Ehrlichiosis- canine 30% Flashcards
What is ehrlichiosis (canine)
Gram negative obligate intracellular bacterium of the Rickettisiales order= Anaplasma platys and Ehrlichia canis- Several species of bacteria can cause ehrlichiosis. With newer genetic analyses, these agents have been reclassified into the genera of Ehrlichia, Anaplasma, and Neorickettsia, all of which are in the family Anaplasmataceae. However, the term “ehrlichiosis” is still sometimes used to broadly describe these infections.
Canine monocytic ehrlichiosis is caused by Ehrlichia canis, which predominantly involves monocytes/ lymphocytes; although it is not considered a primary zoonosis
A platys, which infects platelets, is the cause of infectious cyclic thrombocytopenia of dogs.
The primary vector for E. canis is the Rhipicephalus sanguineus tick.
incubation and pathogenesis- ehrlichiosis (canine)
7-21 days- Ehrlichiosis is a tick-transmitted disease that infects blood cells. E canis is transmitted by the brown dog tick, Rhipicephalus sanguineus. Infection – invade mononuclear cells and reproduce. Form morulae within cells.
Acute E canis cases in dogs may resemble infection with Rickettsia rickettsii (the agent of Rocky Mountain spotted fever, which can also be transmitted by the brown dog tick).
Rhipicephalus ticks become infected with E canis after feeding on infected dogs, and ticks transmit infection to other dogs during blood meals taken in successive life stages.
Blood transfusions, or other means by which infected WBCs can be transferred, may also transmit the pathogen.
Some ehrlichia species have sylvatic cycles in the environment that involve tick species and wildlife reservoir hosts.
clinical signs ehrlichiosis (canine)
Clinical signs can be seen in the acute and chronic phases of disease.
Clinical signs include depression, dehydration, fever, anorexia, weight loss, vomiting, diarrhea, lymphadenopathy, hepatomegaly, and splenomegaly.
Bleeding abnormalities can include epistaxis, petechiae, ecchymoses, and pale mucous membranes.
Ocular abnormalities include ocular discharge, retinal hemorrhages, retinal detachment, blindness, chorioretinitis, uveitis, keratoconjunctivitis sicca, hyphema, corneal ulceration, and glaucoma.
Neurologic abnormalities include vestibular signs, ataxia, hyperesthesia, anisocoria, stupor, seizures, and tremors.
Dogs infected with A platys generally show minimal to no signs of infection despite the presence of the organism in platelets. The primary finding is cyclic thrombocytopenia, recurring at 10-day intervals. Generally, the cyclic nature diminishes, and the thrombocytopenia becomes mild and slowly resolves.
Diagnosis ehrlichiosis
snap test (sensitive and specific), pcr, cbc (anemia, thrombocyopenia), IFA - Diagnosis is based on signs, serology, and PCR.
Clin path- Thrombocytopenia, globulinopathy (mono/poly gamopathy), pancyctopenia, anemia due to bleeding. pancytopenia can lead to secondary infections as well as anemia due to bleeding
Morulae on blood smear or within cells on CSF tap is diagnostic but not common.
Acute polyarthropathy and/or bleeding that leads to non-regen anemia
Ehrlichiosis and anaplasmosis have similar clinical manifestations, with acute fever and hematologic abnormalities. Maintaining an index of suspicion for infection based on known tick activity, and using appropriate diagnostic testing, are important to make diagnoses of ehrlichiosis and anaplasmosis and to implement effective treatment.
Treatment ehrlichiosis
Doxycycline is the treatment of choice. Can use tetracycline or chloramphenicol (young animals). Imidocarb diproprionate as well for resistant infections.
Corticosteroids if if severe TBpenia, polyarthritis, vasculitis.
May require treatment up to three months.
Successful treatment based on clinical recovery and serosurveillance negative or low status in 6 months.
symptoms - prednisone (cbc)
prognosis ehrlichiosis
Overall prognosis for acutely infected dogs is good if treatment is initiated early. Marked improvement is usually seen within 24-48 hours after initiation of appropriate antimicrobial therapy.
Prognosis for dogs with chronic CME is poorer.
Chronic ehrlichiosis caused by E canis may develop in any breed, but certain breeds, eg, German Shepherds, may be predisposed.
Zoonosis ehrlichiosis
E. canis DNA has been detected in people with human monocytic ehrlichiosis. Dogs may serve as a reservoir for infection but direct transmission from dogs to people is unproven. E. canis is not currently considered a zoonotic pathogen.
Multiple ehrlichioses and anaplasmoses may be transmitted by ticks from wildlife to pets and people (or from dog to dog in the case of canine monocytic ehrlichiosis).
Co-infection ehrlichiosis (canine)
Co-infection with other infectious agents or hemoparasites can occur with CME. Hepatozoon canis and Babesia canis vogeli are transmitted by the same tick vector, R. sanguineus. Testing for other infectious agents may be indicated/needed.
Prevention- ehrlichosis (canine)
Tick control routinely, monitoring for ticks, longterm tick control is needed for management, use of effective long-acting collars on all susceptible dogs might be considered; collars containing propoxur, amitraz, or flumethrin have proven activity against R sanguineus.
Prevention of transfusion-associated transmission can be reduced by using seronegative screened blood donors, although new donors with a negative screen cannot be presumed free of infection for several weeks because they may be incubating infection. Prophylactic administration of tetracycline at a lower dosage (6.6 mg/kg/day, PO) is effective in preventing E canis infection in kennels where disease is endemic. Treatment must be extended for many months through at least one tick season if the endemic cycle is to be successfully eliminated, and tick control should be implemented as well.
