Mapping of the environmental contamination of Toxoplasma gondii by georeferencing isolates from chickens in an endemic area in Southeast Rio de Janeiro State, Brazil

Abstract

The environmental contamination of Toxoplasma gondii in an endemic area in Brazil was mapped by georeferencing isolates from chickens in farms in the Southeast of the state of Rio de Janeiro. Tissue samples obtained from 153 adult chickens were analyzed by the mouse bioassay for T. gondii infection. These animals were reared free-range on 51 farms in the municipalities of Rio Bonito and Maricá. The ArcGIS kernel density estimator based on the frequency of T. gondii-positive chickens was used to map the environmental contamination with this parasite. A questionnaire was applied to obtain data on the presence and management of cats and the type of water consumed. Of the farms studied, 64.7% were found to be located in areas of low to medium presence of T. gondii, 27.5% in areas with a high or very high contamination level and 7.8% in non-contaminated areas. Additionally, 70.6% kept cats, 66.7% were near water sources and 45.0% were in or near dense vegetation. Humans used untreated water for drinking on 41.2% of the farms, while all animals were given untreated water. The intensity of environmental T. gondii contamination was significantly higher on farms situated at a distance >500 m from water sources (P=0.007) and near (≤500 m) dense vegetation (P=0.003). Taken together, the results indicate a high probability of T. gondii infection of humans and animals living on the farms studied. The kernel density estimator obtained based on the frequency of chickens testing positive for T. gondii in the mouse bioassay was useful to map environmental contamination with this parasite.

Spatial and simultaneous representative seroprevalence of anti-Toxoplasma gondii antibodies in owners and their domiciled dogs in a major city of southern Brazil

“…In addition to a holistic approach, recent studies have also shown geoprocessing to be an important tool for better interpretation of spatial characteristics and dynamics of infectious diseases [27,28]. In a northern state ranked fourth on the total Brazilian beef export, seropositive clusters for toxoplasmosis in beef cattle have shown a low impact of the disease despite a widespread undercooked barbecue tradition [29].…”

“…In other situations, the use of a spatial approach as an epidemiological tool has been strongly suggested to improve associated risk analysis and prevention of T . gondii through identifying landscape characteristics and mapping environmental contamination [28,30–32]. …”

Waterborne toxoplasmosis investigated and analysed under hydrogeological assessment: new data and perspectives for further research

“…This difference between trends in chicken and human seroprevalence may be explained at least in part by the behaviour of humans with respect to their constant mobility across areas with diverse risk of T. gondii oocyst groundwater contamination, whereas chickens are confined to the same peridomestic areas during their lifespan and also by the differential habits and hygiene behaviour observed in humans. Regarding this last point, Casartelli-Alves et al (2015) published a study on environmental contamination by T. gondii based on georeferencing isolates from chickens in an endemic area of RJ. The researchers applied questionnaires for risk factors that considered the ingestion of unfiltered and untreated water from natural sources, including wells and rivers.…”

“…Ground water would be a more favourable environment than soil for the persistence and “preservation” of oocysts and for the organism's evolution and perpetuation. In fact, soil contamination by T. gondii oocysts is not a stationary event because it can varies depending on the presence of feline excretion of oocysts in faeces and on environmental conditions such as temperature and moisture ( Dubey 2004 , Casartelli-Alves et al 2015 ).…”

“…First, T. gondii oocysts remain viable in fresh and marine water for long periods ( Lindsay et al 2003 ). Second, free-range chickens (and birds in general) that drink unfiltered water from wells and other natural untreated sources of water (such as lakes or lagoons) can become infected ( Casartelli-Alves et al 2015 ). A third aspect that is consistent with this hypothesis is the hydrophilic nature and negative charge of T.gondii oocysts in freshwater ( Shapiro et al 2009 ), which could facilitate widespread contamination of groundwater from unconfined aquifers.…”