Mother to young transmission of Brucella abortus infection in mouse model.

Pregnant mice were challenged intraperitoneally with 2 X 10(5) B. abortus strain 544 (Weybridge), or with one of its two mutant strains, at day 7 of pregnancy. Transmission of brucellosis to infant mice was assessed by enumeration of brucella in spleen, liver and lungs at autopsy. Newborns, taken before any suckling were either autopsied or given to foster nurses, either infected or normal. Infant mice were autopsied at days 10, 20 and 30. Sixty per cent of the newborns were infected at birth. Infection was of low intensity and mainly localized in liver. Infection persisted at the same frequency whatever infection status of the nurses and without any sign of illness. Contact infection of infant mice born from infected or normal dams by suckling milk from infected nurses was observed only on one infant mouse out of 114 controlled. However, intensity and location of infection depended on age and on infection status of the nurses. Intensity of liver infection decreased with age. Splenic infection increased both in frequency and intensity with age. Intensity increased more rapidly on infant mice bred by normal non-infected nurses. Lung infection increased both in frequency and intensity when infant mice were bred by infected nurses whereas, between 20 and 30 days, this lung infection decreased and disappeared when infant mice were bred by normal nurses.