Spatial Variation and Survival of Salmonella enterica Subspecies in a Population of Australian Sleepy Lizards (Tiliqua rugosa)

Abstract

bThe life cycles of many enteric bacterial species require a transition between two very distinct environments. Their primary habitat is the gastrointestinal tract of the host, while their secondary habitat, during transmission from one host to another, consists of environments external to the host, such as soil, water, and sediments. Consequently, both host and environmental factors shape the genetic structure of enteric bacterial populations. This study examined the distribution of four Salmonella enterica subspecies in a population of sleepy lizards, Tiliqua rugosa, in a semiarid region of South Australia. The lizards living within the 1,920-m by 720-m study site were radio tracked, and their enteric bacteria were sampled at regular intervals throughout their active seasons in the years 2001, 2002, and 2006. Four of the six subspecies of S. enterica were present in this population and were nonrandomly distributed among the lizards. In particular, S. enterica subsp. diarizonae was restricted to lizards living in the most shaded parts of the study site with an overstorey of Casuarina trees. Experiments undertaken to investigate the survival of S. enterica cells under seminatural conditions revealed that cell survival decreased with increased exposure to elevated temperatures and UV light. Among the three S. enterica subspecies tested, S. enterica subsp. diarizonae consistently had an average expected life span that was shorter than that observed for the other two subspecies. There was no indication in the data that there was any competitive dominance hierarchy among the S. enterica subspecies within individual hosts. Thus, the nonrandom distribution of S. enterica subspecies in this population of lizards appears to be driven by their different survival characteristics in the external environment.

Climate change-induced increases in precipitation are reducing the potential for solar ultraviolet radiation to inactivate pathogens in surface waters

“…In this latter study, natural waters with higher DOM concentrations reduced this solar UV inactivation, with the extent of the inactivation depending on the source water and DOM concentration. Effective inactivation by sunlight has also been demonstrated in a variety of non-human waterborne pathogens including those that infect lizards 26 , Atlantic salmon 27 , birds 28 , and zooplankton 14 . The effects of UV on the chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd), which has caused worldwide declines in amphibian populations, remains uncertain.…”

The Fine-Scale Landscape of Immunity and Parasitism in a Wild Ungulate Population

“…Spatial variation in parasitism will arise in part as a result of this immune heterogeneity owing to variation in susceptibility, clearance, and tolerance (Jolles et al 2015), as well as from abiotic factors affecting parasite transmission (e.g. sunlight; Parsons et al 2015) or from variation in abundance of secondary hosts or vectors (Sol et al 2011;Olsen et al 2015). In addition, conspecific density can influence resource availability, immune investment, and parasite exposure (Wilson et al 2004;Downs et al 2015;Ezenwa et al 2016).…”

Discovery and Partial Genomic Characterisation of a Novel Nidovirus Associated with Respiratory Disease in Wild Shingleback Lizards (Tiliqua rugosa)

“…Whilst the species is considered common, they form a substantial caseload to urban rehabilitation centres from anthropogenic causes such as motor vehicle strike, dog and cat attack, and lawn mower trauma [11]. Several studies of lizards within the Tiliqua genus have documented ecto-, endo-and haemoparasites [23][24][25][26], and enteric bacteria [27], as well as the influence of their social networks and behavioural ecology on disease transmission [28]. However to date no viruses have been described in this species in Australia, captive or wild.…”