Prolactin evokes lactational transmission of larvae in mice infected with Toxocara canis

We investigated the trans-lactational maternal-neonatal transmission of Toxocara canis larvae in mice, with particular interest in the role of prolactin in their migration to the mammary gland. Two female mice were infected with 300 T canis eggs soon after delivery of 27 offspring. After I week of breast-feeding, seven larvae were recovered from 4 of 13 offspring. After 2 weeks of lactation, 101 larvae were recovered from all the remaining offspring. Daily prolactin administration (5 fig) was performed 2 weeks before T canis infection and continued until 2 weeks after infection in six non-pregnant female mice, which resulted in larval accumulation in the mammary gland. Furthermore, prolactin administration in female mice that had been infected with 7: canis 4 weeks prior to prolactin treatment induced migration of larvae into the mammary gland. These findings suggest that prolactin is a promoting factor contributing to lactational transmission of T canis larvae in mice. (c) 2008 Elsevier Ireland Ltd. All rights reserved.