PREVALENCE AND RISK FACTORS FOR HUMAN TOXOPLASMOSIS IN A RURAL COMMUNITY

: Toxoplasma gondii infection may lead to important pathological questions, especially in rural areas, where several sources of infection exist. Therefore, it is important to determine risk factors in order to establish adequate prophylactic measures. The present study aimed to assess the prevalence and risk factors involved in human toxoplasmosis infection in a rural community, in Eldorado, Mato Grosso do Sul State, Brazil. This community was composed of 185 farms – with 671 inhabitants – from which 20 were randomly chosen. In these farms, blood samples were collected from rural workers, who also answered a risk factor questionnaire. Serum samples were analyzed by means of direct agglutination test for the detection of anti- Toxoplasma gondii antibodies. From 73 samples collected, 79.45% were positive. None of the studied variables was significantly associated with the prevalence of the infection. However, among the individuals who reported eyesight impairments, 94.4% had anti- T. gondii antibodies, compared with 74.0% who did not report eyesight changes (p = 0.0594). Moreover, most individuals in the study (68.20%) were older than 18 years and presented 84.44% positivity, compared with 66.67% of positive individuals younger than 18 years old. We were able to conclude that a high prevalence of antibodies did not imply significant associations with the risk factors studied. results: 79.45%, 60.87%, 57.14%, 47.61%, 22.89%, 14.71% and 5.15%, respectively, for humans (in this study), horses (7), cats (15), dogs (15), poultry (18), pigs (19) and cattle (13). The rate of positive results was significantly lower in dogs, pigs, poultry and cattle, compared with humans.


INTRODUCTION
Toxoplasma gondii (Nicolle & Manceaux, 1909) is classified in the phylum Apicomplexa, with near relatives in the Sarcocystidae family, particularly the following genera: Sarcocystis, Frenkelia, Hammondia and Neospora. Members of these genera have life cycles that alternate between intermediate hosts, in which asexual phases occur, and definitive hosts, in which sexual phases manifest. In intermediate hosts, generally herbivores or omnivores, one or more proliferative cycles arise in different tissues, leading to cyst production. In definitive hosts, usually carnivores, the sexual phase results in oocyst production in the intestines. Sporogony commonly develops within the definitive host, leading to the production of isospora-like oocysts that contain two sporocysts, with four sporozoites each (23).
The life cycle of T. gondii is facultatively heteroxenous: felids are definitive hosts, whereas probably all homoeothermic animals may be intermediate ones.
Toxoplasmosis is one of the most common parasitic zoonosis and also causes significant economic losses to animal breeding industry. Humans and other animals may get infected by any of the three life-cycle forms of the protozoan: • oocysts, eliminated in felid feces, can be ingested -they become infective from one to five days after sporulation; • cysts, present tissues of intermediate hosts, may also be ingested; • tachyzoites can be transmitted via uterine route, throuhg the placenta.
T. gondii may also be transmitted by blood products, organ transplants or by the ingestion of tachyzoites in unpasteurized goat milk (22).
In postnatal life, most human infections manifest after the ingestion of sporulated oocysts, found in the environment, or by the ingestion of tissue cysts, from raw or undercooked meat of intermediate hosts. However, the most important epidemiological route is yet to be determined and the main sources of T. gondii infection are diverse among human populations with different cultural and feeding habits (22).
Although the importance of livestock in toxoplasmosis transmission to humans remains unclear, pork represents the most important source of infection in several countries (7). On the other hand, there is an ever-growing interest in the study of the infection in poultry -mainly in extensively bred animals -caused by oocysts from contaminated soil (8).
Nevertheless, the close contact between humans and pets, mainly dogs and cats, may lead to situations in which shared sources of infection can be evidenced, resulting in human infection (12). In the rural environment, risk factors may get superposed, contributing to high infection rates in humans, as reported in the literature (4,6,11,12,14).
The present study aimed to assess the prevalence and risk factors related to Toxoplasma infection in individuals from a rural community in Eldorado, Mato Grosso do Sul State, Brazil.

Site of Collection and Sampling Plan
Eldorado is a city of 11,934 inhabitants (2) located in southern Mato Grosso do Sul, about 470 km from the state capital, Campo Grande. The local economy is based on agriculture, mainly beef and dairy cattle breeding, as well as watermelon, soy, corn and cassava crops.
Blood samples were collected from members of a rural community, in Eldorado

Collection of Samples
Blood samples were collected by means of a puncture in the cephalic vein. Sera were obtained by centrifugation and stored at -20°C until their analysis by serology for detection of anti-Toxoplasma gondii antibodies.

Serological Examination
Serum samples were analyzed through modified agglutination test (MAT) for detection of anti-T. gondii antibodies employing formalin-fixed antigens (5). Sera were initially screened at a 1:25 dilution, and then two-fold serial dilutions were used in order to determine antibody titers in positive samples for the screening process.

Questionnaire
In addition to blood collection, information related to the characterization of the individuals, their feeding habits and contact with animals were also gathered with a structured questionnaire, developed based on the literature (1, 15-17, 21, 25).

Data Analysis
Univariate analysis was carried out using the general prevalence of anti-T. gondii antibodies given by MAT results associated with data collected in questionnaires, in chi-square and Fischer's exact tests. Significance level was set at 5% (24).  high prevalence observed in the present study did not point at any particular aspect.
Antibody rates recorded for different species may propose that there were different risk factors associated with the prevalence of Toxoplasma infection in the community.
The high prevalence among humans, horses and cats could be justified by the exposure of humans and horses to places highly contaminated with cat feces, or by increased chance of infection determined by the age of these individuals. Therefore, age may also be involved as a factor in the lower antibody rates observed in dogs, pigs, poultry and cattle, due to the fact that most of these animals were young.
Garcia et al. (10) found a similarity between serum antibody titers in humans and those found in dogs and cats. These authors deliberated that a common source of infection may be implied because both species are carnivores, and feeding habits could be responsible for both infections, while cats would have an indirect role, contaminating the environment with oocysts.
Konishi and Takahashi (17), in a study accomplished in a Japanese rural community, collected 3,606 blood samples from farmers, and reported that gender, age and consumption of raw meat were factors associated with seropositive results.
Suárez-Hernández et al. (20), studying 548 samples from Cuban children by IgG-IFAT, observed that the main risk factor was the child origin. Prevalence of positivity in children from rural communities was 57%, whereas in those of urban groups was 27%.
In were significantly associated with the disease, when the same data were evaluated by logistic regression (multivariate analysis).
A review of the literature shows that different factors are associated with Toxoplasma gondii infection, especially the region, period and population under investigation. It is evident that local studies are necessary to determine risk factors associated with T.
gondii infection in a given population -with its own characteristics of interaction between animal populations and the environment, and peculiar feeding and hygienic habits -and to create specific strategies to prevent the infection.

CONCLUSIONS
In the present study, no association between epidemiological factors and risk of infection were drawn. However, human populations may be at a constant risk due to feeding habits and contact with infected animals and soil. Given that, prophylactic measures should be applied to risk groups, i. e., pregnant non-infected women and immunocompromised individuals, due to the risk of ocular diseases and/or reacutization cases.