150
Control of Acute Theileriasis in Calves in the Punjab
young calves and that the infection is transmitted
hereditarily only in the adult stage of the tick
and not in the larval or nymphal stages. As
found by Fotheringham and Lewis [1937], this
is quite different from what has been experienced
in T. parva infection.
The first object was to save the new-born calves.
For this purpose, they were divided into two
groups, viz. weaned at birth and unweaned. For
the former, an area was rendered tick-proof by
first digging up the earth to a depth of about 18 in.
and then burning dry leaves and grass over the
dug-up area. Subsequently, a moat about 9 in.
wide and 6 in. deep surrounding the area was
filled with water. Attendants were engaged
exclusively for this tick-proof paddock. It was
observed that calves, which were detained here
for three months, were susceptible to infection
when removed to an infected area, though none
died. For the calves of the second group, more
elaborate arrangements were made. Cows in
advanced pregnancy were isolated from the main
herd at a place about half-a-mile away. Before
removing them to this segregation camp, all
ticks on the animals were hand-picked, their tails
and ears clipped in, and rest of the body sprayed
every third day with an arsenical solution con-
sisting of soft soap 11 oz., liquid paraffin 1 lb.
2½ oz., sodium arsenite 1 lb. 1 oz. and water 50
gallons. Separate attendants and grazing pas-
tures were arranged. There were also several
calves which were weaned at birth, but were below
two months in age. All these calves were dipped
in the arsenical solution using a Cooper's portable
swim-bath and housed in a paddock at some dis-
tance from the main farm. Dipping was done
every third day as before. A few of these calves
developed the disease, but at the first appearance
of symptoms they were returned to the sick ward
where they were given symptomatic treatment,
along with good nursing. The floor of the sick
ward was covered with hay bedding about 4
to 6 in. thick, to afford comfort and at the same
time to prevent them from licking the earth.
Control by vaccination
In 1940, one of us (H. N. R.) observed that
the introduction of dead parasites rendered healthy
animals immune to subsequent inoculation of
virulent blood containing Koch's bodies. In
the light of this observation, a vaccine was pre-
pared by making a suspension in 5 per cent for-
malin of lymph glands and spleen from a heavily
infected case on the farm. Soon after bi
calves were vaccinated subcutaneously with
c.c. of this vaccine and kept in the tick-free padd
for 14 days before being transferred to the t
infested area. Between May 23 and June
1940, 19 calves (7 females and 12 males) were
treated in this maimer. Of these, 16 were trans¬
ferred to the tick-infested area—the remaining
three, being born of heavy milkers, were detailed
in the tick-free paddock. Some of the calves
14-21 days after being liberated in the tick-infes
area, showed a rise of body temperature, but none
of them died. As a control experiment, se
calves born from June 13 and July 7, 1940, we
liberated into the tick-infested area within
to twenty-five days of birth. Of these, four
caped infection and three died of acute their
iasis. In August 1940, seven calves were
oculated with a dose of 10 c.c. of the vaccine in
tead of 5 c.c. Five males from this batch was
removed to tick-infested area, after the prescribed
period, and none of these calves showed si gns
the disease.
These observations on vaccination are sugges¬
tive and encouraging but, since no strict laboratory
tests, such as the injection of vaccinated calves
with virulent blood, have yet been made, we
frain from drawing conclusions from these
field tests.
In conclusion, we would like to stress the val
of adopting tick control measures on farms wh
outbreaks of acute theileriasis are common among
calves. The information so far obtained from the
farm indicates that since the adoption of ti
control measures, no further cases of theilerial
have been detected.
'Carrier' in theileriasis
A number of cattle in this farm showed parasite
in the peripheral circulation without exhibiting
clinical symptoms. Two experiments were per
formed on the farm to test the infectivity
'carrier' blood to young calves of susceptible as
The results were negative. These experiment
prove that the endoglobular forms of the parasite
as met with in carrier blood, represents the
gametocytes and as such undergo no further dev
lopment in the vertebrate host. So that dev
lopment may proceed to the sporogonic part
the life cycle they must enter an intermediate
host—chiefly an arthropod. Evidently, however
carrier animals are potential sources of in
fection to clean H. aegyptium. These observation