High Prevalence of Simian T-Lymphotropic Virus Type L in Wild Ethiopian Baboons

ABSTRACT Simian T-cell leukemia viruses (STLVs) are the simian counterparts of human T-cell leukemia viruses (HTLVs). A novel, divergent type of STLV (STLV-L) from captive baboons was reported in 1994, but its natural prevalence remained unclear. We investigated the prevalence of STLV-L in 519 blood samples from wild-living nonhuman primates in Ethiopia. Seropositive monkeys having cross-reactive antibodies against HTLV were found among 22 out of 40 hamadryas baboons, 8 of 96 anubis baboons, 24 of 50 baboons that are hybrids between hamadryas and anubis baboons, and 41 of 177 grivet monkeys, but not in 156 gelada baboons. A Western blotting assay showed that sera obtained from seropositive hamadryas and hybrid baboons exhibited STLV-L-like reactivity. A PCR assay successfully amplified STLV sequences, which were subsequently sequenced and confirmed as being closely related to STLV-L. Surprisingly, further PCR showed that nearly half of the hamadryas (20 out of 40) and hybrid (19 out of 50) baboons had STLV-L DNA sequences. In contrast, most of the seropositive anubis baboons and grivet monkeys carried typical STLV-1 but not STLV-L. These observations demonstrate that STLV-L naturally prevails among hamadryas and hybrid baboons at significantly high rates. STLV-1 and -2, the close relative of STLV-L, are believed to have jumped across simian-human barriers, which resulted in widespread infection of HTLV-1 and -2. Further studies are required to know if STLV-L is spreading into human populations.

Clans and Harems in a Colony of Hamadryas and Hybrid Baboons: Male Kinship, Familiarity and the Formation of Brother-Teams

Three features of the hamadryas society, Papio hamadryas, which are quite unique among Old World monkeys, are its multileveled structure (i.e. harems, clans, bands, troop), the reported pattern of female dispersal (i.e. males tend to remain in their natal clans whereas females tend to move between clans and bands), and the special bonds that develop between adult males. It has also been hypothesized that the males of a clan are genetically related. In this paper a causal approach is adopted in order to investigate the proximate factors which can account for the structure/dynamics of socio-spatial group organization observed over two years in a large colony of hamadryas and hybrid baboons housed in an outdoor enclosure in the Madrid Zoo, containing 18 adult males with known kin relations. I first examined the types of grouping observed in the colony and the alternative social strategies used by the different male individuals during their ontogenetic trajectories for acquiring, and maintaining, females. Since the hamadryas baboon is considered a female-transfer species, I studied whether the sex that stays, that is, the males, developed some kind of mutual affiliative relationship, as one would predict, and whether their inter-male bonding preferences were based on genetic relatedness or on familiarity (i.e. sharing the same developmental environment during socialization).