S.
GANAPATHY
IYER
5
Liver and spleen pulp, desiccated in vacuo, over phosphoric anhydride
and stored in the refrigerator, conserved the virulence for about three years.
Exposure of saline emulsion of infected organs to direct sunlight for an hour
had no effect on the virus. At room temperature, the virus died out more
rapidly [Iyer, 1939]. It has been observed that active virus can be recovered
from dead birds 72 hours after death, but that the tissues may be contaminated
with intestinal bacteria. Where fresh virus was used for direct passage, the
bird generally died in four to five days.
Heating to 50°C. and over invariably killed the virus. At 37°C. the virus
died out after three days. Shirlaw [1937] found that the change of virus from
virulency to avirulency was, however, abrupt, a characteristic of this virus.
Refrigerated virus on removal to a higher temperature soon died out.
Doyle [1927] dried various infected organs. Most of his results showed
that at 40 days the virus was virulent, but at 100 days it was avirulent. Virus
in 50 per cent glycerine was active after 197 days, but was dead after 259
days. Virus in normal saline was. viable up to 86 days, but aviable on the
100th day. Spleen in a petri-dish was viable after 80 days, but dead after 150
days. Blood in sealed pipettes remained virulent for 109 days. At 37°C. the
virus was active after 48 hours, but, after 72 hours it was inert.
Doyle [1935] draws attention to the fact that Newcastle virus remained
viable for at least six months in the bone marrow and muscle of carcases stored
under ' trade chilling conditions '.
Cooper [1931] mentioned that the emulsion of internal organs stored un¬
preserved in the refrigerator remained viable up to 169 days. The author had
observed that small pieces of liver and spleen tissue kept in the cold in sealed
tubes retained the virulence of the virus for over a year in the cold (0.5°C).
Minor variations in the results of different workers in a subject of this
nature may be due to the manner in which the virus was collected and the
nature of the virus-containing material.
Farinas [1930] mentioned that heating at 50 to 55°C. killed the virus in
30 minutes and direct sunlight killed it in one hour. In the ice-chest, the virus
remained potent for at least ten months and 20 days ; at room temperature,
the virus in liquid form remained active for 15 days. Virus in garden soil or
in stagnant water, placed in a room with diffuse light through a glass, was ren-
dered inactive in four days. From fowls, active virus was obtained 168 hours
after death. Dobson [1939] refers to the persistence of the virus under natural
conditions in indoor brooders for a period of seven weeks. Proper cleansing
of the infected batteries had not been carried out before re-stocking.
Regarding the distribution of the virus in the system, it is present, as
mentioned previously, in all organs and body fluids. According to Doyle
[1927], inoculation of the lung, bone-marrow and cervical portion of the spinal
cord gave variable results. Inoculation of blood does not always reproduce
the disease, since the virus does not appear to be firmly adherent to the blood
cells. Doyle [1927] reported that the serum from two sick fowls was pooled,
centrifuged and inoculated into a fowl. The fowl sickened on the fifth day
and died on the eighth day. Therefore, serum from sick birds may contain
active virus. Fowls, infected either naturally or artificially, generally die, but
in rare cases they may recover. It has never been found possible to recover
the virus from such birds after recovery.