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CDC Surveillance Data Show Increase In US Tularemia Incidence

Although case numbers remain low, average annual US incidence of a rare bacterial zoonotic disease rose by more than half from 2011 to 2022, according to new surveillance data from the Centers for Disease Control and Prevention (CDC).

In a report published yesterday in Morbidity and Mortality Weekly Report, CDC investigators said 2,462 tularemia cases were reported over the period, with the annual average incidence of 0.064 per 100,000 population representing a 56% increase compared with the previous surveillance period (2001 to 2010). Incidence was highest among children ages 5 to 9 years old, older men, and American Indian or Alaska Natives (AI/AN). 

Tularemia cases were reported by health departments in 47 states overall, but investigators with the CDC's National Center for Emerging and Zoonotic Infectious Diseases say half of all reported cases came from four states—Arkansas (18%), Kansas (11%), Missouri (11%), and Oklahoma (10%). Roughly 205 cases were reported per year, ranging from 149 in 2012 to 314 in 2015. Most patients (78%) were reported to have symptom onset during the months of May through September.

Many potential exposures

Tularemia, also known as "rabbit fever," is a highly infectious disease caused by the bacterium Francisella tularensis, which the CDC has designated a Tier 1 Select Agent—the highest risk category—based on its potential for use as a bioweapon. Humans can become infected through tick or deer fly bites, improper handling of infected animals (such as rabbits, muskrats, prairie dogs, and other rodents), inhaling contaminated dust or aerosols, and drinking contaminated water.

The symptoms of tularemia vary based on how the pathogen enters the body. They can include skin ulcers, mouth ulcers, sore throat, and pneumonia, and are always accompanied by fever. While the infection is treatable with antibiotics and the case fatality rate is under 2%, it can be as high as 24%. 

The demographic characteristics and regional distribution of US tularemia patients from 2011 to 2022 were similar to those described in the previous surveillance period. The median age of case patients was 48 years, and 63% were men. White persons accounted for most tularemia cases (84%), followed by AI/AN (9%), Hispanic or Latino (5%), Black or African American (2%), and Asian or Pacific Islander (1%) persons. 

Increased reporting of probable cases might be associated with an actual increase in human infection, improved tularemia detection, or both.

Incidence among AI/AN persons (0.260 per 100,000) was approximately five times higher than among Whites.

"Many factors might contribute to the higher risk for tularemia in this population, including the concentration of Native American reservations in central states and sociocultural or occupational activities that might increase contact with infected wildlife or arthropods," the authors wrote.

Improved detection

The investigators also note that the proportion of tularemia cases identified as probable from 2011 to 2022 (60%) represents a 71% increase from 2001 to 2010. While this could be related to a 2017 change in surveillance criteria that included detection of F tularensis by polymerase chain reaction in the probable case definition, they say updated surveillance criteria doesn't fully explain the rise in tularemia incidence.

"Increased reporting of probable cases might be associated with an actual increase in human infection, improved tularemia detection, or both," they wrote.

The CDC says reducing tularemia incidence will require tailored prevention strategies that lay out the variety of potential F tularensis exposures in the environment. They also call for increased healthcare provider education on the diverse clinical manifestations of the disease and the importance of early and appropriate antibiotic treatment.

CDC: Rabbit Fever Up 56% In The United States Since 2011

Rabbit fever cases in the United States have risen since 2011 with nearly half of all cases reported in Arkansas, Oklahoma, Missouri, and Kansas.

ARKANSAS, USA — Tularemia, also known as rabbit fever, has risen by 56% in the U.S. Since 2011 with close to half of all cases in Arkansas, Oklahoma, Missouri, and Kansas.

Dr. Laura Rothfeldt, the state public health veterinarian at the Arkansas Department of Health, explained how the disease spreads and how it got the name rabbit fever. 

"It's a bacterial disease that can be transmitted from animals or tick bites. They can also get this bacterial disease from touching a contaminated or infected animal, such as certain rabbits that may be infected with it," Rothfeldt said.

Rabbit fever can cause multiple symptoms, and there are a few ways to know if you or a loved one has it.

"One is kind of more of the generic summer flu-like illness where people just feel yucky, get a fever, they have malaise, muscle aches, things like that," Rothfeldt said. "The other is they can get swollen glands that can even get to softball size big."

It's not just humans who contract rabbit fever — your pets can as well.

"They become ill where they stop eating, they don't want to do anything usually," Rothfeldt said. "That may be a symptom that the animals got a fever, or if they've got a great big swelling that starts to grow on them."

Whether it's you or your pet who has rabbit fever, Rothfeldt advises you to seek medical attention immediately.

"It is one of those conditions that you want to start treating sooner rather than later," she said. 

There are ways to prevent catching the illness, according to Rothfeldt. 

"You'll want to use EPA-registered repellents on your body and your clothing,' she said. "If you see a lot of rabbits dying off or you find a dead rabbit and you want to move it or do something with it, use precautions, use gloves and a mask and even goggles."

The CDC report shows Native American populations had a higher number of cases than other demographics, but the disease was most reported in children ages 5 to 9.

Outdoor Action Guide To Giardia, Lyme Disease And Other 'post Trip' Illnesses

Tuesday December 31, 2024  

by Rick Curtis

We hope that you had an exciting and enjoyable time in the wilderness on your Outdoor Action Trip. After you've gotten a shower and washed your clothes, there are a few important pieces of information you need to be aware of. All outdoor travelers may come in contact with things during the trip that can lead to illnesses later on. Typically, the signs and symptoms of these illnesses don't become apparent until after your trip is over, so it is important that you be able to recognize them. Should you experience some of the symptoms noted below after an Outdoor Action Trip, go to the University Health Center and describe your symptoms to a practitioner or see your own physician. Be sure to inform the health practitioner about your backcountry trip since they may not initially identify the proper cause of the illness without knowing about your wilderness trip. Most of these illnesses can be treated effectively using antibiotics, as long as you go for treatment promptly. For more information on any of these, see the Centers for Disease Control Web site (www.Cdc.Gov).

Water-borne Infections

Giardia: Giardiasis refers to a syndrome of diarrhea, excess gas, and abdominal cramping. It is caused by Giardia lamblia, a water-borne parasite that is worldwide in distribution. The symptoms usually occur one to two weeks after exposure to the parasite. Symptoms initially include diarrhea, bloating, nausea, abdominal cramping, and malaise. Weight loss is also a frequent finding. Backcountry travelers usually contract giardiasis by drinking water from untreated or improperly treated sources. Chemical treatment of the water and commercial water filtration systems, used properly, eradicate the parasite. The diagnosis of giardiasis can be confirmed by inspecting a stool sample for the presence of the parasite. Because this test may not always identify the organism even if it is present, a physician may elect to treat you empirically for the infection. The use of an appropriate antibiotic for seven days is usually highly effective in relieving symptoms and curing the disease.

Cryptosporidium: Cryptosporidium is a protozoan that causes a diarrheal illness similar to Giardia. Symptoms include watery diarrhea, headache, abdominal cramps, nausea, vomiting, and low-grade fever that may appear 2 to 10 days after infection. Some infected people will be asymptomatic. Currently, there is no effective treatment for Cryptosporidium. Symptoms usually last 1 to 2 weeks, at which time the body's immune system is able to stop the infection. People with normal immune systems are generally not at risk and improve without taking antibiotics or antiparasitic medications. For people with compromised immune systems this can be a dangerous disease. Please see your physician.

Cyclospora: Cyclospora is a recently discovered cause of diarrhea. It can cause a prolonged illness (average 6 weeks) with profound fatigue, loss of appetite, and intermittent diarrhea. Cyclospora can be treated with antibiotics. If you develop these symptoms, consult your physician.

Tick-borne Diseases

Lyme Disease: Lyme disease is an infection caused by a spiral shaped bacterium called a spirochete. This bacterium is carried in the gut of the deer tick Ixodes dammini. The tick becomes infected after feeding on the blood of an infected animal. Once infected, the tick can transmit the disease to its next host. Deer ticks are extremely small, with tick nymphs being about the size of the period at the end of this sentence. This means that you may have been bitten without realizing it. The tick needs to feed for an extended period of time (8-12 hours) before infection can occur. So just because you have found a tick does not mean that you have been infected. It is also possible that the tick was not carrying the disease.

Detecting Lyme Disease can be difficult to identify in the early stages as the early symptoms—fever, headache, stiffness, lethargy, and a myriad of other mild complaints, are often dismissed as the flu. In some cases (25%), there is a red, ring-like rash that occurs at the site of the bite. The rash is often referred to as a "bull's eye" rash because it has a white center surrounded by a red ring. Most typically, the rash expands and then fades within a few weeks after the bite. There is a blood test for Lyme Disease, but it is not perfect. The test generally produces positive results in the later stages of the disease but often turns up false negative results in the early stages of infection. Therefore, diagnosis in the early phase is frequently based on symptoms and the likelihood of a deer tick bite. Early detection means early treatment when the disease is most effectively controlled with antibiotics. Lyme disease can result in more serious symptoms if left untreated.

Rocky Mountain Spotted Fever: This disease is carried by a bacterium and can be transmitted by the bites of dog or wood ticks. Contrary to what the name of the disease suggests, it can be found throughout the U.S. Watch for mild chills, appetite loss, and a general run-down feeling. These symptoms may worsen to sever chills, fever, headaches, muscle and bone pain, and sensitivity to light. Also, a spotty red rash may appear (hence the name) usually starting at the wrists and ankles and spreading over the rest of the body. Normal onset of these symptoms is anywhere between 3 and 14 days, so anyone bitten by a tick should be aware of the disease, as it may not present itself until the trip is over. Untreated, the mortality rate is 20 to 30%. Anyone who shows these signs should seek medical attention as soon as possible.

Ehrlichiosis: Ehrlichiosis is a recently recognized tick-borne disease caused by a bacterium. The disease is similar to Rocky Mountain spotted fever and can be life threatening. The most common symptoms are sudden high fever, tiredness, major muscle aches, severe headache, and, in some cases, a rash (similar to the symptoms of Lyme Disease). Symptoms usually appear 3 to 16 days after a tick bite. The same ticks that carry Lyme Disease can also transmit Ehrlichiosis at the same time. Without treatment Ehrlichiosis can be fatal. Ehrlichiosis can be treated with the same antibiotic used to treat Lyme Disease. Anyone who shows these signs should seek medical attention as soon as possible.

Tick Paralysis: A number of species of ticks can transmit tick paralysis. It is not an infection, but a by-product of venom in the tick's saliva that is secreted while the tick is attached. Symptoms are unsteady movement and gait (ataxia) and ascending paralysis starting in the lower extremities and moving up. Paralysis can cause loss of respiratory drive, requiring CPR and immediate evacuation. Once the tick is removed, the source of the venom is gone and the patient generally recovers completely. Children are more likely to be affected than adults. Any patient with an ascending paralysis should be carefully checked for an attached tick.

Tularemia: Tularemia, or rabbit fever, is a bacterial disease of which the most common carriers are rabbits, although it can also be transmitted by ticks. The disease presents with flu-like symptoms and can be treated with antibiotics.

Mosquito-borne Diseases

West Nile Virus: West Nile virus (WNV) is a potentially serious illness that is transmitted by the bite of some mosquitoes. WNV affects the central nervous system. Symptoms vary.

No Symptoms in Most People. Approximately 80 percent of people who are infected with WNV will not show any symptoms at all.

Mild Symptoms in Some People. Up to 20 percent of the people who become infected will display mild symptoms, including fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms typically last a few days.

Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

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