H. R.
KAPUR
355
That A. persicus is a common vector is now a well established fact. In
view of the prevalence of fowl spirochaetosis throughout India and the economic
loss caused by this disease, an effort has been made to determine whether other
species of ticks, and possibly mosquitoes, can be incriminated as vectors.
These species comprised O. papillipes, O. savignyi and the mosquito Aedes
(Stegomyia) albopicta. A series of experiments was also carried out to obtain
confirmation of the finding that the disease can be produced in susceptible
fowls through the unbroken skin without the intermediary of an arthropod
vector.
MATERIAL AND METHODS
The fowls that were selected for transmission work were all in good con-
dition, locally bred and had no previous history of spirochaetosis. They were
maintained in isolated chappars; their morning and evening temperatures
were recorded and blood examined daily for two weeks before work was com-
menced. The same procedure was rigidly followed throughout the actual
experiments. Those birds that did not develop infection were subsequently
tested for immunity with 1 c.c. of virulent blood subcutaneously. Blood
smears from infected fowls were examined and those showing heavy infection
were selected for initial feeding of ticks and mosquitoes. The ticks used were
laboratory-bred. In all experiments nymphs alone were used. Different
methods for feeding were employed for different species.
In the first batch of experiments a number of O. savignyi, which is a quick
feeder, were placed directly on an area of denuded skin. When the feed was
complete, the ticks were collected in glass tubes in which pieces of filter paper
had been placed. The ticks were maintained for further transmissions in an
incubator. In the case of O. papillipes a special method was employed to keep
the ticks in position. An area of about two inches in diameter was prepared
on one side of the breast. This was covered with a piece of muslin of the same
dimensions as the denuded area and the edges of the cloth were fixed to it with
collodion solution, making a pocket in which were enclosed a number of ticks
which were left there for three hours. The muslin was then removed, the
ticks examined, and those engorged separated from the rest and placed in the
incubator. A. persicus being a nocturnal feeder, the process of feeding in this
case was accomplished during the night. The fowl, with its head in a muslin
bag, was enclosed in a large glass jar and a known number of ticks were then
dropped into the jar, which was covered and left overnight. The following
morning, the ticks were collected and those engorged placed in the incubator.
For the experiments dealing with mosquito transmission, larvae of A.
(S.) albopicta were obtained from tree holes harbouring rain water. These
were then kept in glass jars connected with mosquito netting cages to receive
the adults. The females were transferred to glass tubes about three inches
in length and one inch in diameter, covered with mosquito netting at both
ends. These tubes were then inverted over a moist piece of lint and the
mosquitoes starved for three to five days. They were fed by means of
these tubes first on an infected, and three days later on a healthy, fowl. Feed-
ing in the cage was also attempted.
In endeavouring to transmit infection through unbroken skin, two differ-
ent sites were selected for the purpose, viz. the comb and the skin over the