A study has "been made of the serological
responses occurring in domestic animals as a result
of natural infestation with helminth parasites.
The helminth infestations studied were those of
Fasclola hepatica. Cysticereus bovls. Ascaris
lumhrlcoides, Dlctyocaulua vlviparus and Trichlnella
spiralis,F.HEPATLCA.
The serological response, as indicated
by the precipitin test, in F.hepatlca infestation
was most marked when the immature parasites were
in their migratory phase. Thereafter the precipitin
antibody level became lowerSpecific complement fixation antibodies were demonstrated in the sera of only one infested
animal. This was indicative that the complement
fixation technique was unsuitable for the demonstrat¬
ion of antibodies in P,hepatica infestation.
Alcoholic extracts of the parasite were found to
give varying degrees of r.on specific complement
fixation with sheep sera, irrespective of F.hepatica
infestation.The miracidia of F.hepatlca were observed
to suffer a lethal effect when placed in sheep
serum. Complement was necessary for the reaction.Hypersensitivity, demonstrable by an
JLOD#
Intradermal test, was evident in a large percentage
of animals infested with F.hepatica. In some cases
this hypersensitivity was passively transferable, "by
means of serum, to a non sensitive animal. Local
skin desensitisation could "be produced to a marked
degree hut generalised skin desensitisation was
less obvious when large quantities of antigenic
material were administered.G.BOVIS.
Precipitin antibodies were demonstrated
in the sera of animals which showed multiple
eysticerci in the musculature. When only a few
(1 or 2) eysticerci were present a serological
response was frequently absent. Polysaccharide
solutions of the parent parasite, T# saglnata#
produced precipitin reactions with the sera of
animals infested with P.hepatica only. This was
thought to be due to an isoagglutinin like producing
antigen present in both T.saginata and hepatlca.Animals infested with F#hepatica produced
hypersensitive skin reactions to extracts of C.bovls#
A common allergen In the two parasites was thought
to be responsible#A.LUMBRIOOIDEA.
Precipitin antibodies were demonstrated
in the sera of pigs. These were found to bear no
relationship to the presence of mature A.lumbricoides
In the intestine# They did, however, show a
relationship to the degree of chronic focal
interstitial hepatitis.Hypersensitivity to extracts of A.lumbricoldes
was evident in the majority of swine. This was
similar to the precipitin reaction, in that it was
related to the degree of chronic focal interstitial
hepatitis but not to the presence of intestinal
forms of A.lumbrlcolfles.D.VIVLNARUS.
The majority of cattle examined showed
skin hypersensitivity to D.vivlparue extracts.
This hypersensitivity was most evident in the age
group 2-j? to 3-j years. The hypersensitivity
demonstrated occurred in the absence of parasites.
Intestinal helminths did not influence the
hypersensitive state.Hypersensitivity was demonstrated in sheep
undergoing a sub-clinical infestation with 13.filaria
Infestations with other lung worms produced a
hypersensitive state which could be demonstrated by
D.filaria extracts. This was indicative of a group
reaction.T,SPIRALIS.
Hypersensitivity to extracts of T.spiralis
was demonstrated in only 5# 4$ of swine. Only
0.91 of swine showed marked reactions. Since these
occurred in animals possessing marked hypersensitivity
to A.lumbrlcoidea it was concluded that a strong
hypt rsensitivity to A,lmribrlcoltl.es could sensitise
pigs to extracts of T.spiralis. Infestations with
T.trlchiura did not produce hypersensitivity to
T.spiralis extracts.The use of animals at an abattoir afforded
the opportunity to correlate the serological
findings with post mortem evidence of infestation.
Since the lack of helminth eggs in the faeces does
not necessarily indicate absence of helminth
infestation the post mortem examinations carried out
gave a more complete picture of the parasitic burden.
As a result it was found that light infestations
or pathological evidence of helminth infestation
could be correlated with the serological findings
(vide P.hepatica. C.bovls and A.lumbrlcoldes).
If faeces examination had been the sole criterion
of evidence of infestation no correlation between
serological findings and infestation would have
been evident and false conclusions may have been
drawn
