|
Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 97, Num. 1, 2002, pp. 31-35
|
Mem Inst Oswaldo Cruz, Rio de
Janeiro, Vol. 97(1) 2002, pp. 31-35
Epidemiological and Serological
Aspects in Canine Toxoplasmosis in Animals with Nervous Symptoms
Adriana Falco de Brito, Luiz Carlos de Souza*,
Aristeu Vieira da Silva*, Helio Langoni*/+
Faculdade de Ciências Agrárias,
Universidade do Oeste Paulista, Presidente Prudente, SP, Brasil *Núcleo
de Pesquisa em Zoonoses, Departamento de Higiene Veterinária e Saúde
Pública, Faculdade de Medicina Veterinária e Zootecnia, Unesp,
Distrito de Rubião Jr. s/n°, 18610-240 Botucatu, SP, Brasil
+Corresponding author. Fax: +55-14-6802.6075. E-mail: hlangoni@fmvz.unesp.br
Received 6 February 2001
Accepted 28 August 2001
Code Number: oc02004
The presence of anti-Toxoplasma
gondii IgM and IgG antibodies was studied
in samples of blood serum taken from eighty dogs with nervous symptoms at the
Serviço de Enfermidades Infecciosas dos Animais, Faculdade de Medicina
Veterinária e Zootecnia, Unesp, Botucatu, São Paulo, Brazil. The
frequency of IgG titers were 16 (13.7%), 64 (13.7%), and 256 (5%), and for IgM
titers were 16 (7.5%), 64 (15%), and 256 (8.7%). Positive reactions were more
frequent in the older animals, males, from a rural environment, in constant
contact with small animals, principally birds and rodents. There was a higher
frequency of a positive reaction in dogs fed with kitchen food, especially in
those fed with raw ingredients. The most common neurological pictures were alterations
in consciousness, in movement, and in the hand-cart test. The percentage of
reagents with specific IgM antibodies was high, indicating active infections,
but the possibility of co-infection with the distemper virus can not be discarded,
and this may be a predisposing factor for toxoplasmosis infection, once the
distemper virus has a potent immunosupressive action.
Key words: toxoplasmosis - canine - serology
- epidemiology - nervous symptomology
Toxoplasmosis is a parasitic zoonosis with world-wide
distribution, carried by Toxoplasma gondii, a protozoa that can infect
man and warm-blooded animals, by the three forms of its life cycle: (1) orally,
by the ingestion of oocysts, (2) by ingestion of cysts lodged in tissues of
intermediate hosts, and (3) via the uterus, by transplacental transmission of
tachyzoites. T. gondii can also be transmitted in products of blood origin,
or by ingestion of tachyzoites in non-pasteurized goat milk (Tenter 1999).
Although the role of dogs in the spread of the
disease has generally been considered as of secondary importance, intimate contact
between man and dogs has led to much study (Svoboda & Svobodová 1987).
Martins and Viana (1998) highlight the importance of dogs in the epidemiological
chain of the disease, through the habit of ingesting, and rolling in, cat feces,
thus permitting transmission of oocysts by contact of the contaminated hide.
Lindsay et al. (1997) demonstrated that after ingestion of T. gondii
non-sporulate oocysts, these could pass through the intestinal tract of dogs,
and be excreted in their infectious stage, re-enforcing the theory that dogs
act as mechanical vectors of oocysts.
Germano et al. (1985) and Jackson et al. (1987)
point out that the infection rate of the canine population is an indication
of the domestic environment contamination by T. gondii, and the consequent
risk to the human population, due to the fact that both humans and dogs are
exposed to a common source of infection, represented by the environment and
alimentary habits.
Infection in canines has been observed in many
countries, demonstrating its cosmopolitan character (Guimarães et al.
1992). Toxoplasmic infection amounted to 91% in 657 dogs in the city of Campinas,
as detected by the indirect immunofluorescent antibody test (IFAT) (Germano
et al. 1985). Ishizuka and Yasuda (1981) found 63.8% positive anti-T. gondii
antibodies in 1,256 samples of street hounds captured by the Centro de Controle
de Zoonoses in São Paulo. In Botucatu, São Paulo, Salata et al.
(1985) analyzed serum of 47 dogs by IFAT, finding 63.8% positive reactions.
In Belo Horizonte, Minas Gerais, during 1988-1990,
from serum collected from 243 animals, at the College of Veterinary Medicine,
Federal University of Minas Gerais, there were 47.3% positive reactions, 54.3%
of those with titer 16, 30.7% with 64, and 9.65% with 256 (Guimarães
et al. 1992).
Freire et al. (1992) found that of 254 dogs from
Londrina, Paraná, showing signs compatible with toxoplasmosis, 193 (75.9%)
were positive. The distribution of reagents to the IFAT showed the majority
of titers between 16 and 1024. In the same city, Navarro et al. (1997) found
73 positive (23.4%) of a total of 312.
The characteristics of high infectivity and low
pathogenicity of T. gondii justify the research realized as a function
only of the measurement of levels of antibodies. Recent or active infection
may be evidenced by high IgM titers, as 64 or above in samples with negative
IgG, or by demonstration of ascendant titers fourfold or greater
of IgG antibodies in paired serum samples (Dubey et al. 1990, Swango et al.
1992).
This work aimed to evaluate the presence of anti-T.
gondii antibodies in dogs with nervous symptoms, and related this study
to epidemiological data, and to the clinical neurology presented by the animals.
MATERIALS AND METHODS
Animals - Eighty dogs presenting nervous
symptoms, being attended at the Serviço de Enfermidades Infecciosas dos
Animais, Faculdade de Medicina Veterinária e Zootecnia, Unesp, Botucatu,
São Paulo, were selected, regardless of breed, sex, or age, from January
to December 1998.
Epidemiological and neurological data -
Epidemiological data, and data from the neurological clinic, were collected
and entries made according to the system of Svoboda and Svobodová (1987).
The entries included identification (register number in the hospital, in the
clinical center, name of the animal, owner's name and address), characterization
of the animal (age, sex, breed), description of home environment (rural or urban,
confined or with access to street, if confined paved or dirt yard), contact
with other animals (cats, rodents, birds, other dogs, hunting habits), food
(commercial alone; mixed with kitchen food; only kitchen prepared food, or leftover
human food; raw meat, raw vegetables, or raw offal; ingestion of milk, pasteurized
or raw, cow or goat). Neurological data include occurrences of convulsions,
discriminated into large or small, consciousness, walking movements, the results
of hand-cart tests, and reactions of pupils.
Collection of blood samples and serological
examinations - Blood from the jugular vein, 15 to 20 ml, were collected
without anticoagulant, serum separated by centrifugation at 3000 rpm for 15
min, and stored at -20°C until serological examination.
Serological tests for IgM and IgG anti-T.
gondii antibodies were carried out in the Serviço de Diagnóstico
de Zoonoses, using the indirect fluorescent antibody test (IFAT), according
to Camargo (1974). Serum samples were tested in dilutions of 1:16, 1:64, 1:256,
1:1024, and 1:4096, utilizing commercial anti-canine IgM and IgG antibodies
conjugated to fluorescein isothiocianate (Nordic Immunology, lots 4691 and 3859).
Analysis of data - The association between
the serological test results and the epidemical and clinical variables was verified
by the Chi-square and/or Fischer Exact Test, utilizing the program EpiInfo 6.04c
(Centers for Disease Control and Prevention, Atlanta, GA, 1997), and by multivariate
logistic regression analysis, using the program EpiInfo Logistic Regression
6.50 (Centers for Disease Control and Prevention, Atlanta, GA, 1994), taking
a = 0.05.
RESULTS
IgG antibodies were detected in 26 (32.5%) of
the animals, with titers 16, 64, and 256, in 11 (42.3%), 11 (42.3%) and 4 (15.4%)
respectively, of these animals, while for IgM, 25 (31.2%) were positive of which,
6 (24%), 12 (48%) and 7 (28%) with titers 16, 64, and 256, respectively.
With respect to age, 39 (48.7%) were under a
year, 16 (20%) were 12 to 24 months of age, and 25 (31.2%) were 24 to 36 (incomplete)
months. The distribution of reagents to IgG was 28.2%, 31.2%, and 40% for 3
to 12 month's range, 12 to 24, and 24 to 36, respectively (c2
= 0.9803; p = 0.6125). For IgM, the frequency of reaction was 38.5%, 25%,
and 24%, respectively, for those ages (c2 =
1.847; p = 0.3972).
Table I
presents the distribution of reagents according to sex, breed, type of environment,
and exposure to other animals. There was a significant difference between the
proportion of males to females reacting to IgG; a slight preponderance of reaction
among the animals of indeterminate breed; animals with no access to streets
showed a higher rate of reaction to IgG, but the opposite was observed with
anti-IgM reaction; a significant degree of association in the proportion of
reagents to IgG among the dogs that had contact with birds and rodents; and
a tendency for higher rate for IgM reagents among the animals living with other
dogs.
Table II
shows results referring to the proportions of reagents to IgG and IgM, according
to type of feeding habits. There were no significant differences, but some figures
show a tendency toward significant differences, such as the proportion of reactors
to IgG among animals consumers of raw tripe and offal (odds ratio = 3.33) and
to IgM among animals consumers of raw milk (odds ratio = 2.54). It should be
pointed out that the animal that consumed raw goat milk showed titer 256 for
IgM.
Table III
shows the association between the serological reactions and the neurologic analyzed
variables, where no significant associations were found.
Table IV
presents only the variables that showed significative associations with the
results of serology to IgG and IgM antibodies by multivariate logistic regression
analysis.
DISCUSSION
The observed proportion of animals reagents to
IgG agree with international literature. The seroprevalence of toxoplasmosis
in human and animal populations is variable (Frenkel 1990). Jackson et al. (1987)
found the frequency of reagents to be 19.6% among dogs in central Scotland,
and Dubey et al. (1990) cite the prevalence of reagents in the USA as being
about 30% in dogs.
The frequency found in the present study is considerably
lower than that found by other Brazilian authors, such as Ishizuka et al. (1974),
who found 72% in São Paulo, and Ishizuka and Yasuda (1981), with 63.8%,
also in São Paulo. Germano et al. (1985) with 91% in Campinas, and Guimarães
et al. (1992) with 47.3% in Belo Horizonte.
As for age group differences, we found a higher
rate among older dogs, in agreement with the other literature consulted. Jackson
et al. (1987) observed a significant difference in animals less or more than
six months of age, with 20% and 27.9% of reagent dogs, respectively. Ishizuka
et al. (1974) found a higher number of positive reactors in dogs of over two
years of age, while Germano et al. (1985) observed no differences, and Guimarães
et al. (1992) found a higher percentage in animals over two years of age.
Higher frequency of reaction in males, in this
study, is not in agreement with literature, and there seems to be no explanation
for an orally transmissible disease to discriminate between the sexes (Germano
et al. 1985), but the multivariate analysis of this variable shows significance
only when it is associated with raw meat consumption and raw tripe and offal
consumption, for IgG antibodies, and with alterations of consciousness, for
IgM antibodies, showing the association of risk factors (Table
IV). The tendency toward higher frequency for IgM in dogs of indeterminate
breed can be explained by the fact that these animals receive less attention
in their care and feeding, which have more chance of exposure to contaminated
food, either offered by humans or as a result of more predatory habits toward
small animals.
With regard to environment, the frequency of
reagents was higher among those from a rural area, and those raised with access
to dirt, although this last condition alone did not presents significant difference.
Contact with small animals, principally birds and rodents, can lead to predatory
habits and therefore ingestion of tissues with cysts of T. gondii. Svoboda
and Svobodová (1987) found less antibodies in dogs kept in apartments,
and more in animals with the habit of hunting. Germano et al. (1985) and Guimarães
et al. (1992) point that the high receptivity of dogs for toxoplasma, due to
the facility of ingestion of tissue and to contact with contaminated soil. Xenophilia
could be an important means of transmission of the disease (Martins & Vianna
1998).
The results here point out a higher frequency
of antibodies in those animals that are fed home-made food, specially when meat
or offal was included, which agrees with literature (Germano et al.1985, Jackson
et al. 1987).
None of the variables studied in the neurological
examinations demonstrated a significant association with the numbers of reagent
animals, by univariate analysis with Chi-Square Test, but the multivariate analysis
shows that IgM titers are more prevalent in dogs with altered consciousness
(Table IV).
Although it is not possible to be certain that
every case is one of clinical toxoplasmosis, given the possibility of neurological
symptomatology of other infections, such as distemper, these results demonstrate
the importance of toxoplasmosis in the canine species and the risk to public
health, pointing out probable common sources of infection for both humans and
canines, as well as the possibility of direct transmission from dog to man,
since in its acute and generalized form there could occur elimination of viable
parasites by different secretions and excretions, as well as the mechanical
vectoring of oocysts after ingestion of cat feces.
REFERENCES
- Camargo ME 1974. Introdução
às técnicas de imuno-fluorescência. Rev Bras Patol
Clín 10: 143-169.
- Dubey JP, Greene CE, Lappin MP 1990. Toxoplasmosis
and neosporosis. In CE Greene, Infectious Diseases of Dog and Cat, WB
Saunders, Philadelphia, p. 830-835.
- Freire RL, Navarro IT, Vidotto O, Tudury EA,
Vianna CC 1992. Prevalência de anticorpos anti-Toxoplasma gondii
em cães atendidos no Hospital Veterinário da UEL-PR. Semina
Ci Agr 13: 65-69.
- Frenkel JK 1990. Transmission of toxoplasmosis
and the role of immunity in limiting transmission and illness. J Am Vet
Med Assoc 196: 233-240.
- Germano PML, Erbolato EB, Ishizuka MM 1985.
Estudo sorológico da toxoplasmose canina pela prova de imunofluorescência
indireta na cidade de Campinas, 1981. Rev Fac Med Vet Zoot Univ São
Paulo 22: 53-58.
- Guimarães AM, Ribeiro MFB, Lima JD,
Cury MC, Spiewak G 1992. Freqüência de anticorpos anti-Toxoplasma
gondii em cães de Belo Horizonte, Minas Gerais. Arq Bras Med
Vet Zoot 44: 67-68.
- Ishizuka MM, Yasuda PH 1981. Incidência
de infecção por Toxoplasma gondii em cães do município
de São Paulo. Rev Fac Med Vet Zoot Univ São Paulo 18:
161-165.
- Ishizuka MM, Miguel O, Brogliato DF 1974.
Prevalência de anticorpos anti-toxoplasma em soros de cães do
município de São Paulo. Rev Fac Med Vet Zoot Univ São
Paulo 11: 115-125.
- Jackson MH, Hutchison WM, Siim JC 1987. Prevalence
of Toxoplasma gondii in meat animals, cats and dogs in Central Scotland.
Br Vet J 143: 159-165.
- Lindsay DS, Dubey JP, Butler JM, Blagburn
BL 1997. Mechanical transmission of Toxoplasma gondii oocysts by dogs.
Vet Parasitol 73: 27-33.
- Martins CS, Viana JA 1998. Toxoplasmose
O que todo profissional de saúde deve saber Revisão.
Clín Vet 15: 33-37.
- Navarro IT, Freire RL, Vidotto O, Ogawa L,
Kano FS 1997. Estudo comparativo entre soro e plasma na pesquisa de anticorpos
anti-Toxoplasma gondii pela técnica de imunofluorescência
indireta em cães atendidos no Hospital Veterinário da Universi-dade
Estadual de Londrina - PR, 1996. Semina Ci Agr 18: 15-21.
- Salata E, Yoshida ELA, Pereira EA, Corrêa
FMA 1985. Toxoplasmose em animais silvestres e domésticos da região
de Botucatu, Estado de São Paulo, Brasil. Rev Inst Med Trop São
Paulo 27: 20-22.
- Svoboda M, Svobodová V 1987. Effects
of breed, sex, age, management and nutrition on the incidence of Toxoplasma
gondii antibodies in dogs and cats. Acta Vet Brno 56: 315-330.
- Swango LJ, Bankemper KW, Kong LI 1992. Infecções
bacterianas, riquetsiais, protozoais e outras. In SJ Ettinger, Tratado
de Me-dicina Interna Veterinária: Moléstias do Cão e
Gato, Manole, São Paulo, p. 296-298.
- Tenter AM 1999. Current knowledge on the epidemiology
of infections with Toxoplasma. Tokai J Exp Clin Med 23:
391.
© 2002
Instituto Oswaldo Cruz - Fiocruz
The following images related to this document are available:
Photo images
[oc02004t2.jpg]
[oc02004t1.jpg]
[oc02004t3.jpg]
[oc02004t4.jpg]
|