitosis
• Winter: in moderate climate - lambing at end of winter, no. of animals incr ʹ overcrowding, worse quality bedding
• No transmission from animal to animal (but animals shed bacterium in faeces); Food (dairy, veg, fruit ʹ
• source of human infection)

Question 4

Pathogenesis?

Answer 4

Pathogenesis

Infection

• Per os (from environment, feed, milk) can be shed with faeces -> blood -> brain / uterus, foetus/ udder
• (bacteriaemia/septicaemia)
• oral cavity-> facial nerve-> perineural reach brain stem directly
• Contact: conjunctivitis, keratitis
• Ascending infection: udder
• Facultatively Intra cellular bacterium:
• Virulence factors
• Æ Haemolysin, phospholipase, spreads from cell-cell
• Can live outside the host but prefers being in the infected cells!
• Virulence factors: Prevent digestion of the bacterium in the phagosome bacterium liberated& receive actin
• filaments help the bacterium to get into the neighbouring cell
• SPREADING FROM CELL TO CELL! ʹ important factor in immunity
• Wide host range BUT clinical signs restricted to small Ru, cattle, rabbits, rodents, foxes, humans

Question 5

Clinical signs?

Answer 5

Clinical signs

• Subclinical infection common
• Sheep & goat:
• encephalitis most frequent: circling (HL stays still, and FL move so going in a circle)
• strange posture ʹ ears down, head & neck in oblique position, wide stance; disorientation, leaning,
• Opisthonthus paddling legs death
• salivation secondary ʹ cause forget to close mouth
• Abortion (metritis, RFM)
• Septicaemia: in young sucking lambs
• 1-2 months: fever, depression, anorexia, death
• Conjunctivitis, keratitis, mastitis
• Cattle:
• abortion most freq: sporadic, RFM
• encephalitis: circling, less frequent, ataxia, tongue is out because forgets to close mouth, salivation
• weakness, mastitis(subclinical)
• Rodents:
• septicaemia & death
• Rabbits:
• abortion (purulent metritis always after abortion) - death
• Foxes (bred):
• encephalitis
• Birds:
• rarely septicaemia, neurologic signs (generally no clinical signs seen)

Question 6

Pathology?

Answer 6

Pathology

• Encephalitis:
• normally no gross lesions;
• Histo: brain stem, medulla oblongata micro abscesses
• Abortion:
• autolysis (foetus dies 0.5-1 days before the abortion); focal inflammation - necrosis in the liver =
• listerioma; reddish fluid in body cavities (rarely)
• Septicaemia (lambs):
• enlarged spleen,
• haemorrhages,
• listerioma (grey-white dots)

Question 7

Diagnosis?

Answer 7

Diagnosis

• Epidemiology (winter, sp., predisposing factors) ʹ clinical signs ʹ post mortemlesions
• Detection of the agent:
• direct smear (in case of abortion, from foetal membranes/stomach of foetus ʹ typical Gr + rods attached to eachother),
• microscopy; isolation of the bacterium (reliable!)
• Rarely used: IF, immune histochemistry, PCR
• Detection of antibodies (serology): agglutination, CFT, ELISA (cross reactions)
• Rarely used in animal medicine; more often used in human medicine

Question 8

Differential diagnosis?

Answer 8

Differential diagnosis

• Encephalitis:

1. coenurosis,
2. rabies,
3. BSE,
4. Caprine Arthritis Encephalitis,
5. pregnancy toxicosis,
6. ketosis

• Septicaemia: wide range of diseases
• Abortion:

1. chlamydiosis,
2. campylobacter,
3. salmonellosis,
4. brucellosis,
5. Q-fever

Question 9

Treatment?

Answer 9

Treatment

• Stop feeding SPOILED silage
• ABs: Penicillin, tetracycline: penmates; septicaemia
• If see CNS signs then generally cannot treat these animals successfully ʹ but CAN treat pen mates
• (metaphyllactic treatment)
• After abortion (RFM) - uterine treatment

Question 10

Prevention?

Answer 10

Prevention

• Feeding good quality silage
• Prevention of predisposing factors: r
• eduction of feeding silage (only good quality), reduction of overcrowding,
• elimination of puddles
• Vaccination: inactivated vaccine (poor effect), attenuated vaccine
• Intracellular bacteria- circulating ABs have lower importance so can’t be successful with inactivated
• vaccines
• Attenuated vaccines ʹ cannot be sure how safe they are (zoonosis risk): NOT on the market in Europe

Question 11

Public health aspects - ZOONOSIS?

Answer 11

Public health aspects - ZOONOSIS

• Infection
• Animal contact frequently not detected
• Environment, food (milk, dairy products ʹ raw milk soft cheeses, frozen fruit & veg)
• Diseases: foetuses, newborns (foetopathy, stillbirth, septicaemia), patients with other diseases
• All age groups can be affected but young (newborn <1y & foetuses) & elderly are mostly affected
• Clinical signs: fever, abdominal pain, diarrhoea, meningoencephalitis (CNS signs mosttypical)
• HIGH lethality
• Treatment: penicillin, erythromycin (frequently not successful)
• Prevention: pasteurisation of milk, washing vegetables & fruits, hygiene in the kitchen, cooking