Abstract
The recent detection of a novel amoebozoan parasite (Entamoeba sp. CT1) killing invasive cane toads (Rhinella marina) in tropical Australia raises concerns of potential spill-over into native anuran populations. Considering the vulnerability of anuran communities globally, Entamoeba sp. CT1 may pose a serious threat to anuran biodiversity. Through PCR-based detection and molecular identification, we investigated the prevalence of Entamoeba spp. in the faeces and colon tissue of cane toads (Rhinella marina) and eleven native Australian frog species from a single locality in the Northern Territory. No Entamoeba DNA was detected in samples of native frog faeces (N = 57) or colons (N = 17). Entamoeba DNA was detected in 24% of 45 cane toads (95%CI 14.08–38.82). Both E. ranarum and Entamoeba sp. CT1 were present in cane toads. The failure of faecal samples to indicate Entamoeba spp. in infected cane toads may be due to cysts in faeces being shed intermittently, degraded before analysis, or impervious to lysis prior to DNA isolation. Our results suggest that native frogs do not carry the pathogen in an area where 20–30% of cane toads are infected with Entamoeba sp. CT1. We demonstrate the importance of recognising PCR inhibition prior to molecular diagnostics, and the apparent inadequacy of faecal samples for the detection of Entamoeba spp. in anurans.
Highlights
Since its introduction into Australia in 1935 as a strategy for the control of pestiferous cane beetles Dermolepida albohirtum (Waterhouse, 1875), the cane toad Rhinella marina (Linnaeus, 1758) has become widely recognised as one of the most ecologically damaging invasive species (Sabath et al, 1981; Shine, 2018)
Samples of cane toad colon tissue were affected by in hibition less frequently than were faecal samples from the same species (z 1⁄4 3.4258, p 1⁄4 0.0003)
The presence of inhibition was significantly reduced in faecal samples both from cane toads and from native anurans (Table 3)
Summary
Since its introduction into Australia in 1935 as a strategy for the control of pestiferous cane beetles Dermolepida albohirtum (Waterhouse, 1875), the cane toad Rhinella marina (Linnaeus, 1758) has become widely recognised as one of the most ecologically damaging invasive species (Sabath et al, 1981; Shine, 2018). An outbreak of lethal colitis was observed in a wild popu lation of cane toads at the University of Sydney Tropical Ecology Research Facility (TERF) in Australia’s Northern Territory (Shilton et al, 2018). Information on the distribution of Entamoeba in anurans is scant in Australia, with the only reported cases involving an apparently non-pathogenic species, Entamoeba morula, in native frogs from Victoria and New South Wales (Raff, 1911).
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