In order to determine whether dogs in the subclinical phase of canine monocytic ehrlichiosis (CME) are carriers of Ehrlichia canis and to determine the significance of persistent indirect immunofluorescent anti-E. canis antibody titers during this phase, PCR was performed with blood, bone marrow, and splenic aspirates collected 34 months postinoculation from six clinically healthy beagle dogs experimentally infected with E. canis. At least one of the three samples (spleen, bone marrow, and blood) from four of the six dogs was PCR positive. The spleens of all four of these dogs were PCR positive, and the bone marrow and blood of two of the four dogs were PCR positive. Indirect immunofluorescent-antibody titers increased progressively during the first 5 months postinfection, remained high for an additional period of more than 11 months, and declined thereafter, suggesting that the dogs were recovering from the disease. Five of the dogs remained seropositive 34 months postinfection. The data obtained in this study demonstrate for the first time that clinically healthy dogs in the subclinical phase of CME are carriers of the rickettsia. It was shown that dogs can harbor E. canisfor years without developing the chronic clinical disease and that dogs can eliminate the parasite and recover from CME without medical treatment. Our findings suggest that the spleen is the organ most likely to harbor E. canis parasites during the subclinical phase and the last organ to accommodate the parasite before elimination. It was concluded that PCR of DNA extracted from splenic aspirates is a reliable method for determining the carrier state of CME.

This report presents evidence that dogs recover from acute canine monocytic ehrlichiosis (CME) after 16 days of doxycycline treatment (10 mg/kg of body weight every 24 h). Blood PCR was as valuable as splenic aspirate PCR for early diagnosis of acute CME. Splenic aspirate PCR was, however, superior to blood PCR for the evaluation of ehrlichial elimination.Canine monocytic ehrlichiosis (CME) is a tick-borne disease with a global distribution (9). Diagnosis of CME is confirmed by demonstration of morulae in blood smears, serology, culturing of the rickettsiae, and PCR using Ehrlichia canis-specific primers. Tetracyclines are commonly used in the treatment of CME, with doxycycline in particular being the most acceptable and widely used (2, 3).Blood samples are presently used for PCR evaluation of ehrlichial infection and response to therapy (15). A previous study has demonstrated ehrlichial DNA in splenic aspirates of two subclinically experimentally infected dogs whose blood and bone marrow aspirates were found to be negative for E. canis DNA, suggesting the importance of splenic aspirates in the diagnosis of ehrlichial carriers (6). This finding questioned the validity of previous blood-based PCR studies for evaluating treatment regimens for CME, and the length of doxycycline treatment required for E. canis infection remained uncertain.The aims of this study were (a) to investigate whether splenic aspirates are superior to blood samples as a sample source for E. canis PCR; (b) to determine whether dogs with acute CME remain persistently infected despite concurrent treatment; and (c) to determine the duration of doxycycline treatment required to eliminate E. canis DNA, as measured by PCR in cases of acute CME.Five beagle dogs, 4 to 6 years old and negative serologically and by PCR for E. canis, were used in this study. The dogs were artificially infected by intravenous injection of 5 ml of E. canisinfected blood. This blood was drawn from an acutely ill, naturally infected dog. Infection of the donor dog with E. canis was confirmed by serology using the indirect immunofluorescence antibody (IFA) test (11), by blood culture of DH82 cells (4), and by p30-based nested PCR for E. canis (14).

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Six weimaraner puppies, five of which were genetically related, showed systemic signs associated with hypertrophic osteodystrophy, including fever and involvement of the gastrointestinal, respiratory or nervous systems, in addition to the metaphyseal lesions. In five of the dogs the clinical signs developed less than 10 days after they had been vaccinated with a modified live virus vaccine. Radiographic findings suggested that both the hindlimbs and forelimbs were equally involved in the disease process. Abnormal haematological findings included leucocytosis with neutrophilia and monocytosis, and there was a consistent increase in the activity of alkaline phosphatase. Serum protein electrophoretic studies of three of the dogs revealed hypogammaglobulinaemia and abetaglobulinaemia in two of them. Conservative treatment with rest and non-steroidal anti-inflammatory drugs had little effect, and treatment with corticosteroids appeared to give the best results.

Two different vaccination protocols were compared with regard to the development of hypertrophic osteodystrophy (HOD) (also termed metaphyseal osteopathy) and effectiveness of immunisation in a litter of 10 Weimaraner puppies. Five puppies (group 1) were vaccinated with a modified live canine parvovirus vaccine (CPV) and then two weeks later with a trivalent vaccine containing modified live canine distemper virus and adenovirus type 2 combined with a Leptospira bacterin (DHL). The CPV and DHL vaccine protocols were administered a further two times, at two-week intervals. Group 2 was vaccinated with three consecutive multivalent vaccines containing modified live canine distemper virus, canine parvovirus, parainfluenza and adenovirus type 2 combined with a Leptospira bacterin, at four-week intervals. All puppies were first vaccinated at the age of eight weeks. Three dogs in group 1 developed HOD, while all five dogs in group 2 developed HOD during the study period. Dogs in group 2 had more episodes of HOD than those in group 1. Dogs in group 1 developed higher antibody titres to canine distemper virus and parvovirus compared with those in group 2. Only two out of the 10 dogs developed protective antibody titres to parvovirus. The results of this study suggest that the two different vaccination protocols affected the pattern of appearance of HOD and immunisation in this litter of Weimaraner puppies. The results obtained and the previously reported data suggest that a larger controlled study is needed to further elucidate the effect of different vaccination protocols on HOD and immunisation in Weimaraner puppies.