No abstract

The clinical course of generalized Yersinia enterocolitica infection in 13 patients was observed. Two syndromes were apparent; seven patients had an acute septicemic picture, whereas the rest had a subacute localizing infection that usually produced hepatic or splenic abscesses. The latter form often resembled amebic hepatitis clinically, and five of the six patients died despite antibiotic treatment. The acute septicemic form of the disease resembled systemic salmonellosis, and most cases responded to therapy with the appropriate antibiotics.

Reproduction and early postnatal development are discussed in five species of Southern African Muridae and Cricetidae under laboratory conditions, with special reference to early physical development, and the development of sensory and motor abilities, in relation to nature of parental care.Most available data on laboratory breeding of small South African rodents concern the multimammate mouse, Praotrujs (Mastomys) naialensis (Oliff, 19'53; Johnston and Oliff, 19'54; Meester, 1960). Measroch (1954) reported on estrous cycles in the Highveld gerbil, Tatera brantsii, and the Western Cape gerbil, T. ajra, Meester (19'58) described early postnatal development in Aethomys ( Micaelamys) namaquensis and Davis (1963 ) summarized the available reproductive data on several South African species, mainly on the basis of work done by the Medical Ecology Centre, South African Institute for Medical Research, Johannesburg.The present paper compares certain aspects of reproduction and early postnatal development in P. natalensis, T. brantsii, and A. namaquensis, and also in two additional species-the tree rat, Thallorrujs paedulcus, a murid, and the white-tailed rat, Mystromys albicaudatus, a cricetid. MATERIALS AND METHODSThe data here presented are from stocks of rodents as listed below. Mystromys albicaudatus.-Thirty-three litters (six matings) from stock from the Medical Ecology Centre, collected at Baragwanath, southern Transvaal; also, 18 litters (13 matings ) bred at the Medical Ecology Centre. Tatera brantsii.-Three litters (one mating ) from a stock collected at Carolina, southeastern Transvaal. Thallomys paedulcus.-Twenty litters (six matings ) from a stock collected Zebediela northern Transvaal; three litters (one mating) from a stock from farm De Waal, Gobabis district, South West Africa. Aethomys (Micaelamys ) namaquensis.-Two litters (two matings ), pregnant females collected at Pretoria and Uitkomst farm, Krugersdorp district, Transvaal; also, data from Meester (1958). Praomys (Mastomys) natalensis.-Data summarized from Meester (1960) unless otherwise indicated. Most of the data were collected between 1956 and 1960 by one of us (Meester), while employed at the Transvaal Museum, Pretoria. Animals were housed in an office without temperature regulation. Data on 18 litters of M. albicaudatus were collected by Hallett,between September 1963 and February 1965, from animals housed in a temperature-controlled room (± 70°F) in the Animal Block at the South African Institute for Medical Research (S.A.I.M.R.). All matings were checked daily. Young were assumed to have been born on the day when first seen. This day was regarded as day 0 and subsequent days were numbered consecutively. 703 704 4-~~l f-:J u, 0 6_ o z4o JOURNAL OF MAMMALOGY Vol. 51, No.4 THALLOMYS MYSTROMYS J F M A M J J MONTH A 5

A live attenuated Yersinia pestis (Pasteurella pestis) vaccine strain designated EV51f, which had been passaged through guinea pigs previously treated with ferrous sulfate, was shown to be pathogenic for African green vervet monkeys (Cercopithecus aethiops pygerythrus), but not for guinea pigs. The bacilli multiplied in the monkeys, as shown by positive blood cultures, caused an elevation of white cell counts and rectal temperatures, and resulted in death of 26% (13/50) of animals. Postmortem findings of these animals were typical of bubonic-septicemic plague. This vaccine did not cause deaths in 50 guinea pigs even in doses up to 100 million viable bacilli inoculated subcutaneously. It is suggested that the virulence of an attenuated Y. pestis strain which does not produce pigment on a defined medium containing hemin, but possesses all other known virulence determinants, is dependent on the availability of iron in vivo. The serological response of the monkeys as determined by the hemagglutinating and mouse protective antibodies was high one month after vaccination and also in guinea pigs, as shown by virulent challenge. This antibody level declined in monkeys over a period of nearly 6 months, and a decline in immunity was confirmed by virulent challenge which resulted in the death of 30% of vaccinated monkeys. The level of immunity in monkeys did not appear to be related to the dose of vaccine.