Anaplasmosis: Dogs
(Canine Anaplasmosis / Ehrlichiosis)

Clinical Signs and symptoms:
Pyrexia (fever)
Lethargy (weakness / loss of energy)
Depression
Anorexia (loss of appetite leading to weight loss)

More acute signs include:
Lymphadenopathy (swollen / enlarged lymph nodes)
Haemoglobinuria (dark red haemoglobin-containing urine)
Petechial to ecchymotic haemorrhages (spotted areas of blood accumulated within the tissue)
Epistaxis related to thrombocytopenia (nosebleeds leading to reduced platelets)
Neurologic disease
Inflammatory arthritis – maybe mono- or polyarthritis (single or multiple joint involvement)
Vomiting
Diarrhoea
Ocular lesions including uveitis, chorioretinitis, and retinal detachment have been reported

Diagnostic Tests
Classical microscopic diagnosis relies on identification of morulae in circulating monocytes, neutrophils, or platelets in Giemsa- or Wright’s-stained blood smears. However, detectable numbers of morulae are only present during acute infection. Therefore organisms may be difficult to find in blood smears. The gold standard for confirming infection is cell culture isolation.

Serology may be helpful in identifying the presence of antibodies to Ehrlichia and Anaplasma species but will only indicate exposure to the pathogen.

For the organisms that have been successfully cultured, Indirect Fluorescent Antibody (IFA) assays to determine IgM and IgG titres are available. Cross-reaction amongst the Ehrlichia and Anaplasma species is commonly recognised, and nonspecific IFA titres may develop due to infection with related agents.

An enzyme-linked immunosorbent assay is available for identifying antibodies to E. canis and A. phagocytophilum. Note: Cross-reaction of the latter assay with antibodies raised against A. platys has been documented.

Antibody titres may persist months to years after treatment and resolution of clinical signs, suggesting either persistent infection or re-infection; this persistence has been noted particularly in E. canis infections. However, the presence of antibodies alone does not indicate a need for treatment in the absence of any evidence of clinical disease.

Polymerase Chain Reaction (PCR) of whole blood has become more readily available. However, results should be interpreted with caution because the techniques used in different diagnostic laboratories vary. Amplification of related organisms by nonspecific primers has been shown to result in false-positive reactions. Conversely, false-negatives may occur if extraction procedures fail to remove PCR inhibitors present in a blood sample. They may also occur if the level of circulating rickettsaemia falls below the level of assay detection, due to normal decrease in circulating organisms or temporary suppression of infection following antibiotic treatment. To maximise the utility of molecular diagnostics, blood samples should be collected early in the course of clinical disease and before the initiation of antimicrobial therapy, and should be submitted to experienced diagnostic laboratories with stringent quality control measures in place.

Treatment
All Ehrlichia and Anaplasma infections in dogs and cats generally respond to treatment with Doxycycline @ 10mg/kg q24h for 28 days. However, some studies have demonstrated that short courses of therapy in chronically infected dogs have failed to eradicate infection and that recrudescence of infection is possible. Although additional research into this area is needed, re-treatment may be necessary in cases of relapse of a previous infection, or re-infection from ticks. Protective immunity does not appear to develop.

Treating in the subclinical phase is viewed by some veterinarians as potentially beneficial in preventing the development of chronic disease.

Medical Abbreviations
I.V.=intravenous
I.M.=intramuscular
P.O=by mouth
q8h=every 8 hours
q12h=every 12 hours
q24h=every 24 hours

Vaccine
There is currently no vaccine against Anaplasmosis / Ehrlichiosis available in the UK for dogs.