The Delaware Division of Public Health (DPH) is sending this health alert to inform Delaware clinicians of a significant and early-season increase in emergency department (ED) visits related to tick bites across the state.

Summary

· Tick bite-related emergency department (ED) visits have increased substantially compared to previous years in the same time period in Delaware.

· Clinicians should have a heightened clinical suspicion for tick-borne diseases in persons with clinically compatible symptoms.

· Cases of Lyme disease and other tick-borne diseases such as ehrlichiosis, anaplasmosis, babesiosis, spotted fever group rickettsiosis, and alpha-gal syndrome should be reported to Delaware Public Health within 48 hours.

· For questions, call the DPH Office of Infectious Disease at 1-888-295-5156.

Background

Syndromic surveillance data from DPH indicate that tick bite-related ED visits have increased substantially in 2025 compared to previous years for the same time period. This uptick may suggest heightened human-tick interactions and the potential for increased transmission of tick-borne diseases including Lyme disease, anaplasmosis, ehrlichiosis, babesiosis, spotted fever group rickettsiosis, alpha-gal syndrome, and others. Although tick-borne diseases can occur any time of the year, clinicians should have heightened clinical suspicion for tick-borne diseases from April to August.

Epidemiology of Tick-borne Diseases in Delaware

In Delaware, Lyme disease is the most commonly reported tick-borne disease. In 2024, there were 344 cases of Lyme disease reported in Delaware, representing an incidence of 32.7 cases per 100,000 persons. Lyme disease cases were reported in all Delaware counties. Ehrlichiosis, a disease caused by bacteria of the genus Ehrlichia and spread by lone star ticks, is another common tick-borne disease reported in Delaware. In 2024, there were 26 cases of ehrlichiosis reported in Delaware, representing an incidence of 2.5 cases per 100,000 persons. Delaware consistently ranks as one of the states with the highest reported incidence rate of ehrlichiosis.

Several other non-Lyme tick-borne diseases are also reported annually in Delaware including anaplasmosis, babesiosis, and spotted fever group rickettsiosis. Additionally, alpha-gal syndrome (also known as the tick bite mammalian meat allergy) became newly reportable in Delaware in 2024. This condition is associated with the bite of the lone star tick and is a serious and potentially life-threatening allergic condition, with symptoms and severity varying among persons. Symptoms generally appear three to eight hours after eating foods or exposures to other products containing alpha-gal (for example, mammalian meat and dairy products). In 2024, there were 119 cases of alpha-gal syndrome reported in Delaware within each of the three counties.

Lyme Disease Post-Exposure Prophylaxis (PEP)

In Delaware, where Lyme disease is endemic, a single dose of doxycycline may be warranted following an Ixodes scapularis (blacklegged/deer tick) tick bite to aid in the prevention of Lyme disease.1 The decision-making tool found online at https://publichealthalerts.delaware.gov/wp-content/blogs.dir/203/files/sites/203/2025/06/DecisionMaking.png can assist with determining whether Lyme PEP is beneficial.

Although PEP can be used to prevent Lyme disease, it is not 100% effective. If the patient develops signs or symptoms consistent with Lyme disease after PEP, treat accordingly.

PEP has not been shown to be beneficial for the prevention of anaplasmosis, ehrlichiosis or Rocky Mountain spotted fever and may only delay onset in these cases.

Diagnosis of Tick-borne Diseases

For patients with suspected tick-borne diseases, laboratory tests usually include serological testing (detecting antibodies) and, in some cases, molecular tests like PCR to identify the pathogen directly. The specific tests depend on the suspected disease and the duration of symptoms.

For Lyme disease, CDC currently recommends a two-step testing process for Lyme disease serologic testing. Both steps are required and can be done using the same blood sample. If this first step is negative, no further testing is recommended. If the first step is positive or indeterminate (sometimes called “equivocal”), the second step should be performed.

· Note: Antibodies may take several weeks to develop following infection; patients may test negative if recently infected. Also, patients who receive antibiotic treatment early in disease may be less likely to seroconvert.

The CDC produced a reference manual for health care providers that provides comprehensive information on tick identification, disease distribution, clinical signs and symptoms, laboratory testing, and treatment for the tickborne diseases that are endemic to North America. This manual is freely available at the following webpage: https://www.cdc.gov/ticks/hcp/data-research/tickborne-disease-reference-guide/index.html.

Certain species of ticks transmit specific diseases, making accurate identification critical for appropriate diagnosis and treatment. For example, the blacklegged tick (or deer tick) can transmit the pathogens that cause Lyme disease, anaplasmosis, and babesiosis, while the lone star tick is associated with Ehrlichiosis and alpha-gal syndrome. The American dog tick can spread Rocky Mountain spotted fever. Because the risk of disease depends on the tick species and region, recognizing the tick that bit a person can guide testing and treatment decisions.

For health care providers and the public in Delaware, it’s especially important to use resources like the DNREC Tick Identification Page, which offers detailed information and images of ticks found in the state. This tool can help identify the species involved and assess potential health risks.

Clinical Guidance on Tick Bite Prevention and Tick Removal

Tick bite prevention remains the most effective strategy to reduce the incidence of Lyme disease and other tick-borne diseases. Counsel patients on behavioral and environmental modifications that can lower exposure risk:

· Protective clothing: Recommend patients wear long-sleeved shirts, long pants tucked into socks, and light-colored clothing to aid in tick detection when in wooded, brushy, or grassy areas.

· Avoidance of tick habitats: Encourage patients to avoid high-risk environments such as tall grass, leaf litter, and densely wooded areas. Emphasize staying on the center of well-maintained trails when hiking or walking outdoors.

· Use of EPA-registered repellents: Advise use of insect repellents containing ≥20% DEET, picaridin, or oil of lemon eucalyptus on skin and clothing for effective tick deterrence.

· Environmental modification: Discuss tick control in peridomestic environments—e.g., maintaining short grass, removing leaf litter, and installing gravel or wood chip barriers between lawns and forested zones.

· Tick checks: Instruct patients to perform thorough tick checks, particularly in areas such as the armpits, groins, scalp, and behind the knees. Additionally, showering within two hours of coming indoors and placing worn clothing in a dryer on high heat for 10 minutes can reduce the risk of tick attachment and disease transmission.

· Tick removal: If a tick is found, removal should be prompt and performed with fine-tipped forceps. Grasp the tick as close to the skin surface as possible and apply steady, even pressure upward, without twisting. Advise against folk remedies such as burning or suffocation. After removal, cleanse the area with an antiseptic, alcohol, or soap and water. Consider saving the tick in a sealed container for potential species identification and to determine the risk of disease transmission.

Reporting

DPH receives most positive laboratory results for tick-borne diseases automatically from testing facilities. Should you need to manually report a suspected tick-borne disease case, you can complete the case report form here and email it to reportdisease@delaware.gov or fax it to 302-622-4149. We encourage physicians to complete and add all relevant signs and symptoms and exposures in the remarks section to assist the DPH with their investigations. Asking about travel history and mosquito exposure is essential during case investigations.

For additional information, see:

DPH Tick Page: https://dhss.delaware.gov/newsroom/tag/ticks/

CDC Ticks and Tickborne Disease: https://www.cdc.gov/ticks/about/index.html

CDC Lyme Disease Clinical Resources: https://www.cdc.gov/lyme/hcp/communication-resources/index.html#cdc_listing_res2-lyme-disease-prophylaxis-after-tick-bite

Delaware Division of Natural Resources and Environmental Control’s Tick Program: https://dnrec.delaware.gov/fish-wildlife/ticks/

References

1.  Nadelman R.B., et al. Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite. N Engl J Med. 2001 Jul 12;345(2):79-84.