Prepared by: Angela Santos

SWINE LISTERIOSIS

Introduction What is listeriosis?

Listeriosis is an infectious disease caused by a group of bacteria called Listeria monocytogenes. The bacteria are found worldwide and in New

Brunswick. They live in the intestines of infected persons and animals and are passed in the feces.

Etiology

Listeria monocytogenes is ubiquitous in the environment.

The main route of acquisition of Listeria is through the ingestion of contaminated food products.

Listeria has been isolated from raw meat, dairy products, vegetables, and seafood.

Soft cheeses, unpasteurized milk and unpasteurised pâté are potential dangers; however, some outbreaks involving post-pasteurized milk have been reported

Epidemiology Except for tropical countries, the disease is world wide, affecting man,

domestic mammals, several avian species and a

wide range of free-living forms. Even though listeriosis is an uncommon

disease in swine, several cases have been reported as encephalitis or septicemia.

Animals Affected

Listeriosis is relatively uncommon in pigs, with septicemia occurring in those <1 mo old and encephalitis in older pigs;

Transmission

The natural reservoirs of L monocytogenes appear to be soil and mammalian GI tracts, both of which contaminate vegetation.

animals ingest or inhale the organism and further contaminate vegetation and soil. Animal-to-animal transmission occurs via the fecal-oral route

Listeria may be shed for ≥1 mo via the vagina and milk.

Incubation period

The incubation period is mostly unknown. Outbreak cases have occurred 3-70 days after a single exposure to an implicated product. Median incubation is estimated to be three weeks.

Clinical Signs

The bacterium may cause a septicaemia and high temperature in piglets.

Nervous signs possibly meningitis. Weak piglets at birth. Pneumonia. Head on one side. Middle ear infections.

fatal course of 3-4 days after onset of signs

Listeric abortion usually occurs in the last trimester without premonitory signs

Fetuses usually die in utero, but stillbirths and neonatal deaths occur

Clinical signs vary according to the function of damaged neurons but often are unilateral and include depression, trigeminal and facial nerve paralysis, and less commonly, circling.

Contributing factors

Stress causing the bacteria to invade the system.

Heavy environmental exposure

Pathogenesis

Listeria organisms that are ingested or inhaled tend to cause septicemia, abortion, and latent infection.

Listeric encephalitis is essentially a localized infection of the brain stem that develops when L monocytogenes ascends the trigeminal nerve..

Diagnosis

Listeriosis is confirmed only by isolation and identification of L monocytogenes

Specimens of choice are brain from animals with CNS involvement and aborted placenta and fetus.

Occasionally, L monocytogenes has been isolated from spinal fluid, nasal discharge, urine, feces, and milk of clinically ill

Serology is not used routinely for diagnosis because many healthy animals have high Listeria titers.

Differential DiagnosisDisease Comparison Contrast

Listeriosis Abortion, stillbirth, weakness

Abortion during last trimester of gestation

Brucellosis Abortion , stillbirth

Abortion in early in gestation

Japanese – B encephalitis

Stillbirth, sometimes abortion, weakness

Icterus in pigs

Treatment

L monocytogenes is susceptible to penicillin (the drug of choice), ceftiofur, erythromycin, and trimethoprim/sulfonamide.

High doses are required because of the difficulty in achieving minimum bactericidal concentrations in the brain.

Recovery depends on early, aggressive antibiotic treatment.

If signs of encephalitis are severe, death usually occurs despite treatment.

Listeria monocytogenes

Encephalitic form

Sheep with listeria