PARINT-00891; No of Pages 4
Parasitology International xxx (2011) xxx–xxx
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Parasitology International
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p a r i n t
Secnidazole for the treatment of giardiasis in naturally infected cats
Aleksandro S. Da Silva a,⁎, Verônica S.P. Castro b, Alexandre A. Tonin a, Sabrina Brendler a, Marcio M. Costa b,
Jeandre A. Jaques a, Bianca Bertoletti b, Régis A. Zanette a, Alceu G. Raiser b, Cinthia M. Mazzanti b,
Sonia T.A. Lopes b, Silvia G. Monteiro a
a
b
Department of Microbiology and Parasitology, Universidade Federal de Santa Maria, Brazil
Department of Small Animals, Universidade Federal de Santa Maria, Brazil
a r t i c l e
i n f o
Article history:
Received 29 March 2011
Received in revised form 18 June 2011
Accepted 24 June 2011
Available online xxxx
Keywords:
Giardia
Secnidazole
Feline
Hemogram
Biochemical parameters
a b s t r a c t
Giardia duodenalis causes enteric infections in humans and animals worldwide. Inefﬁciency of metronidazole
is commonly reported in the veterinary clinic routine in the treatment of giardiasis in dogs and cats. The aim of
this study was to evaluate the efﬁcacy of secnidazole in the control of infection caused by G. duodenalis in
naturally infected cats. For this purpose two experiments were carried out. In the ﬁrst experiment seven cats
were infected with G. duodenalis and treated orally with a single dose of secnidazole (30 mg kg−1). In the
second experiment a total of 16 cats were used, 11 naturally infected with G. duodenalis and ﬁve negative for
the parasite. Animals were divided into three groups: group A (n = 5) was composed by non-infected animals
(negative control), group B (n = 5) consisted of infected but untreated animals and group C (n = 6) was
composed by cats treated orally with a single dose of secnidazole (30 mg kg−1). Hematological and
biochemical parameters were evaluated before and after treatment. The ﬁrst experiment reached 100% of
efﬁcacy because no cysts were found in the feces after treatment. However, doubts about intoxication and
interference with hematological and biochemical parameters came to light. No side effects were observed,
and the biochemical and hematological parameters of treated animals remained within physiological range,
except for one feline which had elevation of liver enzymes. Based on these results, the utilization of
secnidazole could be suggested for the treatment of giardiasis in cats. The main advantage of this treatment is
that only a single dose is required, which is interesting in animals hard to handle like cats.
© 2011 Elsevier Ireland Ltd. All rights reserved.
1. Introduction
The ﬂagellated protozoan Giardia duodenalis (syn. G. intestinalis,
G. lamblia) commonly causes enteric infections in humans and
animals worldwide [1,2]. Several genotypes have been identiﬁed,
which may have different host species speciﬁcities [3,4]. G.
duodenalis exists in two different forms, the trophozoite and the
cyst. The trophozoite is motile and is found in the intestinal lumen,
whereas the cyst is the transmissible form and is capable of
prolonged survival in the environment [5]. Transmission occurs
through ingestion of the cyst and once in the duodenum each cyst
releases two trophozoites, which then attach to the intestinal
epithelium [4].
Molecular and epidemiological studies showed that G. duodenalis
is composed by at least seven genetically distinct assemblages, but
morphologically identical (A to G). Moreover, assemblages C to G
appear to have host-speciﬁc preferences [6,7]. Genotypes of assem⁎ Corresponding author at: Departamento de Microbiologia e Parasitologia da UFSM,
Faixa de Camobi, Km 9, Campus Universitário, Santa Maria, RS, Brazil, 97105-900,
Prédio 20, Sala 4232. Fax: + 55 55 3220 8958.
E-mail address: [email protected] (A.S. Da Silva).
blages A and B are known to infect humans, cattle and companion
animals such as dogs and cats [8–10]. Assemblage F was detected in
cats [11]. According to researchers, livestock are unlikely to be an
important source of infection in humans, but the greatest risk of
zoonotic transmission appears to be from companion animals such as
dogs and cats [12]. However, the role of dogs and cats as a source of
human giardiasis remains unclear [13], once several reports are
divergent about the zoonotic potential.
Cats can be subclinical or have diarrhea due to maldigestion,
malabsorption and increased motility in consequence of giardiasis
[14]. In Brazil, this protozoan is widely distributed, parasitizing
humans, domestic and wild animals [15,16]. The most severe cases of
giardiasis occur in young or immunosuppressed animals [16].
Metronidazole and fenbendazole have been used in the treatment
of feline and canine giardiasis [1,17,18]. All the studies which showed
the efﬁcacy of metronidazole in eliminating Giardia cysts in cats
naturally and experimentally infected included only a small number
of cats [19,20]. Moreover, drug resistance against giardiasis, especially
to metronidazole and albendazole, has been reported elsewhere [21].
Inefﬁcacy of metronidazole is commonly reported in veterinary
routine when it is used in the treatment of giardiasis in dogs and cats
(personal communication), and reinfection has been implicated as the
1383-5769/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.parint.2011.06.024
Please cite this article as: Da Silva AS, et al, Secnidazole for the treatment of giardiasis in naturally infected cats, Parasitol Int (2011),
doi:10.1016/j.parint.2011.06.024
2
A.S. Da Silva et al. / Parasitology International xxx (2011) xxx–xxx
most common cause of treatment failure [22,23]. Thus, seeking for
new therapeutic options, this study aimed to test the efﬁcacy of
secnidazole in the control of giardiasis in naturally infected cats.
2. Materials and methods
2.1. Experiment 1
Seven female cats aging between six and 12 months were used in
this study. The animals were acquired to perform an experimental
study in the Laboratory of Veterinary Parasitology of the Federal
University of Santa Maria (UFSM), Brazil. When the animals arrived at
the laboratory, three of them had diarrhea and dehydration.
Thereafter, 1 g of fecal samples from each animal was examined by
the zinc sulphate centrifugal ﬂotation technique [24]. As a result, all
animals showed high infection by cysts of Giardia (more than 300
cysts/slide).
Once diagnosed the disease, the cats were weighed and housed in
individual cages in an experimental room with controlled temperature and humidity (25 °C; 70% U.R.). They were fed with commercial
chow and water ad libitum. At the same day, the cats received a single
oral dose (1 mL) of 30 mg kg −1 secnidazole diluted in water. The cats
were daily monitored for clinical signs of drug toxicity and clinical
alterations after the administration of the drug. For the evaluation of
drug efﬁcacy, feces were re-examined at days 6, 7 and 8 posttreatment.
2.2. Experiment 2
The experiment 2 was designed to clarify some doubts remaining
from experiment 1, such as: (1) is secnidazole toxic to cats and
responsible for the clinical signs observed in four cats of experiment 1?;
(2) is the dose able to change hepatic and renal functions?; (3) does
secnidazole cause alterations in the hemogram of cats?; and (4) is the
dose administered really effective in the treatment of giardiasis in
felines?
To address this issue, fecal samples were collected from female
adult cats belonging to a cattery of UFSM. Samples (1 g) were
processed by the zinc sulphate centrifugal ﬂotation technique [24].
Eleven positive cats (more than 30 cysts of Giardia per gram of feces)
were used in this study, as well as ﬁve cats as negative controls. Cats
were divided into three groups. Group A (n = 5) consisted on cats
negative for giardiasis by fecal ﬂotation (negative controls), group B
(n = 5) consisted on cats positive for giardiasis by fecal ﬂotation but
not treated (positive controls) and group C (n = 6) consisted on cats
positive for giardiasis by fecal ﬂotation and treated with a single dose
of secnidazole (30 mg kg −1).
Cats were weighed and housed in individual cages in an
experimental room with controlled temperature and humidity
(25 °C; 70% U.R., respectively). They were fed with commercial diet
and water ad libitum. Hematological and biochemical parameters
were analyzed at days 0 and 5, after anesthesia with midazolam
(0.3 mg kg −1) and ketamine (1.0 mg kg −1). Approximately 1 mL of
blood was stored in tubes containing anticoagulant (EDTA) for
analysis of hemogram and 3 mL of blood was stored in tubes without
anticoagulant to obtain serum, which was used for evaluation of
hepatic and renal functions.
Erythrocyte count, hematocrit, hemoglobin concentration, mean
corpuscular volume, mean corpuscular hemoglobin concentration and
total leukocyte count were evaluated. Hematocrit and hematimetric
indexes were evaluated as previously described [25]. Erythrocyte and
leukocyte count and hemoglobin concentration were determined
using an electronic counter. Serum activity of alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT) and the levels of
creatinine and urea were evaluated in a semi-automatic analyzer
(TP Analyzer Plus®, Thermoplate-China) using commercial kits
(Labtest® Diagnóstica S.A., Lagoa Santa, MG, Brazil). Tests were
carried out in duplicates. For the evaluation of drug efﬁcacy, feces
were re-examined at days 6, 7 and 8 post-treatment.
The results were submitted to analysis of variance (ANOVA)
followed by the Tukey test. Signiﬁcance level was set at P b 0.05.
Statistical analysis was carried out vertically and horizontally to
hematological and biochemical parameters.
3. Results
3.1. Experiment 1
Five of seven cats showed high salivation rates during approximately 5 min after drug administration. The four most debilitated cats
presented apathy and did not eat during the ﬁrst 48 h post-treatment.
After this period, no clinical alterations were observed. Giardia spp.
cysts were not observed in the feces of all cats by microscopic
examination after fecal ﬂotation at days 6, 7 and 8 post-treatment.
Episodes of diarrhea were not more observed after the eighth day of
treatment. Therefore, the therapeutic protocol used obtained 100% of
effectiveness.
3.2. Experiment 2
Six of six cats showed high salivation rates during approximately
3 min after drug administration. No clinical signs were observed in the
cats treated with secnidazole. Giardia spp. cysts were not observed in
the feces of all cats by microscopic examination after fecal ﬂotation at
days 6, 7 and 8 post-treatment (Table 1). Therefore, the therapeutic
protocol used obtained 100% of efﬁcacy. Cats from group B maintained
the elimination of the parasite cysts in feces during the experimental
period (Table 1).
The hematological parameters remained within normal limits in
all cats before and after treatment (Table 2). The therapeutic protocol
used did not affect renal function in all treated cats (groups A and C),
as well as the hepatic function in the majority of animals (10/11)
(Table 3). Only one cat from group C had increased levels of ALT and
GGT post-treatment. ALT increased from 61 to 250 U/L and GGT from
2.56 to 7.2 U/L. Despite this increase, no clinical changes were
observed.
4. Discussion
Secnidazole is a commercialized drug for the treatment of
giardiasis in humans. It has the advantage to be administered in a
single dose with sound curative effects. Children treated with a single
dose of secnidazole (30 mg kg −1) achieved 98% [26] and 78.1% [27] of
cure. Researchers, in a comparative study between secnidazole and
metronidazole found a curative rate of 100% for secnidazole and 96%
for metronidazole [28]. When metronidazole was used in a single
dose, its curative rate was reduced to 36–54% [29,30]. On the other
hand, a single dose of secnidazole reaches the same response achieved
with multiple dosage regimens of metronidazole or tinidazole [26,28].
Table 1
Means and standard deviations of Giardia duodenalis cysts in the feces of cats before and
after treatment with secnidazole in Experiment 2.
Group
Number of Giardia duodenalis cysts
Before treatment
A: Negative control (n = 5)
B: Positive control (n = 5)
C: Treated group (n = 6)
a
0.0 (± 0.0)
97.8b (± 43.7)
89.2b (± 46.1)
After treatment
0.0a (± 0.0)
103.1b (± 51.9)
0.0a (± 0.0)
Comparison among groups: Means followed by same letters in the same column were
not statistically different from each other (Tukey test).
Please cite this article as: Da Silva AS, et al, Secnidazole for the treatment of giardiasis in naturally infected cats, Parasitol Int (2011),
doi:10.1016/j.parint.2011.06.024
A.S. Da Silva et al. / Parasitology International xxx (2011) xxx–xxx
3
Table 2
Means and standard deviations of hematological parameters in cats naturally infected by Giardia duodenalis before and after treatment with secnidazole in Experiment 2.
Parameters
Hematocrit (%)
Erythrocytes (×106/μl)
Hemoglobin (g/dl)
MCV (ﬂ)
MCHC (%)
Leukocytes (×103/μl)
Group A
Group B
Group C
Before treatment
After treatment
Before treatment
After treatment
Before treatment
After treatment
29.6
5.85
9.8
50.7
33.2
9.4
33.6
6.20
10.9
46.6
33.5
13.2
28.6
6.2
9.0
48.2
31.4
10.2
29.0 (± 1.2)
5.58 (± 0.4)
9.2 (± 0.45)
51.9 (± 1.9)
31.0 (± 0.3)
12.6 (± 3.7)
32.2
6.50
10.0
47.3
32.1
9.5
32.4
6.16
10.2
45.5
31.4
12.5
(± 2.01)
(± 0.46)
(± 0.60)
(± 1.3)
(± 0.5)
(± 2.7)
(± 3.1)
(± 0.30)
(± 1.10)
(± 4.1)
(± 0.7)
(± 0.9)
(± 1.5)
(± 0.48)
(± 0.36)
(± 1.7)
(± 0.4)
(± 4.4)
(± 3.90)
(± 0.68)
(± 1.06)
(± 3.1)
(± 0.9)
(± 4.2)
(± 4.40)
(± 0.76)
(± 1.47)
(± 2.7)
(± 0.17)
(± 2.1)
No statistical difference with the hematological parameters was observed among groups or before and after treatment.
In the present study, the curative efﬁcacy of secnidazole in cats
infected by G. duodenalis was 100%. Similar efﬁcacy of this drug
was observed in a comparative study with metronidazole (97%),
fenbendazole (98%) and secnidazole (100%) in mice naturally
infected by G. muris[31]. Studies involving treatment with
secnidazole in cats with giardiasis have not been performed yet,
although some veterinarians in southern Brazil have been using
this drug in a single dose of 30 mg kg −1 for dogs and cats,
achieving good curative rates (personal communication). The main
reason for the limited used of secnidazole in the treatment of feline
giardiasis is because it is not commercially available for veterinary
therapy.
Metronidazole has been used frequently in the treatment of
giardiasis in humans and cats. An experimental study showed that
metronidazole benzoate (25 mg kg −1 orally twice a day for 7 days)
was able to eliminate Giardia cyst shedding in cats with chronic
infection [32]. The metronidazole is in the nitromidazole class of
agents. Once the drug enters the parasite it becomes activated by the
reduction of the nitro group and binds covalently to DNA molecules,
resulting in irreversible helical damage and death of the organism
[23]. Good curative efﬁcacy in cats experimentally infected with
different Giardia species was obtained by researchers [13] when
using a combination product containing febantel, pyrantel and
praziquantel for 5 days. The combination febantel–praziquantel–
pyrantel can also be used to treat dogs with giardiasis, but according
to the authors bathing and changing the environment after treatment may be more important in preventing recurrence than
duration of treatment with or without vaccination with a commercial Giardia vaccine [33].
Salivation was observed in the cats after drug administration but
the symptom was limited only for 3–5 min. Loss of appetite and
apathy observed in four animals of experiment 1 are likely to be
consequence of giardiasis, since these alterations were observed
only in debilitated animals, with dehydration and diarrhea. In
Experiment 2, the treated cats did not show any clinical signs other
than the short period of salivation after drug administration, and
their liver and kidney functions were with normal range. Moreover,
ALT, GGT, urea and creatinine remained within normal physiological
ranges in the majority of the animals. The animal with increased ALT
and GGT levels was the only one of the experiment 2 which showed
high infection by G. duodenalis associated with diarrhea. According
to researchers, secnidazole may interfere with the results of several
biochemical analysis, such as the determination of liver transaminases (AST and ALT) activities and triglycerides [34], being this
information also mentioned in the leaﬂet of the drug. Another
important feature of secnidazole lies in the fact that the dose
administered in the cats did not interfere with hematological
parameters. Therefore, since neither clinical signs nor alterations
were observed in the hematological and biochemical assays, it is
possible to suggest secnidazole may be an additional drug for
treatment of giardiasis in cats.
Absence of Giardia cysts does not guarantee that the infection was
eliminated. Peaks of cyst shedding occur sporadically rather than
cyclically, from undetectable to concentrations above 1,000,000
cysts/gram of feces, and the duration between any two given peaks
is generally from 2 to 7 days [35]. Immunoﬂuorescence and PCR are
more sensitive assays than the fecal ﬂotation technique [36,37].
Notwithstanding, animals of Experiment 1 showed health improvement and absence of diarrhea after treatment.
At the end of the experiment, ﬁve cats from group B were
successfully treated with the same protocol of those from group C.
Therefore, a total of 18 cats were treated in this study with 100% of
efﬁcacy for the protozoan. Based on these results, it is concluded that
the secnidazole-based protocol is effective in cats naturally infected
by G. duodenalis. However, this product is only commercialized for
human medicine usage, and from now on it is expected that the
industry of veterinary products may consider the commercial
production of this medicine for veterinary therapeutic, which would
help in the treatment of giardiasis in domestic cats, that are
particularly difﬁcult to treat. Despite the promising results achieved
with secnidazole further studies with lower doses and different age
groups are required, mainly as attempting to dosage reduction and
evaluating its effectiveness.
Ethics committee
The study was approved by the Committee of Ethics and Animal
Welfare of the Rural Science Center of the Federal University of Santa
Maria (CCR/UFSM), no 11/2011 in accordance with existing legislation
Table 3
Means and standard deviations of biochemical parameters in cats naturally infected by Giardia duodenalis, before and after treatment with secnidazole in Experiment 2.
Parameters
ALT (U/L)
GGT (U/L)
Urea (mg/dL)
Creatinine (mg/dL)
Group A
Group B
Group C
Before treatment
After treatment
Before treatment
After treatment
Before treatment
After treatment
54.3
4.1
38.4
1.0
79.6 (± 26.7)
4.0 (± 1.5)
62.3 (± 13.0)
1.3 (± 0.12)
69.5 (± 17.1)
3.1 (± 0.7)
48.0 (± 5.1)
1.5 (± 0.3)
76.0
2.4
71.9
1.0
62.5
3.8
45.5
1.28
92.6 (± 76.1#)
4.5 (± 3.4#)
48.6 (± 6.5)
1.3 (± 0.25)
(± 11.7)
(± 1.7)
(± 12.4)
(± 0.11)
(± 30.1)
(± 0.9)
(± 15.1)
(± 0.2)
(± 17.0)
(± 2.7)
(± 5.7)
(± 1.14)
No statistical difference with the hematological parameters was observed among groups or before and after treatment. # The high standard deviation observed after treatment in
Group C is due to increased ALT and GGT levels in one cat. ALT increased from 61 to 250 U/L and GGT from 2.56 to 7.2 U/L.
Please cite this article as: Da Silva AS, et al, Secnidazole for the treatment of giardiasis in naturally infected cats, Parasitol Int (2011),
doi:10.1016/j.parint.2011.06.024
4
A.S. Da Silva et al. / Parasitology International xxx (2011) xxx–xxx
and the Ethical Principles published by the Brazilian College of Animal
Experiments (COBEA).
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Please cite this article as: Da Silva AS, et al, Secnidazole for the treatment of giardiasis in naturally infected cats, Parasitol Int (2011),
doi:10.1016/j.parint.2011.06.024