Identification of Zoonotic and Vector-borne Infectious Agents Associated with Opossums (Didelphis virginiana) in Residential Neighborhoods of Orange County, California

Abstract

Opossums and cat fleas have been epidemiologically linked to flea-borne rickettsial disease transmission in residential backyards of Orange County, California. In 2013, a study was initiated to better elucidate the life history of opossums and their role as vectors of disease and hosts for both internal and external parasites. The study population consisted of adult opossums collected year-round from flea-borne rickettsial disease exposure sites, and moribund opossums submitted by wildlife rehabilitators in Orange County. Carcasses were examined for ectoparasites and necropsied, which included the removal and collection of endoparasites, organ tissues, feces, and urine. Reproductive life history data suggested one brood of young per year, with an average litter size of 7 (n = 9, range 2-11). Average adult weight was 2.49 kg (range 1.30-4.41 kg). Cat fleas were present on each opossum with an average of 96 fleas per opossum (n = 82, range 2-725). Thirty of 33 cat flea pools tested PCR-positive for one of the following bacteria: Rickettsia felis (53%), R. typhi (3%), the R. felis-like organisms, Candidatus Rickettsia senegalensis (28%) and Ca. Rickettsia asemboensis (3%), or Bartonella vinsonii subsp. arupensis (1.5%). Sticktight fleas (Echidnophaga gallinacea), the only other flea detected, were present on less than 6% of opossums, and ticks were not detected on any carcasses (n = 83). Endoparasitic nematodes Cruzia americana and Physaloptera turgida were present in each stomach and cecum, and Didelphostrongylus hayesior or Heterstongylus heterostrongylus was noted in lung samples of opossums (n = 83). Salmonella spp. were detected in 52% of fecal samples (n = 50), with subsequent typing of strains indicating the presence of human pathogens in all but three of the samples (n = 26). Blood and spleen samples were negative for Bartonella spp., Brucella spp., and Yersinia pestis (n = 33). Sera were negative for Leptospira-specific antibodies and Leptospira DNA was not detected in urine (n = 83). Results from this multi-agency study show that the presence of opossums in the backyard environment put Orange County residents and their pets at risk of flea-borne bartonella and rickettsial diseases and salmonellosis.

Metagenomic analysis of human-biting cat fleas in urban northeastern United States of America reveals an emerging zoonotic pathogen

“…MT901297) genes from all six positive fleas, which generated a single genotype for each gene. These sequences produced a 100% match with isolates previously described as Rickettsia asembonensis in California, US 15 , Peru 16 and Brazil 17 . We found that five of the six infected fleas had haplotype h6 (83% of h6 fleas were positive for R. asembonensis) and one had haplotype h1 (3% of h1 fleas were positive for R. asembonensis).…”

“…The sca4 gene was omitted from the table to reduce its size. This gene was sequenced in only 4 studies 15,16,18,50,61 , which produced sequences with 100% identity in relation to the R. asembonensis detected in this study. NA = Information not available, C. felis = Ctenocephalides felis, C. canis = Ctenocephalides canis, C. orientis = Ctenocephalides orientis.…”

“…no Identities 2 GenBank acc. no Ctenocephalides felis Human ( Homo sapiens) Grizzly ( Ursus arctosi ) Columbia, SC, USA 2009 371/372 (99.7%) AY953289 432/434 (99.5%) AY953286 Nelder et al 40 C. felis Opossum ( Didelphis virginiana ) Orange Co., CA, USA 2016 1035/1035 (100%) KU597068 1517/1517 (100%) KU597066 1224/1225 (99.9%) KU597069 Krueger et al 15 C. felis Cat ( Felis catus ) Los Angeles Co., CA, USA 2016 787/787 (100%) KP398499 Billeter et al 41 C. felis Cat ( Felis catus ) Georgia, USA 2016 613/613 (100%) KX431974 833/833 (100%) KX431985 Šlapeta and Šlapeta 12 C. felis Opossum ( Didelphis virginiana ) Orange Co., CA, USA 2016 …”

A California without Rodenticides: Challenges for Commensal Rodent Management in the Future

“…Research has shown a lower prevalence of pathogens in urban rodents compared to rural rodents (Inoue et al 2008, Hsieh et al 2010, while other studies have noted the opposite (Halliday et al 2015). A study from an urban center in Southern California shows that the population of fleas on rodents and backyard wildlife has increased significantly since 1967 (Krueger et al 2016). A study of rat ectoparasites in New York City found the number of fleas on Norway rats to be higher than previously recorded (Frye et al 2015).…”

“…Anticoagulant rodenticide has been detected in 70% of nontarget wildlife collected by the California's Depart- ment of Fish and Wildlife (Hosea 2000). High levels of regional detection have also been reported from single species populations in Southern California (Riley et al 2007), as well as multiple raptor species (Krueger et al 2016). It is possibly that the exposure of wildlife to other pesticides is widespread, however, anticoagulant rodenticides are persistent and have the potential to be detected at higher rates for longer periods of time than less persistent compounds (Thompson et al 2014).…”