Effect of heartworm disease and heartworm-associated respiratory disease (HARD) on the right ventricle of cats

Spontaneous pneumothorax in a dog with a history of successfully treated heartworm disease: A case report

OBJECTIVE

To describe a dog presented with spontaneous pneumothorax secondary to chronic pulmonary changes associated with a history of resolved canine heartworm disease.

CASE OR SERIES SUMMARY

A 7-year-old 25.2kg female spayed German Shepherd mix was presented for management of spontaneous pneumothorax. The dog had a history of heartworm disease that underwent therapy prior to adoption, and the dog was heartworm antigen negative (SNAP 4Dx) during hospitalization for the pneumothorax. An exploratory thoracotomy was performed due to an unresolving pneumothorax requiring multiple thoracocenteses. Perioperatively, the lungs did not expand with positive pressure ventilation and diffuse, multifocal to coalescing areas of darkened tissue that were grossly consistent with necrosis and/or hemorrhage were noted. The dog was euthanized intraoperatively due to an assumed poor prognosis. Histopathologic examination findings were consistent with chronic reactive changes related to previous heartworm infection. No neoplastic or infectious etiologies were identified.

NEW OR UNIQUE INFORMATION PROVIDED

Spontaneous pneumothorax is a known complication of active heartworm infection. However, this case represents the first report of spontaneous pneumothorax secondary to chronic pulmonary changes caused by resolved heartworm infection.

Occurrence of Dirofilaria immitis infection in shelter cats in the lower Rio Grande Valley region in South Texas, United States, using integrated diagnostic approaches

Dirofilaria immitis is a mosquito-borne filarioid nematode that affects dogs and cats. Although heartworm infections in cats can be fatal, it is commonly neglected by cat owners and veterinarians. Moreover, diagnosing heartworm infection in cats can be challenging, requiring the integration of multiple laboratorial tests and clinical examination. The objective of this study was to estimate the occurrence of D. immitis infection in shelter cats in the Lower Rio Grande Valley (RGV) region of Texas using a combination of immunodiagnostic and molecular methods. The RGV has a large population of stray animals with limited access to veterinary care. One hundred and twenty-two paired samples of serum and DNA extracted from the blood clots of cats from 14 towns in this region were analyzed. Serum samples were used for heartworm antibody detection (Heska® Solo Step®), and heartworm antigen detection using a commercial ELISA kit (DiroCHEK®) pre- and post-immune-complex dissociation (ICD) via heat treatment. A species-specific probe-based qPCR assay targeting a fragment of the cytochrome oxidase c subunit 1 of the mitochondrial DNA was utilized to detect the presence of parasite DNA. Twenty-two cats (18%) were positive in at least one diagnostic test. Antibody testing detected most cases (19/122; 15.6%); pre- and post-ICD antigen testing detected 6 cases (6/122; 4.9%); and qPCR detected the fewest cases (4/122; 3.3%), with 2 cats positive on all three diagnostic tests. Veterinarians should encourage local cat owners to utilize year-round heartworm prevention.

Feline pulmonary hypertension: are we overlooking an important comorbidity?

Pulmonary hypertension (PH) is a potential complication in many disease states, yet it has been largely overlooked in feline medicine. Recently, increased awareness of potential underlying causes has led to a wider understanding of the disease process in humans, with a focus on tailoring therapy to include specific treatment of the underlying etiology. Most of these treatments are not yet available in veterinary medicine, but as they move from the human to the veterinary field, it would be beneficial to better understand the forms of PH encountered in different species. Recently, diagnosis and classification of PH in dogs has been the focus of an American College of Veterinary Internal Medicine consensus statement, yet this condition has received little attention in cats. It is therefore our intention to raise awareness of this condition in cats and to propose a classification system for the types of PH seen in feline patients. As new medications are developed for the treatment of PH, it is important to recognize which forms of PH are seen in feline patients and understand the etiology of the disease. There are many reports of PH (or suspected PH based on echocardiographic assessment) in cats. In this review, we highlight the large number of conditions, and different etiologies, that are associated with PH. Improving understanding of this condition will bring us closer to being able to investigate the benefits of potential new diagnostics and therapies as they become available.

Fatal Pulmonary Hypertension and Right-Sided Congestive Heart Failure in a Kitten Infected with Aelurostrongylus abstrusus

Simple Summary

Infections caused by lungworms are an emerging issue in feline medicine. Clinical features in cats may vary from subclinical infections to a severe disease, occasionally including fatal pneumonia, depending on different factors, e.g., lungworm species, parasitic burden, and age of the animal. A case of infection caused by Aelurostrongylus abstrusus in a domestic kitten presenting acute dyspnoea and ascites is presented here. Clinical, radiological, echocardiographic, parasitological, molecular, and pathological data are described. This is the first report of life-threatening pulmonary hypertension inducing congestive heart failure caused by A. abstrusus infection in a domestic kitten.

Abstract

Aelurostrongylus abstrusus is considered the most important respiratory nematode of domestic cats worldwide. This parasite inhabits the alveoli, alveolar ducts, and bronchioles and causes a subacute to chronic respiratory clinical disease. Clinical signs may occur in domestic cats of any age, though they are more often described in young animals. Physical examination, echocardiography, thoracic radiography, pulmonary and cardiac pathological findings, classical, and molecular parasitological analysis of a six-month-old kitten referred at the Veterinary Teaching Hospital of the University of Pisa (Italy) led to a diagnosis of parasitic bronchopneumonia caused by A. abstrusus, which was complicated by severe pulmonary hypertension (PH) and right-sided congestive heart failure (R-CHF) that caused the death of the animal. Cases of reversible PH associated with A. abstrusus infection have been seldom reported in cats. This is the first report of fatal PH and R-CHF in a kitten with clinical aelurostrongylosis.

Heartworm prevalence in dogs versus cats: Multiple diagnostic modalities provide new insights

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Prevalence of adult heartworm (HW) infection was 4 % in cats and 28 % in dogs.

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Combining antigen and antibody testing led to an overall 19 % positive cats.

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Prevalence did not differ between dogs and cats with added feline antibody testing.

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Dirofilaria repens microfilariae were identified in one dog and one cat.

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Acanthocheilonema reconditum microfilariae were identified in four dogs.

The cornerstones of diagnosis of heartworm (HW) in dogs are the detection of circulating antigen from adult female Dirofilaria immitis or the visualization of microfilariae in whole blood. These tests are less sensitive in cats because of the feline immune response leading to low numbers of adult worms, but heartworm antibody tests are also licensed for use in cats. HW antibodies in cats are detectable when there has at least been larval development in the tissues, but positive antibody tests cannot distinguish between current and previous larval infections; thus, cats with positive antibody test results are considered currently or previously infected with D. immitis. The aim of the present study was to use multiple HW diagnostic modalities to maximize detection of infection in dogs and cats at high risk of infection and to compare infection prevalence between these two hosts. Blood samples collected from 100 stray dogs and 100 stray cats at Florida animal shelters were tested for HW antigen (before and after heat treatment) and microfilariae; cats were also tested for HW antibody. Dogs were significantly (P = 0.0001) more likely to be diagnosed with adult HW infection (28 %; 95 % CI: 20.1–37.6%) when compared with cats (4 %; 95 % CI: 1.6–10.2%) on the basis of positive antigen and microfilariae test results. Cats with current or previous adult, immature adult, or larval HW infections comprised 19 % (95 % CI: 12.4%–27.9%) of the feline population, which was not significantly different (P = 0.1) from the prevalence of adult D. immitis infection in dogs. Testing unprotected cats for heartworm antibodies demonstrated a similar, high risk of infection to the matched unprotected dog population in Florida, which supports the use of HW preventives in cats in areas where HW transmission occurs.

Doppler-derived echocardiographic evidence of pulmonary hypertension in cats with left-sided congestive heart failure

INTRODUCTION

Pulmonary hypertension (PH) caused by left-sided congestive heart failure (L-CHF) is common in dogs and contributes to clinical signs and outcome. The aim of this study was to evaluate the prevalence of Doppler echocardiography-derived PH in a population of cats with L-CHF.

ANIMALS

The study involved 131 cats with L-CHF and 56 control cats.

METHODS

The study design is retrospective, observational study. Tricuspid regurgitation velocity, right atrial dimension, right ventricular (RV) dimension and function, RV wall thickness, pulmonary artery (PA) dimension, Doppler-derived systolic time intervals of PA flow, and presence of septal flattening were evaluated. Pulmonary hypertension was considered if tricuspid regurgitation velocity was >2.7 m/s.

RESULTS

Tricuspid regurgitation was present in 57/131 (44%) of cats with L-CHF and 24/56 (43%) in control cats based on color flow Doppler. Doppler-derived of PH was identified in 22/131 cats with L-CHF (17%). In 15/22 cats, PH was associated with cardiomyopathy, in 5/22 cases with congenital heart disease, and in 2/22 cases with other causes. Cats with Doppler-derived PH more often had chronic L-CHF, as opposed to acute L-CHF (p<0.05). All cats with Doppler-derived PH had subjectively-assessed right-sided heart enlargement, with larger right atrial and RV diameters (p<0.001), increased RV wall thickness (p<0.05), and higher prevalence of septal flattening (<0.001) and PA enlargement (p<0.05).

CONCLUSIONS

Pulmonary hypertension identified by Doppler echocardiography is not a common finding in cats with L-CHF. Right-sided heart enlargement, more frequently observed, may raise the suspicion of PH in cats with L-CHF.