Feline asthma and heartworm disease: Clinical features, diagnostics and therapeutics

Dirofilaria immitis in Italian Cats and the Risk of Exposure by Aedes albopictus

Background: Dirofilaria immitis, the agent of canine and feline heartworm disease (HWD), is a widespread mosquito-borne helminth. The true prevalence of HW infection in cats is likely underestimated due to the difficulty in establishing a definitive diagnosis. Aedes albopictus, a recognized competent vector for D. immitis, is currently considered the most invasive mosquito species worldwide and Italy presents the highest abundance of Ae. albopictus in Europe. Materials and Methods: The present study was aimed at evaluating the current seroprevalence of D. immitis antibodies in cats in Italy. Further, the ecological niche model (ENM) was applied to evaluate the potential future risk of feline HWD associated with the presence of Ae. albopictus. Results: Sera of 812 Italian cats were analyzed, and the average prevalence of D. immitis antibodies was 12%. Seropositivity was significantly associated with age (<6 years), whereas there was no association with sex or geographical area. Data obtained with the risk map showed that the highest risk of infection was found in northern inland areas and along coastal areas, whereas the lowest risk was identified at higher altitudes. The ENM correctly classified most of the areas where D. immitis seropositive cats were found, with 80.4% occurring in high and very high-risk areas. Conclusions: Results of the present study suggest that cats in Italy are exposed to D. immitis infection, and that routine prevention should be part of the general health care protocols in cats. Moreover, the resulting risk maps indicate that areas with a suitable habitat for Ae. albopictus may put cats at risk of exposure to D. immitis.

Breathe easy: inhalational therapy for feline inflammatory airway disease

PRACTICAL RELEVANCE

Feline inflammatory airway diseases, including (but not limited to) asthma, chronic bronchitis and bronchiectasis, are common and incurable disorders. These diseases require lifelong therapy and may result in substantial morbidity and, in some cases, mortality. Goals of therapy include reduction or resolution of clinical signs and the underlying pathologic processes driving those clinical signs. Inhalational therapy has the advantage of topical delivery of drugs to target tissues at higher doses with fewer systemic effects than oral medications. There are multiple options for delivery devices, and proper selection and training on the use of these devices - including acclimation of the cat to the device - can maximize therapeutic efficacy.

AIM

As inhalational therapy is uncommonly used by many veterinarians and owners, this review article provides a foundation on the selection and use of devices and inhalant medications for specific feline inflammatory airway diseases. Cats present a unique challenge with respect to the use of inhalers, and easy-to-follow steps on acclimating them to the devices are provided. The review also discusses the mechanics of inhalational therapy and helps clarify why certain medications, such as albuterol (salbutamol), fluticasone or budesonide, are chosen for certain diseases. The ultimate aim is that the practitioner should feel more comfortable managing common airway diseases in cats.

EVIDENCE BASE

In compiling their review, the authors searched the veterinary literature for articles in English that discuss inhalational therapy in cats, and which focus primarily on inhaled glucocorticoids and bronchodilators. While most literature on inhalational therapy in cats is based on experimental feline asthma models, there are some studies demonstrating successful treatment in cats with naturally occurring inflammatory airway disease.

A nationwide serological survey for Dirofilaria immitis in companion cats in the United States of America: 3.5% antibody and 0.3% antigen positivity

BACKGROUND

Feline heartworm disease (HWD) is a complex and often misdiagnosed disease in cats, caused by the filarial nematode Dirofilaria immitis. Despite its significant impact, studies reporting the prevalence of D. immitis in apparently healthy pet cats in the USA are lacking.

METHODS

To investigate feline heartworm seroprevalence in apparently healthy pet cats in the USA, serum samples (n = 2165) collected from cats across 47 states and Washington District of Columbia were analyzed for D. immitis antibody (Heska Corp.) and antigen (DiroCHEK®; Zoetis Inc.) with and without acid treatment of the samples.

RESULTS

Antibodies to D. immitis antibodies were identified in 3.5% (76/2165) of cats from 26 states, with a significantly higher prevalence in cats from the westernmost US states (West region; 5.4%, 23/429) compared to those from the South (3.8%, 32/847), Midwest (2.7%, 9/338) and Northeast regions (2.2%, 12/551) (P < 0.04). Antigen from D. immitis was detected in 0.3% (6/2165) of cats, which was significantly lower than the antibody detection (P < 10-4), and no samples were positive for both antibody and antigen.

CONCLUSIONS

This is the largest antibody-based, nationwide serosurvey of feline heartworm in an apparently healthy cat population, and the results suggest that cats in the USA have a high risk of exposure to D. immitis-infected mosquitoes. The high nationwide prevalence (3.5%) indicates that the true prevalence of cats infected with D. immitis in the USA may be significantly underestimated. Our findings emphasize the need for increased awareness and routine testing of cats for heartworm infection, especially in non-endemic areas of the USA. Clinicians should consider appropriate use of broad-spectrum veterinary-approved parasiticides and lifestyle management in feline patients to reduce the risk of infection. Future studies should focus on evaluating the D. immitis infection status in healthy cats and developing better diagnostic assays to detect this complex infection.

Feline heartworm disease and environmental allergens hypersensitivity: is there a link?

BACKGROUND

Cats can be infected by Dirofilaria immitis, the causative agent of heartworm disease, characterized by respiratory signs, airway hyperreactivity, remodelling and inflammation. Allergy is a multifactorial pathology, and the role of a number of helminth parasites in the development of allergies in humans and other species has been demonstrated in many studies. The aim of the present study was to verify whether cats seropositive for D. immitis present hypersensitivity to some environmental allergens.

METHODS

Blood samples were collected from 120 cats and tested for the presence of specific immunoglobulin G antibodies against D. immitis and for hypersensitivity to 20 allergens, using commercial allergen test kits.

RESULTS

Of the 120 cats tested, 72 (60.0%) were seropositive for anti-D. immitis IgG and 55 (45.8%) showed clinical signs of heartworm disease of a respiratory nature. The results of testing with the allergen kits showed that 50.8% of cats were seropositive for ≥ 1 allergens, with the most common allergens being Dermatophagoides farinae (25.8%), Dermatophagoides pteronyssinus (20.0%), Malassezia (17.5%) and Ctenocephalides felis (14.2%). The prevalence of allergies was significantly higher-by almost threefold-in cats seropositive for D. immitis (68.1% vs. 25%). There were no significant differences between the prevalence of allergic cats and presence/absence of symptoms, and the results confirmed that symptoms were not a decisive factor for the presence of allergies. The risk for developing allergies was 6.3-fold higher in cats seropositive for D. immitis than in cats that were seronegative, confirming that seropositivity for D. immitis is a risk factor.

CONCLUSIONS

Cats with confirmed heartworm can develop serious respiratory signs, potentially leading to progression to permanent lung injury and predisposing cats to hyperresponsive airway disease. Previous studies have shown that seropositivity for D. immitis and Wolbachia is related to the presence of bronchoconstriction and bronchospasm in the affected cat. The results support the suspicion that contact with D. immitis may be a risk factor for the presence of allergies.

Comparison of the respiratory bacterial microbiome in cats with feline asthma and chronic bronchitis

Objectives

While feline chronic bronchitis (CB) is known as neutrophilic bronchial inflammation (NI), feline asthma (FA) is defined as an eosinophilic airway inflammation (EI). Feline chronic bronchial disease refers to both syndromes, with similar clinical presentations and applied treatment strategies. Recent studies described alterations of the microbiota composition in cats with FA, but little is known about the comparison of the lung microbiota between different types of feline bronchial disease. The study aimed to describe the bacterial microbiota of the lower respiratory tracts of cats with FA and CB and to identify potential differences.

Methods

Twenty-two client-owned cats with FA (n = 15) or CB (n = 7) confirmed via bronchoalveolar-lavage (BALF)-cytology were included. Next-generation sequencing analysis of 16S rRNA genes was performed on bacterial DNA derived from BALF samples. QIIME was used to compare microbial composition and diversity between groups.

Results

Evenness and alpha-diversity-indices did not significantly differ between cats with FA and CB (Shannon p = 0.084, Chao 1 p = 0.698, observed ASVs p = 0.944). Based on a PERMANOVA analysis, no significant differences were observed in microbial composition between animals of both groups (Bray-Curtis metric, R-value 0.086, p = 0.785; unweighted UniFrac metric, R-value −0.089, p = 0.799; weighted Unifrac metric, R-value −0.072, p = 0.823). Regarding taxonomic composition, significant differences were detected for Actinobacteria on the phylum level (p = 0.026), Mycoplasma spp. (p = 0.048), and Acinetobacteria (p = 0.049) on the genus level between cats with FA and CB, with generally strong interindividual differences seen. There was a significant difference in the duration of clinical signs before diagnosis in animals dominated by Bacteriodetes (median 12 months, range 2–58 months) compared to animals dominated by Proteobacteria (median 1 month, range 1 day to 18 months; p = 0.003).

Conclusions and relevance

Lung microbiota composition is very similar in cat populations with spontaneous FA and CB besides small differences in some bacterial groups. However, with disease progression, the lung microbiome of cats with both diseases appears to shift away from dominantly Proteobacteria to a pattern more dominated by Bacteriodetes. A substantial proportion of cats tested positive for Mycoplasma spp. via sequencing, while none of them tested positive using classical PCR.

Bacterial Contamination of Inhalation Chambers Used for Cats and Dogs with Chronic Airway Diseases

Inhalation chambers (ICs) are regularly used in veterinary medicine for the inhalative treatment of chronic respiratory diseases in dogs and cats. Since therapy is usually required lifelong and daily, devices are frequently in use. The aim of this study was to identify bacterial contamination of ICs used for cats and dogs in relation to the applied cleaning measures. Swabs from ICs of 66 cats and 19 dogs with chronic airway diseases were obtained using a standardized protocol and subsequently cultured. A questionnaire was completed by the pet owners regarding the history of their pet's illness and applied device cleaning measures. Overall, 64% (54/86) of the ICs were found to be contaminated; the mask was significantly (p < 0.001) more often contaminated than other device parts. Most cultured bacteria were environmental contaminants; however, some harbored pathogenic potential. Cleaning frequency and method did not significantly influence the presence of contamination. Bacterial contamination of ICs, used for cats and dogs, is common but is not significantly influenced by the type or frequency of cleaning. To avoid potential infection by opportunistic bacteria, the instruction of pet owners regarding the maintenance of the ICs is recommended.

Online survey to determine client perceptions of feline chronic lower airway disease management: response to therapy, side effects and challenges encountered

OBJECTIVES

The first aim of this survey was to report client experiences associated with the administration of common medications, particularly glucocorticoids and bronchodilators, in managing cats with feline lower airway disease (FLAD). The second aim was to ascertain client perception of response to treatment and level of satisfaction.

METHODS

This was a prospective cross-sectional study. An online survey was distributed worldwide to cat owners caring for cats with a chronic cough. Only cats reported to have FLAD were included.

RESULTS

A total of 153 complete responses describing cats with FLAD were analyzed. Glucocorticoids and bronchodilators were the predominantly prescribed therapeutics for 140/153 (92%) and 80/153 (52%) of FLAD cats, respectively. Oral and inhalant administration routes were reported most commonly: glucocorticoids (64% oral and 75% inhalant) and bronchodilators (21% oral and 88% inhalant). A review of how air quality could be improved was conducted for 54% of cats. Almost half (43%) of owners reported adverse effects secondary to glucocorticoid administration, the most frequent being polyphagia (26%) and polydipsia (21%). Only 10% of owners reported bronchodilator-associated side effects, with restlessness (9%) being the most common. Difficulties giving glucocorticoid or bronchodilator tablets orally were reported for 33% and 71% of owners, respectively. Glucocorticoid or bronchodilator inhalant therapies were difficult to administer for 28% and 31% of owners, respectively. Frequency and severity of coughing were significantly lower after at least 2 months of treatment, with median numerical input on a slider scale (0-100) of 48 and 42 before, and 10 and 7 after treatment, respectively (P <0.0001). Median numerical input of owner satisfaction was 83%.

CONCLUSIONS AND RELEVANCE

Despite significant improvements in client-reported responses to treatment, challenges associated with the administration of medications and their adverse effects still exist. Promoting awareness of client experiences can facilitate appropriate follow-up, guidance and empathy to further optimize outcomes.

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.

Association between feline hyperthyroidism and thoracic radiographic evaluation of cardiomegaly and pulmonary hyperinflation

OBJECTIVES

Hyperthyroidism frequently affects middle-to-older-aged cats that can present with cardiorespiratory signs. The effects of hyperthyroidism on cardiac size and function have been previously documented. Anecdotally, pulmonary hyperinflation identified on thoracic radiographs may also be associated with hyperthyroidism; however, there is no literature to support this claim. The goal of this study was to determine any association between hyperthyroidism, pulmonary hyperinflation and cardiomegaly with the following hypotheses: (1) hyperthyroid cats would not have evidence of radiographic pulmonary hyperinflation compared with control cats; and (2) hyperthyroid cats were more likely to have evidence of radiographic cardiomegaly than control cats.

METHODS

In this retrospective case-control study, the thoracic radiographs of 52 hyperthyroid cats and 46 non-hyperthyroid cats were evaluated for subjective and objective measurements of pulmonary hyperinflation and cardiomegaly.

RESULTS

There were no statistically significant differences between hyperthyroid and non-hyperthyroid cats for any variable indicative of pulmonary hyperinflation. The mean ± SD vertebral heart score on lateral views for hyperthyroid cats was 7.75 ± 0.53 and for control cats was 7.55 ± 0.54, which was significantly different (P = 0.05). Among all cats, a more severe total elevation in thyroxine (T4) was correlated with a larger vertebral heart score on lateral views (Spearman's correlation coefficient = 0.23, P = 0.02).

CONCLUSIONS AND RELEVANCE

While the results of this study suggest that hyperthyroid cats are more likely to have a larger vertebral heart score on lateral views than control cats, the clinical relevance of this finding is unclear given the large degree of overlap between hyperthyroid and non-hyperthyroid cats. In addition, among all cats, a greater total T4 elevation was weakly correlated with a larger vertebral heart score. Hyperthyroidism is not associated with radiographic pulmonary hyperinflation and is an unlikely differential for this radiographic finding.

[Inhalation therapy in dogs and cats with chronic lower airway disease - a literature review]

Chronic respiratory diseases are prevalent medical conditions in dogs and cats requiring lifelong treatment. Mainstay of therapy for chronic inflammatory respiratory diseases are glucocorticoids. Concurrent treatment with bronchodilators may be necessary to control clinical signs sufficiently. Due to the successful use in people as well as subsequent reduction of adverse effects of long-term glucocorticoid therapy, inhalative therapy has become increasingly important in veterinary medicine as well. Primarily spacers or valved holding chambers, in combination with metered dose inhalers, are used in dogs and cats. The technical properties of these devices, as well as their use and maintenance will be described in the following article. Furthermore, the existing literature regarding efficacy of inhalative medications for therapy of chronic inflammatory airway diseases in dogs and cats will be summarized.

Feline Heartworm in Clinical Settings in a High Canine Prevalence Area

Heartworm (HTW) infection in cats is associated with persistent pulmonary pathology, even when clinical signs are absent. Treatment options for cats are limited once infected, making prevention an important topic for discussion with cat owners. In Brazil, tests to detect feline HTW infections are unavailable, likely leading to an underestimation of its impact on the wellbeing of cats. The present study investigated the seroprevalence of HTW antigen in cats living in an area with high canine HTW prevalence and investigated risk factors and clinical signs associated with HTW disease in cats from Rio de Janeiro, Brazil. Clinical examinations were conducted, and serological evaluations performed with a point-of-care test (SNAP^® Feline Triple^® Test, IDEXX Laboratories, Inc.). A total of 586 cats were examined. The HTW antigen seroprevalence was 1.2%. Heartworm positive results were significantly associated with vomiting and abnormal lung sounds. Results from this study indicate that cats residing in areas of high canine HTW prevalence should have HTW disease as a differential diagnosis when presenting with compatible clinical signs. Veterinarians should prioritize client education and promote regular use of effective prophylaxis to protect feline health.

First Autochthonous Infection of a Cat with Dirofilaria immitis in Austria

This case report is about a seven-year-old male neutered European Shorthair cat infected by Dirofilaria immitis as the first reported autochthonous Dirofilaria immitis infection in Austria. There was no history of periods abroad. Echocardiography showed suspected D. immitis in the right cardiac chamber with increased pulmonary pressure and ascites. Surgical removal of the heartworms was performed. Twenty adult heartworms were removed by transvenous jugular approach under general anesthesia and stored in 4% formalin. Five out of 20 specimens were examined via light and stereomicroscopy and feline heartworm infection was confirmed. Amplification of a 203 bp or 724 bp fragment of the cytochrome c oxidase subunit I gene was unsuccessful. After surgery the cat developed acute renal failure but recovered quickly. One year later, the cat underwent a control examination including echocardiography and blood work. There were no more D. immitis detectable at echocardiography. Lung pressure was mildly increased. Complete blood count and creatinine were unremarkable. The Knott's test and Dirofilaria-Antigen-test produced negative results. The cat did not show any clinical signs during the follow-up period. The aim of this case report is to highlight the growing risk of acquiring infection with D. immitis not only for Austrian dogs, but also for cats. This case report represents the first report of autochthonous D. immitis infection in Austria. Moreover, even if the prognosis in cats with caval syndrome due to feline heartworm disease is guarded to poor, surgical removal of the filariae can be a successful treatment option.

Heartworm disease - Overview, intervention, and industry perspective

Dirofilaria immitis, also known as heartworm, is a major parasitic threat for dogs and cats around the world. Because of its impact on the health and welfare of companion animals, heartworm disease is of huge veterinary and economic importance especially in North America, Europe, Asia and Australia. Within the animal health market many different heartworm preventive products are available, all of which contain active components of the same drug class, the macrocyclic lactones. In addition to compliance issues, such as under-dosing or irregular treatment intervals, the occurrence of drug-resistant heartworms within the populations in the Mississippi River areas adds to the failure of preventive treatments. The objective of this review is to provide an overview of the disease, summarize the current disease control measures and highlight potential new avenues and best practices for treatment and prevention.

Clinical Case of Life-threatening Co-infection Due to Dirofilaria Immitis and Aelurostrongylus Abstrusus in a Cat: First Report of Feline Heartworm Disease in Bulgaria

The present report describes the first clinically manifested and serologically proven case of Dirofilaria immitis infection in a cat in Bulgaria. A 10-year-old intact male cat was referred to the Small Animal Clinic, Trakia University with a history of anorexia, weight loss, intermittent coughing and itching skin lesions on the head and neck. Physical examination revealed abnormal heart sounds and respiration, cyanosis of the mucous membranes, and generalized enlargement of the lymph nodes. Mild infestation with hard ticks and fleas was also detected during the initial skin inspection. In addition, adult Otodectes cynotis mites were observed in the skin lesions. The fecal sample was positive for larvae of Aelurostrongylus abstrusus and eggs of Toxocara cati. Blood serology revealed antigens of D. immitis as well as antibodies against both feline immunodeficiency virus and D. immitis. Thoracic radiographic findings included a pronounced generalized reticular interstitial pattern; alveolar and bronchial shades with multiple nodular thickenings throughout the lungs. Electrocardiography demonstrated a sinus tachycardia, a peaked P-wave (P-pulmonale) and an abnormally low ST-segment. The clinical signs disappeared after treatment with selamectin, doxycycline and corticosteroids. Despite the improvement in general health condition, the cat suddenly died several months later.

Unusual feline Dirofilaria immitis infection: a case report

Cats are less susceptible to Dirofilaria immitis infection than dogs. Although rare, the feline disease can be fatal even with low parasitic loads. The infection is often asymptomatic or has non-specific symptoms that are mainly associated with the death of immature worms. Microfilaremia is rare and transient. Normally, microfilaremia, when present, lasts for not more than 33 days. This study describes a feline case presenting with non-specific clinical signs and prolonged microfilaremia. Case: a random bred cat infected by feline leukemia virus (FeLV) that was found to be microfilaremic by chance. The infection was detected by the presence of microfilariae in a blood smear and was confirmed by antigen test (SNAP Feline Triple Test, Idexx®) and echocardiogram.