Parasite spillover: indirect effects of invasive Burmese pythons

Abstract

Identification of the origin of parasites of nonindigenous species (NIS) can be complex. NIS may introduce parasites from their native range and acquire parasites from within their invaded range. Determination of whether parasites are non‐native or native can be complicated when parasite genera occur within both the NIS’ native range and its introduced range. We explored potential for spillover and spillback of lung parasites infecting Burmese pythons (Python bivittatus) in their invasive range (Florida). We collected 498 indigenous snakes of 26 species and 805 Burmese pythons during 2004–2016 and examined them for lung parasites. We used morphology to identify three genera of pentastome parasites, Raillietiella, a cosmopolitan form, and Porocephalus and Kiricephalus, both New World forms. We sequenced these parasites at one mitochondrial and one nuclear locus and showed that each genus is represented by a single species, R. orientalis, P. crotali, and K. coarctatus. Pythons are host to R. orientalis and P. crotali, but not K. coarctatus; native snakes are host to all three species. Sequence data show that pythons introduced R. orientalis to North America, where this parasite now infects native snakes. Additionally, our data suggest that pythons are competent hosts to P. crotali, a widespread parasite native to North and South America that was previously hypothesized to infect only viperid snakes. Our results indicate invasive Burmese pythons have affected parasite‐host dynamics of native snakes in ways that are consistent with parasite spillover and demonstrate the potential for indirect effects during invasions. Additionally, we show that pythons have acquired a parasite native to their introduced range, which is the initial condition necessary for parasite spillback.

Case Report: Invasive Pentastomes, Raillietiella orientalis (Sambon, 1922), in a Free-Ranging Banded Water Snake (Nerodia fasciata) in North Central Florida, USA

“…Primer sequences were trimmed and compared to known sequences using the NCBI Basic Local Alignment Search Tool ( 5 ). The amplified 18S sequence was 100% identical to numerous R. orientalis isolates, including those previously identified in Florida and reported by Miller et al ( 6 ) and Farrell et al ( 7 ).…”

“…Raillietiella orientalis has been reported in several snake species in Asia and Australia, including those from the families Colubridae, Elaphidae, Viperidae, and Boidae ( 3 , 8 , 9 ). Raillietiella orientalis was first identified in the United States in 2017 in free-ranging, invasive Burmese pythons in the Florida Everglades as well as nine native snake species in six southern Florida counties ( 6 ) ( Figure 4 , purple counties). In that study, no parasites were identified during surveillance in northern Florida (including Alachua County) and southern Georgia.…”

“…The natural range of Nerodia fasciata is extensive, inhabiting coastal plains from southwest Alabama to North Carolina, along the Gulf States into Texas, and up the Mississippi River to Indiana ( 10 ). Along with sympatric species identified by Miller et al ( 6 ) to be susceptible to infection, such as cottonmouths ( Agkistrodon piscivorus ), salt marsh snakes ( Nerodia clarkii ), garter snakes ( Thamnophis sirtalis ), and corn snakes ( Pantherophis guttatus ), there is a substantial risk that Raillitiella orientalis may spread throughout the southeastern United States, and potentially further.…”

“…While R. orientalis is of limited clinical significance to the Burmese python, these invasive pentastomes are likely contributing to morbidity and mortality in native snake species ( 6 , 7 ). Morbidity and mortality associated with these parasitic infections may be due to additional co-infections.…”

Host-specific phenotypic variation of a parasite co-introduced with invasive Burmese pythons

“…Non-native species can harbor parasites and pathogens capable of infecting native taxa within their introduced range, a process known as parasite spillover [1–3]. For species with indirect lifestyles, potential obstacles to parasite spillover include low host density and lack of an appropriate intermediate host [4].…”