Tularemia Rises in Minnesota: Five Human and 27 Animal Cases in 2024

Summary

• Already known: tularemia is an uncommon but potentially serious bacterial disease spread from animals, usually by arthropod bites or contact with infected animals, and most often reported in the central U.S. From 2000 to 2023, Minnesota saw a median of one human and two animal cases a year.
• This report: in 2024, Minnesota reported five human and 27 animal cases. Every patient was hospitalized; none died. No definite source was found.
• Implication: consider tularemia in feverish patients and in animals with compatible signs; animal cases can guide warnings to pet owners and others at risk.

The disease

Caused by Francisella tularensis, a Tier 1 select agent, tularemia affects 200–300 people a year in the U.S. Symptoms depend on how it's caught — commonly fever with local signs such as swollen lymph nodes and skin ulcers. People and animals are infected by bites of ticks and deer flies, contact with infected animals, or inhaling contaminated material. There is no FDA-approved vaccine.

In 2023, animal cases jumped to 20 (no human cases). In 2024, all cases were in the seven-county Minneapolis–St. Paul area.

Human cases

In three cases, tularemia wasn't identified until after discharge. Two lab workers who handled cultures outside a biosafety cabinet monitored themselves for 14 days; neither got sick.

Animal cases

• 27 animals: 21 (78%) cats, 5 (19%) dogs, 1 wild rabbit.
• Forms: mostly typhoidal (widespread infection) and oropharyngeal (fever, mouth ulcers, swollen lymph nodes).
• Outcomes: 78% of pets survived; 4 died and 2 were euthanized.
• People exposed: three owners and one veterinary staff member; one owner scratched by an infected cat took preventive antibiotics. No owner got sick.

Looking for the source

Investigators interviewed patients and owners and checked sites. Tick sampling at the likely exposure sites of three people and two animals found no ticks. Two patients with pneumonic disease had mowed over animal carcasses; a rabbit and a mouse carcass were found but were too decomposed to test.

What changed, and what to do

• Why more cases: a real increase, plus more testing and reporting by veterinarians after 2023 alerts. On June 20, the Minnesota Department of Health warned the public; vets and doctors got alerts too.
• Doctors: consider tularemia in feverish patients with tick or deer fly bites, contact with sick animals, or mowing over a rabbit or rodent — even where it's uncommon. Warn the lab so staff use a biosafety cabinet, gloves, gowns and eye protection.
• Veterinarians: consider it in cats and dogs with high fever, mouth ulcers and swollen lymph nodes; dogs are less often acutely ill but can get severe infections.
• Exposed people: anyone bitten, scratched, exposed to aerosols or to an infected animal's body fluids should get prompt post-exposure prophylaxis (usually doxycycline or ciprofloxacin).

Sources

Based on "Notes from the Field: Increase in Human and Animal Tularemia Cases — Minnesota, 2024," by Maria Bye, Jordan Mandli, Aaron Barnes, Elizabeth Schiffman, Kirk Smith and Stacy Holzbauer, of the Minnesota Department of Health and CDC, Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; a work of the United States government in the public domain. More: CDC on reducing tularemia risk.