Environmental, Climatic, and Residential Neighborhood Determinants of Feline Tularemia

Abstract

Background: Tularemia, caused by a Gram-negative bacterium Francisella tularensis, is an occasional disease of cats in the midwestern United States and a public health concern due to its zoonotic potential. Different environmental, climatic, and pet-owner's housing and socioeconomic conditions were evaluated as potential risk factors for feline tularemia using Geographic Information Systems (GIS) in a retrospective case-control study. Methods: The study included 46 cases identified as positive for tularemia based upon positive immunohistochemistry, isolation of F. tularensis using bacterial culture, and 4-fold or greater change in serum antibody titer for F. tularensis. Cats with a history of fever, malaise, icterus, and anorexia but no lesions characteristic of tularemia and/or negative immunohistochemistry, no isolation of bacteria in bacterial culture, and less than 4-fold raise in serum antibody titer for F. tularensis were treated as controls (n = 93). Candidate geospatial variables from multiple thematic sources were analyzed for association with case status. Variables from National Land Cover Dataset, Soil Survey Geographic Database, US Census Bureau, and Daymet were extracted surrounding geocoded case-control household locations. Univariable screening of candidate variables followed by stepwise multivariable logistic modeling and odds ratios were used to identify strengths of variable associations and risk factors. Results: Living in a residence located in newly urbanized/suburban areas, residences surrounded by areas dominated by grassland vegetation, and mean vapor pressure conditions recorded during the 8 th week prior to case arrival at the hospital are significant risk factors for feline tularemia. Conclusions: Prevention strategies such as acaricide applications in residential backyards during spring and early summer periods and any behavior modifications suitable for cats that will prevent them from contracting infection from ticks or dead animals are necessary. Mean vapor pressure conditions recorded during the 8

Current and Future Distribution of the Lone Star Tick, Amblyomma americanum (L.) (Acari: Ixodidae) in North America

“…The medical significance of this tick species has been discussed amply [1, 32]: lone star ticks are the most frequently encountered ticks by humans in some parts of the US, particularly in the southern and central Midwest [33, 34]. This species is a growing public health concern since spatiotemporal dimensions of several lone star tick-transmitted diseases appear to be worsening [35–37]. Lone star ticks are well-known as a vector of human ehrlichiosis [38] and Southern Tick Associated Rash Illness [39], but recent laboratory and field investigations have confirmed that the recently discovered human pathogens Heartland Virus (HRTV) and Bourbon Virus (BRBV) are also transmitted by nymphs of this species [40–42].…”

Assessing the current and future potential geographic distribution of the American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae) in North America

“…variabilis is one of the most medically significant tick species that transmit disease-causing pathogens to humans and animals in North America [e.g., 47 , 48 ]. Spatiotemporal patterns of county-level incidences for some of the diseases transmitted by this tick species, tularemia [ 49 ], bovine anaplasmosis [ 10 ], and Rocky Mountain spotted fever (RMSF) [ 9 ] have worsened steadily over the past decade, indicating a steady increase in disease burden likely related to this tick species. Such increases in incidences could be related to several factors: better disease surveillance programs at state and local levels, expansion of non-Lyme tick-borne diseases on the Centers for Disease Control and Prevention (CDC)’s reportable diseases list, improved diagnostic methods, and increased awareness of, and interest in tick-borne diseases among physicians and patients, to name a few.…”

Maximum Entropy-Based Ecological Niche Model and Bio-Climatic Determinants of Lone Star Tick (Amblyomma americanum) Niche

“…Other diseases vectored by these ticks could also be increasing in the region. The number of cases of feline tularemia (Raghavan et al 2013) and cytauxzoonosis (Raghavan et al 2014b) in the region diagnosed at the Kansas State Veterinary Diagnostic Laboratory (KSVDL) have increased steadily over the years, at least partly owing to the wider geographic distribution of A. americanum. An important contributing factor for the current distribution of this species in the state and increases in A. americanum-vectored diseases could be the almost exponential population increase of their primary host, the whitetailed deer, in Kansas in the past two decades (Paddock andYabsley 2007, Kansas Department of Wildlife, Parks andTourism [KDWP] 2015).…”

“…Some evidence suggests that the disease agents transmitted by A. americanum ticks in Kansas may be increasing (Raghavan et al 2013(Raghavan et al , 2014. The spatio-temporal pattern of human monocytic ehrlichiosis, vectored by A. americanum, used to be concentrated in the southeastern counties in the state but is now reported commonly from most eastern and many central Kansas counties (Raghavan et al 2014).…”