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- Author or Editor: Yoshihide Sasaki x
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Abstract
Objective—To compare the mechanisms of heartworm (HW) extract-induced shock and endotoxininduced shock in dogs by determination of serum tumor necrosis factor (TNF) concentrations.
Animals—11 mixed-breed dogs (7 without and 4 with HW infections).
Procedure—Eight dogs were treated with 2 ml of HW extract IV, and 3 dogs were given endotoxin (Escherichia colili popolysaccharide [LPS]) at 40 or 400 μg/kg of body weight, IV. Changes in clinical and hematologic findings and serum TNF concentrations were examined from before treatment to 120 minutes after treatment in dogs given HW extract or from before treatment to 180 minutes after treatment in dogs given LPS. Tumor necrosis factor concentration was determined by cytotoxic assay, using WEHI-164 murine sarcoma cells, and plasma endotoxin concentration was determined in 2 dogs treated with HW extract, using the endotoxin-specific chromogenic test.
Results—Eight dogs developed shock 3 to 16 minutes after HW extract treatment. Rectal temperature did not change during examination. Serum TNF concentration was detected at a low concentration only 60 and 120 minutes after HW extract treatment, and plasma endotoxin was not detected during examination. In dogs treated with LPS, rectal temperature increased to > 40 C in 2 of 3 dogs, and serum TNF concentration began to increase 30 minutes after LPS treatment, reaching a maximum concentration by 60 minutes.
Conclusions—The cause and mechanism of HW extract-induced shock may be different from those of endotoxin-induced shock, because TNF, which was a pivotal mediator in endotoxin-induced shock, increased minimally in serum of dogs treated with HW extract. (Am J Vet Res 2001;62:765–769)
Abstract
Objective
To examine pathologic findings in dogs with shock induced by IV administration of heartworm (HW) extract.
Animals
22 mixed-breed adult dogs.
Procedures
Heartworm extract was administered IV, and pathologic changes in dogs that died or were euthanatized at 24 hours were examined.
Results
The most severe lesions observed during initial collapse were centralobular congestion in the liver, hemorrhage and edema in the gallbladder wall, and congestion and hemorrhage in mucous membranes of the gastrointestinal tract. These findings disappeared with recovery from collapse. Hyalinization of venous walls of the liver and cardiac muscle were observed in dogs that died during initial collapse. Focal coagulation necrosis in hepatic cells was seen in dogs that were euthanatized at 24 hours. One dog with profuse bloody diarrhea that died during secondary collapse had severe hemorrhage in mucous membranes of the large intestine.
Conclusion
Heartworm extract appeared to contain some substances constricting hepatosplanchnic vessels and some toxic substances that injured the smooth muscle of venous walls, cardiac muscle, and hepatic cells directly or indirectly.
Clinical Relevance
The shock-inducing substances in HW extract may have an important role in the pathophysiologic mechanism of HW disease, and investigation of them may contribute to prevention of the shock reaction attributable to microfilaricide and adulticide use. (Am J Vet Res 1998;59:1417–1422)
Abstract
Objective—To determine whether heartworm (HW) extract-induced shock in dogs is consistent with anaphylactic shock by examining the role of histamine.
Animals—6 mixed-breed dogs (3 without and 3 with HW infections) and 4 specific pathogen-free (SPF) Beagles.
Procedure—Four experiments were performed as follows: 1) 6 mixed-breed dogs were treated IV with 2 ml of HW extract, and plasma histamine concentrations were determined; 2) 4 SPF dogs were treated IV with 2 ml of HW extract and examined for shock; 3) sera from 6 dogs of experiment 1 and from 4 SPF dogs of experiment 2 that were obtained before HW extract treatment were tested for heterologous passive cutaneous anaphylaxis (PCA), using rabbits during a sensitization period of 48 to 72 hours; and 4) mast cell degranulation by HW extract was tested, using rat mesentery and canine cultured mast cells.
Results—Experiment 1: 6 dogs developed shock, and plasma histamine concentrations increased significantly from 0.3 ± 0.2 (mean ± SD) ng/ml before HW extract treatment to 44.6 ± 68.9 ng/ml at the onset of shock; experiment 2: all SPF dogs developed shock and had an increase in plasma histamine concentrations; experiment 3: sera from mixed-breed dogs without HW infection and from SPF dogs had negative PCA reactions; experiment 4: HW extract degranulated rat mesentery mast cells and released histamine directly from canine mast cells.
Conclusions and Clinical Relevance—Results of our study indicate that an unknown mast cell-degranulating substances contained in HW extract may degranulate mast cells directly, consequently releasing histamine that may participate in the onset of shock in HW extract-induced shock in dogs. (Am J Vet Res 2001;62:770–774)
Objective
To compare results of laboratory tests in dogs with vena caval syndrome before and after surgical removal of heartworms.
Design
Longitudinal uncontrolled clinical trial.
Animals
51 dogs with vena caval syndrome.
Procedure
Heartworms were removed from the area of the tricuspid valve and pulmonary arteries via venotomy and by use of flexible alligator forceps. Blood samples were obtained before and 10 days after removal of heartworms. Red and white blood cell counts were determined, using an automated cell counter. Biochemical tests were performed, using a dry chemical method.
Results
45 dogs survived the procedure, and 6 died or were euthanatized after surgical treatment. After surgery, RBC count and total protein, albumin, calcium, and sodium concentrations increased, and total bilirubin, ammonia, BUN, creatinine, uric acid, and potassium concentrations decreased in dogs that survived. Creatine kinase, L-lactate dehydrogenase, and amylase activities decreased, whereas alkaline phosphatase and ɣ-glutamyltransferase activities and total cholesterol concentration increased. Alanine transaminase activity decreased in 27 dogs but increased in 3 dogs. Changes in test results in dogs that did not survive were similar to those in dogs that did survive. Significant differences were found in RBC count, ɣ-glutamyltransferase activity, and total protein, total cholesterol, BUN, and total bilirubin concentrations before and after removal of heartworms.
Clinical Implications
Hepatic and renal functions improve rapidly after surgical removal of heartworms, presumably because general and pulmonary circulation is normalized. However, cholestasis may develop, and dogs that survive may need additional treatment to preserve hepatic function. (J Am Vet Med Assoc 1998;213:1134-1136)
