THE REVOLUTIONARY EquiSal
test, using horse saliva to diagnose
tapeworm burdens, was first made
available to horse owners in 2014.
Validation of the test has since been
published by Veterinary Clinical Pathology,
and reports the accuracy of the saliva
test in comparison to blood testing and
to tapeworm numbers counted at post
mortem.
Tapeworm
infections pose
a significant
threat to horse
health as they
are associated
with clinical
cases of
colic. Of the
three species
of tapeworm capable of infecting
horses, Anoplocephala perfoliata is the
most common worldwide. A. perfoliata
adult worms can grow up to 8cm
long by approximately 1.5cm wide.
Although relatively small, they can
cause significant problems due to
clustering around their preferred site
for colonisation: the caecal wall and the
ileocecal junction.
Currently there are only two effective
drugs for the control of tapeworm
in horses: praziquantel and pyrantel
pamoate. Resistance to anthelmintics
has not yet been reported in
tapeworms, but increasingly frequent
reports of resistance to various
anthelmintics in other equine parasites,
such as cyathostomins, make it
imperative for special attention to be
paid to the management of tapeworm
in horses. The potential for the
development of resistance to the two
available drugs could result in problems
with the control of tapeworm burdens
in the future.
The intensity of infection in the
horse is important to consider as larger
burdens are more likely to cause colic
symptoms, but even moderate burdens
can result in damage to the intestinal
mucosa. Given the correlation of
infection intensity to horse intestinal
health, and concerns for anthelmintic
resistance, there is an increasingly
recognised need for accurate diagnostic
tests.
Standard faecal egg count (FEC) methods, such as the McMaster
method, are widely used for detecting
cyathostomins (redworms) and
ascarids (roundworms) but, due to
the way in which tapeworm eggs are
released, these methods are generally
considered unreliable for the diagnosis
of tapeworm burdens. FECs tend
to substantially underestimate the true level of
tapeworm
infection and
sensitivity has
been shown
to be highly
variable. A
commercial
blood testis available; however,
it requires a veterinarian to take the blood sample, resulting in the test
being relatively expensive.
EquiSal Tapeworm detects
tapeworm-specific antibodies in
horse saliva to provide a tapeworm
burden diagnosis of low, borderline
or moderate/high. The test has the
bene t that horse owners themselves
can collect the sample to send back to
the laboratory for analysis.
Scientific validation of the test has
been peer-
reviewed and
published in the journal Veterinary
Clinical Pathology.
To summarise
the validation,
serum and saliva
samples were
collected from
horses at a UK
abattoir where
tapeworms had
been counted.
Samples were then analysed in the
EquiSal Tapeworm test or blood
test. EquiSal saliva scores had strong
correlations with both tapeworm
numbers and the blood test results.
The majority of horses with one or
more tapeworms at post-mortem were
correctly identified by the test. The
remaining few were diagnosed as being
low, but these horses had burdens
considered by experts to be not pathogenic – fewer than 20 tapeworms
present.
Most importantly, no high burden
(more than 20 tapeworms) horses
were misdiagnosed by the test. This
is similar to the current guidelines for
redworm FEC, where a result of fewer
than 200 eggs/gram is not considered
harmful. The EquiSal Tapeworm test
can be relied upon to correctly identify
the majority of horses with one or
more tapeworms and correctly identify
all horses with pathogenic burdens.
In scientific terms, the EquiSal
Tapeworm test has both high
sensitivity (83%) and specificity (85%),
which is important for correctly
identifying horses with more than one
tapeworm present, and the test has
equivalent accuracy to the blood test.
Two-week testing
In an ongoing study, EquiSal
Tapeworm testing is carried out
every two weeks following tapeworm
treatment on horses diagnosed with
tapeworm but with no access to
grazing.
Data collected so far (19 horses)
show that 50% of horses’ saliva scores
had reduced to low within six weeks,
90% had reduced within 10 weeks and the remaining
10% of horses
taking a further
two weeks to
drop to low.
This suggests
that antibody
responses in
saliva have less memory
to tapeworm
infection than
that reported
for antibodies
in blood.
It is important to understand that
the situation is complicated in grazing
horses by the risk of reinfection
from tapeworm larvae after worming
treatment. Tapeworm reinfection is
evident in studies undertaken using
horses kept in poorly managed
paddocks where reinfection can
obviously happen very
easily.
But, given that
the tapeworm’s life-
cycle requires an
intermediate host (an
oribatid mite), even
well managed paddocks
containing horses
with high tapeworm
burdens could harbour
infected oribatid mites
within the grass. This means that there is still a reinfection
risk after worming for horses grazing
in these circumstances too.
Salivary tapeworm-specific IgG(T)
antibodies are part of the mucosal
immune response to tapeworm
infection. A previous study showed
tapeworm-speci c IgG(T) antibodies
being produced at the site of infection
and secreted as a local mucosal
antibody response. In contrast to
humoral antibody responses (detected
in blood testing), mucosal antibody
responses have a much shorter
persistence and immunological
memory.
It can, therefore, be reasonably
concluded that the tapeworm-specific
antibodies measured in the EquiSal
Tapeworm test are mucosal antibodies
produced in the salivary glands
by plasma cells that originated as
recirculating (via the lymphatic system)
B-blasts triggered in the gut submucosa
at the site of infection.
It remains possible that low levels
of humoral antibodies could leak into
the saliva by transudation or passage
through the gingival crevicular space;
however, our data suggest that this is
not a significant factor.
In summary, the EquiSal Tapeworm
test has been scientifically validated
to accurately diagnose tapeworm
burdens in horses and can be used to target worming for tapeworm
burdens. Current advice is to integrate
tapeworm testing into your existing
worm egg count schedule by using
EquiSal Tapeworm every six months
before worming.
