title: Evolution of infection in mice inoculated by the oral route with different developmental forms of Trypanosoma cruzi I and II.
abstract: Oral infection has become the most important transmission mechanism of Chagas disease in Brazil. For this study, the development of Trypanosoma cruzi infection in mice, induced by the oral and intraperitoneal (IP) routes, was compared. Four groups of Swiss mice were used to evaluate the influence of parasite genetics, number of parasites, inoculation volume and developmental stages on the development of the orally induced infection: 1 - blood trypomastigotes (BT) via oral; 2 - BT via IP; 3 - culture metacyclic trypomastigotes (MT) via oral; and 4 - culture MT via IP. Animals inoculated orally showed levels of parasitemia, as well as infectivity and mortality rates, lower than animals inoculated via IP, regardless of DTU (discrete typing unit) and inoculum. Animals infected with TcII showed higher levels of these parameters than did animals infected with TcI. The larger volume of inoculum showed a greater capacity to cause an infection when administered via the oral route. BT infection was more virulent than culture MT infection for both routes (oral and IP). However, mice inoculated orally with BT showed lower levels than via IP, while mice inoculated orally with culture MT showed similar levels of infection to those inoculated via IP. Mice inoculated with culture MT showed more histopathological changes than those inoculated with BT, regardless of the inoculation route. These results indicate that this alternative experimental model is useful for evaluating infection by T. cruzi isolates with subpatent parasitemia and low virulence, such as those belonging to the TcI and TcIV DTUs, which are prevalent in outbreaks of orally transmitted Chagas disease.
authors.affiliation: Post-Graduate Program in Health Sciences at the State University of Maringá (UEM), Av. Colombo 5790, Bloco 126, CEP 87020-900 Maringá, Paraná, Brazil. Electronic address: gremalaquias@hotmail.com.
authors.forename: Greicy Brisa Malaquias
authors.initials: GB
authors.lastname: Dias
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Gruendling
authors.forename: Silvana Marques
authors.initials: SM
authors.lastname: Araújo
authors.forename: Mônica Lúcia
authors.initials: ML
authors.lastname: Gomes
authors.forename: Max Jean de Ornelas
authors.initials: MJ
authors.lastname: Toledo
mesh_terms: D000284:Administration, Oral; D000818:Animals; D014355:Chagas Disease / Q000469:parasitology* / Q000473:pathology / Q000635:transmission; D005506:Food Contamination; D016266:Food Parasitology; D008297:Male; D051379:Mice; D010529:Peritoneal Cavity / Q000469:parasitology; D014349:Trypanosoma cruzi / Q000145:classification* / Q000254:growth & development / Q000472:pathogenicity; D014774:Virulence
keywords: %INF; %MOR; AUC; BT; ChD; Chagas disease; DMOR; DMP; DTU; DTUs; FBE; HC; IP; Infectivity; LIT; MPP; MT; Mice; Oral transmission; PCR; PP; PPP; Parasitemia; State University of Maringá; Student’s t test; T; TP; Trypanosoma cruzi; UEM; area under the parasitemia curve; blood trypomastigotes; culture metacyclic trypomastigotes; d.i.; day after inoculation; day of maximum parasitemia; discrete typing units; fresh blood examination; hemoculture; intraperitoneal; liver infusion tryptose; maximum peak of parasitemia; mean day of mortality; mean patent period; mean pre-patent period; mean total parasitemia; percentage of cumulative mortality; percentage of infected mice; polymerase chain reaction