SELECTED ARTICLE
LEPTOSPIRAL INFECTIONS
By R. LOVELL
(Reprinted from The Veterinary Record, Vol. 55, No. 15, April 1943)
LEPTOSPIRAL jaundice (Weil's disease) has long
been recognised in man and the infecting spiro-
chaete Leptospira icterohaemorrhagiae has been
demonstrated in all five continents. Weil's
disease, however, is not the only form of leptospiro-
sis and diseases have been described which are rela-
ted to it and caused by other leptospirae. Animals,
too, may suffer from leptospirosis and the persis-
tence and spread of some of the diseases are
through their agency. Thus, the reservoirs of
Lept. icterohaemorrhagiae are rats, and field mice,
Mus norvegicus, Mus rattus alexandrinus and
Microtus montebelloi, whilst the reservoir of Lept.
canicola is the dog.
The forms of leptospirosis in man can be classi-
fied into several clinical groups. In the first
group there are mild types of disease such as
'mud fever' and the Pomona or seven-day
fever of Australia caused by Lept. grippotyphosa
and Lept. pomona respectively. There is a con-
nection between the first disease and floods, but
none between Pomona disease, mud and water.
The second clinical group includes infection with
Lept. canicola and this usually causes neither
jaundice nor death; the source of infection is the
dog, the only known carrier. The third group
consists of diseases caused by types of leptospirae
known as Rachmat, Salinem, Swart van Tienen
and Andaman A. These infections occur in
Sumatra, Batavia, Macassar and Borneo; some are
associated with rats and in some the carrier is
unknown. Jaundice may occur and there are
some deaths. The fourth group consists of Hasami
fever caused by Lept. autumnalis and endemic in
Nagasaki during the autumn and leptos-
pirosis icterohaemorrhagia or true Weil's
disease. In both conditions jaundice is frequent;
the animal reservoir in the former is Apodemus
speciosus and there is a fatality rate of 1.9 per
cent, whereas in true Weil's disease this rate may
be as high as 30 per cent. Weil's disease is mainly
an occupational hazard and the risk of infection
with Lept. icterohaemorrhagiae appears to be
highest in persons whose work brings them into
contact with water which is subject to pollution
with rat urine.
Substantial clinical differences, therefore, exist
between the various forms of leptospirosis and
there are epidemiological differences and different
animals reservoirs. The leptospirac responsible
also differ in their serological properties and in
their degrees of virulence for guinea-pigs. From
the aspect of animal pathology two types of infec-
tion are important, those caused by Lept. ictero-
haemorrhagiae and Lept. canicola.
Okell, Dalling and Pugh [1925] gave an account
of leptospiral jaundice as it occurred in the dog
in this country and from three of ten cases they
isolated leptospirae which agreed in every respect
with a known rat strain of Leptospira icterohae-
morrhagiae. They pointed out that up to 30
per cent of the adult rats in many areas both
in England and abroad harbour virulent leptos-
pirae in their kidneys and excrete them in their
urine. In human outbreaks of Weil's disease a
close relationship between man and rat can nearly
always be established and they believed that the
disease in dogs was caused mainly by contamina-
tion of food and bedding with urine of carrier
rats. Complete but temporary protection against
the disease could be induced by the injection of
potent anti-leptospira serum. It was shown later
[Walch-Sorgdrager, 1939] that all strains of
leptospirae cultivated from dogs were not identical
for Klarenbeek and Schüffner working in
Holland had found a strain which was reacted
upon by its own antiserum to a titre of 1:10,000
whereas with a serum prepared against Lept.
icterohaemorrhagiae the titre was 1 : 25. The
new strain, known as Lept. canicola, is morpho-
logically identical with Lept. icterohaemorrhagiae
and can be cultivated in the same medium. Sero-
logically and in its action on guinea-pigs it is
different and it does not occur in rats. Its re-
covery has, been recorded in Holland, Germany,
Denmark and California.
Okell, Dalling and Pugh described two clinical
forms of leptospirosis in the dog, (a) the hyper-
acute haemorrhagic type with a sudden onset and
a rapid course, and (b) the icteric type in which
the rapidity of the onset varies and there is jaun-
dice of varying degree. Meyer, Stewart-
Anderson and Eddie [1939] describe this latter
form as the typical Weil's disease or 'yellows'
in which the conjunctivae are coppery red in
colour and the tongue and gums of the mouth
are covered by yellowish crusts and erosions.
Post mortem: the liver may or may not be enlarged
and is pulpy and clay coloured; the portal lymph
nodes are sprinkled with haemorrhages. The
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