Abstract
This experiment studied congenital transmission in sheep experimentally infected with oocysts of Toxoplasma gondii and reinfected at one of three stages of pregnancy. Twenty ewes were experimentally infected with T. gondii strain ME49 (day 0). After the T. gondii infection became chronic (IFAT≤512), the ewes were allocated with rams for coverage. After the diagnosis of pregnancy, these ewes were allocated into four experimental groups (n = 5): I-reinfected with T. gondii on the 40th day of gestation (DG); II-reinfected on DG 80; III-reinfected on DG 120; and IV-saline solution on DG 120 (not reinfected). Five ewes (IFAT<64) were kept as negative controls (uninfected, group V), therefore in groups I-III were infected prior to pregnancy and re-infected during pregnancy, group IV was only infected prior to pregnancy, and group V was not infected. Parasitism by T. gondii was investigated (histopathology, immunohistochemistry, mouse bioassay and PCR) in mothers and lambs tissue. All ewes produced lambs serologically positive for T. gondii. The results of the mouse bioassay, immunohistochemistry and PCR assays revealed the presence of T. gondii in all 20 sheep and their lambs. The congenital transmission of T. gondii was associated with fetal loss and abnormalities in persistently infected sheep and in ewes infected and subsequently reinfected by this protozoan. Therefore, congenital T. gondii infection was common when ewes were chronically infected prior to pregnancy, with or without reinfection during at various stages of gestation.
Highlights
Until recently, it was believed that most sheep acquire Toxoplasma gondii infection after birth
After the T. gondii infection became chronic (indirect fluorescent antibody test (IFAT) 512), the ewes were allocated with rams (99 days primary infection) for coverage
Three groups were reinfected (group I: 40th day of gestation (DG); group II: DG 80; and group III: DG 120), one group was primarily infected only and one group was uninfected as a negative control
Summary
It was believed that most sheep acquire Toxoplasma gondii infection after birth. October 27, 2016 to the generation[1,2,3] These conclusions are based on one recent study [4] and three older studies[5,6,7]. In Hartley’s study [5] of 38 ewes infected with T. gondii during a previous pregnancy, all but one ewe gave birth to uninfected lambs, and T. gondii was isolated from only one placenta [5]. Watson and Beverly studied [7] 26 ewes inoculated with T. gondii during a previous pregnancy; 24 ewes had uninfected live lambs, one ewe aborted twins, and one ewe was barren. Munday [6] studied 178 lambs born to 135 persistently naturally infected ewes; none had pre-colostral T. gondii antibodies, the placenta of one ewe was infected with T. gondii
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