Title: Ehrlichiosis (canine)

{{short description|Tick-borne disease of dogs}}
'''Ehrlichiosis''' ({{IPAc-en|ˌ|ɛər|l|ᵻ|k|i|ˈ|oʊ|s|ᵻ|s}}; also known as '''canine rickettsiosis''', '''canine hemorrhagic fever''', '''canine typhus''', '''tracker dog disease''',  and '''tropical canine pancytopenia''') is a [[tick-borne disease]] of dogs usually caused by the rickettsial agent ''[[Ehrlichia canis]]''. ''Ehrlichia canis'' is the pathogen of animals. Humans can become infected by ''E. canis'' and other species after tick exposure. [[German Shepherd Dog]]s are thought to be susceptible to a particularly severe form of the disease; other breeds generally have milder clinical signs. Cats can also be infected.

==''Ehrlichia''==
{{contradicts others|Ehrlichia|discuss=Talk:Ehrlichia#When was Ehrlichia first recognized?|date=June 2020}}
''[[Ehrlichia]]'' is a [[rickettsia]]l genus of 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]]'', which 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&lt;ref&gt;{{Cite web|last=Fitzgerald|first=Roxanne|date=2021-07-15|title=This once-rare dog disease appeared in the outback last year. Now it's arrived in the city|url=https://www.abc.net.au/news/2021-07-16/nt-dog-disease-ehrlichiosis-endemic-in-northern-territory/100289234|url-status=live|access-date=2021-07-16|website=www.abc.net.au|language=en-AU|archive-url=https://web.archive.org/web/20210715202826/https://www.abc.net.au/news/2021-07-16/nt-dog-disease-ehrlichiosis-endemic-in-northern-territory/100289234 |archive-date=2021-07-15 }}&lt;/ref&gt; and was first recognized in [[Algeria]] in 1935.&lt;ref&gt;{{Cite journal|last1=Sainz|first1=Ángel|last2=Roura|first2=Xavier|last3=Miró|first3=Guadalupe|last4=Estrada-Peña|first4=Agustín|last5=Kohn|first5=Barbara|last6=Harrus|first6=Shimon|last7=Solano-Gallego|first7=Laia|date=2015-02-04|title=Guideline for veterinary practitioners on canine ehrlichiosis and anaplasmosis in Europe|journal=Parasites &amp; Vectors|volume=8|issue=1|pages=75|doi=10.1186/s13071-015-0649-0|issn=1756-3305|pmc=4324656|pmid=25649069 |doi-access=free }}&lt;/ref&gt; During the [[Vietnam War]] ehrlichiosis became well known as a dog disease due to the infection and death of many military working dogs.&lt;ref name=Ettinger&gt;{{cite book|author1=Ettinger, Stephen J. |author2=Feldman, Edward C. |title=Textbook of Veterinary Internal Medicine(4th ed.)|publisher=W.B. Saunders Company|year=1995|isbn=0-7216-6795-3}}&lt;/ref&gt; Two types of human ehrlichiosis have been identified in the United States: human monocytic ehrlichiosis and human granulocytic ehrlichiosis.&lt;ref&gt;{{Cite journal|last=Biggs|first=Holly M.|display-authors=et al|date=13 May 2016|title=Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States. A Practical Guide for Health Care and Public Health Professionals|url=https://www.cdc.gov/mmwr/volumes/65/rr/pdfs/rr6502.pdf|journal=Centers for Disease Control and Prevention: Morbidity and Mortality Weekly Report|volume=65: 2|pages=44}}&lt;/ref&gt;

==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 transfusion]] from an infected dog.&lt;ref name=&quot;Ettinger&quot;/&gt; There are three stages of ehrlichiosis, each varying in severity.&lt;ref&gt;{{Cite journal|last=Harrus|first=Shimon|display-authors=et al|date=21 December 2020|title=Recent Advances in Determining the Pathogenesis of Canine Monocytic Ehrlichiosis|journal=Journal of Clinical Microbiology|volume=37 |issue=9 |pages=2745–2749 |language=en|doi=10.1128/jcm.37.9.2745-2749.1999|doi-access=free|pmid=10449445 |pmc=85367}}&lt;/ref&gt; 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 disorder|neurological]] and [[Ophthalmology|ophthalmic disorders]], 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. [[Sign (medicine)|Clinical sign]]s include a [[fever]], [[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.

==Diagnosis==
[[medical diagnosis|Diagnosis]] is achieved most commonly by [[Serology|serologic testing]] of the blood for the presence of [[Antibody|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. A PCR (polymerase chain reaction) test can be performed during this stage to detect genetic material of the bacteria. The PCR test is more likely to yield a negative result during the subclinical and chronic disease phases.&lt;ref&gt;{{cite web|title=Canine Monocytic Ehrlichiosis: An In-depth Review|url=http://www.idexx.com|publisher=Idexx Laboratories|accessdate=2012-09-26}}&lt;/ref&gt;  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]].

==Prognosis==
The [[prognosis]] 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 transfusion]]. Treatment for ehrlichiosis involves the use of antibiotics such as [[tetracycline]] or [[doxycycline]] for a period of three to four weeks; Alternatively [[minocycline]] or [[rifampicin]] can be used as a second option.&lt;ref&gt;{{Cite journal |last1=Mylonakis |first1=Mathios E. |last2=Harrus |first2=Shimon |last3=Breitschwerdt |first3=Edward B. |date=April 2019 |title=An update on the treatment of canine monocytic ehrlichiosis (Ehrlichia canis) |journal=The Veterinary Journal |language=en |volume=246 |pages=45–53 |doi=10.1016/j.tvjl.2019.01.015 |pmid=30902188 |s2cid=85456868}}&lt;/ref&gt; Treatment with [[macrolide]] antibiotics like clarithromycin and azithromycin is being studied. In addition, steroids may be indicated in severe cases in which the level of [[platelet]]s is so low that the condition is life-threatening.{{Citation needed|date=June 2024}}

==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 [[endemic (epidemiology)|endemic]] regions.

==References==
&lt;references /&gt;

==External links==
{{Wikispecies|Rhipicephalus}}
* [http://www.veterinarypartner.com/Content.plx?P=A&amp;S=0&amp;C=0&amp;A=2103 ''Ehrlichia Infection in Dogs'' from The Pet Health Library]

[[Category:Dog diseases]]
[[Category:Animal bacterial diseases]]