The High Prevalence and Diversity of Chlamydiales DNA within Ixodes ricinus Ticks Suggest a Role for Ticks as Reservoirs and Vectors of Chlamydia-Related Bacteria

Abstract

bThe Chlamydiales order is composed of nine families of strictly intracellular bacteria. Among them, Chlamydia trachomatis, C. pneumoniae, and C. psittaci are established human pathogens, whereas Waddlia chondrophila and Parachlamydia acanthamoebae have emerged as new pathogens in humans. However, despite their medical importance, their biodiversity and ecology remain to be studied. Even if arthropods and, particularly, ticks are well known to be vectors of numerous infectious agents such as viruses and bacteria, virtually nothing is known about ticks and chlamydia. This study investigated the prevalence of Chlamydiae in ticks. Specifically, 62,889 Ixodes ricinus ticks, consolidated into 8,534 pools, were sampled in 172 collection sites throughout Switzerland and were investigated using pan-Chlamydiales quantitative PCR (qPCR) for the presence of Chlamydiales DNA. Among the pools, 543 (6.4%) gave positive results and the estimated prevalence in individual ticks was 0.89%. Among those pools with positive results, we obtained 16S rRNA sequences for 359 samples, allowing classification of Chlamydiales DNA at the family level. A high level of biodiversity was observed, since six of the nine families belonging to the Chlamydiales order were detected. Those most common were Parachlamydiaceae (33.1%) and Rhabdochlamydiaceae (29.2%). "Unclassified Chlamydiales" (31.8%) were also often detected. Thanks to the huge amount of Chlamydiales DNA recovered from ticks, this report opens up new perspectives on further work focusing on whole-genome sequencing to increase our knowledge about Chlamydiales biodiversity. This report of an epidemiological study also demonstrates the presence of Chlamydia-related bacteria within Ixodes ricinus ticks and suggests a role for ticks in the transmission of and as a reservoir for these emerging pathogenic Chlamydia-related bacteria.

Molecular Evidence of Chlamydia-Like Organisms in the Feces of Myotis daubentonii Bats

“…In the phylogenetic tree, group 2 sequences were nearly identical to the reference sequence originating from ticks. Indeed, the most prevalent Chlamydiales DNA detected in Ixodes ricinus ticks belonged to the families Rhabdochlamydiaceae and Parachlamydiaceae (14,24). Taking all these data together, we believe that the group 2 sequences detected in bat droppings belong to the family Rhabdochlamydiaceae.…”

“…Rhabdochlamydia porcellionis," first detected in terrestrial isopods (25,26), and "Ca. Rhabdochlamydia crassificans," found in the cockroach Blatta orientalis (27) Since then, rhabdochlamydial DNA has also been detected in dwarf spiders (28), sea birds (29), and ticks (14,24) but also in human respiratory samples (11,17,30). However, it is unknown how Rhabdochlamydiaceae could be transmitted between animal species and to humans, but ticks could serve as vectors (23).…”

“…Altogether, 108 of 200 (54%) bat dropping samples were shown to contain Chlamydiales DNA by quantitative PCR (qPCR) (samples with a threshold cycle [C T ] value of Յ37.0 were considered positive [14]; the mean C T [C Tmean ] Ϯ standard deviation [SD] was 31.6 Ϯ 3.41, the minimum C T [C Tmin ] was 21.47, and the maximum C T [C Tmax ] was 36.82). Purified qPCR products were sequenced.…”

Simkania negevensis, an insight into the biology and clinical importance of a novel member of the Chlamydiales order

“…mammalian cells, arthropods, amebae) (Kahane et al, 2008(Kahane et al, , 2007a(Kahane et al, , 2001Sixt et al, 2012). Evidence of Simkaniaceae was documented in vivo in ticks Pilloux et al, 2015) and in granulomatous lesions in reptiles (Soldati et al, 2004). Fritschea were discovered in arthropods (Everett et al, 2005) and Syngnamydia in fish (Fehr et al, 2013;Nylund et al, 2015).…”

“…Vector transmission is quite common for other intracellular bacteria such as Rickettsia (Walker & Ismail, 2008). Moreover, Simkania-associated DNA was amplified from Swiss Ixodes ricinus ticks, though with a lower prevalence and amount than Rhabdochlamydiaceae Pilloux et al, 2015).…”