98
REVIEW
Co-ordinated trials with phenothiazine against
nematodes in lambs Imp. Agric. Bureaux,
Joint Publication 4, 1-56, 1943 Price. 35. 6 d.
As an insecticide, phenothiazine has been in use since
1934. Harwood et al (1938) for the first time reported
its efficacy against Ascaris and Oesophagostomum of pigs.
Subsequently, numerous reports have been published on
its use as an anthelmintic. In view of certain discrepan-
cies in these reports and the fact that different workers
used different criteria in assessing its efficacy, the Agri-
cultural Research Council, U. K., initiated a series of
planned trials, carried out by the same technique at several
centres in Great Britain. These trials, involving some
280 lambs, were so planned as to yield results susceptible
of adequate statistical analysis and afford data on the
effect of phenothiazine, in single doses, against sheep
nematodes, using lamb weights, egg and worm counts as
criteria of efficacy.
The drug used fulfilled the specification suggested by
Imperial Chemical Industries as desirable for phenothia-
zine for veterinary use. Only lambs with a level of
infestation of about 1,000 eggs per gm. of faeces were
selected. Each unit flock, besides reserves, consisted of
28 lambs and was given the following doses (in grams) of
phenothiazine in batches of four: 0 (controls), 5, 10, 20,
30, 40 and 50. In each batch, except the controls, two
lambs received the drug as compressed tablets and two as
powder made into a drench with water. Two per cent
sodium cetyl sulphate was used as a wetting and dispersing
agent in both cases. Four of such unit flocks were
maintained for six weeks inside, i.e. under conditions
precluding reinfestation, and six unit flocks were kept for
sixteen weeks outside, under natural conditions.
The observations recorded provide information on (
the effect of the drug on particular species of worms
revealed by egg and worm counts of the inside flock, a
(II) resulting net effect of the drug upon the lam
themselves, as shown by periodical weighings of lambs
the outside flock. The following points of interest emer
from these trials.
The greatest relative reduction in egg count w
achieved by the lowest dose (5 gm.) used; higher dos
reduced the counts further to a relatively small extent
irregularly.
From the worm counts, the stomach worms Haemonch
appeared to be markedly susceptible to lower levels
gm.) of phenothiazine. With the intestinal worm
Bunostomum, Trichostrongyius and Cooperia-the respon
was less marked but continued up to the highest do
used. Anomalous responses were obtained with Strong
loides, Trichurus, Nematodirrus and Moniezia .
In the outside flocks kept under natural condition
though the reductions in egg count were obliterated
reinfestation, there was a relatively large weight respon
which increased roughly in proportion to dosage up to
highest dose used. This must be due, judging from
'inside' worm counts, to the reduction not merely
stomach worms but also of certain intestinal won
usually considered of little clinical importance.
No difference in efficacy was observed between tali
and drenches containing the same weight of phenothiazi
The report contains a concise historical review
previous work on the anthelmintic efficacy of phenothiaz
The methods and techniques used are fully described
are satisfactory. A useful list of references is append