Variation in the gene acidic repeat protein (ARP) in syphilis causing bacteria may have clinical as well as evolutionary significance, researchers at Emory University, Atlanta, have discovered.
In the current study, the scientists described how sequence variations in ARP clearly differentiate between venereal syphilis and non-venereal Treponema pallidum subspecies.
The findings may support an earlier theory that Christopher Columbus and his men may have introduced syphilis into Renaissance Europe after contracting it during their voyage to the New World.
"This finding can lead to improved diagnoses of cases, enabling doctors to prescribe the right treatment, and public health workers to determine the best prevention strategies," says Kristin Harper, who led the research team as a Howard Hughes Medical Institute pre-doctoral fellow in Emory's Population Biology, Ecology and Evolution program.
It is the family of Treponema bacteria that leads to venereal syphilis and the non-venereal diseases of yaws and bejel, which are transmitted through skin-to-skin or oral contact.
In Africa, public health workers have faced difficulty in distinguishing yaws from syphilis in children, and have not yet discovered if the child may have contracted a venereal disease either congenitally or through sexual abuse.
"As yaws eradication efforts near their goal, and case diagnosis becomes more difficult due to the relative rarity of yaws, a molecular means of determining whether the infection is venereal or non-venereal becomes essential," said Harper.
After analysing the repeat region of the ARP gene in 32 strains of pathogenic Treponema, researchers found that the sexually transmitted strains contained multiple types of repeat motifs, while the non-venereal subspecies contained only one type of motif.
Besides, they also discovered the presence of multiple, but distinct, repeat motifs in the two types of sexually transmitted Treponema examined, indicating that a diverse range of repeat motifs has evolved at least two times in association with sexual transmission.
"The kind of changes we found in the ARP gene are consistent with rapid evolution. This scenario lends further support to several prominent theories about the origin of syphilis, including that the pathogen arose with the return of Columbus from the New World," said Harper.
The study was published online in the journal FEMS Immunology and Medical Microbiology.