Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.
Issue link: http://todaysveterinarypractice.epubxp.com/i/38074
| DIAGNOSIS OF CANINE HEARTWORM INFECTION phologic diagnosis by 2 diagnostic laboratories.11 Molecular speciation identified microfilaria from sever- al samples as D immitis, differ- ing from an original morphologic diagnosis as Acanthocheilonema (Dipetalonema) reconditum. Currently, the clinical relevance of PCR testing for CHW is low because it is not available through large com- mercial laboratories. Imaging Ultrasound and radiology can be useful tools for diagnosing and staging CHW disease. Radiographic findings in a heartworm positive dog can be variable due to several factors such as: UÊ in}ÌhÊovÊinviVÌionÊ>n`ÊVoÀÀiëon`- ing disease progression UÊ-iâiÊ ovÊ ÌhiÊ «o«Õl>ÌionÊ ovÊ ÜoÀmÃÊ present UÊ7oÀmÊloV>ÌionÊinÊÌhiÊV>À`io«Õlmo- nary system.12 nÊ>nÊ>nim>lÊÜiÌhÊÀiVinÌÊ 7ÊinviV- Figure 3. Ventrodorsal thoracic radiograph from a 6-year-old neutered male pug that was presented for labored breathing. The patient spent the last 3 years in Louisiana and had not been receiving heartworm preventive. The ventrodorsal thoracic radiograph revealed blunted, enlarged, and tortuous pulmonary arteries (large arrows) and an enlarged pulmonary trunk (small arrows). These radiographic findings are consistent with heartworm disease. tion, there may be no radiographic Vh>n}iÃÊ«ÀiÃinÌÆÊhoÜiÛiÀ]Ê>ÃÊÌhiÊ`ÕÀ>- tion of infection increases, common changes include (Figure 3): UÊ,i}hÌÊÛinÌÀiVÕl>ÀÊinl>À}iminÌ UÊ*Õlmon>ÀÞÊÛ>ÃVÕl>ÌÕÀiÊ`il>Ìion UÊ*>ÀinVhÞm>lÊlÕn}ÊinvilÌÀ>ÌiÃ°Ê nÊ`o}ÃÊÜiÌhÊÃiÛiÀiÊ`iÃi>Ãi]ÊÌhiÊ«Õl- monary arteries can appear tortuous or have nodular opacities. Hepatomegaly and pleural effusion may also be seen radiographically if the progression of the CHW infection leads to right-sided heart failure.12 On ultrasound, adult worms can appear as parallel hyperechoic lines present in the pulmonary artery and occasionally in the right ventricle (Figure 4). Echocardiography can also be a useful tool in detecting the extent of right heart enlargement and functional impairment due to CHW infection.4,13 The presence of worms in the orifice of the tricuspid valve in dogs with hemoglobinuria is indica- tive of caval syndrome.4 Figure 4. B-mode echocardiogram obtained in the left parasternal approach during diastole. The right ventricular wall (RVWd), right ventricle (RVd), and interventricular septum (IVSd) are identified. The heartworms (arrow) are identified in the right atrium (RAd). 34 Today’s Veterinary Practice July/August 2011 EVALUATION OF CHW ANTIGEN TESTS Given that in-clinic antigen assays are now the primary method for detecting CHW infection in dogs, it is im«oÀÌ>nÌÊ ÌoÊknoÜÊhoÜÊÜillÊVÕÀÀinÌÊ