The initial RMSF presentation is characterized by the classical triad of fever, headache and rash, which begins to appear after 3 to 4 days from pathogen exposure. A history of tick bite is present only in two thirds of the cases, because the bite itself is painless and subjects do not even remember being bitten. The incubation period may span from 2 to 8 days, and a clear picture of the illness becomes evident only in the second week from exposure, with the appearance of other classical signs such as muscle and joint pain, lack of appetite and forgetfulness.

Most frequent are also CNS symptoms like encephalitis (which later progresses to stupor, delirium and coma) and gastrointestinal signs, like nausea, vomiting and abdominal pain. It is important to note that this clinical picture is nonspecific and the combination of symptoms varies greatly from patient to patient. Thus, Rocky Mountain spotted fever is difficult to diagnose and frequently confused with other nonspecific febrile illnesses. For this reason RMSF has also been defined as the “great imitator” of other diseases [15].

Rash is among the most important pathognomic features of Rocky Mountain spotted fever and usually appears only by the second or third day from exposure. It has a typical centripetal or “inward” diffusion pattern. It begins at the extremities and moves towards the trunk and the central parts of the body. Rash initially appears with blanching maculopapular lesions, which slowly turn in petechial lesions after 6 days on the palms of the hands and the soles of the feet. The prompt recognition of maculopapular eruption is vital for diagnosis, because the appearance of petechial spots is a clear sign of the RMSF advanced stage.

• Splenomegaly

  The clinical signs associated with infection in dogs are lethargy, anorexia, ocular and nasal discharge, lymphadenopathy and splenomegaly. A thrombocytopenia also occurs. Kennel epizootics have been recorded. [medical-dictionary.thefreedictionary.com]

  Mucosal ulcers, postinflammatory hyperpigmentation, jaundice, cough, pneumonia, acute renal failure, lymphadenopathy, hepatomegaly, splenomegaly, conjunctivitis, peripheral, periorbal and optic disk oedema, arterial occlusion, retinal vein engorgement [canada.ca]

  […] abdominal pain that mimics acute appendicitis ( 102 ), cholecystitis ( 103 ), or gastroenteritis; diarrhea; conjunctival suffusion; periorbital and peripheral edema (more common in children); calf pain; acute transient hearing loss; hepatomegaly; and splenomegaly [doi.org]

• Fever

  The fever and rash often appear together. Sick contacts are common. Dengue fever, also known as "breakbone fever," has severe arthralgias. Vasculitis is marked by palpable purpura rather than petechiae. [visualdx.com]

  Triad of Fever, Rash, and Tick Exposure is not commonly seen initially. < 50% have a rash present within first 3 days of illness. Rash typically appears 2-4 days after onset of fever, so patients may seek care before rash develops. [pedemmorsels.com]

  For more information on Rocky Mountain Spotted Fever, contact SWNPHD by calling 308-345-4223. [nebraska.tv]

  (Open Table in a new window) Organism Disease or Presentation Geographic Location Rickettsia rickettsii Rocky Mountain spotted fever North, Central and South America Rickettsia conorii Mediterranean spotted fever, boutonneuse fever, Israeli spotted fever [emedicine.com]

• Chills

  Definition of Rocky Mountain spotted fever : an acute disease that is characterized by chills, fever, prostration, pains in muscles and joints, and a red to purple eruption and that is caused by a rickettsial bacteria ( Rickettsia rickettsii ) usually [merriam-webster.com]

  A 32-year-old black man from rural southeastern Texas had headache, fever, chills, bronchopneumonia, and an atypical rash, complicated by hypotension, lethargy, confusion, liver dysfunction, thrombocytopenia, and acute renal failure. [ncbi.nlm.nih.gov]

  See your doctor immediately if you have been bitten by a tick and experience sudden onset of high fever, deep muscle pain, severe headache and chills.” A rash may also develop but is often absent in the first few days. [nebraska.tv]

  In addition to the rash, the infection can cause fever, chills, muscle aches, vomiting, and nausea. Typically, RMSF is treated with antibiotics and patients recover without any complications. [kidshealth.org]

  […] rickettsial disease (disorder) Spotted fever rickettsiosis Clinical Information Acute, infectious, sometimes fatal disease caused by rickettsia rickettsii usually transmitted by ixodid ticks; occurs only in north and south america; manifestations include chills [icd9data.com]

• Gangrene

  A case of Rocky Mountain spotted fever complicated by gangrene of the extremities required amputation and showed persistent rickettsial infection in the margins of the gangrene at 5 and 7 weeks after onset of illness. [ncbi.nlm.nih.gov]

  Breathing becomes laboured and circulation poor, and areas of gangrene may develop on the hands and feet. In the worst cases, the patient may become comatose and die, but in most cases fever gradually abates and the patient slowly recovers. [britannica.com]

  In rare cases, severe necrosis and gangrene may require amputation. [dermnetnz.org]

  If the infection is severe, areas of skin may die and turn black, indicating gangrene. About 10% of people with Rocky Mountain spotted fever do not develop a rash. [msdmanuals.com]

• High Fever

  Early clinical manifestations of RMSF include high fever, severe headache, myalgias, nausea, and vomiting. Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. [visualdx.com]

  Tumble clothes in a dryer on high heat for an hour to kill remaining ticks. For more information on Rocky Mountain Spotted Fever, contact SWNPHD by calling 308-345-4223. [nebraska.tv]

  Rocky Mountain spotted fever is a potentially fatal rickettsial infection that is transmitted by dog ticks and wood ticks. It causes a rash, headache, and high fever. People become infected when a tick carrying the infection bites them. [msdmanuals.com]

  There is a high fever — often 103°-105°F (39°-40°C) — with chills, muscle aches, and a severe headache. Eyes can become red, muscles may feel tender, and there may be abdominal pain, nausea, vomiting, poor appetite, and fatigue. [kidshealth.org]

• Malaise

  The patient had no dental problems other than the need for routine prophylaxis but mentioned a recent problem with swelling of her extremities with an accompanying rash and general malaise and soreness in her neck region. [ncbi.nlm.nih.gov]

• Cough

  Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. Rash occurs more frequently in children and young adults than in older individuals. [visualdx.com]

  Diagnosis of Rocky Mountain Spotted Fever in Dogs Owners who notice their dog has suddenly taken ill with fever, coughing or vomiting should be rushed immediately to a veterinarian’s office. [wagwalking.com]

  coughing, sneezing, or inhaling (known as pleuritic chest pain) red eyes resembling a pink eye infection Another common symptom is a rash that begins on the wrists and ankles and may spread to feet, palms of hands, arms, legs, and torso. [medicalnewstoday.com]

  In addition to the early symptoms, cough, bleeding, edema, confusion, focal neurologic signs, and seizures may also be present. [aocd.org]

  A hacking, dry cough may also develop. Nausea and vomiting are common. Between the first and the sixth day of the fever, a rash appears on the wrists, palms, ankles, soles, and forearms. [msdmanuals.com]

• Dry Cough

  A hacking, dry cough may also develop. Nausea and vomiting are common. Between the first and the sixth day of the fever, a rash appears on the wrists, palms, ankles, soles, and forearms. [msdmanuals.com]

  Signs of RMSF include: fever digestive problems, such as nausea, diarrhea, vomiting, or lack of appetite severe abdominal pain headache, particularly at the front of the head muscle aches a dry cough, sore throat, or both chest pain that feels worse when [medicalnewstoday.com]

• Vomiting

  Viral or bacterial enterocolitis presents with nausea and vomiting. Acute surgical abdomen has severe abdominal pain. Hepatitis presents with jaundice. Meningitis has prominent neurological signs. [visualdx.com]

  Rocky Mountain spotted fever can present with predominantly abdominal symptoms including nausea, vomiting, diarrhea, and abdominal pain. Two elderly patients presented with an acute febrile illness and abdominal symptoms. [ncbi.nlm.nih.gov]

• Nausea

  Viral or bacterial enterocolitis presents with nausea and vomiting. Acute surgical abdomen has severe abdominal pain. Hepatitis presents with jaundice. Meningitis has prominent neurological signs. [visualdx.com]

  Rocky Mountain spotted fever can present with predominantly abdominal symptoms including nausea, vomiting, diarrhea, and abdominal pain. Two elderly patients presented with an acute febrile illness and abdominal symptoms. [ncbi.nlm.nih.gov]

• Abdominal Pain

  Acute surgical abdomen has severe abdominal pain. Hepatitis presents with jaundice. Meningitis has prominent neurological signs. Idiopathic thrombocytopenic purpura (ITP) presents with a petechial rash. [visualdx.com]

  Rocky Mountain spotted fever can present with predominantly abdominal symptoms including nausea, vomiting, diarrhea, and abdominal pain. Two elderly patients presented with an acute febrile illness and abdominal symptoms. [ncbi.nlm.nih.gov]

  The following symptoms are commonly seen with this disease; fever, rash (occurs 2-5 days after fever, may be absent in some cases; see below), headache, nausea, vomiting, abdominal pain (may mimic appendicitis or other causes of acute abdominal pain), [health.ri.gov]

• Abdominal Cramps

  She is reporting headache, myalgias, mild nausea and abdominal cramps. No recent travel, no tick bites and no other exposures are elicited. The family has a dog. Tomorrow is the last day of school, and the patient wants to feel well enough to go. [acphospitalist.org]

• Hypotension

  A 32-year-old black man from rural southeastern Texas had headache, fever, chills, bronchopneumonia, and an atypical rash, complicated by hypotension, lethargy, confusion, liver dysfunction, thrombocytopenia, and acute renal failure. [ncbi.nlm.nih.gov]

  Hypotension develops in severe cases. Hepatomegaly may be present, but jaundice is infrequent. Nausea and vomiting are common. Localized pneumonitis may occur. [msdmanuals.com]

  The endothelial cell injury triggers a series of important physiological modifications, like increased vascular permeability, edema, hypotension and hypoalbuminemia, which cause the blood vessels to become blocked and inflamed (vasculitis). [symptoma.com]

• Tachycardia

  Other than fever of 39 °C and tachycardia of 100 beats/min, her vital signs are normal. There are no meningeal signs. [acphospitalist.org]

• Hepatomegaly

  Hepatomegaly may be present, but jaundice is infrequent. Nausea and vomiting are common. Localized pneumonitis may occur. Untreated patients may develop pneumonia, tissue necrosis, and circulatory failure, sometimes with brain and heart damage. [msdmanuals.com]

  Mucosal ulcers, postinflammatory hyperpigmentation, jaundice, cough, pneumonia, acute renal failure, lymphadenopathy, hepatomegaly, splenomegaly, conjunctivitis, peripheral, periorbal and optic disk oedema, arterial occlusion, retinal vein engorgement [canada.ca]

• Hepatosplenomegaly

  Some individuals with RMSF may also develop abnormal enlargement of the liver and/or spleen (hepatosplenomegaly). [rarediseases.org]

• Myalgia

  The combination of fever, headache, myalgias, marked left shift in the differential white blood cell count, severe thrombocytopenia, and hyponatremia all help to suggest the correct diagnosis early in the course of the illness. [ncbi.nlm.nih.gov]

  Early clinical manifestations of RMSF include high fever, severe headache, myalgias, nausea, and vomiting. Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. [visualdx.com]

• Arthralgia

  Dengue fever, also known as "breakbone fever," has severe arthralgias. Vasculitis is marked by palpable purpura rather than petechiae. Drug eruptions will have a history of exposure. [visualdx.com]

  The abrupt onset of the disease includes severe headache, fever, chills, arthralgia, and myalgia. After 2–3 days of these constitutional symptoms, erythematous macules erupt on the wrists, hands, forearms, legs, and ankles, as seen in these figures. [webmd.com]

  The early phase symptoms include a fever, headache, malaise, myalgias, arthralgias, and nausea with or without vomiting. [aocd.org]

  Symptoms of RMSF include fever, malaise, headache, myalgias and arthralgias, abdominal pain, nausea/vomiting, and photophobia. [neurology.org]

• Back Pain

  Four days later, she was treated by a chiropractor for neck and back pain, without relief. The next day she was hospitalized for further evaluation and treatment. [dx.doi.org]

• Photophobia

  Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. Rash occurs more frequently in children and young adults than in older individuals. [visualdx.com]

  Symptoms can include fever, headache, photophobia, malaise, myalgias, and a petechial rash that begins on the wrists and ankles and spreads to the trunk. [ncbi.nlm.nih.gov]

  Initial symptoms include sudden onset of: [ Biggs, 2016 ] Fever, chills Headache Malaise, myalgia, anorexia Nausea, vomiting, and abdominal pain Photophobia Rash ? [ Biggs, 2016 ] Begins as small, blanching pink macule on ankles, wrists/forearms. [pedemmorsels.com]

  Other neurologic manifestations include meningitis, cranial neuropathies, deafness, paralysis, spasticity, vertigo, aphasia, and photophobia. Ophthalmologic complications can also occur. [columbia-lyme.org]

  […] usually include a fever that may reach 103 or 104 degrees Fahrenheit; chills; extreme exhaustion (prostration); muscle pain (myalgia); and severe headaches that are often associated with pain upon moving the eyes and increased sensitivity to light (photophobia [rarediseases.org]

• Skin Rash

  Late appearance of a skin rash in Rocky Mountain spotted fever is associated with a high mortality. Our patient's rash appeared 14 days after the onset of illness, during his recovery. [ncbi.nlm.nih.gov]

  The skin rash typically begins as small, flat pinkish spots (macules) that initially become white (blanch) when pressure is applied. [rarediseases.org]

• Petechiae

  Vasculitis is marked by palpable purpura rather than petechiae. Drug eruptions will have a history of exposure. Secondary syphilis can also present with a palm and sole rash; occasionally, the rash imparts a rust-colored hue. [visualdx.com]

  As illness progresses, the rash can develop associated petechiae (days 5-6). Triad of Fever, Rash, and Tick Exposure is not commonly seen initially. < 50% have a rash present within first 3 days of illness. [pedemmorsels.com]

  Areas of petechiae may result in tiny scars. In rare cases, severe necrosis and gangrene may require amputation. [dermnetnz.org]

  This accounts for the production of petechiae. [medical-dictionary.thefreedictionary.com]

  He had a third heart sound, enlarged liver, and diffuse petechiae ( figure, A ). The remaining examination was unremarkable. [neurology.org]

• Eruptions

  Definition of Rocky Mountain spotted fever : an acute disease that is characterized by chills, fever, prostration, pains in muscles and joints, and a red to purple eruption and that is caused by a rickettsial bacteria ( Rickettsia rickettsii ) usually [merriam-webster.com]

  We discuss the case of a patient treated with an anti-TNF-alpha inhibitor for rheumatoid arthritis who later developed a generalized erythematous macular eruption accompanied by fever. [ncbi.nlm.nih.gov]

  Drug eruptions will have a history of exposure. Secondary syphilis can also present with a palm and sole rash; occasionally, the rash imparts a rust-colored hue. [visualdx.com]

  Some patients may suddenly develop a petechial rash without a prior maculopapular eruption. [aocd.org]

• Purpura

  Idiopathic thrombocytopenic purpura (ITP) presents with a petechial rash. Thrombotic thrombocytopenic purpura (TTP) is characterized by fever, anemia, thrombocytopenia, renal impairment, and neurological deficits. [visualdx.com]

  Clinical symptoms and hematologic parameters of severe Rocky Mountain spotted fever may resemble thrombotic thrombocytopenic purpura, implying that there may be similarities in the pathophysiology of both disorders. [ncbi.nlm.nih.gov]

  Meningoencephalitis Acute Renal Failure ARDS Shock Arrhythmia Cutaneous necrosis May become look similar to other conditions like Kawasaki or thrombocytopenic purpura.[ Biggs, 2016 ] Common lab abnormalities include: Thrombocytopenia (consumptive) Hyponatremia [pedemmorsels.com]

  purpura (TTP), and Henoch-Schönlein purpura/hemolytic-uremic syndrome (HSP/HUS), among others. [clinicaladvisor.com]

  […] common. 1, 3 The triad becomes apparent in 60%–70% of patients within the first 2 weeks of illness. 1 Rash typically develops between 2 and 5 days after fever, and is initially maculopapular in appearance, progressing to petechiae, or less frequently purpura [neurology.org]

• Palpable Purpura

  Vasculitis is marked by palpable purpura rather than petechiae. Drug eruptions will have a history of exposure. Secondary syphilis can also present with a palm and sole rash; occasionally, the rash imparts a rust-colored hue. [visualdx.com]

  On admission, she had petechiae in some areas and blanching erythematous papules in others, but no palpable purpura. It was unclear when her rash had developed petechial characteristics. [dx.doi.org]

• Kidney Failure

  Untreated, the infection may lead to health problems such as: Brain damage Clotting problems Heart failure Kidney failure Lung failure Meningitis Pneumonitis (lung inflammation) Shock Call your provider if you develop symptoms after exposure to ticks [nlm.nih.gov]

  These blood tests can help monitor for any potential complications, such as kidney failure or problems with blood clotting. [medicinenet.com]

  Possible Complications Untreated, the infection may lead to health problems such as: Brain damage Clotting problems Heart failure Kidney failure Lung failure Meningitis Pneumonitis (lung inflammation) Shock When to Contact a Medical Professional Call [ufhealth.org]

  Severe cases can result in kidney failure and death. How is RMSF diagnosed? Early diagnosis of RMSF relies on symptoms and history or suspicion of a tick bite. Blood tests are not useful within the first week of illness. [cdph.ca.gov]

• Headache

  Be vigilant during peak seasons: Summer-time “Headache and Fever” needs to have RMSF on the top of the DDx. [pedemmorsels.com]

  Symptoms (severe headache, chills, prostration, muscle pain) begin abruptly, followed by fever and usually a rash. Neurologic symptoms (headache, restlessness, insomnia, delirium, coma) may develop, indicating encephalitis. [msdmanuals.com]

  "If you start running a fever and you're having a headache or your child complains about having a headache or talks about their throat being sore or they're tired....get them to the doctor immediately," said Melton. [wymt.com]

  Symptoms can include fever, headache, photophobia, malaise, myalgias, and a petechial rash that begins on the wrists and ankles and spreads to the trunk. [ncbi.nlm.nih.gov]

• Confusion

  A 32-year-old black man from rural southeastern Texas had headache, fever, chills, bronchopneumonia, and an atypical rash, complicated by hypotension, lethargy, confusion, liver dysfunction, thrombocytopenia, and acute renal failure. [ncbi.nlm.nih.gov]

  Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. Rash occurs more frequently in children and young adults than in older individuals. [visualdx.com]

  This tick is often confused with the American dog tick since the two look very similar to the naked eye. Illness caused by Rickettsia parkeri is less severe than RMSF and rarely fatal. [epi.publichealth.nc.gov]

• Meningism

  Meningitis has prominent neurological signs. Idiopathic thrombocytopenic purpura (ITP) presents with a petechial rash. [visualdx.com]

  Eosinophilic meningitis was documented in a patient with Rocky Mountain spotted fever. Rickettsial disease should be considered a diagnostic possibility in patients with cerebrospinal fluid eosinophilia. [ncbi.nlm.nih.gov]

  […] of the meninges, the membranes that surround the brain, and the spinal cord. [humanillnesses.com]

  Untreated, the infection may lead to health problems such as: Brain damage Clotting problems Heart failure Kidney failure Lung failure Meningitis Pneumonitis (lung inflammation) Shock Call your provider if you develop symptoms after exposure to ticks [nlm.nih.gov]

  Meningitis, or inflammation of the membrane covering the brain and spinal cord; and pneumonitis, or inflammation in the lungs, have also been reported as complications Prompt treatment of Rocky Mountain Spotted Fever with antibiotics is recommended, if [dovemed.com]

• Ataxia

  CASE REPORT We describe an advanced case of RMSF in a 45-year-old female patient with pet dog exposure who presented with altered mental status, dyspnea, and ataxia progressing to septic shock and acute hypoxic respiratory failure requiring intubation [ncbi.nlm.nih.gov]

  Later manifestations include rash, photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, and severe abdominal pain. Rash occurs more frequently in children and young adults than in older individuals. [visualdx.com]

  Other symptoms include: Depression Lethargy Anorexia Blood in the urine Irregular heart beat (arrhythmia) Discolored spots along the skin, often bruised or purplish in color Inability to walk normally, loss of coordination ( ataxia ) Swelling or edema [petmd.com]

  Central nervous system manifestations include lethargy and confusion (about 25% of all cases), ataxia (18%), coma (9-10%), and seizures (8%). [columbia-lyme.org]

• Altered Mental Status

  CASE REPORT We describe an advanced case of RMSF in a 45-year-old female patient with pet dog exposure who presented with altered mental status, dyspnea, and ataxia progressing to septic shock and acute hypoxic respiratory failure requiring intubation [ncbi.nlm.nih.gov]

  mental status and/or coma may be observed in late stages Evaluation Diagnosis is primarily clinical based on fever, rash, and history of tick exposure Indirect immunoflourescence of skin biopsy may identify pathogen Serologies may identify immune response [medbullets.com]

  Symptoms may include: Fever Headache Rash—begins as small, flat pink spots on wrists and ankles Nausea and vomiting Abdominal pain Muscle or joint pain Lack of appetite Red eyes Light hurting the eyes Fatigue Altered mental status Severe bleeding Difficulty [cancercarewny.com]

  CT and MRI are strongly indicated, especially for those cases showing altered mental status, together with lumbar puncture if the presence of meningitis is suspected. [symptoma.com]

The diagnosis of Rocky Mountain spotted fever is heavily based on laboratory findings, through methods like blood count (CBC), electrolytes and renal and liver function tests. CT and MRI are strongly indicated, especially for those cases showing altered mental status, together with lumbar puncture if the presence of meningitis is suspected. Chest radiography and electrocardiography are also indicated, to reveal pulmonary and myocardial complications.

• Cerebrospinal Fluid Abnormality

  Cerebrospinal fluid abnormalities, particularly leukocytosis, were the rule in those patients who underwent lumbar puncture. Neurologic sequelae occurred in several patients. [ncbi.nlm.nih.gov]

• Pulmonary Infiltrate

  Patients with RMSF can develop ARDS or pulmonary infiltrates related to microvascular leakage that might be erroneously attributed to cardiac failure or pneumonia ( 184 ). [doi.org]

• X-Ray Abnormal

  The first step that your veterinarian will take in order to determine what is causing your dog’s illness will be to perform basic blood tests and possibly a urinalysis or X-rays. [vcahospitals.com]

• Hyponatremia

  The combination of fever, headache, myalgias, marked left shift in the differential white blood cell count, severe thrombocytopenia, and hyponatremia all help to suggest the correct diagnosis early in the course of the illness. [ncbi.nlm.nih.gov]

  Thrombocytopenia and hyponatremia and acute respiratory distress syndrome with organ failure may also be seen. A serious complication of RMSF is rhabdomyolysis. Long-term sequelae include central nervous system deficits and amputations. [visualdx.com]

  Meningoencephalitis Acute Renal Failure ARDS Shock Arrhythmia Cutaneous necrosis May become look similar to other conditions like Kawasaki or thrombocytopenic purpura.[ Biggs, 2016 ] Common lab abnormalities include: Thrombocytopenia (consumptive) Hyponatremia [pedemmorsels.com]

• Hypoalbuminemia

  The endothelial cell injury triggers a series of important physiological modifications, like increased vascular permeability, edema, hypotension and hypoalbuminemia, which cause the blood vessels to become blocked and inflamed (vasculitis). [symptoma.com]

  Serum biochemical abnormalities may include hypoproteinemia, hypoalbuminemia, azotemia, hyponatremia, hypocalcemia, and increased liver enzyme activities. Case fatality rates of ~1%–10% are expected. [msdvetmanual.com]

  The major pathophysiologic effect of endothelial cell injury is increased vascular permeability, which results in edema, hypovolemia, hypotension, and hypoalbuminemia. The organisms also routinely infect vascular smooth-muscle cells. [emedicine.com]

• Decreased Platelet Count

  Age and decreased platelet count at presentation have been independently associated with the development of ARF by multivariate analysis. ARF development increases the odds ratio of dying by a factor of 17. [emedicine.com]

• Leukopenia

  Leukopenia develops during the early stages of infection and, in untreated cases, is followed by progressive leukocytosis. [msdvetmanual.com]

  Leukopenia, thrombocytopenia, elevated hepatic transaminase levels, and mild anemia are characteristic laboratory findings in anaplasmosis. [doi.org]

  The white blood cell count is usually within normal limits, although both leukopenia (9%) and leukocytosis (24%) are sometimes observed. Platelet counts are low in 59% of cases (mean 128,000 platelets/μL). [clinicaladvisor.com]

  Leukopenia, thrombocytopenia, or elevated liver enzyme levels may occur in patients with RMSF as well as other tick-borne diseases, such as the ehrlichioses. 29, 49 - 52 A good history is essential to the diagnosis. [dx.doi.org]

• Rickettsia Rickettsii

  Alerts and Notices Synopsis   Rocky Mountain spotted fever (RMSF) is caused by the gram-negative bacterium Rickettsia rickettsii. It is the most severe rickettsial illness of humans; without treatment, the case fatality rate is 20%-30%. [visualdx.com]

  […] fever; mountain, Rocky Mountain spotted fever, koorts; Sao Paulo, mountain; fever, Rocky Mountain spotted fever, rickettsii; Rickettsia rickettsii, spotted fever, rickettsiose; Rickettsia rickettsii, spotted fever; Rickettsia rickettsii, spotted fever [fpnotebook.com]

  Da Wikimedia Commons, l'archivio di file multimediali liberi Jump to navigation Jump to search Rocky Mountain spotted fever is caused by Rickettsia rickettsii, a species of bacteria that is spread to humans by hard ticks (Ixodidae). [commons.wikimedia.org]

  Infection cycle of Rickettsia rickettsii in chicken embryo and L929 cells in culture. Infect Immun, 14 (1976), pp. 1052-1064 [55.] D.J. Silverman. Adherence of platelets to human endothelial cells infected by Rickettsia rickettsii. [elsevier.es]

• Leukocytosis

  Cerebrospinal fluid abnormalities, particularly leukocytosis, were the rule in those patients who underwent lumbar puncture. Neurologic sequelae occurred in several patients. [ncbi.nlm.nih.gov]

  Leukopenia develops during the early stages of infection and, in untreated cases, is followed by progressive leukocytosis. [msdvetmanual.com]

  The patient had leukocytosis to 36 × 10 3 /μL (reference range 4–14.6), anemia with hemoglobin 8.9 g/dL (10.5–13.5), and thrombocytopenia with platelets 76 × 10 3 /μL (150–400). Electrolytes and renal function were normal. [neurology.org]

  The white blood cell count is usually within normal limits, although both leukopenia (9%) and leukocytosis (24%) are sometimes observed. Platelet counts are low in 59% of cases (mean 128,000 platelets/μL). [clinicaladvisor.com]

Rocky Mountain spotted fever is usually treated with doxycycline-based antibiotic therapy. Treatment should be initiated immediately, without waiting for the laboratory confirmation. Preventive treatment for patients with tick bite history is not recommended, because it might only delay the disease presentation [16] and reduce the prospect of recovery. Chloramphenicol is a valid alternative to doxycycline, even though less used because of its numerous side effects.

The vascular inflammation triggered by Rickettsia rickettsii causes the blood vessels to leak or form clots, and the loss of fluid ultimately results in loss of circulation at the extremities of the body, which may even become paralyzed or gangrenous without prompt treatment. The disease determines a series of severe long-term health problems to the organs and tissues encountered along the way, which mainly involve the following systems:

• Nervous system, like headache, confusion, seizures, delirium, and in general signs of encephalitis.
• Respiratory system, like  pneumonia, pulmonary edema and lung failure in the most severe cases.
• Gastrointestinal problems, like the loss of bowel control.
• Renal system, like loss of bladder control or kidney failure.

Mortality rate depends on a series of factors, like age [7], race [8], gender and wrong diagnosis [9] [10] due to partial or total absence of the key RMSF features [7] [11]. It also seems to have significantly declined since 1980s, from 4% in 1982 to 1,4% and less in 2002 [12] [13] [14].

Rickettsia rickettsii is an obligate intracellular parasite which thrives in the cytoplasm of its eukaryotic host cells, especially those belonging to the endothelial tissue [2]. The natural RMSP hosts are ticks of the genus Dermacentor, like Dermacentor variabilis (the American dog tick), which largely feeds on big mammals. Because of this intra-species transmission, RMSP is a classical example of zoonosis. Dog is the excellent vector for Rickettsia rickettsii, given its high susceptibility to this bacterium and its higher rate to tick exposure.

Cases of RMSF have been reported in the United States since 1920’s. According to the most recent statistical data over the last decade, RMSF prevalence has increased, from an initial rate of 2 cases per million persons in 2000 to a final one of over 6 cases per million persons in 2010 [3]. By contrast, fatality has heavily declined over the same period, arriving at the current rate of 0,5% [3], perhaps as a consequence of the positive effects of better diagnostic and surveillance practices. No RMSP case has been reported outside the Americas, even though a variety of related diseases have been described in other continents. In any case, a clear picture of RMSP incidence worldwide still remains largely unknown.

Peaks of RMSP have been observed in North Carolina, Oklahoma, Arkansas, Tennessee, and Missouri, with more than the 60% of the cases reported. The peaks mostly appear in summer, between June and July, but some cases can also spring up in other months of the year. This seasonality varies from state to state, and it is strictly linked to the life cycle of the vector involved.

The persons at risk are mostly American Indians, males and people over 70 years of age [4]. Additional factors might be the exposure to dogs and wooded areas and the state of the immune system [4]. Particularly susceptible are also children under 10 years of age [3] [4] [5].

The main site of Rickettsia rickettsii is the endothelium of blood vessels, where the bacterium easily propagates tdue to the mechanism of actin polar polymerization [6].

The endothelial cell injury triggers a series of important physiological modifications, like increased vascular permeability, edema, hypotension and hypoalbuminemia, which cause the blood vessels to become blocked and inflamed (vasculitis). This systemic vascular damage is soon followed by a series of severe complications, like interstitial pneumonia.

RMSP prevention is very easy if a few simple precautions are followed, like wearing long pants and sleeves and using insect repellents. In the areas where RMSP cases have been reported, you are also strongly advised to tick-proof your yard and check yourself for ticks.

Rocky Mountain spotted fever (RMSP) is spread to humans by ticks. Very difficult to diagnose, especially in the early stages, its typical signs include sudden fever, headache and muscle pain. Without proper treatment, this disease may sometime be lethal [1]. Its name is a misnomer, since although very frequent in the Rocky Mountain region, where it was first recognized towards the end of the nineteenth century with the name of “black measles”, the illness has been diagnosed throughout the American continent, from as far north as Canada to as far south as Central America.

Rocky Mounatin spotted fever (RMSP) is an illness caused by Rickettsia rickettsii, a bacterium belonging to a group responsible for diseases such as typhus and rickettsialpox. Its natural hosts are the ticks of the species Dermacentor variabilis (the American dog tick), which largely feeds on big mammals. Once in the body, the bacterium infects the endothelium of blood vessels, causing vascular inflammation and thereby a series of severe complications, like interstitial pneumonia and a rash with the characteristic “inward” diffusion patters. The initial symptoms of fever, rush and headache are soon followed by muscle pain and other complications of key apparatuses such as the nervous and gastrointestinal systems. The RMSP is usually treated with doxycycline-based antibiotic therapy, but chloramphenicol can be a valid alternative.

1. Masters EJ, Olson GS, Weiner SJ, Paddock CD. Rocky Mountain spotted fever: a clinician's dilemma. Arch. Intern. Med. 2003 163 (7): 769–74
2. Walker DH. Rickettsiae. In: Barron's Medical Microbiology (4th ed.). Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 38. 
3. Openshaw JJ, Swerdlow DL, Krebs JW, Holman RC et al.  Rocky Mountain spotted fever in the United States, 2000-2007: Interpreting contemporary increases in incidence. Am J Trop Med Hyg. 2010 Jul;83(1):174-82.
4. Dahlgren FS, Holman RC, Paddock CD, Callinan LS, McQuiston JH. Fatal Rocky Mountain spotted fever in the United States, 1999–2007. Am J Trop Med Hyg(86)2012, 713
5. Demma LJ, Traeger MD, Nicholson WL, Paddock CD et al. Rocky Mountain spotted fever from an unexpected tick vector in Arizona. N Engl J Med. 2005 Aug 11;353(6):587-94.
6. Carlsson F, Brown EJ. Actin-based motility of intracellular bacteria, and polarized surface distribution of the bacterial effector molecules. J Cell Physiol. 2006 Nov; 209 (2):288-96.
7. Holman RC, Paddock CD, Curns AT, Krebs JW, McQuiston JH, Childs JE. Analysis of risk factors for fatal Rocky Mountain spotted fever: evidence for superiority of tetracyclines for therapy. J Infect Dis. 2001; 184:1437-1444.
8. Helmick CG, Bernard KW, D'Angelo LJ. Rocky Mountain spotted fever: clinical, laboratory, and epidemiological features of 262 cases. J Infect Dis. 1984;150:480-488.
9. Buckingham SC, Marshall GS, Schutze GE, Woods CR et al. Clinical and laboratory features, hospital course, and outcome of Rocky Mountain spotted fever in children. J Pediatr. 2007;150:180-184.
10. Chapman AS, Bakken JS, Folk SM, Paddock et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep. 2006;55:1-27.
11. Hattwick MA, Retailliau H, O'Brien RJ, Slutzker M, Fontaine RE, Hanson B.Fatal Rocky Mountain spotted fever. JAMA. 1978;240:1499-1503.
12. Treadwell TA, Holman RC, Clarke MJ, Krebs JW, Paddock CD, Childs JE. Rocky Mountain spotted fever in the United States, 1993-1996. Am J Trop Med Hyg. 2000;63:21-26.
13.  Dalton MJ, Clarke MJ, Holman RC, Krebs JW et al. National surveillance for Rocky Mountain spotted fever, 1981-1992: epidemiologic summary and evaluation of risk factors for fatal outcome. Am J Trop Med Hyg. 1995;52:405-413.
14. Chapman AS, Murphy SM, Demma LJ, Holman RC et al. Rocky Mountain spotted fever in the United States, 1997-2002. Vector Borne Zoonotic Dis. 2006;6:170-178.
15. Sexton DJ, Corey GR. Rocky Mountain "spotless" and "almost spotless" fever: a wolf in sheep's clothing.Clin Infect Dis. Sep 1992;15(3):439-48
16. Gammons M, Salam G. Tick removal. Am Fam Physician 2002 66 (4): 643–5.