Tick-borne disease in Kansas

The diseases the state keeps a chart for

KDHE's Environmental Public Health Tracking Network publishes a Kansas case series for four tick-borne diseases: anaplasmosis, ehrlichiosis, Lyme disease and spotted fever rickettsiosis^[1]. The department's investigation guideline treats three of those as one group, the tick-borne rickettsial diseases, and says where each one sits: anaplasmosis is uncommonly found in Kansas, while ehrlichiosis is widely endemic here^[3].

In June 2024 the department issued a notice naming what is present in the state. Ehrlichiosis, Rocky Mountain spotted fever and other spotted fever group rickettsioses, and tularemia are all caused by bacteria and all occur in Kansas. Two rare tick-borne viruses, Heartland virus and Bourbon virus, have been identified here in both humans and ticks. All of them are transmitted by the lone star tick, which the notice calls the most abundant tick in Kansas and places widely through at least the eastern two thirds of the state^[4].

That notice is dated and its figures are 2024 figures. As of May 29, 2024 the department had received over 200 laboratory reports of tick-borne disease that year, and it recorded investigating cases with severe outcomes including hospitalizations from Rocky Mountain spotted fever and tularemia and a fatal case of Bourbon virus^[4]. Laboratory reports and cases are not the same unit and the department does not present them as one.

How something becomes a case

Tick-borne rickettsial disease is reportable in Kansas, which means the duty runs in a specified direction on a clock. All cases are to be reported by fax or electronic laboratory report within 24 hours, or by the next business day where the period ends on a weekend or a state holiday. Health care providers and hospitals report to the local public health jurisdiction; local jurisdictions and laboratories report to KDHE's Bureau of Epidemiology and Public Health Informatics^[3].

Classification is where a report turns into a number. A confirmed case needs confirmatory laboratory evidence together with the clinical criteria: detection of nucleic acid by a molecular method, a fourfold change in IgG-specific antibody by indirect immunofluorescence assay on paired serum samples taken in the first week and again two to ten weeks later, demonstration of a specific antigen in a biopsy or autopsy specimen, or isolation of the agent in cell culture. A probable case rests on presumptive evidence, which for these diseases means an elevated IgG titre at 1:128 within 60 days of onset, or microscopic identification of morulae in leukocytes. A suspected case is laboratory evidence with too little clinical information to classify^[3].

The published counts are the confirmed and probable ones, as the charts state^[1]. Behind each of them is an investigation with its own deadlines. The investigator confirms the diagnosis with the ordering provider within three days of notification and interviews the patient within 14, recording the result in the state's EpiTrax system. The interview asks whether there was a tick bite in the 30 days before onset and in which county, whether there was exposure to wooded or brushy areas, whether the patient traveled to other Kansas counties or out of state, and what the patient does for a living^[3]. A case is then assigned to a year by the epidemiological week year the reporting jurisdiction gives it^[5].

Ten years of counts, and the year a definition moved

The four series run from 2016 to 2025 and they do not move together. Ehrlichiosis reached 76 cases in 2025 and 75 in 2024, the two highest years in the series against a ten-year mean of 54.4. Anaplasmosis, the disease the guideline calls uncommon here, reached 9. Lyme disease fell from 40 in 2016 to 10 in 2025^[1].

Spotted fever rickettsiosis is the series that will mislead anyone who reads it as a picture of disease. It runs 130, 218, 181 and 212 for 2016 to 2019 and then 22 in 2020, and it has stayed near that level since^[1]. The department's data notes for that disease give the reason without ambiguity: as a result of the changes made to the spotted fever rickettsiosis case definition in 2020, a sharp decrease in the number of confirmed and probable cases is expected from 2020 onward^[6].

What changed was the evidence a case has to meet. The CDC raised the minimum titre for reporting and eliminated some test types that had been used for surveillance, and because antibodies to the disease can stay high for months to years after an infection, the department reads the change as one that better identifies new cases. Cases stay classified under the definition in force for their own year, because earlier years are not reclassified^[6]. The two halves of that column are not comparable.

The aggregate detail across the ten years is where the two endemic diseases look different from each other. The median age at onset is 62 for ehrlichiosis and 52 for spotted fever rickettsiosis. Likely exposure was in Kansas for 84.9 percent of ehrlichiosis cases and 84.5 percent of spotted fever cases, against 61.5 percent for Lyme disease, which is the series most often acquired somewhere else. June carried 174 ehrlichiosis cases over the ten years by estimated month of onset, more than any other month^[1]. The guideline puts the national seasonal pattern at 90 to 93 percent of reported cases falling between April and September^[3].

Where the ticks are, county by county

Alongside the case series KDHE maintains a county layer for each of the three ticks that matter here, and it uses the standard two tiers of vector surveillance. Established means a population has been shown to be present. Reported means specimens have been recorded without that threshold being met. The two are not interchangeable and the department keeps them apart.

Of the 105 Kansas counties, the lone star tick is established in 45 and reported in a further 14^[2]. The American dog tick is established in 26 and reported in 42^[7]. The blacklegged tick is established in 4 and reported in 20^[8]. All three layers were last edited on May 4, 2026, and the department's dashboard states the same currency date in its own title^[9].

The distribution matches the disease pattern the guideline describes. The lone star tick carries Ehrlichia chaffeensis and Ehrlichia ewingii, and ehrlichiosis is the series that keeps rising. The blacklegged tick carries Anaplasma phagocytophilum and the one Ehrlichia species the guideline says has never been found outside Minnesota and Wisconsin^[3], and anaplasmosis has never reached ten cases in a Kansas year^[1].

What the count cannot see

Everything above describes a system that starts with a laboratory result. A person who never sought care, or who was seen without a test being ordered, or whose test was ordered too early, is not in any of these numbers. The guideline is explicit about that last one: antibodies become detectable 7 to 10 days after illness onset, so serology taken before then can be negative, and IgM results alone are unreliable for diagnosis^[3].

The 2024 notice names one condition that has no case series at all here, alpha-gal syndrome, which it calls an emerging tick-associated condition with lifelong consequences for those affected^[4]. It is not among the four diseases the tracking network charts.

What KDHE recommends people do about ticks is on the department's own pages and in its notice, and anyone with a question about their own health has a clinician and a local health department to take it to^[4]. This page reports the surveillance system: what it counts, on what rule, in which counties, and where the rule changed under the series. The three other measurements this section works through are reached the same way, through Health for Kansas.