Abstract
It has been known for decades that wild baboons are naturally infected with Treponema pallidum, the bacterium that causes the diseases syphilis (subsp. pallidum), yaws (subsp. pertenue), and bejel (subsp. endemicum) in humans. Recently, a form of T. pallidum infection associated with severe genital lesions has been described in wild baboons at Lake Manyara National Park in Tanzania. In this study, we investigated ten additional sites in Tanzania and Kenya using a combination of macroscopic observation and serology, in order to determine whether the infection was present in each area. In addition, we obtained genetic sequence data from six polymorphic regions using T. pallidum strains collected from baboons at two different Tanzanian sites. We report that lesions consistent with T. pallidum infection were present at four of the five Tanzanian sites examined, and serology was used to confirm treponemal infection at three of these. By contrast, no signs of treponemal infection were observed at the six Kenyan sites, and serology indicated T. pallidum was present at only one of them. A survey of sexually mature baboons at Lake Manyara National Park in 2006 carried out as part of this study indicated that roughly ten percent displayed T. pallidum-associated lesions severe enough to cause major structural damage to the genitalia. Finally, we found that T. pallidum strains from Lake Manyara National Park and Serengeti National Park were genetically distinct, and a phylogeny suggested that baboon strains may have diverged prior to the clade containing human strains. We conclude that T. pallidum infection associated with genital lesions appears to be common in the wild baboons of the regions studied in Tanzania. Further study is needed to elucidate the infection's transmission mode, its associated morbidity and mortality, and the relationship between baboon and human strains.
Highlights
IntroductionIn the 1960s and 1970s, researchers demonstrated that wild African primates were naturally infected with Treponema pallidum, the bacterium that causes syphilis (subsp. pallidum), yaws (subsp. pertenue), and bejel (subsp. endemicum) in humans
In the 1960s and 1970s, researchers demonstrated that wild African primates were naturally infected with Treponema pallidum, the bacterium that causes syphilis, yaws, and bejel in humans
Our goals were to: 1) begin mapping the distribution of T. pallidum infection in wild baboons in the broader East Africa region; 2) further investigate the clinical manifestations of infection at Lake Manyara National Park (LMNP); and 3) better characterize the strains circulating among baboons by sequencing six polymorphic regions in strains gathered from two different sites in Tanzania, LMNP and Serengeti National Park (SNP)
Summary
In the 1960s and 1970s, researchers demonstrated that wild African primates were naturally infected with Treponema pallidum, the bacterium that causes syphilis (subsp. pallidum), yaws (subsp. pertenue), and bejel (subsp. endemicum) in humans. Investigators have noted that baboons living in regions in which humans had historically suffered from yaws or endemic syphilis appear to have a high seroprevalence of infection with T. pallidum themselves [1,2,5]. A T. pallidum strain collected from a baboon in Guinea in the 1960s, known as the Fribourg-Blanc strain, was found to be more closely related to T.p. subsp. Pallidum or endemicum strains [7,8,9] It remains unclear whether this baboon strain will eventually be classified within the pertenue subspecies or whether it is closely related but distinct
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