C611 - LISTERIOSIS

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C611 - LISTERIOSIS

Nature of the disease
Listeriosis is an opportunistic bacterial disease caused by Listeria monocytogenes. It affects a large range of animal species and is a severe zoonosis. 
Classification
OIE, List C disease
Susceptible species
Many species are susceptible: bovines, ovines, caprine, equines, porcine, rabbits, birds, humans. 
Distribution
Listeriosis is worldwide distributed. In the Pacific Region it is known to occur in Australia and in New Zeeland, it has never been reported from Guam and Vanuatu, elsewhere the disease is poorly documented.
Clinical signs 
In adult bovines and ovines the listeriosis often appears as an encephalitis. Signs include:
  • Fever, anorexia
  • Conjunctivitis,
  • Opisthotonos, Paralysis,
  • Facial paralysis, flaccid lip and lowered eye lip, salivation,
  • Involuntary movements, circling movements
  • Coma,

Recovery rate is about 50 % in cattle and 30% in small ruminants.

In pregnant animals late abortion is common, sometimes mastitis. 

Septicaemia may occur in young animals.

The disease is often unapparent in pigs and horses. In birds the disease affects young animals and causes septicaemia and encephalitis.

Post-mortem findings 
  • Encephalitis: congestion of meninges
  • Septicaemia: small necrotic foci in many organs, very numerous on liver, haemorrhagic gastroenteritis
Differential diagnosis 
Specimens required for diagnosis 
Isolation of L. monocytogenes can be done from brain, cerebrospinal fluid and aborted foetuses.

Serological tests are available but are of low interest as many animals exhibit high titres. 

Transmission
Listeriosis is shed in intestines of reservoir hosts and is transmitted by contaminated food, water and between animals via the faecal-oral route.

It is commonly associated with spoiled silage and it can survive for months in the soil. Transplacental transmission is possible.

Listeriosis in humans is usually a food borne disease. 

Risk of introduction
As Listeria monocytogenes is an usual host of the intestine of ruminants it is difficult to prevent the risk of introduction of the organism through the importation of live animals. However protection of human from being contaminated by imported animal products should be considered.
Control / vaccines  
Vaccination is possible but it is no economically interesting because of the character sporadic of the disease.
References
  • Listeriosis In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p. 479-481
  • McLAUCHLIN J, VAN DER MEE-MARQUET N, Listeriosis In Zoonoses, ed by SR PALMER, Lord SOULSEY and D.I.H. SIMPSON, Oxford University Press, Bath Press, Avon, 1998, p.127-140
  • Office International des Epizooties, 2002
  • Office Vétérinaire Fédéral Suisse