Ehrlichiosis
Encyclopedia
Ehrlichiosis is a tick-borne disease
of dogs usually caused by the organism Ehrlichia canis. Ehrlichia canis is the pathogen of animals. Humans can become infected by E. canis and other species after tick exposure. German Shepherd dogs are thought to be particularly affected by the disease, other breeds generally have milder clinical signs. Cats can also be infected.
l bacteria belonging to the family Ehrlichiaceae
. There are several species of Ehrlichia, but the one that most commonly affects dogs and causes the most severe clinical signs is Ehrlichia canis. This species infects monocyte
s in the peripheral blood. The brown dog tick, or Rhipicephalus sanguineous, that passes the organism to the dog is prevalent throughout most of the United States
, but most cases tend to occur in the Southwest and Gulf Coast regions where there is a high concentration of the tick. Ehrlichia is found in many parts of the world and was first recognized in Algeria
in 1935. During the Vietnam War
ehrlichiosis became well known as a dog disease due to the infection and death of many military working dogs. Two types of human ehrlichiosis have been identified in the United States: human monocytic ehrlichiosis and human granulocytic ehrlichiosis.
from an infected dog. There are three stages of ehrlichiosis, each varying in severity. The acute stage, occurring several weeks after infection and lasting for up to a month, can lead to fever and lowered peripheral blood cell counts due to bone marrow
suppression. The second stage, called the subclinical phase, has no outward signs and can last for the remainder of the dog's life, during which the dog remains infected with the organism. Some dogs are able to successfully eliminate the disease during this time. In some dogs the third and most serious stage of infection, the chronic phase, will commence. Very low blood cell counts (pancytopenia
), bleeding
, bacterial infection, lameness, neurological
and ophthalmic disorders
, and kidney disease, can result. Chronic ehrlichiosis can be fatal.
, petechiae, bleeding disorders, vasculitis
, lymphadenopathy
, discharge from the nose and eyes, and edema
of the legs and scrotum. There are no outward signs of the subclinical phase. Clinical signs of the chronic phase include weight loss, pale gums due to anemia, bleeding due to thrombocytopenia
, vasculitis, lymphadenopathy
, dyspnea
, coughing, polyuria
, polydipsia
, lameness, ophthalmic diseases such as retinal hemorrhage and anterior uveitis
, and neurological disease. Dogs that are severely affected can die from this disease.
Although people can get ehrlichiosis, dogs do not transmit the bacteria to humans; rather, ticks pass on the ehrlichia organism. Clinical signs of human ehrlichiosis include fever, headache, eye pain, and gastrointestinal upset. It is quite similar to Rocky Mountain spotted fever
, but rash
is not seen in patients.
is achieved most commonly by serologic testing
of the blood for the presence of antibodies
against the ehrlichia organism. Many veterinarians routinely test for the disease, especially in enzootic areas. During the acute phase of infection, the test can be falsely negative because the body will not have had time to make antibodies to the infection. As such, the test should be repeated. In addition, blood test
s may show abnormalities in the numbers of red blood cell
s, white blood cell
s, and most commonly platelet
s, if the disease is present. Uncommonly, a diagnosis can be made by looking under a microscope
at a blood smear for the presence of the ehrlichia morula
e, which sometimes can be seen as intracytoplasmic inclusion bodies
within a white blood cell
.
is good for dogs with acute ehrlichiosis. For dogs that have reached the chronic stage of the disease, the prognosis is guarded. When bone marrow suppression occurs and there are low levels of blood cells, the animal may not respond to treatment.
. Treatment for ehrlichiosis involves the use of antibiotics such as tetracycline or doxycycline
for a period of at least six to eight weeks; response to the drugs may take one month. In addition, steroids may be indicated in severe cases in which the level of platelets is so low that the condition is life threatening.
regions.
Tick-borne disease
Tick-borne diseases are diseases or illnesses transmitted by ticks. As the incidence of tick-borne illnesses increases and the geographic areas in which they are found expand, it becomes increasingly important that health professionals be able to distinguish the diverse, and often overlapping,...
of dogs usually caused by the organism Ehrlichia canis. Ehrlichia canis is the pathogen of animals. Humans can become infected by E. canis and other species after tick exposure. German Shepherd dogs are thought to be particularly affected by the disease, other breeds generally have milder clinical signs. Cats can also be infected.
Ehrlichia
Ehrlichia is a rickettsiaRickettsia
Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...
l bacteria belonging to the family Ehrlichiaceae
Ehrlichiaceae
The Ehrlichiaceae are a family of bacteria, included in the order Rickettsiales....
. There are several species of Ehrlichia, but the one that most commonly affects dogs and causes the most severe clinical signs is Ehrlichia canis. This species infects monocyte
Monocyte
Monocytes are a type of white blood cell and are part of the innate immune system of vertebrates including all mammals , birds, reptiles, and fish. Monocytes play multiple roles in immune function...
s in the peripheral blood. The brown dog tick, or Rhipicephalus sanguineous, that passes the organism to the dog is prevalent throughout most of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, but most cases tend to occur in the Southwest and Gulf Coast regions where there is a high concentration of the tick. Ehrlichia is found in many parts of the world and was first recognized in Algeria
Algeria
Algeria , officially the People's Democratic Republic of Algeria , also formally referred to as the Democratic and Popular Republic of Algeria, is a country in the Maghreb region of Northwest Africa with Algiers as its capital.In terms of land area, it is the largest country in Africa and the Arab...
in 1935. During the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...
ehrlichiosis became well known as a dog disease due to the infection and death of many military working dogs. Two types of human ehrlichiosis have been identified in the United States: human monocytic ehrlichiosis and human granulocytic ehrlichiosis.
Disease overview
Dogs get ehrlichiosis from the brown dog tick, which passes an ehrlichia organism into the bloodstream when it bites. It is also possible for dogs to become infected through a blood transfusionBlood transfusion
Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...
from an infected dog. There are three stages of ehrlichiosis, each varying in severity. The acute stage, occurring several weeks after infection and lasting for up to a month, can lead to fever and lowered peripheral blood cell counts due to bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...
suppression. The second stage, called the subclinical phase, has no outward signs and can last for the remainder of the dog's life, during which the dog remains infected with the organism. Some dogs are able to successfully eliminate the disease during this time. In some dogs the third and most serious stage of infection, the chronic phase, will commence. Very low blood cell counts (pancytopenia
Pancytopenia
Pancytopenia is a medical condition in which there is a reduction in the number of red and white blood cells, as well as platelets.If only two parameters from the full blood count are low, the term bicytopenia can be used...
), bleeding
Bleeding
Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...
, bacterial infection, lameness, neurological
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...
and ophthalmic disorders
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...
, and kidney disease, can result. Chronic ehrlichiosis can be fatal.
Signs and symptoms
The acute stage of the disease, occurring most often in the spring and summer, begins one to three weeks after infection and lasts for two to four weeks. Clinical signs include a feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, petechiae, bleeding disorders, vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
, lymphadenopathy
Lymphadenopathy
Lymphadenopathy is a term meaning "disease of the lymph nodes." It is, however, almost synonymously used with "swollen/enlarged lymph nodes". It could be due to infection, auto-immune disease, or malignancy....
, discharge from the nose and eyes, and edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
of the legs and scrotum. There are no outward signs of the subclinical phase. Clinical signs of the chronic phase include weight loss, pale gums due to anemia, bleeding due to thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
, vasculitis, lymphadenopathy
Lymphadenopathy
Lymphadenopathy is a term meaning "disease of the lymph nodes." It is, however, almost synonymously used with "swollen/enlarged lymph nodes". It could be due to infection, auto-immune disease, or malignancy....
, dyspnea
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
, coughing, polyuria
Polyuria
Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine . Frequent urination is sometimes included by definition, but is nonetheless usually an accompanying symptom...
, polydipsia
Polydipsia
Polydipsia is a medical symptom in which the patient displays excessive thirst. The word derives from the Greek πολυδιψία, which is derived from πολύς + δίψα...
, lameness, ophthalmic diseases such as retinal hemorrhage and anterior uveitis
Uveitis
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye....
, and neurological disease. Dogs that are severely affected can die from this disease.
Although people can get ehrlichiosis, dogs do not transmit the bacteria to humans; rather, ticks pass on the ehrlichia organism. Clinical signs of human ehrlichiosis include fever, headache, eye pain, and gastrointestinal upset. It is quite similar to Rocky Mountain spotted fever
Rocky Mountain spotted fever
Rocky Mountain spotted fever is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” , “São Paulo fever” or “febre...
, but rash
Rash
A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
is not seen in patients.
Diagnosis
DiagnosisMedical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
is achieved most commonly by serologic testing
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
of the blood for the presence of antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
against the ehrlichia organism. Many veterinarians routinely test for the disease, especially in enzootic areas. During the acute phase of infection, the test can be falsely negative because the body will not have had time to make antibodies to the infection. As such, the test should be repeated. In addition, blood test
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
s may show abnormalities in the numbers of red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s, white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
s, and most commonly platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
s, if the disease is present. Uncommonly, a diagnosis can be made by looking under a microscope
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
at a blood smear for the presence of the ehrlichia morula
Morula
A morula is an embryo at an early stage of embryonic development, consisting of cells in a solid ball contained within the zona pellucida....
e, which sometimes can be seen as intracytoplasmic inclusion bodies
Inclusion bodies
Inclusion bodies are nuclear or cytoplasmic aggregates of stainable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins...
within a white blood cell
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
.
Prognosis
The prognosisPrognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
is good for dogs with acute ehrlichiosis. For dogs that have reached the chronic stage of the disease, the prognosis is guarded. When bone marrow suppression occurs and there are low levels of blood cells, the animal may not respond to treatment.
Treatment
Supportive care must be provided to animals that have clinical signs. Subcutaneous or intravenous fluids are given to dehydrated animals, and severely anemic dogs may require a blood transfusionBlood transfusion
Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...
. Treatment for ehrlichiosis involves the use of antibiotics such as tetracycline or doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...
for a period of at least six to eight weeks; response to the drugs may take one month. In addition, steroids may be indicated in severe cases in which the level of platelets is so low that the condition is life threatening.
Prevention
Tick control is the most effective method of prevention, but tetracycline at a lower dose can be given daily for 200 days during the tick season in endemicEndemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
regions.
Humans
- CDC - Human Ehrlichiosis in the United States basic Q&A
- NIH basic facts
- Tick-Borne Diseases, Ehrlichiosis detailed medical treatment
- Directors of Health Promotion and Education basic facts and advice