OBSERVATIONS ON A CONTAGIOUS KERATITIS OF INDIAN SHEEP
By P. N. NANDA, M.R.C.V.S., Superintendent, Government Cattle Farm, Hissar, and M. ABDUSSALAM,
Punjab Veterinary College, Lahore
(Received for publication on 6 March 1942)
(With Plate XVII)
DURING the past few years, there have occurred
frequent outbreaks of a severe form of keratitis in
flocks of all the three breeds of sheep bred at the
Hissar Cattle Farm. Two of these breeds, the
Bikaneri and Lohi, are purely indigenous and the
third is a cross between the Australian Merino and
the Bikaneri. A perusal of the available literature
shows that this disease has not, so far, been re-
corded as occurring in India but an almost identi-
cal affection is known, though under different
names, from many parts of the world. Coles
[1931] described it from South Africa and for the
first time demonstrated the constant occurrence
of a Rickettsia in the conjunctival epithelium of
affected sheep. In the same year, Edgar studied
the disease in Australia, and since then a number
of other workers have recorded it from different
parts of the world. Hopkirk [1934] encountered
it in New Zealand, Donatienet Lestoquard [1937]
in Algeria, Cordier et Menager [1937] in Tunis,
Melbrant [1939] in French Congo, Pigoury [1937]
in the Levant, Johnson [1938] in the United States,
Viera and Castelo [1940] in Uruguay, and Lafe-
nêtre [1938] in France. Nicolas [1914] quotes
Repiquet [1897] as having encountered, what
appears to be the same disease, in France and
Hughes in England; Coles [1933] also stated that
the disease was prevalent in Europe.
CLINICAL OBSERVATIONS
At Hissar, the disease is more commonly en-
countered in spring and early winter, when flies
(Musca spp.) are most abundant in the sheep
baras,* but outbreaks in other parts of the year
are not unknown. Young animals below one year
have been more commonly noticed to suffer but
older animals are also attacked fairly frequently.
Clinically the disease begins as a conjunctivitis;
there is a marked redness and swelling of the con-
junctiva lining the eyelids, with profuse lacry-
mation. In the course of a day these symptoms
become more aggravated, lacrymation becomes
more profuse and the sclerotic conjunctiva shows
an intense diffuse reddening with injected blood
vessels standing prominently on it. At this stage,
there is marked photophobia and partial protru-
sion of the membrana nictitans over the eye-ball.
The discharge then becomes purulent and a kera-
titis develops fairly rapidly, rendering the cornea
at first hazy and then milky white and opaque.
The animal becomes somewhat dull and depressed
and feeding (grazing) is markedly impaired, pro-
bably on account of loss of sight; this results in a
rapid loss of condition. The severity of symp-
toms usually passes off in about a week to ten
days; photophobia and swelling of the conjunctiva
is reduced and the discharge becomes watery again.
The corneal opacity and diffuse redness of the
conjunctiva, however, persist for a longer period.
In the great majority of cases, recovery is the rule
and the eye becomes normal again in about three
weeks. The cornea gradually clears and the eye-
sight is restored but the conjunctiva may present a
granular appearance for a long time, in rare cases,
the cornea ulcerates, the progressive ulceration
tending to produce keratocele and perforation with
all its sequalae and loss of the eye. In most cases
the disease affects only one eye at first and the
other eye follows suit in the course of a few days.
Rarely, however, both the eyes are affected
simultaneously.
In large flocks the disease may continue for
months, three or four animals being attacked at a
time. Quite often, the outbreaks starting in early
winter have been noticed to continue till the follow-
ing spring. More commonly, however, a large
number of animals are attacked at a time and the
outbreak is over in six to eight weeks' time.
ETIOLOGY
Coles [1931, 1] demonstrated the constant occur-
rence of a rickettsoid organism in the conjunctival
epithelium during early stages of the disease.
He has given an excellent and well illustrated
description of the organism and has provisionally
named it as Rickettsia conjunctivae. This protista
has since been found in association with the disease
in Algeria, Congo, Tunis, the Levant, Uruguay and
America by the workers who have encountered the
disease in those countries (loc. cit). At Hissar also,
the present writers invariably found in the con-
junctival epithelium of all cases in early stages, an
organism morphologically indistinguishable from
Rickettsia conjunctivae Coles, 1931, (Plate XVII).
A brief description of our methods and material
is as follows.
In the beginning of September 1940, an out-
break of the disease among the stud rams at this
Farm afforded us an opportunity to examine the
conjunctival scrapings for infection, Six cases
* Fenced enclosures for housing sheep
228