Canine Monocytic Ehrlichiosis - Health - Lecture Slides, Slides of Public Health

Download Canine Monocytic Ehrlichiosis - Health - Lecture Slides and more Slides Public Health in PDF only on Docsity! Canine Monocytic Ehrlichiosis docsity.com PATHOGENESIS Ehrlichia canis is transmitted by the brown dog tick Rhipicephalus sanguineus and by Dermacentor variabilis. Larvae and nymphs have been shown to become infected while feeding on infected dogs. Male and female brown dog ticks Rhipicephalus sanguineus.docsity.com CLINICAL PRESENTAION Naturally occurring CME may be manifested by a wide variety of clinical signs. Large variations in clinical signs have been reported for different studies and have been proposed to be due to a number of factors, including differences in pathogenicity between strains of the ehrlichia, breed of dog, coinfections with other tick transmitted diseases and the immune status of the dog. There is no predilection for age or sex in infection with E. canis and all breeds may be infected. However, the GSD seems to be more prone to develop clinical CME. docsity.com Ocular signs are not uncommon and include anterior uveitis + corneal opacity (edema and deposition of cellular precipitates), hyphema, tortuous retinal vessels and focal chorioretinal lesions consisting of central pigmented spots with surrounding areas of hyperreflectivity. Subretinal hemorrhages, resulting in retinal detachment and blindness may occur. Other clinical signs may include vomiting, serous to purulent oculonasal discharge, lameness, ataxia and dyspnea. docsity.com HEMATOLOGY Thrombocytopenia is the most common and consistent hematological finding in acute CME. A concurrent significant increase in the mean platelet volume is also usually seen reflecting active thrombopoiesis. Mild leukopenia and mild anemia (usually normocytic, normochromic, non-regenerative) commonly occur in the acute stage of the disease. Mild thrombocytopenia is a common finding in the subclinical stage of the disease. A decline in the neutrophil counts may occur. docsity.com BIOCHEMICAL FINDINGS Hypoalbuminemia, hyperglobulinemia and hypergammaglobulinemia are the principal biochemical abnormalities seen in dogs infected with CME. Serum protein electrophoresis usually reveals polyclonal gammopathy. Infected dogs on rare occasions may present with monoclonal gammopathy, which may be misdiagnosed as paraproteinemia. Pancytopenic dogs reveal significantly lower concentrations of total protein, total globulin and gammaglobulin concentrations as compared to nonpancytopenic dogs. docsity.com DIAGNOSIS The majority of CME cases occur in endemic areas during the spring and summer months when the tick population is most active. Diagnosis of CME is based on anamnesis, clinical presentation, clinical pathological findings and confirmed by laboratory tests. Owners may report previous tick infestations or a recent visit to an endemic area. Diagnosis of CME is confirmed by visualization of the morulae in circulating monocytes, detection of increased serum antibodies to E. canis, or by the demonstration of E. canis DNA by polymerase chain reaction (PCR). docsity.com Dot-ELISA tests have recently been developed for use in the clinic. These tests require the minimum of equipment and will make serologic diagnosis of CME available on a wider basis. This should prove to be an invaluable in-clinic aid in the serodiagnosis of CME. When assessing IFA antibody titers for E. canis in dogs it is essential that the diagnostician take in account the range of cross-reactivities that may also confound the diagnosis. In areas endemic to other Ehrlichia species, crossreactivity between E. canis and E. ewingii, E. equi or E. risticii should be taken into consideration. docsity.com TREATMENT Doxycycline at a dose of 10 mg/kg once daily (or 5 mg/kg twice daily) for a period of 3 weeks at least, is the treatment of choice for acute CME. Short term treatment with doxycycline (10 mg/kg, once daily, for 7 days) has been shown to result in failure, while 10 days doxycycline treatment has shown success. Ten days treatment may not be enough in all cases. Most dogs suffering acute CME respond to treatment and show clinical improvement within 24-72 hours. Dogs in the subclinical stage may need a prolonged treatment compared to dogs suffering the acute stage. docsity.com Other drugs with known efficacy against E. canis include tetracycline hydrochloride (22 mg/kg, q 8 hrs), oxytetracycline (25 mg/kg, q 8 hrs), minocycline (20 mg/kg, q 12 hrs) and chloramphenicol (50 mg/kg, q 8 hrs). In a recent report it has been shown that oral enrofloxacin (5 or 10 mg/kg q 12h for 21 days) was not effective in elimination of the rickettsia from experimentally infected dogs. The use of immunosuppressive doses of glucocorticosteroids in the treatment of the acute stage of CME can be considered. However, as no clinical studies have been performed to prove the efficacy of steroids in the treatment of CME, these steroids should be used with caution. docsity.com Treatment of the chronic severe form of the disease is unrewarding and the prognosis of these pancytopenic dogs is grave. Only one report described a successful treatment of a dog with severe chronic CME, using a combination of hematopoietic growth factors (recombinant human granulocyte colony stimulating factor and recombinant human erythropoietin) low dose vincristine, doxycycline and a long course of glucocorticoid therapy. However, the use of growth factors in the treatment of chronic ehrlichiosis has not been proven effective and requires much further investigation. docsity.com