Antibiotics and the Wasting Disease in Neonatally Thymectomized Rats

Abstract

The administration of the antibiotic, Chloramphenicol, to pregnant rats just prior to, and for four days after delivery, diminishes the incidence of the so-called Wasting Disease in neonatally thymectomized rats. A total of 50 rats were divided into the following groups: Thymectomy only---nonmedicated 17 rats Thymectomy only---medicated 12 rats Thymectomy-adrenalectomy---nonmedicated 5 rats Thymectomy-adrenalectomy---medicated 8 rats Controls---nonmedicated 4 rats Controls---medicated 4 rats Chloramphenicol was administered in the drinking water to the mothers of groups 2, 4 and 6 for about 2 days prior to delivery and 4 days after. On the day of birth or within three days after birth, the male progeny were thymectomized. Approximately 2 weeks after thymectomy adrenalectomies were carried out on some of the progeny (groups 3 and 4). Growth rate and weight records were kept of all groups. At the 12th week white blood cell counts were made on all groups expect 1 and 3. At the end of the 24th week, all survivors were autopsied for presence of thymus and adrenal tissue and those with evidence of such were excluded. Routine tissue sections were made of various organs of all groups and search made for any evidence of hormonal deprivation or infection. The medicated control animals exhibited a higher growth rate than all other groups. The medicated thymectomized rats showed an average weight just slightly under that of the nonmedicated controls. The thymectomized-adrenalectomized animals appeared to show the same average weight at the end of the experiment but the medicated group had a faster growth rate and weight gain during the early weeks of the experiment. The medicated animals of groups 2 and 4 showed a 20 percent wasting incidence while wasting occurred in 40 percent of group 1 and 50 percent in group 3. The lowest white blood counts were 8,800 for the medicated thymectomized animals and 9,200 for the thymectomized-adrenalectomized animals, probably due to the lymphopenia reported by others. The white blood count of the nonmedicated control group was 12,000. The administration of antibiotic to a pregnant rat just prior to and for few days after birth of the young appears to lessen the incidence of the wasting disease in its progeny thymectomized within three days after birth leading to the conclusion that the wasting disease is primarily a pre-occupation of the immunologic system during the early weeks of life with infections acquired in the immediate post-operative period, These results corroborate the conclusions of Azar (1964) relative to the efficacy of antibiotic administration in preventing the wasting disease, and also are in accord with the findings of Miller (1964) that germ free thymectomized mice do not evidence the wasting syndrome