Dog and Heartworm Relationship by Hermione Granger on Prezi
Learn about the veterinary topic of Overview of Heartworm Disease. Dogs. Heartworm (HW) disease is caused by the filarial organism, Dirofilaria immitis. Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, Host- Parasite Interactions*; Humans; Male; Symbiosis; Wolbachia/growth & development. Dog heartworm is a mosquito-transmitted disease with a cosmopolitan . A relationship between pet relinquishment and foreclosures has been .. investigation of the symbiosis responsible for canine heartworm disease.
Thus, a positive antibody test indicates infection by HW larval stages, and possibly HARD, but not necessarily of a mature infection. In conjunction with other provocative findings, antibody seropositivity is useful in making a clinical diagnosis of HW disease in cats, and it certainly identifies cats at risk.
False-positive results from cross-reactivity with other parasites have not been seen. This is because of the relative sizes of the heartworm s and the right heart and pulmonary arterial system of cats. Heartworms, particularly the females, are long enough to occupy the pulmonary arteries as well as the right heart, where they can be easily imaged. Parallel hyperechoic lines, produced by the HW cuticle, may be seen in the right heart and pulmonary arteries. Echocardiography is more important in cats than in dogs because of the increased difficulty of diagnosis in cats low antigen test sensitivity and low antibody test specificity for mature infection and the relatively high sensitivity of the test in experienced hands.
In addition to special diagnostic tests in cats and dogs, a CBC, chemistry profile, urinalysis, and particularly thoracic radiographs are indicated.
Laboratory data are often normal.
Eosinophilia and basophilia alone or together may occur in dirofilariasis. Eosinophilia is most often seen at the time that stage 5 young adult larvae arrive in the pulmonary arteries. Subsequently, eosinophil counts vary but are usually high in dogs with immune-mediated occult infections, especially if eosinophilic pneumonitis develops Hyperglobulinemia due to antigenic stimulation may be present in dogs and cats. Serum ALT and alkaline phosphatase are occasionally increased but do not correlate well with abnormal liver function, efficacy of adulticide treatment, or risk of drug toxicity.
Urinalysis may reveal proteinuria that can be quantitated by a urine protein: Occasionally, severe glomerulonephritis can lead to hypoalbuminemia and nephrotic syndrome.
Dogs with hypoalbuminemia, secondary to glomerular disease, also lose antithrombin III and are at risk of thromboembolic disease. Hemoglobinuria is associated with caval syndrome and occurs when RBCs are lysed in the circulation. In dogs, thoracic radiography provides the most information on disease severity and is a necessary screening tool to assess the clinical status of dogs with dirofilariasis, particularly when symptomatic.
High-risk infections are characterized by a large main pulmonary artery segment and dilated, tortuous caudal lobar pulmonary arteries.
Right ventricular enlargement may also be seen and, along with enlarged pulmonary arteries, is indicative of pulmonary hypertension. With pulmonary thromboembolism and pulmonary infiltrate with eosinophils pneumonitisill-defined parenchymal infiltrates surround the caudal lobar arteries, typically most severe in the right caudal lobe.
In cats, cardiac changes and pulmonary hypertension are less common. Patchy parenchymal infiltrates may also be present in cats with respiratory signs.
The main pulmonary artery segment usually is not visible because of its relatively midline location. In ferrets, the diagnosis is less readily made with thoracic radiographs, because only the right ventricle tends to be enlarged. However, the commercial antigen tests have detected HW antigen experimentally, as early as 5 mo after infection, and have been shown to be effective in clinical situations.
Heartworm Pathophysiology in Dogs and Cats - WSAVA - VIN
False-negative results may occur, especially in species that harbor lower worm burdens cats and ferrets. Furthermore, although microfilaria testing is only rarely helpful, adult worms can often be seen with echocardiography and nonselective angiography. The extent of the preadulticide evaluation varies, depending on the clinical status of the dog, the likelihood of coexisting diseases that may affect the outcome of treatment, the owner's ability to restrict the dog's exercise, and cost considerations.
Clinical laboratory data should be collected selectively to complement information obtained from a thorough history, physical examination, antigen test, and thoracic radiography. Two important variables known to directly influence the probability of thromboembolic complications after adulticide treatment and the outcome of treatment are the extent of concurrent pulmonary vascular disease and the current worm burden.
Assessment of cardiopulmonary status is indispensable for evaluating a dog's prognosis. Pulmonary thromboembolic complications after adulticide treatment are most likely to occur in heavily infected dogs already exhibiting clinical and radiographic signs of severe pulmonary vascular disease, especially when severe pulmonary hypertension and CHF are present.
Heartworm disease in animals and humans.
Before adulticide therapy, HW-infected dogs are assessed and rated for risk of postadulticide thromboembolism. Dogs can be categorized as follows: Dogs in the low-risk category would ideally fulfill the following conditions: The low-risk group would also include dogs having previously undergone adulticidal therapy but that remain antigen positive.
Dogs with near-normal thoracic radiographs may develop severe thromboembolic disease, occurring most often when exercise is not restricted. Dogs at high risk of thromboembolic complications include those with signs related to HW infection eg, coughing, dyspnea, ascitesabnormal thoracic radiographs, high level of circulating antigen, worms visualized by echocardiography, concurrent disease, and little or no possibility that the owners will restrict exercise.
The only approved heartworm adulticide is melarsomine dihydrochloride, which is variably effective against mature adult and immature heartworms of both sexes, with male worms being more susceptible. Melarsomine is given at 2.
Pressure at the injection site is applied and maintained for 5 min to prevent drug migration. Approximately one-third of dogs will exhibit local pain, swelling, soreness with movement, or sterile abscessation at the injection site.
Local fibrosis is not uncommon and is the reason for targeting the belly of the epaxial musculature. The graphic shows that heartworm is most prominent in the lower Mississippi River Valley and nearly absent in Northern Montana.
This map was generated using annualized data no seasonal features were considered. The results represent the prevalence of positive tests for circulating heartworm antigen over a full year amongst a population of dogs that are visiting a veterinarian and receiving care that includes at the least a test for heartworm infection.
The proportion of positive heartworm tests was computed for each county in the contiguous 48 states.
Proportions are analyzed in preference to total positive test counts as the number of positive tests can be influenced by local testing practices. These proportions were then spatially smoothed via a procedure known as the head-banging algorithm and grouped into nine probabilistic categories.
The methods account for the varying number of tests made in different counties; for example, ten positive tests in a sample of size one hundred statistically suggests more of a problem than one positive test in ten, although the sample infection proportions are the same. The map will be updated in future years as additional data become available. While this map quantifies the baseline heartworm infection rates for US counties, it is desirable to understand what factors explain heartworm risk.
Our immediate goal was to assemble a list of factors, which are available and quantifiable, that may influence canine heartworm infection rates.