Influence of Neospora caninum infection in BALB/c mice during pregnancy in post-natal development.

The influence of Neospora caninum infection during pregnancy on the post-natal period has been poorly investigated. In a previous study, we suggested that infection with N. caninum during pregnancy could affect the normal post-natal development of the offspring. For this reason, in the present work we evaluated the influence of N. caninum infection in pregnant BALB/c mice at days 0, 7 and 14 of gestation (groups A, B and C, respectively) on the post-natal development of the offspring from birth to day 60 post-partum (PP). Morbidity and mortality, vertical transmission, and histopathological lesions were investigated. The humoral immune response (IgG) of pups was also evaluated. Results showed that infection with N. caninum during pregnancy had fatal consequences for pups, especially during mid-gestation (day 7). Infection provoked a delay in the general development of neonates, clinical signs compatible with neosporosis and severe histopathological lesions. A high mortality rate was found in all infected groups. A 69% of mortality rate was found in group A, a 100% in group B and a 46% in group C. Necrotizing encephalitis and multifocal hepatocellular necrosis were the most severe lesions found. All neonates, except four animals from group C, had antibodies against N. caninum but the immune response was not sufficient to control parasite infection. We have demonstrated that extension of the observation period after N. caninum infection permits a more accurate study of vertical transmission, the major route of parasite transmission, and mortality rates. We propose that infection at mid-gestation (day 7) in BALB/c mice and its study during the post-natal period constitutes a valuable experimental model for testing new chemotherapeutic agents and vaccines designed to protect against congenital neosporosis, in order to select effective protocols before its use on bovine.