ABSTRACTS
161
Ovine bacterial encephalitis (Circling disease) and the bacterial genus
Listerella. GILL, D. A. (The Australian Veterinary Journal, 13, 2, 46).
IN his previous two communications to the Veterinary Journal in 1931 and 1933,
the author had described an encephalomyelitis or " circling disease " in sheep in New
Zealand, associated with a Gram-positive motile bacillus seen in the mid-brain, and had
given the biological and cultural characters of the organism. In the present article he
has placed the organism under the genus Listerella which has been only recently created
[ 1927 ] but is likely to assume considerable importance in veterinary and medical science
as it is known to cause fatal disease in rodents like rabbits and guinea-pigs, and in sheep,
cattle, fowls and human beings. In support, a review of literature is given which would
be particularly useful to workers interested in the subject.
Since the disease resembles louping ill but is distinct from it, Gill has proposed for
it the name " Ovine Bacterial Encephalitis ", and has placed the causative bacillus
under the species Listerella ovis.
The disease appears to be wide spread and has been reported from Britain, Australia
and America. In New Zealand it occurs during the end of summer and early winter
months and is responsible for heavy losses. The symptoms are indicative of encephalitis
and include circling movement. The patient is, in a few days, unable to stand and dies
quickly thereafter. At autopsy, apart from the congested meninges and cloudy cere¬
bro-spinal fluid no other abnormality can be detected microscopically. Histologically,
however, " cuffing " of blood vessels and foci of leucocytic infiltration, often containing
the causative organism, are seen in the brain and spinal cord. The cerebral lesions are
common in the mid-brain and the causative organism can be isolated from this site by
inoculating blood agar plates with aseptically triturated material.
The cloudy cerebro-spinal fluid shows a greatly increased (over 2,000 cells per cubic
mm.) cell count.
The ovine organism is rapidly fatal, by intravenous injection, to rabbits, the autopsy
revealing acute meningitis and miliary necrotic foci in the liver. In both the situations
the injected bacilli are abundant.
Broth cultures of the organism given subcutaneously (1 c.c.) into sheep had no effect;
given daily (10 c.c.) by stomach tube, produced a rapid rise of temperature which returned
to normal after the first three days ; given intravenously (2 to 9 c. c.), produced a high
fever, up to 108°F., which subsided after forty-eight hours ; given into the carotid artery
(1 c.c.), produced typical " circling disease " clinically and histologically ; and given in¬
transally (10 c.c.), produced similarly positive results.
The natural mode of infection is believed to be via the respiratory tract, and in this
connection larvae of Oestrus ovis are suspected.
The bacillus isolated by Gill grows with case and equally satisfactorily under aerobic
and anaerobic conditions. No exotoxin appears to be formed. A filtrable form of the
organism could not be detected. In serum agar slope cultures the bacillus gradually
tends to lose the Gram-positive character.
Work in connection with the epidemiology and immunology of the disease is in-
dicated. [M. Y. M.].