Background Ascaris lumbricoides and Ascaris suum are nematode parasites that infect millions of people and pigs worldwide, respectively. Reports of cross-infection between the two host species has stimulated molecular epidemiological studies of the Ascaris genus. In this study, we evaluated the dynamics of Ascaris transmission between Guarani indigenous schoolchildren, pigs, and the environment of a village in the state of Paraná, southern Brazil. Methodology/Principal findings Parasitological and molecular analyses of fecal samples from humans and pigs, and soil samples from the village were carried out. Eggs of Ascaris spp. were observed in 8.4% (7/83) of human samples, 44.4% (8/18) of pig samples, and 8.9% (6/68) of soil samples. PCR amplification of the ITS-1 locus of the rDNA gene in samples that were positive in the parasitological examination revealed cross-infection by the two species, A. lumbricoides and A. suum, in human and swine hosts. The soil, which was contaminated by both human and swine feces, also contained eggs of the two Ascaris species, thus constituting a source of Ascaris infection for both hosts. DNA from both nematode species, individually and mixed, was detected in samples from both hosts and the soil. Conclusions/Significance The results of this study indicate that more effective control measures, aimed at the correct disposal of both human and animal feces, should be implemented.

The authors have declared no competing interest.

Yes

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Not Applicable

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

National Research Ethics Commission through Opinion 1.756.060/2016

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Not Applicable

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Not Applicable

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Not Applicable

Our article does not report data and the data availability policy is not applicable to the article.