Tick Paralysis in Spectacled Flying-Foxes (Pteropus conspicillatus) in North Queensland, Australia: Impact of a Ground-Dwelling Ectoparasite Finding an Arboreal Host

Petra G Buettner,Richard Speare,Adam Mckeown,Lawrence Brown,Jennefer Maclean,Lee Skerratt,Reinhold Muller,David A Westcott,Ashleigh Johnson,Karen Wilson,Jonathan Luly,David Blair

doi:10.1371/journal.pone.0073078

Abstract

When a parasite finds a new wildlife host, impacts can be significant. In the late 1980s populations of Spectacled Flying-foxes (SFF) (Pteropus conspicillatus), a species confined, in Australia, to north Queensland became infected by paralysis tick (Ixodes holocyclus), resulting in mortality. This Pteropus-tick relationship was new to Australia. Curiously, the relationship was confined to several camps on the Atherton Tableland, north Queensland. It was hypothesised that an introduced plant, wild tobacco (Solanum mauritianum), had facilitated this new host-tick interaction. This study quantifies the impact of tick paralysis on SFF and investigates the relationship with climate. Retrospective analysis was carried out on records from the Tolga Bat Hospital for 1998–2010. Juvenile mortality rates were correlated to climate data using vector auto-regression. Mortality rates due to tick paralysis ranged between 11.6 per 10,000 bats in 2003 and 102.5 in 2009; more female than male adult bats were affected. Juvenile mortality rates were negatively correlated with the total rainfall in January to March and July to September of the same year while a positive correlation of these quarterly total rainfalls existed with the total population. All tick affected camps of SFF were located in the 80% core range of S. mauritianum. This initial analysis justifies further exploration of how an exotic plant might alter the relationship between a formerly ground-dwelling parasite and an arboreal host.

Highlights

Disease is increasingly recognised as a factor in the population dynamics of wild animals
The number of animals found to be affected by I. holocyclus varied greatly, from 165 in 1999 to 720 in the partial count of 2009 (Table 1)
For the years with complete counts (1998 to 2005; 2010) more female adults than male adults were affected by tick paralysis (p = 0.008)

Summary

Introduction

Disease is increasingly recognised as a factor in the population dynamics of wild animals. Wildlife disease is of particular interest when there is the potential for human or agricultural impact (i.e., zoonoses including emerging infectious diseases), it is of concern in the context of the conservation management of threatened species [10,11,12]. Disease has been noted as a threatening process for, among others, amphibians, seals, whales, canids, birds, dasyurids and flying-foxes [12,13,14,15,16,17,18,19]. Pathogens that infect a new species of host can have marked effects on that species, the most spectacular example being the global pandemic due to the chytrid fungus (Batrachochytrium dendrobatidis) in amphibians resulting in massive mortalities with some species driven to extinction [15]

Methods

Results

Conclusion