Shimon Harrus

Significance of serological testing for ehrlichial diseases in dogs with special emphasis on the diagnosis of canine monocytic ehrlichiosis caused by Ehrlichia canis

Dogs are susceptible to a number of ehrlichial diseases. Among them, canine monocytic ehrlichiosis is an important and potentially fatal disease of dogs caused by the rickettsia Ehrlichia canis. Diagnosis of the disease relies heavily on the detection of antibodies and is usually carried out using the indirect immunofluoresence antibody (IFA) test. The IFA test may be confounded by cross-reactivities between a number of the canine ehrlichial pathogens. This article presents a review of the ehrlichial diseases affecting dogs with reference to their immune responses, host specificities, cross-reactivites and diagnosis. Diagnostic means such as Western immunblot, dot-blot and PCR are discussed. The use of the IFA test as a diagnostic means for E. canis is presented along with its potential pitfalls. The review emphasizes that the disease process, cross-reactivites with other ehrlichial species, multiple tick-borne infections and persistent IFA antibody titers post-treatment, should all be considered when interpreting E. canis serological results.

Diagnosis of canine monocytotropic ehrlichiosis (Ehrlichia canis): an overview.

Canine monocytotropic ehrlichiosis (CME), caused by the rickettsia Ehrlichia canis, an important canine disease with a worldwide distribution. Diagnosis of the disease can be challenging due to its different phases and multiple clinical manifestations. CME should be suspected when a compatible history (living in or traveling to an endemic region, previous tick exposure), typical clinical signs and characteristic hematological and biochemical abnormalities are present. Traditional diagnostic techniques including hematology, cytology, serology and isolation are valuable diagnostic tools for CME, however a definitive diagnosis of E. canis infection requires molecular techniques. This article reviews the current literature covering the diagnosis of infection caused by E. canis.

Clinical manifestations of infectious canine cyclic thrombocytopenia

This paper describes five naturally occurring clinical cases of infectious canine cyclic thrombocytopenia that were the first serologically confirmed cases of Ehrlichia platys infection in Israel. In the USA this disease is considered subclinical, but the dogs in this study developed distinct clinical abnormalities. The signs observed by the owners included anorexia, lethargy, depression, weight loss and a mucopurulent nasal discharge. The principal findings on physical examination included lymphadenomegaly, pale mucous membranes, fever and the presence of ticks. The main abnormal haematological and biochemical findings included thrombocytopenia, the presence of giant platelets, low haematocrit, monocytosis and low albumin concentrations. All five dogs were less than two years of age, and four were purebred dogs, suggesting that these two factors may be associated with increased risk to infection and clinical disease. Two of the dogs were seropositive to E canis, a finding which is compatible with other reports, and which confirms that combined infections of E platys and E canis are common; it also suggests that E canis infections may contribute to the pathogenesis of E platys. The distinct clinical manifestation of the disease in these five dogs suggests that there may be a different, more virulent strain of E platys in Israel.

Canine spirocercosis: clinical, diagnostic, pathologic, and epidemiologic characteristics

The nematode Spirocerca lupi is a parasite of dogs with beetles of several species serving as intermediate hosts. The medical records of 50 dogs diagnosed with spirocercosis at the Hebrew University Veterinary Teaching Hospital (HUVTH) in Israel during 1991-1999 were retrospectively reviewed and compared to a control group (n=100). There was a seven-fold increase in the annual number of dogs diagnosed with spirocercosis during these years while the hospital caseload increased by 80%, indicating an emerging outbreak of this infection. Dogs from the greater Tel Aviv area were at the highest risk of being diagnosed with spirocercosis with 74% of the cases originating from this region compared to only 17% of the controls. The disease appeared to have a primarily urban pattern of distribution with a significantly higher percentage (P=0.025) of dogs from cities versus rural areas, as compared to the control group. Sixty-two percent of the cases were diagnosed during the colder months of December through April. The median age of infected dogs was 5 years, with dogs 1 year old or younger at the lowest risk of being diagnosed with spirocercosis. Large breeds were at a higher risk of infection in comparison to small breeds and the Labrador Retriever was significantly over represented (P=0.027) in the study group compared to the control population. The most common signs were vomiting or regurgitation (60%), pyrexia (24%), weakness (22%), respiratory abnormalities (20%), anorexia (18%), melena (18%) and paraparesis (14%). A caudal esophageal mass was identified by radiography in 53% of the dogs and spondylitis of the thoracic vertebrae in 33%. Fecal flotation was positive for S. lupi eggs in 80% of the dogs, and endoscopy was found to be the most sensitive diagnostic procedure and allowed diagnosis in 100% of the examined dogs. Fifty-three percent of the dogs were anemic and creatine kinase (CK) activities were elevated in 54%. Necropsy of 14 dogs revealed esophageal or gastric granulomas in 13 dogs, and an esophageal osteosarcoma in a single animal. Aortic aneurysms were found in six (43%) dogs. Out of 24, 15 dogs (63%) for which follow-up information was available died or were euthanized within 1 month of admission. The case-fatality rate decreased toward the end of the study period when improved therapy with avermectins became available.

Canine monocytic ehrlichiosis: a retrospective study of 100 cases, and an epidemiological investigation of prognostic indicators for the disease

One hundred cases of monocytic ehrlichiosis diagnosed in Israeli dogs were confirmed by the presence of anti-Ehrlichia canis indirect immunofluorescent antibody titres greater than 1:40. The disease occurred in all age groups and there was no sex predilection. German shepherd dogs were significantly over-represented whereas crossbreed dogs were significantly under-represented (P>0.0005). The most common clinical signs were depression, lethargy, lymphadenomegaly, fever, anorexia, panting, pale mucous membranes and bleeding, of which epistaxis was most common. Thrombocytopenia, anaemia (mainly normocytic normochromic) and lymphopenia were the predominant haematological findings. Forty-nine of the 100 cases were followed up for a year. Thirty-two dogs survived and 17 died. A Cox proportional hazards regression model was used to examine the effect of host, environmental, and haematological prognostic factors on survival. It was concluded that severe anaemia, severe leucopenia, pancytopenia, a tendency to bleed (especially epistaxis) and being a German shepherd dog were important indicators of poor survival in cases of monocytic ehrlichiosis in dogs.

CHARACTERIZATION OF THE SUBCLINICAL PHASE OF CANINE EHRLICHIOSIS IN EXPERIMENTALLY INFECTED BEAGLE DOGS

Beagle dogs were examined during the subclinical phase of canine ehrlichiosis under controlled conditions. Emphasis was placed on gathering data before artificial inoculation with Ehrlichia canis, and comparing these data with those of the subclinical phase of the disease. In this study all dogs were clinically healthy throughout the 6 month examination period. All subclinically infected dogs had IFA antibody titers to E. canis at a dilution varying from 1:2560 to 1:20480. The most prominent haematological finding was mild thrombocytopenia with a concomitant increase in platelet size, seen in eight of the nine dogs examined. Leukocyte counts were statistically significantly reduced in 78% of the dogs, compared with their preinfection values, with 71% of dogs having significantly reduced absolute neutrophil counts. None of the dogs were either leukopenic nor neutropenic. Six of the nine dogs had increased serum gamma-globulin concentrations. No dogs were overtly anemic, although declines in packed cell volume, haemoglobin concentration and total erythrocyte count were detected in an inconsistent manner among the dogs. It was concluded that, the most reliable parameters for judging possible subclinical ehrlichial infection in beagle dogs was mild thrombocytopenia, together with a persistently high antibody titer to E. canis. Hypergammaglobulinemia would increase the suspicion further. Based on the results presented, routine testing of dogs in E. canis endemic areas is recommended in order to identify and treat dogs in the subclinical phase of the disease.

Demonstration of serum antiplatelet antibodies in experimental acute canine ehrlichiosis

This report presents evidence for the presence of antiplatelet antibodies in sera of dogs experimentally infected with Ehrlichia canis, during the acute phase of the disease. Six healthy adult male beagle dogs were inoculated intravenously with blood from a longstanding infected dog with the Israel strain 611 of E. canis. Thrombocytopenia and concurrent increase in mean platelet volume were the most consistent haematological signs of the disease. The dogs developed an antibody titre to E. canis from Day 15 postinoculation. All dogs were antiplatelet antibody negative before inoculation. Twenty-four days postinoculation with E. canis, when the platelet count was at its lowest, antibodies to platelets were demonstrated, in the sera of five of the six dogs.

Comparison of Simultaneous Splenic Sample PCR with Blood Sample PCR for Diagnosis and Treatment of Experimental Ehrlichia canis Infection

ABSTRACT 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.

Serum protein alterations in canine ehrlichiosis

Serum protein electrophoresis was performed in 42 dogs with naturally occurring Ehrlichia canis infection and in 15 clinically healthy dogs (control dogs). The infected dogs were found to have a significant hypoalbuminaemia, hyperglobulinaemia and hypergammaglobulinaemia compared to the control dogs (P < 0.001). A polyclonal gammopathy was found in all but one of the infected dogs which presented a monoclonal gammopathy. alpha-1 globulin was lower while alpha-2 and beta-2 globulin concentrations were significantly higher in the infected dogs (P < 0.0001, P < 0.05 and P < 0.005, respectively). The infected dogs were divided into two subgroups according to haematological parameters, defined as pancytopenic (n = 13) and non-pancytopenic (n = 29). When compared, the pancytopenic group revealed significantly lower concentrations of total protein, total globulin and gammaglobulin (P < 0.01, P < 0.05 and P < 0.005 respectively). The lower concentrations of the gammaglobulins coupled with the pancytopenia suggest that the immune state of the pancytopenic E. canis infected dogs is more compromised, and therefore secondary infections should be expected more frequently in these dogs.

Phylogenetic Analysis of Hemoplasma Species: an International Study

ABSTRACT Nearly complete 16S rRNA gene sequences for feline and canine hemoplasma isolates from Europe, Australia, Africa, and Asia showed almost 100% identity to those previously reported for United States isolates. Partial sequences of the RNA subunit of the RNase P gene were also determined, and RNase P-based phylogenetic analysis showed that the hemoplasmas are most closely related to the members of the Mycoplasma pneumoniae group.