Borrelia burgdorferi exposure in coyotes: an indicator of B. burgdorferi levels in urban versus rural environments

a Knowledge Summary by

Laura Shultz BS BA LAT MPVM DVMc (‘23) ^1*

Erik Fausak MSLIS MA RVT LVT RLAT ²

¹University of California, Davis School of Veterinary Medicine, 1 Garrod Dr, Davis, CA 95616
²University Library, University of California, Davis, 1 Shields Ave, Davis, CA 95616
^*Corresponding Author (lcshultz@ucdavis.edu)

Clinical scenario

A dog presents with fever, painful/swollen joints, shifting lameness, lack of appetite, lethargy, and swollen lymph nodes. The patient is not up to date on parasite preventatives, and Lyme disease is suspected. Knowing the prevalence of Borrelia burgdorferi in the area and whether the patient lives in an urban or rural environment could influence how likely that diagnosis is and if it should be given serious consideration. Coyotes occupy urban, rural, and wilderness environments and can serve as a sentinel species to indicate Borrelia disease levels and geographical trends to help inform diagnoses and vaccination recommendations.

The evidence

While cross-sectional studies provide a high level of evidence for prevalence questions assessing exposure to this pathogen, neither of the two studies evaluated here were directly investigating whether Borrelia burgdorferi levels vary between urban and rural environments in wild coyotes of the United States. Due to this, the evidence that they provide towards the PICO question of interest is extremely limited.

In the Olson et al. study from 2000, seroprevalence was determined for canines including both dogs and coyotes in San Diego County, CA, allowing an assessment of risk for human cases of Borreliosis to be conducted. No statistical association was found between disease prevalence and lifestyle (rural vs urban vs indoors) of the canine host, but prevalence of B. burgdorferi antibodies was higher in metropolitan dogs, with the lowest prevalence being found in the most natural habitat; they postulated this could be due to importation of seropositive animals by high mobility owners or ‘brush-border habitat’ styles in urban landscaping supporting tick populations (Olson et al., 2000). However, when looking solely at coyotes, the sample size is small (n = 83), and there was only one positive individual, which was from a rural environment (Olson et al., 2000).

Five years later, Foley et al. (2005) published a study that looked deeper at variation in B. burgdorferi seroprevalence by vegetation type and climate within Ixodes pacificus­­-infested counties of California. While Foley et al. (2005) did not directly classify the tested individuals as urban or rural, ‘urban’ was a habitat option and urban areas are included in mapped visualisations of the data; examining their maps, it appears no or few coyotes from urban habitats were tested. With no tested urban coyotes clearly identifiable, this study does not allow us to answer the target PICO question but does explore variation within rural environments at a finer scale (Foley et al., 2005). Prevalence was higher in areas with higher rainfall as well as in blue oak woodland, montane hardwood, and redwood vegetation habitats, with seasonal peaks in June – July and November – April (Foley et al., 2005).

There were no papers that directly addressed this PICO question, which identifies a gap in knowledge where further research is needed.

Summary of the evidence

Appraisal, application and reflection

Lyme disease in the United States is caused by the bacterium Borrelia burgdorferi sensu stricto (s.s.) and is vectored by Ixodes ticks, namely Ixodes scapularis in the eastern United States and Ixodes pacificus in the western United States that feed on many animal species including humans (Steere et al., 2016). Throughout the United States, Lyme borreliosis is an important emerging disease causing approximately 30,000 new human cases annually (CDC, 2019). While the majority of cases are in the northeastern/mid-Atlantic United States have occurred in all 50 states (CDC, 2019) and the highly diseased regions are expanding (Steere et al., 2016). This is also driven by climate change, allowing ticks to expand their geographic ranges and increase in abundance in recent decades presenting new and increased health risks to humans and animals (Sonenshine, 2018).

While Lyme disease is more debilitating in humans, dogs and other domestic animals can also contract Borrelia infections (Self et al., 2018). In fact, canines can act as sentinels of Lyme disease; testing for exposure to B. burgdorferi in dogs can be done during annual wellness visit examinations by veterinarians (Self et al., 2018). Veterinarians can then act as stewards of public health by reporting seroprevalence and cases of Lyme Borreliosis to the local public health department, helping to effectively track the spread of Ixodes ticks and B. burgdorferi as climate change advances. This serves not only additional animal patients that may present as cases in new areas, but also as a warning flag for human health; public health policy makers can make informed interventions if made aware of new or increasing cases of Lyme disease.

While useful, in private practice domestic animals as a sentinel may be limited because diagnostics is often limited by the permission and finances of pet owners. Coyotes (or other wild canids) are another sentinel species that can be sampled via convenience through animal control agencies, rehab facilities, and roadkill to add to the field’s understanding or Borreliosis risk. While a convenience sample (use of easily available samples or samples on hand) is non-probabilistic and thus does have limitations on the amount it can inform the epidemiologic understanding of a disease, it is a good starting method that limits the challenges of wild species monitoring such as sampling effort and cost of the monitoring efforts. Despite these inherent challenges that exist in monitoring wildlife such as varying population densities and smaller sample sizes, using coyotes as a sentinel is an established practice for other pathogens such as Anaplasma phagocytophilum or Yersinia pestis, which are both zoonotic vector-borne diseases (Foley et al., 2005; and Brown et al., 2011). Testing coyotes can allow us to characterise disease levels in many different environments because coyotes will utilise and have successfully adapted to not only wilderness and rural but also urban environments (Crooks, 2002). Because coyotes utilise multiple environments and have large home ranges (Gehrt et al., 2009), they could also serve as conduits to take Borrelia-infected ticks between habitats or into new areas.

By characterising the exposure and role of Borrelia in coyotes, there is potential that daily clinical decisions of veterinarians can be informed. If veterinarians are aware of the prevalence of Borrelia in surrounding wildlife and the risk posed to their patients, it can hold an appropriate place on their differential list for clinically affected patients and can be utilised to inform testing and vaccination decisions. At the time of this writing, there is a paucity of information concerning how prevalence varies between urban and rural environments and if this can inform clinical decisions of veterinarians; more research is needed in order to determine if wild coyotes have a higher prevalence of B. burgdorferi seroconversion in an urban habitat compared to a rural habitat, and if wild coyotes are indeed a good sentinel species for B. burgdorferi in urban environments.

Methodology

Search strategy
Databases searched and dates covered:	CAB Abstracts on CAB Direct Platform 1973 – 2021 (included products: CAB ABSTRACTS, VetMed Resource, CABI Full Text, Global Health, Animal Health and Production Compendium (AHPC))   Medline on PubMed 1902 – 2021 (Included products: Medline, in process citations, “ahead of print” citations, out-of-scope citations, journals indexing prior to medline inclusion, pre-1966 citations, PubMed Central, author manuscripts NIH funding, NCBI Bookshelf )   Scopus by Elsevier 1976 – 2021
Search strategy:	CAB Abstracts: Coyote* OR “Canis latrans” Borrelia OR “Lyme Disease” OR “lyme disease” OR “B. burgdorferi” OR  “Borrelia spp.” OR “Borrelia sp.” Serology OR seroconversion OR antibodies OR ELISA #1 AND #2 AND #3   PubMed: (((Serology OR seroconversion OR antibodies OR ELISA) AND (Borrelia OR Lyme Disease OR B. burgdorferi OR Borrelia spp. OR Borrelia sp.)) AND (Coyote OR Canis latrans)   Scopus: ( TITLE-ABS-KEY ( serology  OR  seroconversion  OR  antibodies  OR  elisa  OR  "enzyme-linked immunosorbent assay" ) )  AND  ( TITLE-ABS-KEY ( borrelia  OR  lyme  OR  lyme's  OR  {b. burgdorferi} ) )  AND  ( TITLE-ABS-KEY ( coyote  OR  coyotes  OR  "canis latrans"  OR  {C. latrans } ) )
Dates searches performed:	10 Nov 2021

Exclusion / Inclusion criteria
Exclusion:	Not in English Study area is outside the US Borrelia burgdorferi not actually measured / not in coyotes Urban / rural distinction not made for tested coyotes Not peer-reviewed
Inclusion:	English Study area is within the US Borrelia burgdorferi measured by authors in coyotes Urban / rural distinction not made for tested coyotes Peer-reviewed

Search outcome
Database	Number of results	Excluded – Not in English	Excluded – Study area is outside the USA	Excluded – Does not measure Borrelia burgdorferi in coyotes	Excluded – Urban / rural data not included	Excluded – Not peer-reviewed	Total relevant papers
CAB Abstracts	9	0	2	0	6	0	1
PubMed	10	0	2	1	5	0	2
Scopus	10	0	2	1	5	0	2
Total relevant papers when duplicates removed							2

The authors declare no conflicts of interest.

The authors would like to acknowledge Andres Mauricio Lopez-Perez for his mentorship of L. Shultz and proof-reading this manuscript. Additional acknowledgement goes to the 2020 MPM208 Class at University of California, Davis through which this project was undertaken.

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2. Centers for Disease Control and Prevention (CDC). (2019). Lyme Disease Data and surveillance. [online] Available from: https://www.cdc.gov/lyme/datasurveillance/index.html [Accessed 10 Dec 2020].
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