The Fever Files: Weed Whacked

The Case

The sun setting on the horizon sets the Great Lake aglow as you enjoy a promenade drive at the start of your night shift. The cool evening breeze brings relief to a scorching day, and the long days mean both your drive to and from the graveyard shift is in full daylight.

A loud ping reverberates through the cab of your rig as your map lights up with a new call. You click to acknowledge and are relieved to find out you don’t need to make a U-turn as you navigate the street full of people along the lakefront. You eventually turn left, heading toward the blue dot on your screen. The call details are sparse; a 41-year-old woman has a fever and rash, and you roll your eyes wondering what could have compelled her to dial 9-1-1.

You arrive at a detached residence and ring the doorbell. A woman in a housecoat answers and welcomes you in, sitting on a sofa in the living room. Your partner obtains a set of vitals while she describes her illness.

“It began today. I woke up feeling horrible. All my joints are sore, and my muscles ache. My neck is sore and my head is pounding.”

Your Spidey senses are on alert, and you worry about meningitis. But she has no photophobia, and he neck moves quite well and doesn’t trigger worse pain; it’s just achy, like the rest of her. You search her body for petechial rashes, finding none, but you do find this rash on her back when you slip the housecoat down to auscultate her lungs, which were clear. Her abdominal exam is normal. Her extremities are not swollen, and her joints have a normal range of motion without redness but are sore when moved.

Your partner barks off the vitals: HR 98, regular; RR 24 unlaboured; Sat 99% RA; BP 136/70; Temp 38.6C / 101.5F.

You summarize the situation: A 41-year-old woman without medical history whose vitals are normal-ish, new fever that isn’t terribly high, and a benign exam except for a target-like rash. Her complaints are not very specific; this could be something benign, like the flu, or something serious, like meningococcemia.

Pop Quiz: What’s your differential diagnosis?

Road Test: Although meningitis is typically diagnosed with lumbar puncture, it does have classic signs. Can you list 3 exam findings that might indicate a diagnosis of bacterial meningitis?

You recall that not all fevers are related to infections, but she has no history of arthritis, lupus, or other autoimmune diseases. She has no medical history at all.

It's clear that we're missing some key information. So, you delve deeper into your fever history. Recall the list here: (Link to fever files intro post)

She has no exposure risks – no one she knows has been sick, she hasn’t eaten anything unusual, and she hasn’t been around any animals other than her two dogs. She has no social risk factors such as unprotected sex or illicit drug use. She is fully vaccinated. She has not traveled outside of her state in years.

You look at her two dogs, beautiful golden retrievers. Can dogs cause a fever, you wonder?

Diagnostic Detour: Domestic dogs are of relatively low concern in the fever workup (unlike cats!). Dogs can harbor a slow-growing organism in their mouths called Capnocytophaga canimorsus, usually transmitted by a bite. Other “bite” infectious organisms, like Pasturella and Salmonella, are less common from dog bites, but far more serious infections. (Compare this to cats, which… wait, let’s save cat infections for another case of the Fever Files.)

She catches you lost in your thoughts. “They’re beautiful, aren’t they,” she says. “I don’t really want to to the hospital, my boys will be miserable if they don’t get their long walk. But maybe it’s for the best.”

Something catches your ear. “Why would that be for the best?” you ask, while your partner gently reaches for the paperwork to sign off a patient and leave them on the scene.

“Oh, the ticks are so bad this time of year. I spend more time pulling ticks off my dogs than I do walking them through the ravine!”

Tick-Borne Diseases

While Lyme disease is the most famous of the tick-borne infections, babesiosis, ehrlichiosis, Rocky Mountain Spotted Fever (rickettsiosis), anaplasmosis, and other tick diseases are not uncommon. Most present similarly; fever, malaise, and sore muscles and joints (myalgias and arthralgias). Rashes are variable and sometimes help in the differential diagnosis; for example, Lyme disease has a typical “target lesion” that looks like a bullseye, called erythema migrans, as demonstrated in the picture for this case.

These rashes all have variable presentations, and appear differently on different skin colors; it’s easy to be tricked, so relying on the presence or absence of a rash when considering tick-borne infections should be reserved for experts. But look out for them! Rashes can be anywhere – not just at the site of the bite.

While you’re at it, look for ticks! Hairlines, behind the ears, and wherever clothes might not have provided protection – like where socks or shorts end – are other spots to look at. As my favorite dermatologist says, “The skin is one organ, and you must inspect the entirety of it!”. Tick removal must be done carefully so that the entire tick is extracted.

Lyme disease is caused by the organism Borrelia bergdorferi, a member of a unique family of bacteria called spirochetes. They are spiral-shaped. Syphilis is also a spirochete. Spirochetes are usually diagnosed with blood tests that detect antibodies. Treatment consists of antibiotics. Dog ticks do not carry Borrelia bergdorferi but deer ticks do. Entomologists can identify these, but lay people should not try to; various ages and feeding stages of the bug can make identification difficult.

Some tick-borne diseases require very specialized medications, so identifying the actual organism is important; disease prevalence maps and tick testing can help establish risk factors based on geography. Many – including Lyme – can cause meningitis, though differentiating tick-borne disease meningitis from the myalgias and headaches of systemic Lyme infection is difficult.

Back to the Case

It all makes sense now. Although this patient hasn’t traveled out of state, she does have the risk for tick exposure and the classic marking of Lyme Disease. She agrees to come to the emergency department, where a physician agrees that this is not meningitis.

“That rash is a dead giveaway. Serology can be negative this early on, so we can skip it. Let’s treat for Lyme disease with 3 weeks of oral doxycycline” she says.

A good physical exam and history solved this case of the Fever Files! Well done.

Blair Bigham worked for a decade as a flight paramedic on four continents, a job he misses every day. He is now an ER and ICU physician at the University of Toronto and a public health researcher at the Dalla Lana School of Public Health. @BlairBigham blairbigham.com