Interstitial lung disease in feline immunodeficiency virus (FIV) infected cats

Left Pulmonary Artery Coarctation Associated with Pneumonia and Pulmonary Hypertension in a Cat

A five-month-old European shorthair female kitten was referred because of recurrent episodes of respiratory distress. Results of physical examination, thoracic radiography, and echocardiography led to a presumptive diagnosis of severe precapillary pulmonary hypertension (PH) and interstitial pneumonia associated with right-sided cardiac remodeling. The cat rapidly died because of respiratory insufficiency. Pulmonary and cardiovascular pathological findings evidenced left pulmonary artery coarctation, severe right-sided cardiac hypertrophy, and bilateral pneumonia. This is the first report of pulmonary artery coarctation associated with pneumonia and PH in a cat.

Interstitial lung diseases in dogs and cats part I: The idiopathic interstitial pneumonias

Interstitial lung diseases (ILDs), also called diffuse parenchymal lung diseases, are a large heterogenous group of non-infectious, non-neoplastic disorders characterized by varied patterns of inflammation and fibrosis (Travis et al., 2002). In humans, accurate classification of interstitial lung diseases (ILDs) requires multidisciplinary collaboration between clinicians, radiologists and pathologists. The same is likely to be true for canine and feline ILDs; however, this collaborative approach is rarely taken, leading to a paucity of knowledge of ILDs in small animal species. A proposed classification scheme of canine and feline ILDs, modified from a human classification scheme, consists of three major groups: idiopathic interstitial pneumonias (IIPs), ILDs secondary to known causes, and miscellaneous ILDs (Travis et al., 2002). The focus of this review is on the IIPs in dogs and cats. A framework of what is known about the major IIPs in humans will be used to draw parallels when relevant to the canine and feline species. Differences will also be highlighted. When available from the veterinary literature, clinical presentation, diagnostic results, treatment and/or prognosis will be reported. The review underscores that to advance in our knowledge of veterinary IIPs and other ILDs, clinicopathologic features, advanced imaging and histopathology must be carefully integrated and larger groups of animals studied.

Infection with equine infectious anemia virus vaccine strain EIAVDLV121 causes no visible histopathological lesions in target organs in association with restricted viral replication and unique cytokine response

The live equine infectious anemia virus (EIAV) vaccine strain EIAVDLV121 was developed by in vitro attenuation of a virulent strain, EIAVLN40, in the 1970s, and it has been demonstrated to induce protective immunity under laboratory and natural EIAV infection conditions. The detailed biological features of this attenuated virus remain to be further investigated. Experimental inoculation with EIAVDLV121 did not result in clinical symptoms even with immunosuppressive treatment in our previous studies. Here, we further investigated whether the replication of the vaccine strain EIAVDLV121 in experimentally infected horses causes histopathological lesions to develop in the targeted organs. Both the lungs and the spleen have been demonstrated to support EIAV replication. By evaluating the gross macroscopic and histological changes, we found that EIAVDLV121 did not cause detectable histopathological lesions and that it replicated several hundred times more slowly than its parental virulent strain, EIAVLN40, in tissues. Immunochemical assays of these tissues indicated that the primary target cells of EIAVDLV121 were monocytes/macrophages, but that EIAVLN40 also infected alveolar epithelial cells and vascular endothelial cells. In addition, both of these viral strains promoted the up- and down-regulation of the expression of various cytokines and chemokines, implicating the potential involvement of these cellular factors in the pathological outcomes of EIAV infection and host immune responses. Taken together, these results demonstrate that the EIAV vaccine strain does not cause obvious histopathological lesions or clinical symptoms and that it induces a unique cytokine response profile. These features are considered essential for EIAVDLV121 to function as an effective live vaccine.

Interstitial lung disease associated with Equine Infectious Anemia Virus infection in horses

EIA (Equine Infectious Anemia) is a blood-borne disease primarily transmitted by haematophagous insects or needle punctures. Other routes of transmission have been poorly explored. We evaluated the potential of EIAV (Equine Infectious Anemia Virus) to induce pulmonary lesions in naturally infected equids. Lungs from 77 EIAV seropositive horses have been collected in Romania and France. Three types of lesions have been scored on paraffin-embedded lungs: lymphocyte infiltration, bronchiolar inflammation, and thickness of the alveolar septa. Expression of the p26 EIAV capsid (CA) protein has been evaluated by immunostaining. Compared to EIAV-negative horses, 52% of the EIAV-positive horses displayed a mild inflammation around the bronchioles, 22% had a moderate inflammation with inflammatory cells inside the wall and epithelial bronchiolar hyperplasia and 6.5% had a moderate to severe inflammation, with destruction of the bronchiolar epithelium and accumulation of smooth muscle cells within the pulmonary parenchyma. Changes in the thickness of the alveolar septa were also present. Expression of EIAV capsid has been evidenced in macrophages, endothelial as well as in alveolar and bronchiolar epithelial cells, as determined by their morphology and localization. To summarize, we found lesions of interstitial lung disease similar to that observed during other lentiviral infections such as FIV in cats, SRLV in sheep and goats or HIV in children. The presence of EIAV capsid in lung epithelial cells suggests that EIAV might be responsible for the broncho-interstitial damages observed.

Small ruminant lentiviruses: immunopathogenesis of visna-maedi and caprine arthritis and encephalitis virus

The small ruminant lentiviruses include the prototype for the genus, visna-maedi virus (VMV) as well as caprine arthritis encephalitis virus (CAEV). Infection of sheep or goats with these viruses causes slow, progressive, inflammatory pathology in many tissues, but the most common clinical signs result from pathology in the lung, mammary gland, central nervous system and joints. This review examines replication, immunity to and pathogenesis of these viruses and highlights major differences from and similarities to some of the other lentiviruses.

Lower respiratory tract infections in cats: reaching beyond empirical therapy

PRACTICAL RELEVANCE

Lower respiratory tract infections (LRTIs) in cats can be due to bacteria, parasites, fungi and viruses. This review details the practical investigation of these infections and highlights specific therapy where possible. The aim is to avoid the all-too-frequent temptation in practice to treat cats with lower respiratory tract signs empirically for feline bronchial disease (FBD)/asthma. This is potentially hazardous as immunosuppressive therapy for FBD/asthma could exacerbate disease due to a LRTI. Empirical treatment of suspected LRTI is also difficult to recommend given the wide range of potential pathogens.

CLINICAL CHALLENGES

Making a clinical ante-mortem diagnosis of LRTI in a cat can be challenging. Consistent historical, clinical, haematological and radiographic abnormalities are often lacking and findings may be non-specific. Astute clinical acumen, thorough investigation and high quality laboratory analysis are usually required for a diagnosis. Bronchoalveolar lavage, if feasible, and tests for lungworm should be routine in cats with lower respiratory tract signs. Lung fine needle aspiration may be useful in cases of diffuse or nodular pulmonary disease. Histopathology is rarely employed in ante-mortem investigations.

EVIDENCE BASE

The authors have reviewed a substantial body of literature to provide information on many of the reported bacterial, parasitic, fungal and viral pathogens, including some that occur in Asia. Attention has been given to specific therapy for each pathogen, with evidence-based comments when there is a deviation from routine recommendations.

Interstitial Lung Diseases

Several noninfectious nonneoplastic interstitial lung diseases (ILDs) have been recognized in dogs and cats. Overall, these ILDs are poorly characterized in dogs and cats, although awareness of the conditions based on descriptions of clinical case series may be increasing. Lung biopsy remains crucial to the diagnosis, characterization, and classification of ILDs. Histopathologic findings can help to guide clinicians in selecting appropriate therapy and providing an accurate prognosis to pet owners. Only with definitive recognition of these pulmonary conditions can our knowledge of the clinical course and response to therapy be improved.

Malignant and benign lymphoid lesions of the lung

Lymphoid lesions of the lung produce a complex of problems for the practicing pathologist. Although these lesions are eventually referred to hematopathologists, it is still the general surgical pathologist who first encounters them and confronts the problem of formulating an initial diagnosis. Over the last 20 years there has been a revolution in our knowledge of the classification and natural history of the pulmonary lesions, a plethora of information which warrants a thorough review. The purpose of this discussion is to report the clinical features and courses, pathologic features and, when known, etiologies or pathogenesis of the major "primary" pulmonary lymphoid lesions and present a brief approach to differential diagnosis. I will divide the lesions into malignant and benign, discussing each in turn.

A retrospective analysis of feline bronchoalveolar lavage cytology and microbiology (1995-2000)

A retrospective study of 88 bronchoalveolar lavage specimens from 80 cats presenting to the University of Sydney Veterinary Centre between 1995 and 2000 was performed. Bronchoalveolar lavage cytology and microbiology in conjunction with other diagnostic aids and patient records were used to classify cases as lower respiratory tract infections (LTRIs), LRTI revisits, feline bronchial disease, cardiac disease, neoplastic disease and multisystemic disease. Cases for which a definitive diagnosis could not be made were classified as inconclusive. Infectious agents identified were Mycoplasma spp., Pasteurella spp., Bordetella bronchiseptica, Salmonella typhimurium, Pseudomonas sp., Cryptococcus neoformans, Aelurostrongylus abstrusus and Eucoleus aerophilus. The study highlights the importance of bronchoalveolar lavage cytology and microbiology in the evaluation of feline lower respiratory tract disease.

Clinicopathologic and radiographic features and etiologic agents in cats with histologically confirmed infectious pneumonia: 39 cases (1991-2000)

OBJECTIVE

To determine clinicopathologic and radiographic features and etiologic agents in cats that died as a result of infectious pneumonia.

DESIGN

Retrospective study.

ANIMALS

39 cats.

PROCEDURE

Medical records of cats in which infectious pneumonia was confirmed by histologic examination of necropsy specimens were reviewed. Signalment, clinical signs, and results of a CBC, viral serologic tests, and thoracic radiography were evaluated. Infectious agents were classified as bacterial, viral, fungal, protozoal, or parasitic. Histologic features (severity, duration, anatomic location, and distribution) were analyzed.

RESULTS

Clinical signs referable to the respiratory tract were not detected in 14 of 39 (36%) cats, and results of a CBC (4/18 cats) and radiography (3/13) were unremarkable. Sixteen of 39 (41%) cats lacked clinical signs of systemic illness. Etiologic agents identified included bacteria (n = 21), viruses (11), fungi (6), protozoa (2), and parasites (1). Cats with clinical signs related to the respiratory tract (19/24 [79%] cats) were more likely to have severe histologic changes than cats without signs related to the respiratory system (6/14). Twenty-nine of 38 (76%) cats had histologic evidence of systemic disease, whereas the remaining cats had lesions limited to the respiratory tract.

CONCLUSIONS AND CLINICAL RELEVANCE

Infectious pneumonia is uncommon in cats. Cats with infectious pneumonia may lack clinical signs and have unremarkable results for a CBC and thoracic radiography, yet frequently have systemic infections. Therefore, clinicians should maintain an index of suspicion for pneumonia and evaluate the respiratory tract when infection is detected in other organ systems.

Use of keyhole lung biopsy for diagnosis of interstitial lung diseases in dogs and cats: 13 cases (1998-2001)

OBJECTIVE

To characterize interstitial lung diseases (ILDs) and evaluate use of keyhole lung biopsy for diagnosis of ILDs in dogs and cats.

DESIGN

Retrospective study.

ANIMALS

11 dogs and 2 cats.

PROCEDURE

Medical records of dogs and cats undergoing keyhole lung biopsy to confirm ILDs were reviewed. Signalment, clinical signs, results of thoracic radiography and other respiratory diagnostic tests, postoperative complications, and patient outcome were analyzed.

RESULTS

Clinical respiratory signs included cough, tachypnea, exercise intolerance, and hemoptysis. Thoracic radiographic abnormalities included interstitial, alveolar, and bronchointerstitial patterns and multiple discrete pulmonary nodules. Lung biopsy and histologic examination revealed interstitial pulmonary fibrosis, bronchiolitis obliterans with organizing pneumonia, or unclassified lesions. Outcome after biopsy included no response to treatment, euthanasia, partial or complete remission while receiving medication, and cure.

CONCLUSIONS AND CLINICAL RELEVANCE

Recognition and classification of ILDs in dogs and cats are likely to be important in guiding appropriate treatment and providing accurate prognostic information. Ancillary respiratory diagnostic tests are beneficial in ruling out infectious and neoplastic disorders that may mimic ILDs; however, their present use in the diagnosis of ILDs is limited. Results suggest that keyhole lung biopsy is an effective means for obtaining a specimen for histologic diagnosis in dogs and cats with ILDs.

Investigation of some Hypericum species native to Southern of Brazil for antiviral activity

Three plant species, Hypericum connatum, Hypericum caprifoliatum, Hypericum polyanthemum (Guttiferae), growing in Southern of Brazil were chemically investigated and tested for their antiviral activity against feline immunodeficiency virus (FIV). The chemical analysis revealed the presence of polyphenolic compounds such as tannins and flavonoids. Hypericin was not detected in these species. The aqueous extract (AE), the aqueous extract with low tannin concentration (LTCAE) and the methanolic extract (ME) were tested for their cytotoxic properties in concentrations of 50-150 microg/ml. AE was toxic to CRFK for the three species in all concentrations. LTCAE and ME varied between different concentrations being not toxic or allowing 80% of cell growth. LTCAE and ME (10-50 microg/ml) were analyzed for antiviral activity by inhibition of CPE and measuring FIV genome from cell culture supernatant. LTCAE of all species in this work did not cause any inhibition of FIV. Although no difference was seen in CPE, a lower number of viral particles in the supernatant was observed when FIV infected cells were treated with ME of H. connatum. These results suggest that some plants of the genus Hypericum from Southern Brazil contain compounds with potential antiviral activity against lentiviruses.

Constitutive expression of types 1 and 2 cytokines by alveolar macrophages from feline immunodeficiency virus-infected cats

Evidence suggests that feline immunodeficiency virus (FIV), causes pulmonary immunodeficiency. The overall objective of this study was to explore FIV-induced alterations in cell counts and cytokine gene expression in the pulmonary compartment during the acute stage infection. Bronchoalveolar lavage (BAL) cells were collected from FIV-infected and control cats at 0, 4, 10, and 16 weeks post-FIV infection for phenotype and cytokine analysis. The major change in BAL cellular populations following FIV-infection was the development of a neutrophilia. Total BAL cell counts and relative numbers of alveolar macrophages (AM), eosinophils, and lymphocytes remained similar in both groups. The RT-qcPCR analyses of AM purified from BAL showed constitutive expression of TNFα, IL6 and IL10 mRNAs that peaked during the acute stage of infection then declined. The TNFα and IL6 bioactive protein secretion showed a similar response. In contrast, IFNγ expression increased progressively with time after infection and paralleled a progressive increase in FIV-gag mRNA in AM. The IL12 p40 expression also differed from the other cytokines in that there was a progressive decrease in the number of cats with AM IL12 expression following FIV infection. Infection of AM in vitro with FIV also caused an increase in TNFα and IL6 mRNA and bioactive protein suggesting that the increased cytokine response by AM following infection of cats with FIV is an intrinsic characteristic of FIV-infected AM. In summary, pulmonary immune changes seen in FIV-infected cats are similar to those seen in HIV-infected human patients.