December, 1954 ]
S.
L.
MANJREKAR
219
Before this finding a disease in man caused by R. conori producing Mediterranean
fever (Fievre boutonneuse), was found to have been transmitted by this tick, which is
also responsible for the transmission of R. canis. The cross immunity tests, however,
revealed that R. conori was quite different from R. canis though the vector tick is
the same for both.
Under experimental conditions, the incubation period (after inoculation) is
from six to twelve days, followed by a rise in body temperature, with subsequent
fluctuations during the next few days. The animal is dull, refuses food and water
and rapidly becomes emaciated. There may be exanthematous patches in various
parts of the body. Mortality is very high.
Rickettsia can easily be demonstrated by lung or liver puncture smears, the
organisms being present in the monocytes. There is an increase in the number
of monocytes in the blood stream. Dogs which are carriers of P. canis or Bartonella
canis get a relapse when infected with these organisms, which can be seen in the
blood stream.
A state of premunition follows recovery from the disease. Animals are found
to be resistant to subsequent infection.
(ii) R. ovina [Donatien and Lestoquard, 1936]. These two investigators had
observed a species of Rickettsia causing a systemic disease, taking a heavy toll of life
among sheep. They termed it as R. ovina. The parasite is found in the monocytes
of the blood stream, in sheep suffering from the disease which is febrile in nature and
occurs after inoculation of an emulsion of organs of the tick Rhipicephalus bursa.
Some observers thought that it produced only a mild infection with low mortality
and differed from R. ruminantium. But from the observations made at a later
date in Anatolia, it has been proved beyond doubt that this organism causes serious
losses in sheep under natural conditions. The incubation period is about nine days.
(iii) R. bovis [Donatien and Lestoquard, 1936]. This organism was discovered
accidently, following sub-inoculation from cattle which had originally been infected
with Theileria dispar as a result of infestation with the tick Hyalomma aegyptium.
The incubation period was about fourteen days. The temperature reaction in
infected animals was severe and prolonged. Rickettsia was demonstrated in the
monocytes of the circulating blood. It was observed that the parasites persisted
in the blood till ten months. The organism was found to be transmissible to sheep
with mild reaction.
The cross immunity tests with R. ruminantium showed the two organisms to be
quite different.
Four more species have been added to this classification, viz. R. belgaumii,
R. phagocytophilia, R. suis and R. burneti.
(iv) R. belgaumii [Manjrekar, 1949-51]. A mild febrile condition among
sheep and goats, especially highly pedigreed ones as the Merino sheep or the Angora
goats, has been shown to be due to a Rickettsia named as R. belgaumii.
Though morphologically it resembles R. ovina and is located in the cytoplasm
of the monocytes in the circulating blood of the naturally affected and experimentally
infected sheep and goats, it has been found to be antigenically and in its biological