Listeriosis
By Dr Mackie Hobson BSc(Agric),BVSc

1. Diseases

Listeriosis  has not been diagnosed in Angora goats in the Karoo and is not economically important. It potentially, but rarely, effects most farm animals as well as humans.

Listeriosis is caused by a bacterium Listeria monocytogenes and can occur in 4 different forms

1. Meningoencephalitis (brain form)

• The goat walks in circles
• Ataxia
• Head tilts to one side
• Paralysis of one side of its face
• The goat cannot swallow
• They usually die after 2-3 days

1. Abortion

• Enteritis

1. Septicaemia

This is the most common form in very young kids

Where can Listeria occur?

Listeria lasts for long periods in soil and decaying matter. Goats can carry the bacteria in their intestinal tract and so contaminate the environment. The bacteria can also be spread by water and milk. Bird droppings have also been implicated in the spread of the bacteria.

Silage is seldom used as a feed for Angora goats in the Karoo but potentially a source of infection in parts of the country where symptoms can be seen about a month after the introduction of poor quality silage.

How can the goat get the Listeriosis?

The bacteria enter through wounds in the mouth such as when teething to reach the facial nerve endings . From here it travels to the brain causing neurological symptoms.

Where the abortions or septicaemia forms occur the infection usually enters via the intestinal tract.

Diagnosis

A presumptive diagnosis can be made on history and clinical signs but in dead goats diagnosis is more difficult.

Histopathology samples may detect micro-abscesses in the brain.

Treatment

Listeria is susceptible to penicillins and tetracyclines but treatment is often of limited value as brain damage has already occurred.

 There is no vaccination.

Conditions that may show similar neurological clinical signs include:

Brain abscess (caused by tick bites)

Coenurus cerebralis (tapeworm cyst).

Heartwater

Vit B1 (Thiamine deficiency)

Rabies

References:

 Coetzer, J.A.W. and Tustin, R.C. 2004. Infectious diseases of livestock.

The Sheep Health, Disease and Production : West, Bruere and Ridler