No evidence for yaws infection in a small-scale cross-sectional serosurvey in Ghanaian monkeys

Treponema pallidum (TP) is a spirochaete bacterium with subspecies that in humans cause syphilis (subsp. pallidum), bejel (subsp. endemicum) and yaws (subsp. pertenue; TPE). The latter is target for eradication which requires detailed information on yaws epidemiology. It has been shown that African nonhuman primates (NHPs) are infected with TPE strains that are closely related to the human infecting yaws bacterium. While human yaws infection is known to be endemic in Ghana, there is a paucity of information regarding TPE infection of Ghana's native NHPs.

The objective was to perform a small-scale cross-sectional serological screening for antibodies against TPE in Ghanaian monkeys. Due to the reports of TPE-infected NHPs from neighbouring Côte d'Ivore, we hypothesised that monkeys in Ghana are infected with TPE and, therefore, are seropositive for antibodies against-Treponema.

We sampled blood from 37 NHPs representing four species: Erythrocebus patas (16/37) 43.2%, Papio anubis (15/37) 40.5%, Chlorocebus sabaeus (3/37) 8.1% and Cercopithecus mona (3/37) 8.1%. Samples were tested using the NHP validated treponemal test ESPLINE TP.

All 37 animals were seronegative for yaws infection.

We cannot exclude yaws infection in NHPs in Ghana at this point. Our study, in combination with the absence of reports of clinically infected NHPs in a yaws endemic country is, however, supportive for the current thinking that interspecies infection with TPE is extremely rare. This is an important finding for the current ongoing yaws eradication campaign.