An Ixodes minor and Borrelia carolinensis enzootic cycle involving a critically endangered Mojave Desert rodent

Abstract

Microtus californicus scirpensis is an endangered, isolated subspecies of California vole. It requires water pools and riparian bulrush (Schoenoplectus americanus) and occupies some of the rarest habitat of any North American mammal. The minimally vegetated, extremely arid desert surrounding the pools is essentially uninhabitable for Ixodes species ticks. We describe an enzootic cycle of Borrelia carolinensis in Ixodes minor ticks at a site 3500 km distant from the region in which I. minor is known to occur in Tecopa Host Springs, Inyo County, eastern Mojave Desert, California. Voles were live-trapped, and ticks and blood samples queried by PCR and DNA sequencing for identification and determination of the presence of Borrelia spp. Between 2011–2013, we found 21 Ixodes minor ticks (prevalence 4–8%) on Amargosa voles and Reithrodontomys megalotis. DNA sequencing of 16S rRNA from ticks yielded 99% identity to I. minor. There was 92% identity with I. minor in the calreticulin gene fragment. Three ticks (23.1%), 15 (24%) voles, three (27%) house mice, and one (7%) harvest mice were PCR positive for Borrelia spp. Sequencing of the 5S-23S intergenic spacer region and flagellin gene assigned Amargosa vole Borrelia strains to B. carolinensis. Ixodes minor, first described in 1902 from a single Guatemalan record, reportedly occurs only in the southeast American on small mammals and birds. The source of this tick in the Mojave Desert and time scale for introduction is not known but likely via migratory birds. Borrelia strains in the Amargosa ecosystem most closely resemble B. carolinensis. B. carolinensis occurs in a rodent-I. minor enzootic cycle in the southeast U.S. although its epidemiological significance for people or rodents is unknown. The presence of a tick and Borrelia spp. only known from southeast U.S. in this extremely isolated habitat on the other side of the continent is of serious concern because it suggests that the animals in the ecosystem could be vulnerable to further incursions of pathogens and parasites.

Species composition and temporal distribution of adult ixodid ticks and prevalence of Borrelia burgdorferi sensu lato and Rickettsia species in Orange County, California

“…In the United States alone, more than 30,000 cases of Lyme disease are reported each year but it is believed that the actual number of cases may reach as high as 300,000 (Mead ). In California, members of the B. burgdorferi sensu lato (sl) complex, including B. burgdorferi ss, B. americana, B. bissettiae (formerly B. bissettii ), B. californiensis, B. carolinensis , and several uncharacterized genospecies have been detected in I. pacificus and mammals throughout the state (Lane et al , Foley et al , Padgett et al , Swei et al ). Two pathogenic tick‐borne Rickettsia species are also known to occur in California: R. rickettsii , the causative agent of Rocky Mountain spotted fever (RMSF), documented in Dermacentor species and R. philipii (formerly Rickettsia sp.…”

A Pilot Serosurvey for Selected Pathogens in Feral Donkeys (Equus asinus)

“…Given the sensitivity of Ixodes ticks to desiccation [ 41 ] and the rugged, arid environment of Death Valley, it was surprising to find that a small number of donkeys had evidence of infection with B. burgdorferi . However, B. burgdorferi has been identified in ticks in areas of the Mojave desert surrounding Death Valley [ 42 ]. There is no significant information available regarding the susceptibility of donkeys to Lyme disease; however, the high seroprevalence in the diagnostic submissions from domestic Equidae suggests that these wild donkeys will be at risk for infection with B. burgdorferi if they are moved to a Lyme endemic area.…”

Chronic Lyme Disease: An Evidence-Based Definition by the ILADS Working Group

“…In Europe, Borrelia afzelii, Borrelia garinii and Bbss cause the majority of cases [32]. Additional Bbsl species are known to cause Lyme-like illnesses but the pathogenic capabilities of other Bbsl species have not been fully characterized [43,[51][52][53][54][55][56][57]. Please see Appendix A for a list of identified Bbsl species and their status as a human pathogen.…”

“…Blurred vision [76] Double vision [190] Progressive visual loss [72] Decreased visual acuity [191] Nystagmus [190] Photophobia [192,193] Eyelid swelling [192] Facial flushing [75] Facial pain [72,138] Tinnitus [76] Headache [74][75][76]189,194] Stiff neck [74,75] Hearing loss [55,189] Arthralgia [106,182,186,[195][196][197][198] Arthritis [73,75,124,183,[198][199][200][201] Joint swelling [72,106,183,186,198,200] Morning stiffness [196] Muscle cramps [197] Muscle weakness [189,202] Myalgia [106,193,…”