First reported outbreak of severe spirorchiidiasis in Emys orbicularis, probably resulting from a parasite spillover event

Abstract

The importance of disease-mediated invasions and the role of parasite spillover as a substantial threat to the conservation of global biodiversity are now well known. Although competition between invasive sliders Trachemys scripta elegans and indigenous European turtles has been extensively studied, the impact of this invasive species on diseases affecting native populations is poorly known. During winter 2012−2013 an unusual event was detected in a population of Emys orbicularis (Linnaeus, 1758) inhabiting a pond system in Galicia (NW Spain). Most turtles were lethargic and some had lost mobility of limbs and tail. Necropsies were performed on 11 turtles that were found dead or dying at this site. Blood flukes belonging to the species Spirorchis elegans were found inhabiting the vascular system of 3 turtles, while numerous fluke eggs were trapped in the vascular system, brain, lung, heart, liver, kidney, spleen, and/or gastrointestinal tissues of all necropsied animals. Characteristic lesions included miliary egg granulomas, which were mostly found on serosal surfaces, particularly of the small intestine, as well as endocarditis, arteritis, and thrombosis. The most probable cause of death in the 3 turtle specimens which were also examined histologically was a necrotic enteritis with secondary bacterial infection associated with a massive egg embolism. The North American origin of S. elegans, the absence of prior recorded epizootics in the outbreak area, and the habitual presence of its type host, the highly invasive red-eared slider, in this area suggest a new case of parasite spillover resulting in a severe emerging disease. KEY WORDS: Emys orbicularis · Blood flukes · Spirorchis · Spirorchidiiasis · Mortality · Parasite spillover · Trachemys scripta Resale or republication not permitted without written consent of the publisherDis Aquat Org 113: [75][76][77][78][79][80] 2015 In this sense, competition between the red-eared slider Trachemys scripta elegans (Wied, 1838), which is included in the 20 worst invasive species in Spain (GEIB 2006), and the autochthonous turtles Emys orbicularis (Linnaeus, 1758) and Mauremys leprosa (Schweigger, 1812) has been extensively studied (Cadi & Joly 2003, 2004, Polo-Cavia 2009). In contrast, although the importance of disease-mediated invasions and the role of parasite spillover/spillback as a substantial threat to the conservation of global biodiversity have recently been highlighted (Smith et al. 2006, Peeler et al. 2011, McCallum 2012, Strauss et al. 2012, the impact of alien sliders on diseases affecting indigenous European turtles is poorly known.E. orbicularis is found in East and Central Europe, the Mediterranean countries (including some islands), and North Africa (Fritz 2001(Fritz , 2003. At present, this species is threatened and declining in several regions of its range, mainly due to habitat destruction. It is therefore included in the Bern Convention and protected by European Union laws. However, it is still listed as a lower risk/near threatened ...

The good, the bad and the ugly: Emys trinacris, Placobdella costata and Haemogregarina stepanowi in Sicily (Testudines, Annelida and Apicomplexa)

“…Iglesias et al 2015). The genetic characterisation of Sicilian and Italian populations of H. stepanowi, possibly implementing fast-evolving molecular markers, would allow testing for the existence in Sicily of autochthonous vs introduced strains of H. stepanowi, and for the development of adequate management plans.…”

Borrelia bavariensis: Vector Switch, Niche Invasion, and Geographical Spread of a Tick-Borne Bacterial Parasite

“…The invading parasite may cause changes in the population dynamics of the invaded population of the original host either directly through parasitism (Dunn, 2009), or indirectly by affecting the success of the original host's competitors and predators (Hatcher et al, 2006). In addition, it may affect populations of new host species through parasite "spillover" (Iglesias et al, 2015), and also alter the success of other parasites already present in the new domain through competition for existing and new hosts (Dunn, 2009). In turn, the parasite itself may as a result of its introduction undergo evolutionary change in order to adapt to its new circumstances (e.g., Juhasova et al, 2016).…”

Infection by invasive parasites increases susceptibility of native hosts to secondary infection via modulation of cellular immunity

“…Invasive parasites can directly and indirectly influence disease outbreaks in the invaded ecosystem. Either such parasite spillover can directly lead to the emergence of diseases in native biota (Goedknegt et al., ) or indirectly favour secondary infections (Iglesias, García‐Estévez, Ayres, Acuña, & Cordero‐Rivera, ). The mass mortalities of blue mussel M. edulis shortly after the invasion of the parasite M. intestinalis (Blateau et al., ; Korringa, ) represent a good example for strong effects on the newly infected host species resulting from a parasite invasion.…”