Linda Kidd

Prognostic Factors for Mortality and Thromboembolism in Canine Immune-Mediated Hemolytic Anemia: A Retrospective Study of 72 Dogs

Medical records of 72 dogs diagnosed with immune-mediated hemolytic anemia (IMHA) were reviewed to find risk factors for the disease, for mortality, and for thromboembolism. Coagulation data of 32 patients were evaluated for mortality or thromboembolism risk factors. Cocker Spaniels were at increased risk for IMHA (P = .012). Timing of vaccination was not associated with development of IMHA. PCV ranged from 5 to 33%, with a mean of 16 +/- 5%. Autoagglutination was present in 42% of the dogs. Platelet counts (n = 60) varied from 3,000 to 793,000/microL (mean, 160,117 +/- 133,571; median, 144,000). Thrombocytopenia (platelet count, <200,000/microL) was present in 70% of the dogs, with severe thrombocytopenia (platelet count, <50,000/microL) being present in 22%. One-step prothrombin time (OSPT) was prolonged in 28% of the dogs tested, and activated partial thromboplastin time (APTT) was prolonged in 47% of the dogs tested. Fibrin(ogen) degradation products (FDPs) were detected in 16 of 28 dogs tested (57%). Disseminated intravascular coagulation (DIC) was diagnosed in 10 of 31 (32%) dogs and was suspected in 8 dogs. Thromboemboli were found in 20 of 25 dogs given postmortem examinations. Mortality rate was 58%. Thrombocytopenia (P = .008) and serum bilirubin concentration of >5 mg/dL (P = .015) were risk factors for mortality, and hypoalbuminemia approached significance (P = .053). Severe thrombocytopenia (P = .046), serum bilirubin concentration of >5 mg/dL (P = .038), and hypoalbuminemia (P = .016) were risk factors for thromboembolism. On evaluation of continuous data, decreased platelet count (P = .057), increased bilirubin (P = .062), and decreased albumin (P = .054) approached significance for decreased survival. A higher risk for thrombosis was found with increased alkaline phosphatase (ALKP) (P = .042), increased bilirubin (P = .047), and decreased albumin (P = .012).

Febrile Illness Associated with Rickettsia conorii Infection in Dogs from Sicily

We report serologic and molecular evidence of acute, febrile illness associated with Rickettsia conorii in 3 male Yorkshire terriers from Sicily (Italy).

Insulin Activation of the Phosphatidylinositol 3-Kinase/Protein Kinase B (Akt) Pathway Reduces Lipopolysaccharide-Induced Inflammation in Mice

Insulin is used to control pro-inflammatory hyperglycemia in critically ill patients. However, recent studies suggest that insulin-induced hypoglycemia may negate its beneficial effects in these patients. It is noteworthy that recent evidence indicates that insulin has anti-inflammatory effects that are independent of controlling hyperglycemia. To date, the mechanism by which insulin directly reduces inflammation has not been elucidated. It is well established that insulin activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling in many cell types. We and others have shown that this pathway negatively regulates LPS-induced signaling and pro-inflammatory cytokine production in monocytic cells. We hypothesized that insulin inhibits inflammation during endotoxemia by activation of the PI3K/Akt pathway. We used a nonhyperglycemic mouse model of endotoxemia to determine the effect of continuous administration of a low dose of human insulin on inflammation and survival. It is noteworthy that insulin treatment induced phosphorylation of Akt in muscle and adipose tissues but did not exacerbate lipopolysaccharide (LPS)-induced hypoglycemia. Insulin decreased plasma levels of interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein 1 (MCP1)/JE, and keratinocyte chemoattractant, and decreased mortality. The PI3K inhibitor wortmannin abolished the insulin-mediated activation of Akt and the reduction of chemokine and interleukin-6 levels. We conclude that insulin reduces LPS-induced inflammation in mice in a PI3K/Akt-dependent manner without affecting blood glucose levels.

Prothrombotic mechanisms and anticoagulant therapy in dogs with immune-mediated hemolytic anemia

OBJECTIVE To review the pathophysiology of thrombosis in hemolytic disease, and the efficacy of thromboprophylaxis in dogs with immune-mediated hemolytic anemia (IMHA). DATA SOURCES Computerized searches of Pubmed, INDEX VETERINARIUS, and the journal database of the Veterinary Information Network, and a manual search of bibliographies of published manuscripts. HUMAN DATA SYNTHESIS Experimental data suggest that hemolysis leads to the induction of the potent procoagulant tissue factor on monocytes and endothelial cells and subsequent activation of coagulation. In addition, damaged red cells, activated platelets, and small cell-derived membrane vesicles called microparticles may contribute to coagulation by providing membrane surfaces containing exposed anionic phospholipids that serve as docking sites for prothrombinase (factor Va-factor Xa) and tenase (factor VIIIa-factor IXa) complexes of the coagulation cascade. Some microparticles also contain tissue factor, further fueling coagulation. Thromboprophylaxis for hemolytic disease in people primarily targets the coagulation cascade rather than platelets, as most thromboemboli are of venous rather than arterial origin. The use of unfractionated heparin is closely monitored to ensure therapeutic levels are reached. VETERINARY DATA SYNTHESIS Thromboembolic disease is a major factor affecting survival in dogs with IMHA. It is likely that hemolysis contributes to the prothrombotic state. Thrombosis occurs in both veins and arteries, with pulmonary thromboembolism (a venous thrombus) occurring very commonly. Evidence suggests that tissue factor mediates the development of the prothrombotic state. Heparin, and the anti-platelet agents aspirin, and clopidogrel have been used for thromboprophylaxis in dogs with IMHA. However, a lack of validated therapeutic endpoints and controlled studies make it difficult to determine if survival is affected or if 1 drug is more effective than another. CONCLUSIONS Prospective clinical trials comparing individually adjusted heparin or other anti-coagulant drugs to anti-platelet drugs are needed to make evidence-based recommendations for thromboprophylaxis in dogs with IMHA.

Clinical Presentation of 26 Anaplasma phagocytophilum-Seropositive Dogs Residing in an Endemic Area

Anaplasma (A.) phagocytophilum, the etiological agent of canine granulocytic anaplasmosis, is capable of inciting moderate to severe clinical disease in a variety of mammals and is endemic in the upper midwest. The purpose of this study was fourfold: to describe the range of clinical signs in dogs seropositive to A. phagocytophilum; to examine the prevalence of immune-mediated hemolytic anemia (IMHA) in this population; to evaluate whether specific clinical signs were associated with coexposure to Borrelia (B.) burgdorferi in actively infected dogs; and to determine whether clinical response to doxycycline was complete in treated dogs. Medical records of dogs seropositive for A. phagocytophilum were reviewed retrospectively. Peripheral blood smears were also reviewed retrospectively for granulocytic Anaplasma morulae. Lethargy (81%), inappetence (58%), and lameness (50%) were the most common clinical signs, followed by fever (46%). Thrombocytopenia was the most common laboratory abnormality, and IMHA was diagnosed in three dogs. Dogs that were thrombocytopenic and had antibodies to both A. phagocytophilum and B. burgdorferi had a median platelet count of 51,000/μL (range 20,000 to 171,000/μL), which was significantly lower than the count in dogs with antibodies only to A. phagocytophilum (P=0.04). Some dogs had an apparent relapse of clinical signs after an appropriate course of doxycycline. Testing for A. phagocytophilum by polymerase chain reaction, serum antibody assays, and/or blood smear evaluation should be considered in dogs with IMHA, cough, or epistaxis and that reside in A. phagocytophilum-endemic areas. If moderate to severe thrombocytopenia is present, testing for concurrent B. burgdorferi infection may be warranted.

Canine red blood cell thiopurine S-methyltransferase: companion animal pharmacogenetics.

Thiopurine S-methyltransferase (TPMT) plays an important role in the metabolism of thiopurine drugs. In humans, a common genetic polymorphism for TPMT is a major factor responsible for individual variation in the toxicity and therapeutic efficacy of these drugs. Dogs (Canis familiaris) are also treated with thiopurine drugs and, similar to humans, they display large individual variations in thiopurine toxicity and efficacy. We set out to determine whether dogs might also display genetically determined variation in TPMT activity. As a first step, we observed that canine red blood cell (RBC) TPMT activity in samples from 145 dogs varied over a nine-fold range. That variation was not associated with either the age or sex of the animal. Subsequently, we cloned the canine TPMT cDNA and gene. The canine cDNA encoded a protein that was 81.2% identical to the enzyme encoded by the most common TPMT allele in humans. A genotype-phenotype correlation analysis was performed by resequencing the canine gene using DNA samples from 39 animals selected for high, low or intermediate levels of RBC TPMT activity. We observed nine polymorphisms in these 39 DNA samples, including three insertion/deletion events and six single nucleotide polymorphisms (SNPs), one of which was a nonsynonymous cSNP (Arg97Gln). However, when the variant allozyme at codon 97 was expressed in COS-1 cells, it did not display significant differences in either basal levels of TPMT activity or in substrate kinetics compared with the wild-type allozyme. Six of the nine canine TPMT polymorphisms were associated with 67% of the variation in level of RBC TPMT activity in these 39 blood samples. When those six SNPs were assayed using DNA from all 145 animals studied, 40% of the phenotypic variance in the entire population sample could be explained by these polymorphisms. Therefore, inheritance is a major factor involved in the regulation of variation in RBC TPMT in the dog, just as it is in humans. These observations represent a step towards the application of pharmacogenetic and pharmacogenomic principles to companion animal drug therapy.

Clinical findings and coronary artery disease in dogs and cats with acute and subacute myocardial necrosis: 28 cases.

Records of final diagnoses based on necropsies performed on dogs and cats over a 4.5-year period at a university teaching hospital were examined for the diagnosis of acute or subacute myocardial necrosis. Clinical findings signaling the occurrence of myocardial necrosis were often not specific, due to simultaneously occurring disease processes. However, of 28 animals identified, dyspnea occurred frequently (17/28; 61%) and in some cases in the presence of minimal pulmonary pathology (2/3; 66%) or otherwise unexplained pulmonary edema (4/4; 100%). Elevations in serum aspartate aminotransferase (10/10; 100%) and creatine kinase (5/9; 55%) were also frequent. Disease processes associated with thrombus formation were present for each case in which a coronary artery thrombus occurred (5/28; 18%).

Re-emergence of Babesia conradae and effective treatment of infected dogs with atovaquone and azithromycin

Babesia conradae (B. conradae) causes hemolytic anemia in dogs. This organism has not been reported clinically since it was originally described in southern California in 1991. To date, no anti-protozoal therapies have been associated with clearance of B. conradae. This report describes the use of atovaquone and azithromycin for the treatment of dogs naturally infected with B. conradae and report the re-emergence of B. conradae in southern California. Twelve dogs naturally infected with B. conradae were identified by practicing veterinarians and public health officials in southern California. Treatments consisted of a 10 day course of atovaquone (13.3mg/kg PO q 8h) and azithromycin (10-12.5mg/kg PO q 24h). Four dogs were treated in a randomized blinded placebo-controlled fashion, four additional cases were treated in a non-random, non-blinded fashion and one dog received no treatment. All dogs were tested for B. conradae DNA by polymerase chain reaction (PCR) initially and then once or 3 times post treatment (60-210 days). B. conradae infected dogs that received treatment did not have any detectable Babesia DNA by PCR after treatment. In contrast, dogs receiving placebo had detectable Babesia DNA by PCR throughout the study period. Combination therapy with atovaquone and azithromycin appears to be effective for acute and chronic babesiosis caused by B. conradae.

Thiopurine methyltransferase activity in red blood cells of dogs

Thiopurine methyltransferase (TPMT) is an important enzyme in the metabolism of thiopurine medications such as azathioprine. In humans, activity varies widely among individuals, primarily because of genetic polymorphisms. Low TPMT activity increases the risk of myelosuppression from azathioprine and 6-mercaptopurine, whereas high TPMT activity is associated with poor drug efficacy. The purpose of this study was to determine whether dogs also show a wide range of TPMT activity. Heparinized blood samples were obtained from 177 dogs associated with a veterinary teaching hospital. Red blood cell (RBC) TPMT activity was measured by means of a modification of a radiochemical method as established for use in people. TPMT activity varied across a 9-fold range (7.9-71.8 U of RBC per milliliter; median, 21.7). Variation in TPMT activity was not associated with age, sex, or neutering status. Giant Schnauzers had much lower TPMT activity (7.9-20 U of RBC per milliliter; median, 13.1; P < .001) than did other breeds, and Alaskan Malamutes had much higher TPMT activity (22.7-71.8 U of RBC per milliliter; median, 36.0; P < .001) than did other breeds. Such variations in TPMT activity in the canine population and within groups of related dogs could affect thiopurine drug toxicity and efficacy in canine patients.

Lack of Evidence for Perinatal Transmission of Canine Granulocytic Anaplasmosis From a Bitch to Her Offspring

Granulocytic anaplasmosis is an emerging infectious disease affecting dogs and humans in the United States and other regions of the world. Relatively few cases have been described in pregnant women, and perinatal transmission appears to occur infrequently in humans. Infection in pregnant dogs has not been reported. Diagnosis of infection during pregnancy poses therapeutic challenges, because doxycycline, the treatment of choice, is teratogenic. Also, infection during pregnancy may result in more severe disease. When infection is diagnosed after parturition, knowledge of the risk of perinatal transmission to offspring is important, because prophylactic therapy in neonates is also not without risk. In this report, we describe relatively severe clinical manifestations of Anaplasma phagocytophilum infection in a postpartum bitch and a lack of perinatal transmission to her puppies.