148 Phenothiazine—A Remarkably Efficient Anthelmintic
The method followed in carrying out the faecal examinations was as
follows : First, an estimate of the number of eggs per gramme was made by
applying the new McMaster technique,* then the faeces were cultured at
26° C. and in eight days time the third-stage larvae separated by means of
Baermann's apparatus ; these were then differentiated into species and groups
of species, and the original egg count divided proportionately.
These trials demonstrate a very remarkable efficiency for all of the strongy-
loid parasites of the large intestine, the adults at least, being completely eradi-
cated as the result of the administration of a dose of between 30 and 60
grammes.
Trichostrongylus axei, presumably because of its different situation (in the
stomach), is more resistant and in several instances appears to have been the
only strongyloid parasite to withstand the treatment. Ascaris also responds
to the treatment but Anoplocephala, data concerning which are not given in the
table, did not.
TOLERANCE OF HORSES.—Horses appear to be very good subjects for
treatment with phenothiazine, the large number of trials, data from which
are set down in Table VIII, a, b, and c, having been carried out without any
definite symptoms of intoxication although in several instances slight inappe-
tence was observed about 24 hours after treatment.
SUMMARY OF OBSERVATIONS IN HORSES.—Phenothiazine at a dose rate
of 0.16 gramme to 0.08 gramme per kg. body weight (30 grammes to 40
grammes for a hunter) is 100 per cent. efficient against red-worms. A dose of
20 grammes is also effective but less reliable, but a dose of 10 grammes pro-
duces no anthelmintic effect. Trichostrongylus axei does not respond well nor
do Anoplocephala spp. but Ascaris is, as a rule, satisfactorily expelled.
Horses appear to tolerate this drug very well indeed, no clear instance of
intoxication having been observed.
EFFECT OF PHENOTHIAZINE ON EGGS AND ON THE DEVELOPMENT OF INFEC-
---- LARVAE IN THE FAECES
Examination of faeces from a calf which had received 45 grammes of phe-
nothiazine on the previous day showed all of the eggs (some 1,100 per gramme)
to be dead ; the contents being opaque and shapeless and showing signs of
degeneration.
Observations subsequently made on goats receiving small doses of pheno-
thiazine showed that amounts too small to have any effect upon the adult
worms were nevertheless sufficient to prevent the development of the larvae.
The smallest dose employed was 0.25 gramme and as a goat passes something
*The McMaster egg counting technique has been found, in our hands, to be as accurate
as the dilution method previously in use at this Laboratory and is a quicker and more
convenient way of working. We have introduced one slight improvement in that the
3 gramme sample of faeces is first mixed with water, centrifugalised and the supernatant
cloudy liquid discarded before a 66 per cent saturated salt solution is added and the count
made in the special cell described by Gordon and Whitlock (1939). This preliminary
washing not only allows a greater amount of light to make its way through the preparation
but permits of the enumeration of the eggs of Ascaris, Trichuris and Fasciola and of
lungworm larvae. These do not float to the top of the two-thirds saturated salt solution
that is found to be the most useful medium for the enumeration of strongyloid eggs,