ORIGINAL ARTICLES
STUDIES ON CONTAGIOUS BOVINE PLEUROPNEUMONIA IN ASSAM
By J. F. SHIRLAW AND P. R. KRISHNA IYER, Imperial Veterinary Research Institute, Izatnagar
(Received for publication on 18th April 1946)
( With Plate IX )
IN a previous article [Shirlaw, 1939] summarized reports on contagious bovine pleuropneumonia
from the provinces, extending over a period of 50 years, and stated, in conclusion, that no
direct evidence of the existence of the disease in India was availabe. Further work now shows the
disease to exist in Assam.
The disease has acquired the name 'Brahmaputra Valley Disease' owing to its prevalence in
the area. It is sporadic and occasional in this area, the probable explanation being that the country
is divided by the river into numerous small islands, each with its groups of villages. These isolated
agricultural settlements, called chars afford no contact between cattle of adjoining chars except
through occasional cattle fairs, which, apparently, are the origin of fresh outbreaks and new centres
of infection.
The disease runs an acute course, usually of one to three weeks with a mortality said to be 100
per cent. The carrier problem does not, apparently, exist and this may account for the periodicity
of the disease in char lands. Buffaloes are not affected. The statement that the disease has spread
rapidly in Assam in recent years is somewhat conflicting and such figures as are available would
hardly support the statement. During some years the incidence may be higher than in others, but
accurate data are not available. The neighbouring province of Bengal is said to be free, largely
because there is little movement of cattle between the two provinces.
STRAINS OF THE VIRUS
The original Assam strain (Assam 1 virus) came as crude lymph virus from an outbreak of
contagious bovine pleuropneumonia (October, 1939) in district Balishapara. This was of relatively
feeble virulence when received, but acquired full virulence after a few passages in Kumaoni cattle.
The second strain (Assam 2 virus), obtained for comparative study, came from an outbreak in
Majuly district, about 300 miles from Balish? para. Both samples when tested by the Veterinary
Investigation Officer, Assam, provoked classic lesions on subcutaneous inoculation of Assamese
calves. Four African strains designated Kenya Narok, Kenya V4, Kenya ML and Rhodesian R
manual were later received from Kenya. Kenya Narok strain was a 46th generation culture, Kenya
V4 sctain was a 15th subculture from a 2nd animal passage, Kenya ML strain was a 2nd subculture
from a 4th animal passage and Rhodesian R natural strain was a 35th generation culture. No
information was received on the reaction of these strains in Kenya cattle, although it was stated
that Kenya Narok and Rhodesian R. strains has been successfully used in vaccination. These strains
were approximately three weeks in transit and proved viable in subculture in Bennett's broth. They
were subcultured at 7-day intervals for nine more generations and then used in immunity experiments
described later. About the same time, two bovine pleuropneumonia culture vaccine strains, labelled
173 and 264 were received from Australia. These cultures were ten weeks in transit; both grew
satisfactorily when subcultured in Bennett's broth and one culture (264) proved, as will be seen later,
highly pathogenic in Kumaoni cattle. Strain 264 was a 63rd, and strain 173 a 72nd generation
culture in B.V.F.O.S. medium. Both these strains had been used successfully in the vaccination
of Australian cattle.
Culture media. Bennett's medium has proved, in our hands, to be the medium of choice for
primary isolation and maintenance of the Assam bovine pleuropneumonia organism. The formula
of this medium is beef-heart meat extract with addition of 2 per cent 'Difco' bactopeptone and 0.5
per cent pure Nacl, the pH being adjusted at 7.4. After sterilization in bulk, the medium is tubed
in 5 c.c. quantities, the tubes autoclaved and, when cool, 0.5 c.c. sterile horse serum added to each
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