Transmission dynamics of simian T-lymphotropic virus type 1 (STLV1) in a baboon breeding colony: predominance of female-to-female transmission.

We investigated the prevalence, distribution, and transmission of simian T-lymphotropic virus type 1 (STLV1) in a baboon breeding colony over a 4-y period. We used polymerase chain reaction amplification of the proviral tax gene to assess the infection status of 272 animals housed in 4 separate corrals. Sequencing the proviral envelope gene from individual baboons detected several molecular subtypes (genotypes) of STLV1. At the start of the study, 31% (54 of 176) of all baboons were infected; the majority of infections (91%) were in mature females, with only 3 of 12 mature males and 2 of 48 infants and juveniles being infected. Over the next 4 years, 41 new infections were diagnosed. Of these, 83% occurred in sexually mature female baboons (at least 3 y of age), 17% in infants and juveniles (younger than 3 y), and 0% in mature males. The 7 infections in juveniles were probably derived from mother-to-infant transmission because mother-infant pairs consistently were infected with the same viral genotype. Of the 34 new infections in sexually mature female baboons, the genotyping data showed that 25 (73%) originated from other infected females as opposed to males. Male-to-female sexual transmission may have accounted for the remaining 9 new infections. There was no evidence of female-to-male sexual transmission. The high percentage of female-to-female transmission of STLV1 in our baboons was unexpected; we speculate that transmission may have occurred due to blood contamination from biting during aggressive behavior between females in establishing hierarchical dominance.

The effects of confinement environment on reproductive efficiency in the baboon.

Historically, to supply animals for medical research, both captive-bred baboons and imported wild-caught animals have been available. Now that imported animals are difficult to obtain, it is important to maximize domestic production. To this end, it is necessary to determine the optimum housing conditions (i.e., environmentally dependent factors) under which baboons have the greatest reproductive efficiency. At our institution, the Oklahoma University Health Sciences Center Primate Facility, we recently moved the majority of our baboon breeding colony into a large indoor-outdoor facility (El Reno) from a small, indoor facility (Annex). Fortuitously, this move allowed a direct comparison of baboon reproductive efficiency between the two radically different environments. The environment at the Annex is exclusively indoor and possesses limited but adequate living space (per Guide for the Care and Use of Laboratory Animals recommendations), whereas the El Reno environment is indoor-outdoor and naturalistic with living space exceeding Guide recommendations. Although we expected animals at the El Reno facility to exhibit somewhat increased reproductive efficiency, the magnitude of the increase was surprising: the mean number of days post-partum to first estrus was 165 for animals housed in the Annex, but 69 for those at the El Reno facility. In addition, the mean number of days from first estrus to conception was 61 for baboons in the Annex compared with 47 for those at El Reno, and the mean number of days from conception to next conception was 403 for animals in the Annex but 296 for those at El Reno. These results demonstrate that a change in housing environment can dramatically increase baboon breeding efficiency.

The effects of uncomplicated miscarriages and stillbirths on the ability of baboons to return to cyclicity and subsequently conceive.

Pregnant baboons are used regularly in medical research studies. Occasionally these studies have resulted in stillbirths and/or miscarriages. In addition, pregnant animals can spontaneously undergo stillbirths or miscarriages unrelated to any medical or research procedure. In the absence of identifiable inflammatory, infectious, or pathologic processes, it generally was assumed that these events had no bearing on the baboon's future ability to return to cyclicity and conceive. However, these assumptions were based on observational and anecdotal evidence. To test the validity of these assumptions, we established two data groups: baboons that had uncomplicated stillbirths (Gp-1; n = 11) and those that had uncomplicated miscarriages (Gp-2; n = 12). The mean number of days from first detectable postpartum estrus (i.e., perineal swelling/turgescence) to conception was 49 days for Gp-1 and 53 days for Gp-2. In addition, for Gp-1 animals we determined that the mean number of days to the first indication of estrus was 29 days; these data were unavailable for Gp-2 because of the lack of parturition as a reference point. Control baboons (lactating mothers) required approximately 59 days from first detectable estrus to conception, and our findings for Gp-1 and Gp-2 were consistent with this value. Therefore, within the limits of our study parameters, we suggest that uncomplicated stillbirth and miscarriage had no profound effects on a baboon's future ability to return to cyclicity and conceive.