HISTOPATHOLOGY AND RISK FACTORS ASSOCIATED WITH NEOTROMBICULA MICROTI INFESTATION IN THE ENDANGERED AMARGOSA VOLE (MICROTUS CALIFORNICUS SCIRPENSIS)

Abstract

ABSTRACT:The Amargosa vole (Microtus californicus scirpensis) is a profoundly endangered rodent found only in the Central Mojave Desert, Inyo County, California, US. In 2010, severe cases of trombiculiasis, caused by larval Neotrombicula microti mites, were discovered among voles and sympatric small mammals. We evaluated Amargosa voles and sympatric rodents for infestation with N. microti December 2011-November 2012 and evaluated histopathology of ear tissue from 13 actively N. microti-infested Amargosa voles and 10 Amargosa voles with no gross evidence of current or past infestation. Rodents with current infestation had mites visible on tissue, typically ear pinnae, whereas mites were not seen on rodents with presumptive past infestation, but some of these animals had gross tissue scarring and loss consistent with healing from infestation. Ears from infested voles had severe granulocytic and necrotizing dermatitis, most associated with stylostome fragments, whereas few lesions were present in grossly uninfested voles. There was no association between body condition and infestation or severity of lesions. Significantly more voles were infested (37%) with N. microti than sympatric rodents (3%), suggesting that sympatric rodents do not serve as an important source of N. microti exposure to voles. Although this chigger infestation was common and induced severe localized pathology, we did not detect a fitness cost to infestation and recommend further evaluation of the disease to discern its significance in this conservation context.

Host species and environment drivers of ectoparasite community of rodents in a Mojave Desert wetlands

“…Despite that chigger infestation is relatively common in some rodents, it is rarely associated with disease with the exception of scrub typhus, an important disease of people in parts of Asia that is transmitted by chiggers [ 103 , 113 , 114 ]. For instance, Amargosa voles experience severe and highly prevalent lesions due to chiggers [ 115 ], while California voles (the larger species of which Amargosa voles are a subspecies) have been shown to be fatally susceptible to plague and tularemia [ 6 , 116 ]. Chiggers on Amargosa voles are highly prevalent, and often associated with severe lesions, although their presence did not appear to impact body mass or fitness [ 117 ].…”