Rocky Mountain Spotted Fever During Pregnancy

Rocky Mountain spotted fever (RMSF) is the name of an infection due to the Rickettsia rickettsi, a type of bacteria that is carried by ticks, which spread the infection by biting people and other animals. There are many types of tick-borne illnesses, which together afflict approximately 25,000 people in the United States alone. RMSF has been spreading to an increasing number of people in North America since the beginning of the 21st century. During 2014, 11 cases per 1 million people in the US were reported, the highest number of cases occurring in the central east region of the US.  Summer is when the highest number of cases occur, because this is when ticks are most active, but the illness can develop at any time of the year. Incidence of RMSF among pregnant women in particular has not been reported, but pregnant women are often exposed to ticks if they spend time outside. In recent times, four cases of RMSF were reported in pregnant women in the Sonora region of Mexico.

RMSF is fairly challenging to diagnose. Symptoms of the disease include fever, rash, nausea, vomiting, headache, muscle pain, abdominal pain, and loss of appetite. These symptoms develop in numerous diseases, which makes it difficult to see that the patient has RMSF. However, the symptoms, plus a history of being outside in places where infected ticks may be active can point doctors toward a RMSF diagnosis, especially if tests for more common infectious conditions come out negative. Another big clue is the presence of tick bit on the woman’s body. Now, the rash, consisting of red splotches appearing like pinpoint dots typically develops a few days after infection from the tick. This can be enough of a clue for the need for specialized tests carried out on samples of your blood, which can determine if you have been infected with Rickettsia species, particularly R. rickettsia. These tests include polymerase chain reaction (PCR) and antibody tests for the presence of proteins of Rickettsia. Such blood tests may not come out negative within the first week or so after infection, and this can make diagnosis of RMSF more difficult.

As noted earlier, symptoms of RMSF include rash, fever, and headache. These symptoms will develop whether you are pregnant of not, but pregnant patients can dehydrate more easily than non-pregnant patients. If not treated with the appropriate antibiotic therapy early, RMSF can kill. Any fever during pregnancy, including fever from RMSF, may possibly increase a baby’s risk of having congenital defects involving the heart and other organs. Additionally, there have been reports of women with RMSF suffering spontaneous abortion (miscarriage) during the first trimester. Another factor is that  symptoms of RNSF may be confused with those of a serious pregnancy complication called preeclampsia.

The main treatment for RMSF is the antibiotic doxycycline, which is generally thought to be fairly safe in pregnancy, although more studies are needed to be certain if this is the case. The same antibiotic also can be given for prevention of RMSF and some other tick-borne diseases in the event of a tick bite.

For treating the fever itself, there are three main categories of antipyretic (fever-fighting) drugs. One group consists of acetaminophen in the United States and paracetamol in several other countries. Another group is called non-steroidal anti-inflammatory drugs (NSAIDs), which include ibuprofen, naproxen, and many others. Along with being antipyretic, NSAIDs also reduce inflammation. The third group, called salicylates, includes aspirin, which technically is also a kind of NSAID, because it reduces inflammation. There is concern that NSAIDs and salicylates may be harmful to the embryo or fetus, but acetaminophen and paracetamol are thought to be safe. Acetaminophen, paracetamol, NSAIDs, and doxycycline are thought to be relatively safe in mothers who breastfeed.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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