THE VECTOR OF CANINE PIROPLASMOSIS DUE TO
                                              PIROPLASMA GIBSONI

                                                         BY

                                          S. K. SEN, M.Sc., F.R.E.S.,

                       Imperial Institute of Veterinary Research, Muktesar.

                      (Received for publication on the 23rd October 1933.)

                                  (With Plate XXXIV and one chart.)

A perusal of the available literature shows that the earliest attempts to
determine the vector of this protozoan infection of dogs were made by Patton
shortly after his discovery of the parasite in the blood of hounds of the Madras
Hunt in 1910. Concerning these attempts, Symons and Patton, in an article which
appeared in 1912, wrote as follows :—" Knowing that this piroplasm is almost
certainly transmitted from the jackal to the hounds by the bite of a tick, one of
us (W. S. P.) has made repeated attempts to try to transmit it by placing ticks
from jackals on clean dogs. So far, Haemaphysalis bispinosa has been used, and
although a large number have been placed on young dogs, we have so far failed to
infect them. We have long known that there is a species of Rhipicephalus, which
is fairly common on the jackal, but unfortunately we have so far failed to obtain
suitable specimens for our transmission experiments." No further work in this
connection appears to have been undertaken during the following 14 years, but in
1926, Rao, in Madras, reported the results of a short series of experiments carried
out by him to test the possibility of the infection being conveyed through the
agency of H. bispinosa (the species of tick originally experimented with by Patton)
and the common dog tick Rhipicephalus sanguineus, the former, according to Rao,
being the most common ecto-parasite on hounds and jackals in Madras. In experi-
menting with H. bispinosa, laboratory-bred larvae were fed upon an infected dog
and the infectivity of the nymphs obtained from these larvae was tested upon
three " clean " dogs, with the following results :—two did not develop the infection
at all, but the third " showed fever and on the 17th day enlargement of the spleen
and other clinical symptoms simulating those of a true case of P. gibsoni, but the
typical parasite was not seen in its blood during the whole period of observation ".
The infectivity of adults bred from infected larvae was tested in one instance and
the dog showed a rise in temperature from the 5th day, with " a few bodies that
appeared like P. gibsoni" on the 9th day, but these bodies were not seen again on
any of the following days. R. sanguineus would appear to have been given only a

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