Trench fever is an ancient disease with a surprisingly short history. Named after its discovery in the trenches of World War I, its case history is only about a century old. Yet, the louse transmitted Bartonella quintana that causes trench fever has been found in human remains as old as 4000 years and is one of the most common infectious organisms found in human ancient DNA (for example). Once thought of as a self-limited moderate ‘five-day’ fever (aka quintana) it is now known that it can also cause endocarditis and a chronic bacteremia. It persists today in most countries anywhere that human body lice are common, often among the homeless.
After the chance discovery of trench fever in captive macaques transported in both directions between the United States and China, a Chinese team investigated the extent of Bartonella quintana in macaques in captive primate centers in China (1). They collected blood from Rhesus macaques at three geographically distant primate centers and cynomologus macaques from one additional primate center. They found Bartonella quintana in macaques from all four centers with enough genetic diversity to suggest multiple sources originating in the wild (1). By Multilocus sequence typing (MLST), a type of genetic fingerprinting, they found more genetic diversity just in the macaques from these centers than from all human isolates analyzed to date around the world. This suggested to the Chinese team that the macaques are the likely original host population of an ancient zoonosis (1). The limited genetic variation in humans suggests that the zoonotic transmission events occurred in the distant past and are not continuing today at a level detected in human populations. Further, the Bartonella quintana sequences fell neatly into three groups that corresponded to the species they were isolated from, suggesting to the Chinese group that B. quintana has co-evolved with species specific exoparasites, mostly lice (1).
Although they found B. quintana in a high percentage of macaques in all of these facilities, the conditions at the primate centers could account for the high incidence rate. A related study also found that B. quintana spread very easily within the captive Rhesus macaque centers through the macaque specific louse Pedicinus obtusus (2). They were also able to demonstrate that the macaques developed the chronic bacteremia found in humans suggesting some evolved tolerance (2). Samples from wild macaques will have to be sampled to determine what the natural carrying load of these species are. Rhesus macaques have a range from China to Afghanistan with a large population in India. Other macaque species extend the historic range of possible carriers to the Mediterranean and North Africa.
- Li H, Bai JY, Wang LY, Zeng L, Shi YS, Qiu ZL, Ye HH, Zhang XF, Lu QB, Kosoy M, Liu W, & Cao WC (2013). Genetic diversity of Bartonella quintana in macaques suggests zoonotic origin of trench fever. Molecular ecology, 22 (8), 2118-27 PMID: 23517327
- Li H, Liu W, Zhang GZ, Sun ZZ, Bai JY, Jiang BG, Zhang YY, Zhao XG, Yang H, Tian G, Li YC, Zeng L, Kosoy M, & Cao WC (2013). Transmission and maintenance cycle of Bartonella quintana among rhesus macaques, China. Emerging infectious diseases, 19 (2), 297-300 PMID: 23347418