Bald Eagle Nestling Mortality Associated with Argas radiatus and Argas ricei Tick Infestation and Successful Management with Nest Removal in Arizona, USA.

Eight Bald Eagle ( Haliaeetus leucocephalus ) nestlings heavily infested with larval ticks were found in or under a nest near the confluence of the Verde and Salt rivers in Arizona in 2009-11. The 8-12-wk-old nestlings were slow to respond to stimuli and exhibited generalized muscle weakness or paresis of the pelvic limbs. Numerous cutaneous and subcutaneous hemorrhages were associated with sites of tick attachment. Ticks were identified as Argas radiatus and Argas ricei. Treatment with acaricides and infection with West Nile virus (WNV) may have confounded the clinical presentation in 2009 and 2010. However, WNV-negative birds exhibited similar signs in 2011. One nestling recovered from paresis within 36 h after the removal of all adult and larval ticks (>350) and was released within 3 wk. The signs present in the heavily infested Bald Eagle nestlings resembled signs associated with tick paralysis, a neurotoxin-mediated paralytic syndrome described in mammals, reptiles, and wild birds (though not eagles). Removal of the infested nest and construction of a nest platform in a different tree was necessary to break the cycle of infection. The original nesting pair constructed a new nest on the man-made platform and successfully fledged two Bald Eagles in 2012.