Accurate diagnosis of Giardia spp and proper fecal examination procedures

Abstract

A series of investigations evaluated the ability of different testing methods - a swing-head centrifugation technique using two flotation solutions (1.18-specific gravity zinc sulfate and 1.27-specific gravity Sheather's sugar solution), a passive commercial flotation technique, and the SNAP Giardia Test Kit from IDEXX Laboratories - to identify Giardia-positive dogs and recover the eggs of other intestinal parasites. It was determined that the SNAP Giardia test can improve a practice's ability to identify Giardia-infected dogs. Because of its higher specific gravity, the sugar solution was better for recovering heavy parasite eggs, such as Taenia spp, and thus is the flotation solution of choice when conducting routine centrifugation fecal examinations.

Full text

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
4
*Sponsored by IDEXX Pharmaceuticals, Inc.,
Greensboro, NC.
CLINICAL RELEVANCE
Aseries of investigations evaluated the ability of different testing methods—a
swing-head centrifugation technique using two flotation solutions (1.18–specif-
ic gravity zinc sulfate and 1.27–specific gravity Sheather’s sugar solution), a
passive commercial flotation technique, and the SNAP Giardia Test Kit from
IDEXX Laboratories—to identify Giardia-positive dogs and recover the eggs of
other intestinal parasites. It was determined that the SNAP Giardia test can im-
prove a practice’s ability to identify Giardia-infected dogs. Because of its high-
er specific gravity, the sugar solution was better for recovering heavy parasite
eggs, such as Taenia spp, and thus is the flotation solution of choice when con-
ducting routine centrifugation fecal examinations.
Accurate Diagnosis of Giardia spp and Proper
Fecal Examination Procedures*
M. W. Dryden, DVM, PhD
P. A. Payne, DVM, PhD
V. Smith, RVT
Department of Diagnostic Medicine/Pathobiology
College of Veterinary Medicine
Kansas State University
Manhattan, KS 66506
nINTRODUCTION
Afecal examination is considered a routine
procedurein many veterinary practices, but in
our experience, often little thought is given to
performing the procedurecorrectly.Although
fecal flotations should be performed byveteri-
narians or trained veterinary technicians, the
assignment is commonly given to the newest
staff member, with very little instruction or
emphasis on the importance of the task pro-
vided. For the past 10 years, informal surveys
of second-year veterinary students at Kansas
State University indicate that more than 90%
of the students had conducted “fecal examina-
tions” in practices where they had worked or
volunteered, yet most of these students had no
formal training in the proper performance of a
fecal flotation or identification of parasite eggs,
oocysts, or cysts.
Accurate evaluation of fecal samples is im-
portant and must be taken seriously by all
members of the clinical practice. Not only is
pet health at stake, but several of the parasites
that may be recovered and identified are po-
tentially zoonotic, such as Toxocara canis, Tox-
ocara cati, Ancylostoma caninum,Giardia spp,
Cryptosporidium parvum,and Toxoplasma
gondii. Arecently published study demonstrat-
ed that a 5-minute swing-head centrifugation
technique could recover more parasite eggs and

5
M. W. Dryden, P. A. Payne, and V. Smith
and emails we receive, we realize that many vet-
erinary practices find it difficult to diagnose
this disease using fecal examinations. There are
several reasons why identifying giardiasis is dif-
ficult in private practice. Many pseudoparasites,
such as yeasts (Figure 1), plant remnants, and
debris, havebeen mistaken for these tiny or-
ganisms. Identification of Giardia cysts is fur-
ther compromised because microscopes used in
private practice areoften not equipped with
micrometers that can allowmeasurement of
cysts as small as 8 to 12 ×7 to 10 µm. Cysts are
shed intermittently,and repeated fecal analyses
may be needed beforecysts are recovered in a
sample.2,3 Cysts aredelicate and deteriorate rap-
idly in fecal flotation solutions; if a fecal exam-
ination is conducted using a solution other
than zinc sulfate (ZnSO4), the cysts may be dis-
torted (Figures 2 and 3). In many clinics, the
only technique used is the direct smear; howev-
er, trophozoites are fragile and are often found
only in very fresh, diarrheic feces. Finally, be-
cause of the difficulty in detecting Giardia spp,
veterinarians have told us that they often rely
on a patient’s response to metronidazole treat-
ment as a presumptive diagnosis.
Several studies have demonstrated that re-
covery of Giardia cysts can best be accom-
oocysts and had fewer false-negative results
than passiveflotation techniques.1While a
swing-head centrifugation technique is more
efficient than passive flotation and will signifi-
cantly aid in the diagnosis of many parasites, it
is our experience that many practices using this
technique still struggle with the accurate iden-
tification of Giardia spp.
Giardiasis is a diagnostic dilemma. Weagree
that Giardia is one of the most commonly mis-
diagnosed, underdiagnosed, and overdiagnosed
parasites. Based on the numerous phone calls
Figure 1. Yeasts (12–15 µm) recovered in a fecal ex-
amination and incorrectly identified as Giardia cysts
in a referring veterinarypractice.
Figure 2. Giardia cysts stained with Lugol’s iodine re-
covered using 1.18-SG ZnSO4in a swing-head cen-
trifugation technique.
Figure 3. Giardia cysts recovered using 1.27-SG
Sheather’s sugar solution in a swing-head centrifuga-
tion technique.

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
6
plished using a 1.18–specific gravity (SG)
ZnSO4centrifugation technique.2–5 This has
been the diagnostic test of choice for many vet-
erinarypractices and veterinary diagnostic lab-
oratories, including that of Kansas State Uni-
versity. While the ZnSO4centrifugation
technique recovers and maintains the integrity
of Giardia cysts more consistently than other
flotation techniques, it still does not alleviate
the problem of proper cyst identification. Sev-
eral fecal antigen tests have been developed
that appear to have high sensitivity in detecting
Giardia antigen in human feces; however, they
do not have the same level of sensitivity in de-
tecting giardiasis in dogs and cats when com-
pared with centrifugation using ZnSO4.3,4,6
This article describes several investigations
that were designed to compare the fecal antigen
SNAP Giardia T
est Kit (Idexx Laboratories) and
aZnSO4centrifugation fecal flotation tech-
nique. Additional data on centrifugation versus
apassivefecal flotation technique for the recov-
eryof parasite eggs and oocysts arealso present-
ed so that more complete recommendations can
be made concerning routine parasite diagnostic
procedures for private veterinary hospitals.
nMATERIALS AND METHODS
Two groups of purpose-bred beagles (14 in
2004; 12 in 2005) housed at the Animal Re-
source Facility at Kansas State University for
other research projects were found to be natu-
rally infected with Giardia spp and shedding
cysts on a routine basis. In 2004, the 14 dogs
had been allocated for the other research proj-
ect to eight runs, with two dogs in each of six
runs and one dog each in two other runs. In
2005, the 12 dogs had been allocated to seven
runs, with two dogs in each of five runs and
one dog each in two other runs. Once a week
for 4 to 5 weeks, feces was collected from the
runs and examined for the presence of Giardia
cysts. An attempt was made to collect feces
from each dog in pens that housed two dogs.
The fecal samples from a pen were mixed thor-
oughly and split into two subsamples. One
Standard Swing-Head Centrifugation Fecal Examination Technique
1. Weigh out 2–5 g of feces.
2. Mix feces with approximately 10 ml of flotation solution.
3. Pour mixture through a tea strainer into a beaker or fecal cup.
4. Pour strained solution into a 15-ml centrifuge tube.
5. Fill tube with flotation solution so that a slight positive meniscus forms.a
6. Place a coverslip on the tube, and put the tube in the centrifuge.
7. Make sure the centrifuge is balanced.
8. Centrifuge at 1,200 rpm (280 ×g)for 5minutes.
9. Remove the tube and let stand 10 minutes.
10. Remove the coverslip, and place it on a glass slide. Systematically examine the entire area under the
coverslip at 100×magnification (i.e., 10×objective). You may wish to use the 40×objective lens to
confirm your diagnosis and make measurements; however, with practice, most parasites can be iden-
tified using the 10×objective (100×magnification).
aDo not overfill the tube. Doing so will cause some of the floating eggs to be forced down the side of the tube when
the coverslip is placed.
Adapted from: Dryden MW, Payne PA, Ridley R, Smith V: Comparison of common fecal flotation techniques for the
recovery of parasite eggs and oocysts. Vet Ther 6(1):16, 2005.

subsample was evaluated with a swing-head
centrifugation technique (see box on page 6)
using 1.18-SG ZnSO4,with one drop of Lu-
gol’s iodine placed on the slide before place-
ment of the coverslip. The second subsample
was evaluated using the SNAP Giardia Test Kit
according to label directions. Samples were
scored as either positive or negative. Each fecal
sample was evaluated by one of the authors
(V.S.), who has more than 14 years of experi-
ence conducting and examining fecal samples
at Kansas State University.
Athird evaluation of the SNAP Giardia Test
Kit was conducted by second-year veterinary
students during the fall of 2005. Fecal samples
from 116 puppies were provided by a local bro-
ker. These students had just listened to a lecture
on giardiasis, been given a short visual presenta-
tion on identification of Giardia cysts, and had
previously conducted direct smears and fecal ex-
aminations using the swing-head centrifugation
technique before participating in this exercise.
Students were also given written directions on
conducting SNAP Giardia tests.
For the direct smear, a small sample of feces
was placed on a glass slide and mixed with a
drop or two of saline. The material was spread
thinly, a drop of Lugol’s iodine was added, and
the slide was covered with a glass coverslip.
Each fecal sample was analyzed using a direct
smear technique, centrifugation, and the
SNAP Giardia Test Kit. Samples and tech-
niques were recorded as either positive or neg-
ative. Each of the 107 veterinary students con-
ducted at least one fecal examination, and nine
students evaluated two samples.
Data for the final evaluation of diagnostic
techniques came from a “wet lab” conducted at
the 2005 Central Veterinary Conference. A
group of veterinarians and veterinarytechni-
cians attended a wet lab on conducting proper
fecal examinations. Participants were provided
with a fecal sample from naturally parasitized
dogs. The sample was a pooled sample from
several dogs and contained eggs of A. caninum,
Eucoleus boehmi, Taenia spp, T. canis, and
Trichuris vulpis; oocysts of Cystoisospora spp;
and Giardia spp cysts. In addition, the sample
tested positive on the SNAP Giardia fecal anti-
gen test kit.
Participants were given a short lecture before
the wet lab on how to conduct the various
techniques, provided written instructions, and
shown color images of all parasite eggs,
oocysts, and cysts that were in the fecal sample.
Visual instruction included images of Giardia
cysts recovered in ZnSO4and sugar solutions
(Figures 2 and 3). Each participant collected
two “quarter-sized” samples from the feces and
conducted a 15-minute Ovassay (Synbiotics), a
swing-head centrifuge technique (5-minute
spin at 280 ×gfollowed by a 10-minute wait
beforeanalysis; see boxon page 6), and a
SNAP Giardia test. The participants were di-
vided into two groups:
• Group 1 used 1.18-SG ZnSO4for the flota-
tion solution and added one drop of Lugol’s
iodine to the slide beforeplacing the coverslip.
Modified Sheather’s Solution (SG 1.27)a
454 g granulated sugar
355 ml tap water
6ml formaldehyde
Dissolve sugar and water in the top of a dou-
ble boiler or with gentle heat. If solution is
not clear, filter it through coarse filter paper.
aCheck specific gravity (SG) with a hydrometer that
has a range compatible with the solution being test-
ed. Hydrometers with ranges of 1.000–1.400 are
available.
Adapted from: Dryden MW, Payne PA, Ridley R,
Smith V: Comparison of common fecal flotation
techniques for the recovery of parasite eggs and
oocysts. Vet Ther 6(1):17, 2005.
7
M. W. Dryden, P. A. Payne, and V. Smith

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
8
• Group 2 used 1.27-SG Sheather’s sugar so-
lution (see box on page 7).
Participants were asked to record the number
of eggs, oocysts, or cysts recovered as 0, 1 to
10, 11 to 50, or more than 50 per slide. Com-
pleted results were returned by 14 participants
in Group 1 and 13 in Group 2.
nRESULTS
As is typical of Giardia infections, cyst shed-
ding was not consistent during the evaluation
period of the naturally infected beagles (Tables
1and 2). Fecal samples from beagles evaluated
in 2004 werefound to be positive using the
ZnSO4centrifugation method 87.5%, 75%,
37.5%, and 50% of the time during weeks 1,
2, 3, and 4, respectively (Table 1). The SNAP
Giardia fecal antigen test produced a positive
reaction in 62.5%, 50.0%, 50.0%, and 62.5%
of the fecal samples during weeks 1, 2, 3, and
4, respectively. During 2005, fecal samples
from the beagles were found to be positive us-
ing the ZnSO4centrifugation method 57.14%
of the time in week 1 and 85.57% during
weeks 2 and 3, and all were positive in week 5
(Table 2). The SNAP Giardia fecal antigen test
produced a positive reaction 85.57% of the
time in fecal samples collected during weeks 1
to 3, and all samples were antigen positive in
weeks 4 and 5 (Table 2).
Interestingly,there weretimes when one or
both tests produced false-negative results (Ta-
bles 1 and 2). In 2004, when results from both
tests werecombined, the accuracy of diagnosis
was increased during three of the four weeks.
Combining test results led to a positive diag-
nosis in 100.0%, 75.0%, 50.0%, and 75.0%
TABLE 1. Evaluation of Repeated 1.18-SG ZnSO4Centrifugation Fecal Flotations and
SNAP Giardia Tests to Identify Giardia-Positive Beagles: Trial 1, 2004
Pen No. of Week 1 Week 2 Week 3 Week 4
No. Dogs ZnSO4SNAP ZnSO4SNAP ZnSO4SNAP ZnSO4SNAP
12++++––+–
22+–––––++
32++++++++
42+++++–––
52+++––+++
62+–+–++––
71–+++–+–+
81+––––––+
No. of dogs or 7 5 6 4 3 4 4 5
pens testing
positive
Total no.of dogs 8 6 5 6
or pens testing
positive

of the fecal samples during weeks 1, 2, 3, and
4, respectively. In the 2005 trial, however, only
during week 3 did combining test results in-
crease diagnostic accuracy (Table 3).
In the evaluations conducted by the second-
year veterinary students, almost half (56 of
116) of the puppy fecal samples were recorded
as positive for Giardia (Table 3). The direct
smear technique detected the fewest number of
positive samples, with students recording only
four positivesamples. These direct smear tech-
nique data may be artificially low since the fe-
cal samples were collected several hours before
being tested and trophozoites may have been
dead at the time of examination. Students
recorded that the SNAP Giardia fecal antigen
test identified 11 samples as Giardia positive
even though they did not identify any cysts
with the ZnSO4centrifugation technique
(Table 3). There was only one fecal sample that
was positivein the ZnSO4centrifugation tech-
nique and negative on the SNAP Giardia fecal
antigen test.
Twenty-seven participants returned complet-
ed forms from the Central Veterinary Confer-
ence wet lab. The centrifugation versus passive
flotation technique data from the wet lab
demonstrated that centrifugation with either
1.18-SG ZnSO4or 1.27-SG Sheather’s sugar
solution routinely recovered more eggs and
oocysts than the passive Ovassay technique
(Table 4). Not only did the centrifugation tech-
nique recover more eggs and oocysts, but the
participants also recorded many more samples
as positive with the centrifugation technique.
Only once did the Ovassay technique recover
all parasites in all samples; in contrast, only
once did the centrifugation technique fail to re-
cover all parasites in all samples (Table 4). Only
two of 14 participants in Group 1 (1.18-SG
ZnSO4solution) recovered T
aenia eggs using
the centrifugation procedure, whereas all 13
TABLE 2. Evaluation of Repeated 1.18-SG ZnSO4Centrifugation Fecal Flotations and
SNAP Giardia Tests to Identify Giardia-Positive Beagles: Trial 2, 2005
Pen No. of Week 1 Week 2 Week 3 Week 4 Week 5
No. Dogs ZnSO4SNAP ZnSO4SNAP ZnSO4SNAP ZnSO4SNAP ZnSO4SNAP
12––––+–++++
22–+++++++++
31++++++++++
42++++–+++++
52–+++++++++
62++++++++++
71++++++–+++
No. of dogs or 4 6 6 6 6 6 6 7 7 7
pens testing
positive
Total no. of 6 6 7 7 7
dogs or pens
testing positive
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M. W. Dryden, P. A. Payne, and V. Smith

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
10
participants in Group 2 (1.27-SG Sheather’s
sugar solution) recovered Taenia eggs using the
centrifugation technique (Table 4).
Even though the participants in the wet lab
weretold the samples were positive for Giardia
cysts, recoveryand identification of Giardia
cysts was problematic for the participants re-
gardless of the technique used. Only six of 27
participants wereable to recover and identify
Giardia cysts from a known positive sample:
One participant using the centrifugation tech-
nique with ZnSO4,one using Ovassay with
ZnSO4, one using Ovassay with Sheather’s sug-
ar solution, and three using the centrifugation
technique with Sheather’s sugar solution. All
27 participants had a positive SNAP Giardia
fecal antigen test on the sample provided.
nDISCUSSION
A1.18-SG ZnSO4flotation with centrifuga-
tion should be adequate for the diagnosis of
Giardia spp bytrained personnel,2–4 but be-
cause many clinics do not use centrifugation
techniques and cyst shedding is intermittent, it
is often necessaryto examine several sequential
daily samples to ensureaccuracy of diagnosis.
The intermittent natureof cyst shedding was
particularly evident in the evaluation of sam-
ples from beagles during 2004. Inthe trials
evaluating repeated fecal examinations from re-
search beagles, a single ZnSO4fecal flotation
with centrifugation was positive 37.5% to
87.5% of the time in the 2004 investigation
and 57.14% to 100% of the time in the 2005
investigation. The sensitivity of the SNAP Gi-
ardia fecal antigen test was comparable, with
positive results obtained 50% to 62.5% of the
time in the 2004 investigation and 85.57% to
100% in the 2005 investigation. This further
demonstrates that a single negative ZnSO4fe-
TABLE 3. Evaluation by Second-Year Veterinary Students of 1.18-SG ZnSO4
Centrifugation Fecal Flotations and SNAP Giardia Tests to Identify Giardia spp in
Puppies
Giardia+
by
SNAP+/ ZnSO4+/ SNAP+/ SNAP– / Combined
Category SNAP+ ZnSO4+ ZnSO4– SNAP– ZnSO4+ ZnSO4– Methods
No. of samples in 55 45 11 1 44 60 56
each category (total
no. of samples
tested = 116)
Percentage of 47.41% 38.79% 9.48% 0.86% 37.93% 51.72% 48.28%
samples in each
category
Percentage of 56 98.21% 80.36% 19.64% 1.79% 78.57%
samples recorded
as Giardia positive
identified as positive
by each specific
procedure

cal flotation with centrifugation or a negative
in-clinic Giardia fecal antigen test does not
necessarily rule out Giardia infection. Interest-
ingly, if three consecutive weekly ZnSO4fecal
flotations with centrifugation were performed
on the beagles in either trial, a positive diagno-
sis would haveoccurred in 100% of the bea-
gles. This is in agreement with a previous in-
vestigation that demonstrated that it may take
three consecutiveZnSO4fecal flotations to
achieve 94% accuracy in positive Giardia diag-
nosis.2The problem is that in a private prac-
tice, conducting three fecal examinations on
samples collected on consecutive days is often
impractical.
Although the ZnSO4centrifugation proce-
dure conducted by a well-trained technician has
been considered the gold standard for the diag-
nosis of Giardia spp in dogs2–5 and was highly
accurate in the evaluation of the beagles when
the fecal samples were examined by a highly
trained technician, the second-year veterinary
students with less experience and training
recorded 11 samples as cyst negative that were
positiveon the SNAP Giardia fecal antigen test
kit. We werethe instructors during that class
TABLE 4. Veterinarian and Veterinary Technician Comparison of Ovassay and
Centrifugation Techniques for Recovery of Parasite Eggs and Oocysts Using 1.18-SG
ZnSO4aor 1.27-SG Sheather’s Sugar Solution
GROUP 1—ZnSO4(n = 14)
Ovassay Centrifugation
PARASITES 0 1–10 11–50 >50 % Positive 0 1–10 11–50 >50 % Positive
T. canis 0 7 7 0 100.0 0 1 4 9 100.0
T. vulpis 2 9 3 0 85.71 0 2 8 4 100.0
A. caninum 1 12 1 0 92.86 0 4 7 4 100.0
Taenia spp 13 1 0 0 7.69 12 2 0 0 14.29
Eucoleus boehmi 10 4 0 0 28.57 0 9 5 0 100.0
Cystoisospora spp 10 4 0 0 28.57 0 6 8 0 100.0
GROUP 2—Sheather’s Sugar Solution (n = 13)
Ovassay Centrifugation
PARASITES 0 1–10 11–50 >50 % Positive 0 1–10 11–50 >50 % Positive
T. canis 3 5 5 0 76.92 0 0 4 9 100
T. vulpis 2 7 4 0 84.62 0 0 6 7 100
A. caninum 7 4 2 0 46.15 0 0 7 6 100
Taenia spp 5 8 0 0 61.54 0 3 10 0 100
Eucoleus boehmi 10 3 0 0 23.08 0 4 9 0 100
Cystoisospora spp 7 6 0 0 46.15 0 3 10 0 100
aParticipants recorded the number of eggs recovered as 0, 1–10, 11–50, or >50 eggs/slide.
11
M. W. Dryden, P. A. Payne, and V. Smith

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
12
period and noted that while some of the sam-
ples contained numerous cysts (Figure 2), oth-
ers contained only a few cysts. We were unable
to examine every sample examined by the stu-
dents, but there were several samples that the
students identified as SNAP positive–float neg-
ative in which an instructor subsequently iden-
tified cysts. It must be noted that, in these in-
vestigations, we were unable to ascertain if any
of the SNAP positive–float negative samples
were in fact true false-positives.
The inability to recognize a few Giardia
cysts is likely one of the problems encountered
by the veterinarians and veterinary technicians
who participated in the wet lab. The sample
did not contain numerous Giardia cysts, and
they are smaller than the other parasite eggs
and oocysts in the sample. As wewalked
around the room to assist the participants, we
observed cysts in almost every sample evaluat-
ed using either ZnSO4or Sheather’s sugar so-
lution. Many of the participants were unable
to recognize the small cysts.
Since cyst shedding is notoriously intermit-
tent, the number of Giardia cysts recovered on
any given day is likely not a good indicator of
the level of infection. In a previous investiga-
tion, it was noted that dogs could have almost
a10-fold change in the number of cysts recov-
ered on quantitative fecal examinations con-
ducted 3 days apart.3Inthat study,the cysts/g
of one control dog went from less than 10 to
3,190 within 3 days. Inanother dog, the cyst/g
count increased from 150 to 44,610 within 3
days. The clinical implication of finding only a
fewGiardia cysts on fecal analysis may be no
different from finding hundreds. Therefore, fe-
cal examination from dogs or cats suspected of
having giardiasis requires careful microscopic
examination in case they are shedding low
numbers of cysts.
As noted previously, ZnSO4has been shown
to be the most efficient flotation solution for
recovery of Giardia cysts and is often used in
veterinary practices. The wet lab conducted at
the Central Veterinary Conference highlighted
apotential problem in using 1.18-SG ZnSO4,
even in a centrifugation procedure. Only two
of 14 (14.29%) participants using the 1.18-SG
ZnSO4centrifugation procedure correctly
recorded that the sample was positive for Tae-
nia eggs, while 100% of the participants using
the 1.27-SG Sheather’s sugar solution recov-
ered Taenia eggs from the same sample. This
result was not completely unexpected since
Taenia eggs have an average SG of 1.2251.7
This indicates that veterinary practices using
1.18-SG ZnSO4as their flotation solution are
likely failing to identify some dogs infected
with Taenia tapeworms and possibly other par-
asites that shed heavy eggs, such as Physaloptera
spp, which have eggs with an average SG of
1.2376.7Another investigation that evaluated
the SG of a fecal flotation solution indicated
that solutions with SGs of 1.22 to 1.35 would
be best for routine laboratory use.8
If giardiasis is on the differential list of a dog
(or cat) with diarrhea, the data indicate that
conducting both ZnSO4centrifugation fecal
flotation and a SNAP Giardia fecal antigen test
may increase the chances of recording a posi-
tive finding. However, it must also be remem-
bered that a single negative examination, even
if both tests areconducted simultaneously,
It may take three consecutive ZnSO4fecal flotations to
achieve 94% accuracy in positive Giardia diagnosis.

does not necessarily rule out giardiasis. Three
fecal examinations over a 7-day period using
both techniques will almost ensure a correct di-
agnosis. While using the proper Giardia cyst
recovery technique is important, identification
of recovered cysts is critical. In the Central Vet-
erinary Conference wet lab, registered veteri-
nary technicians and veterinarians had great
difficulty identifying cysts even when informed
the samples were positive. Proper training of
veterinarians and clinical staff on how to cor-
rectly identify Giardia cysts is important and
would greatly improve diagnostic accuracy, but
training or retraining of personnel already in
practices may be difficult on a large-scale basis.
The major question is, “What procedure or
procedures should be conducted for routine fe-
cal examinations?” Data from this current
study and another previously published study1
would suggest that the swing-head centrifuga-
tion technique using 1.27-SG Sheather’s sugar
solution is an efficient method of recovering
many commonly encountered parasite eggs
and oocysts. However, while the sugar solution
is effective for many eggs and oocysts, it dis-
torts and/or destroys most Giardia cysts, often
rendering them unrecognizable to most veteri-
narians and technicians (Figure 3). In addition,
currently used sugar solutions must be mixed
on site (see boxon page 7) and some chemical
needs to be added (e.g., phenol, formalin) to
prevent bacterial growth. Sugar solutions are
also sticky and can attract flies. Many practices,
therefore, have used commercially available salt
solutions for routine fecal examinations, in-
cluding ZnSO4. However,as demonstrated in
this investigation, a 1.18-SG ZnSO4flotation
solution may not be able to float parasite eggs
with a higher SG.
nCONCLUSION
Because of the inability of 1.18-SG ZnSO4
flotation solution to consistently recover heav-
ier parasite eggs, it may be prudent for many
veterinary practices to conduct routine fecal
examinations using 1.27-SG Sheather’s sugar
solution. While some salt solutions may be
used as a practical alternative, the use of a cen-
trifugation technique will undoubtedly in-
crease diagnostic efficacy. Veterinary practices
should also consider the routine use of a hy-
drometer so that the proper SG of their flota-
tion solution can be assured. In addition, if gi-
ardiasis is encountered in the practice area,
fecal examinations should include a SNAP
Giardia fecal antigen test. The difficulty we
noted in the ability of veterinarians, veterinary
technicians, and veterinarystudents to identify
Giardia cysts in our studies is likely reflective
of the situation in many practices. Therefore,
the in-clinic soluble SNAP Giardia fecal anti-
gen Test Kit likely will improve a clinic’s abili-
ty to arrive at a correct diagnosis. In addition,
the proper recovery and identification of para-
sites should allowfor a moretargeted thera-
peutic approach.
nACKNOWLEDGMENTS
We thank IDEXX Laboratories for partial support of this
study and for supplying the SNAP Giardia Test Kits.
Thanks also to the second-year veterinary students at
Kansas State University who took Veterinary Parasitology
during the fall of 2005. Wealso thank Bayer Animal
The in-clinic soluble SNAP Giardia fecal
antigen Test Kit likely will improve a clinic’s
ability to arriveat a correct diagnosis.
13
M. W. Dryden, P. A. Payne, and V. Smith

Veterinary Therapeutics •Vol. 7, No. 1, Spring 2006
14
Health for sponsoring the wet lab at the Central Veterinary
Conference.
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