Association of Ixodes pacificus (Acari: ixodidae) with the spatial and temporal distribution of equine granulocytic ehrlichiosis in California.
Abstract: This study was conducted to determine if the biology of certain ticks associated with horses regulates the spatial and temporal distribution of equine granulocytic ehrlichiosis (EGE) in California north of Monterey County. We compared the spatial and temporal distribution of EGE cases with the seasons of activity and life histories of ticks that infest horses. Spatially, cases collected from equine veterinarians clustered around each other in a manner different from the way in which control cities of practice were distributed, with foci limited to the Sierra Nevada and coastal foothills. Cases also clustered seasonally: most were diagnosed between November and April. The spatial and temporal pattern of EGE cases closely parallels the well-characterized life history and distribution of Ixodes pacificus Cooley & Kohls, but not other ticks commonly associated with horses. Building on previous studies, there is compelling evidence that this tick has the vectorial capacity to transmit Ehrlichia equi to horses. Based on the life history and distribution of I. pacificus in relation to EGE cases, we reason that this tick is the only biologically plausible vector of E. equi in California, and provide evidence for a tightly linked association between I. pacificus and the epidemiology of EGE.
Publication Date: 1999-10-27 PubMed ID: 10534948DOI: 10.1093/jmedent/36.5.551Google Scholar: Lookup
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- Journal Article
- Animal Health
- Animal Studies
- Diagnosis
- Disease control
- Disease Diagnosis
- Disease Etiology
- Disease Management
- Disease Outbreaks
- Disease Prevalence
- Disease Surveillance
- Disease Transmission
- Disease Treatment
- Epidemiology
- Equine Diseases
- Equine Health
- Horses
- Infectious Disease
- Ticks
- Vector-borne disease
- Veterinary Medicine
- Veterinary Research
Summary
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The research confirms that the life-cycle and distribution of the tick Ixodes pacificus greatly influences the distribution and occurrence of equine granulocytic ehrlichiosis, a horse disease, in Northern California.
Conduct and Aim of Study
- The authors carried out this research to uncover if the biology and life cycle of specific breeds of ticks that are usually found on horses can dictate the geographical and temporal distribution of Equine Granulocytic Ehrlichiosis (EGE), a disease affecting horses, in the northern region of California, specifically above Monterey County.
- The research involved comparing the geographical and temporal occurrence of EGE cases with the activity periods and life histories of ticks known to infest horses.
Spatial and Temporal Findings
- Geographically, the gathered EGE cases from equine veterinarians appeared to cluster in patterns different from the control city distribution patterns, being focused primarily in the Sierra Nevada and coastal foothills.
- Time-wise, most cases were diagnosed between November and April, indicating a seasonal clustering of EGE.
Link with Ixodes Pacificus
- The study found that the geographical and temporal pattern of EGE cases closely mirrors the known life cycle and distribution of a tick species named Ixodes pacificus, but not other ticks that commonly infest horses.
- Building on previous work, the study strengthens the evidence suggesting that the Ixodes pacificus tick possesses the capacity to transmit the causative agent of EGE, Ehrlichia equi, to horses.
Conclusion
- Based on the correlation found between the lifecycle and distribution of this tick species and the occurrence of EGE cases, the authors concluded that Ixodes pacificus is likely the only viable carrier of the Ehrlichia equi bacteria in California.
- Consequently, there is a significant association between I. pacificus and the epidemiology of EGE, highlighting the need for specific control and prevention strategies.
Cite This Article
APA
Vredevoe LK, Richter PJ, Madigan JE, Kimsey RB.
(1999).
Association of Ixodes pacificus (Acari: ixodidae) with the spatial and temporal distribution of equine granulocytic ehrlichiosis in California.
J Med Entomol, 36(5), 551-561.
https://doi.org/10.1093/jmedent/36.5.551 Publication
Researcher Affiliations
- Biological Sciences Department, California Polytechnic State University, San Luis Obispo 93407, USA.
MeSH Terms
- Animals
- Arachnid Vectors
- California
- Ehrlichiosis / parasitology
- Ehrlichiosis / veterinary
- Granulocytes
- Horse Diseases / parasitology
- Horses
- Ixodes
Citations
This article has been cited 7 times.- Eisen L, Saunders MEM, Kramer VL, Eisen RJ. History of the geographic distribution of the western blacklegged tick, Ixodes pacificus, in the United States. Ticks Tick Borne Dis 2024 May;15(3):102325.
- Pollock NB, Gawne E, Taylor EN. Effects of temperature on feeding duration, success, and efficiency of larval western black-legged ticks (Acari: Ixodidae) on western fence lizards. Exp Appl Acarol 2015 Oct;67(2):299-307.
- Pollock NB, Vredevoe LK, Taylor EN. How do host sex and reproductive state affect host preference and feeding duration of ticks?. Parasitol Res 2012 Aug;111(2):897-907.
- Foley J, Nieto NC, Foley P, Teglas MB. Co-phylogenetic analysis of Anaplasma phagocytophilum and its vectors, Ixodes spp. ticks. Exp Appl Acarol 2008 Aug;45(3-4):155-70.
- Teglas MB, Foley J. Differences in the transmissibility of two Anaplasma phagocytophilum strains by the North American tick vector species, Ixodes pacificus and Ixodes scapularis (Acari: Ixodidae). Exp Appl Acarol 2006;38(1):47-58.
- Song C, Kulldorff M. Power evaluation of disease clustering tests. Int J Health Geogr 2003 Dec 19;2(1):9.
- Ogden NH, Casey AN, French NP, Woldehiwet Z. A review of studies on the transmission of Anaplasma phagocytophilum from sheep: implications for the force of infection in endemic cycles. Exp Appl Acarol 2002;28(1-4):195-202.
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