Introduction

Lyme disease, Rocky Mountain spotted fever, anaplasmosis and babesiosis – these are some of the most common and well-known tick-borne diseases. Ticks are a family of blood sucking arachnids that feed from warm-blooded vertebrates such as humans, cows, dogs, birds, etc. Ticks themselves do not cause disease, but they act as vectors (carriers), transmitting infections once they become infected by viruses or bacteria. These pathogens can then be passed on through a tick bite, leading to various tick-borne diseases.

These diseases are significant health concerns because as can cause severe complications and could even be life-threatening if they are not diagnosed and treated promptly.

Accurate diagnosis is important to ensure appropriate treatment, which is crucial for ensuring the best patient outcomes. If tick-borne diseases are misdiagnosed or if treatment is delayed, this could lead to severe complications, including prolonged illness or even long-term health issues. Thus, it is important to understand the characteristics and symptoms of each disease in order to help individuals seek appropriate care and for healthcare providers to make informed decisions to ensure accurate and timely treatment. 

This article will discuss the differences in symptoms and treatments between Lyme disease and some of the other most common tick-borne diseases, guiding you on how to spot and identify infection, alongside measures that can be taken to reduce the risk of developing these diseases. 

Lyme disease

Causative agent

Lyme disease is caused by the bacterium Borrelia burgdorferi. In the Northern Hemisphere, it is the most common tick-borne disease and is transmitted mostly by the Ixodes ricinus tick, otherwise known as the sheep tick, deer tick, or castor bean tick, in the UK. 

Symptoms

Early symptoms

Within 3 to 30 days following an infected tick bite, early symptoms of Lyme disease will typically manifest, appearing as a bull's eye rash, called erythema migrans. This rash often presents as a round, red area surrounded by a ring-shaped rash around the tick bite.¹

However, not all rashes appear as the typical bull's-eye shape. You should also look out for rashes that are uniformly red, round and expanding. It is essential to be aware of the differing presentations of rashes in Lyme disease to avoid overlooking a potential early sign of infection.. 

Additionally, not all people who are infected with Lyme disease through a tick bite will develop a rash, and in some cases, the rash may be difficult to detect, especially in hard-to-see areas or on darker skin tones.

Without the rash, early-stage Lyme disease can be difficult to diagnose as symptoms resemble flu-like illnesses and are not specific to Lyme disease. A common cause of misdiagnosis in the early stages of disease is the failure to recognise the rash or its complete absence. If the distinctive bullseye ring is not visible, there is a risk of mistaking it for  a non-specific insect bite or spider bite, delaying proper treatment 

As shown in the image below, a Lyme rash could present in various forms.

In the first two to three weeks of Lyme disease, blood tests may return false negative results as the body has not had sufficient time to make enough antibodies against the bacteria. This delay in antibody production makes it crucial to recognise the Lyme rash as the primary early diagnostic indicator. 

If you develop a rash or have recently had a tick bite, consult a healthcare professional, especially if you experience:

• Fever
• Chills, or feeling hot and shivery
• Headache
• Muscle and joint pain
• Fatigue and loss of energy

Late symptoms

If Lyme disease remains untreated for weeks or months, it can lead to more severe symptoms affecting multiple body systems. Some symptoms include:

• Severe headaches 
• Neck stiffness (due to meningitis)
• Arthritis, joint pain and swelling, particularly in the knees
• Heart palpitations and irregular heartbeat (Lyme carditis)
• Numbness, tingling, and shooting pains
• Problems with short-term memory
• Facial palsy (drooping on one or both sides of the face)

Diagnosis

Diagnosis is often based on clinical evaluation, particularly the presence of the characteristic bull's-eye rash, history of tick exposure, and associated symptoms.

Laboratory testing to confirm Lyme disease requires blood testing to look for the presence of antibodies against Borrelia burgdorferi. However, since antibodies take time to develop, testing may not be reliable in the early stages of infection. Therefore, early diagnosis often relies on clinical signs rather than lab tests alone.

Treatment

Antibiotics

The standard treatment for Lyme disease is antibiotics. Depending on the stage of disease, the chosen antibiotic and duration of treatment will differ. Early-stage disease is usually treated for around 10-21 days, but more severe or late-stage disease requires longer courses of antibiotics, which may need to be administered intravenously. Amoxicillin, cefuroxime or doxycycline are the most common choices of antibiotics.

Rocky mountain spotted fever

Causative agent

Rocky Mountain spotted fever (RMSF) is caused by the bacteria Rickettsia rickettsii. It is transmitted through the bites of several species of ticks:

• Dermacentor variabilis – the American dog tick
• Dermacentor andersoni – the Rocky Mountain wood tick
• Rhipicephalus sanguineus – the brown dog tick

Geographical location plays a role in the prevalence of RMSF as it is mainly reported in the United States, predominantly in the states of North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma.

Symptoms

Two to five days following the onset of a fever, a distinctive rash will typically be observed. It usually begins as small, flat, pink and non-itchy spots on the wrists, forearms and ankles, which may spread to the trunk. In some cases, the rash may appear as red or purple spots caused by bleeding.²

Other symptoms to look out for include:

• High fever
• Severe headache
• Muscle pain
• Nausea
• Vomiting 
• Abdominal pain

In severe cases, RMSF can also cause:

• Encephalitis
• Pulmonary oedema
• Kidney failure

The symptoms of RMSF usually progress rapidly; hence, prompt diagnosis and treatment is vital as the disease can be fatal within a few days.

Diagnosis

The diagnosis of RMSF often relies on clinical evaluation of symptoms, such as the characteristic rash and a history of exposure to ticks or any known instances of tick bites. 

Diagnosis can be confirmed in the laboratory through blood tests to detect antibodies against the Rickettsia rickettsii bacteria.

Treatment

The antibiotic doxycycline is the most commonly used first line of treatment for RMSF. The course of doxycycline is typically 7-14 days for both children and adults. Prompt treatment is crucial, as RMSF progresses rapidly and can become life-threatening if left untreated. Doxycycline should be started as soon as RMSF is suspected, even before laboratory confirmation, to prevent severe complications and fatal outcomes.

Summary

This article compares Lyme disease and Rocky Mountain spotted fever (RMSF), two of the most common tick-borne illnesses, focusing on their symptoms, diagnosis, and treatment.

• Lyme disease, caused by Borrelia burgdorferi, is transmitted primarily by Ixodes ticks. Early symptoms include a bull’s-eye rash (erythema migrans), fever, fatigue, and muscle aches, though not all patients develop a rash. Delayed diagnosis can lead to serious complications such as arthritis, facial palsy, and heart issues. Diagnosis is based on symptoms and history of tick exposure; blood tests may not be reliable in the early stages. Treatment involves antibiotics like doxycycline, amoxicillin, or cefuroxime, with duration depending on disease severity
• RMSF, caused by Rickettsia rickettsii, is mainly found in the U.S. and spread by ticks like the American dog tick. It begins with high fever, headache, and rash that can turn red or purple. RMSF progresses rapidly and can be fatal if untreated. Diagnosis is clinical and confirmed with blood tests. Immediate treatment with doxycycline is critical, even before lab results, to prevent severe outcomes

Understanding these differences helps ensure early recognition, proper diagnosis, and timely treatment, reducing the risk of complications.