Pneumocystis carinii in the miniature dachshund: case report and literature review

Detection of Pneumocystis and Morphological Description of Fungal Distribution and Severity of Infection in Thirty-Six Mammal Species

Pneumocystis spp. are thought to adapt to the lungs of potentially all mammals. However, the full host range, fungal burden and severity of infection are unknown for many species. In this study, lung tissue samples originating from 845 animals of 31 different families of eight mammal orders were screened by in situ hybridization (ISH) using a universal 18S rRNA probe for Pneumocystis, followed by hematoxylin and eosin (H&E) staining for determining histopathological lesions. A total of 216 (26%) samples were positive for Pneumocystis spp., encompassing 36 of 98 investigated mammal species, with 17 of them being described for the first time for the presence of Pneumocystis spp. The prevalence of Pneumocystis spp. as assessed by ISH varied greatly among different mammal species while the organism load was overall low, suggesting a status of colonization or subclinical infection. Severe Pneumocystis pneumonia seemed to be very rare. For most of the Pneumocystis-positive samples, comparative microscopic examination of H&E- and ISH-stained serial sections revealed an association of the fungus with minor lesions, consistent with an interstitial pneumonia. Colonization or subclinical infection of Pneumocystis in the lung might be important in many mammal species because the animals may serve as a reservoir.

X-linked CD40 ligand deficiency in a 1-year-old male Shih Tzu with secondary Pneumocystis pneumonia

An approximately 1‐year‐old male intact Shih Tzu dog was referred to a tertiary facility with a history of progressive tachypnea, increased respiratory effort, and weight loss over a 3‐month period that failed to improve with empirical antimicrobial treatment. Upon completion of a comprehensive respiratory evaluation, the dog was diagnosed with severe Pneumocystis pneumonia and secondary pulmonary hypertension. Clinical signs resolved and disease resolution was confirmed after completion of an 8‐week course of trimethoprim‐sulfonamide, 4‐week tapering dose of prednisone to decrease an inflammatory response secondary to acute die‐off of organisms, a 2‐week course of clopidogrel to prevent clot formation, and a 2‐week course of a phosphodiesterase‐5 inhibitor to treat pulmonary hypertension. Immunodiagnostic testing and genetic sequencing were performed to evaluate for potential immunodeficiency as an underlying cause for the development Pneumocystis pneumonia, and identified an X‐linked CD40 ligand deficiency.

Pneumocystosis in a lurcher puppy

A 10-month-old lurcher with history of recurrent skin problems, presented with tachypnoea which had progressively become severe. Investigations included haematology, serum biochemistry, blood coagulation profile, diagnostic imaging, bronchoscopy and bronchoalveolar lavage (BAL). Cytological evaluation of the BAL revealed the presence of Pneumocystis cysts. The patient was euthanased on humane grounds prior to treatment against Pneumocystosis. To the best of our knowledge this is the first case of Pneumocystosis in a lurcher puppy.

Disseminated Pneumocystosis in a Toy Poodle

A 1-year and 7-months-old neutered male toy poodle was presented with persistent respiratory distress, gradual weight loss and melaena. Thoracic radiography showed an unstructured interstitial lung pattern. Histopathological examination of tissues collected at necropsy examination revealed disseminated infection by Pneumocystis carinii. The organisms were detected in the lungs, lymph nodes, liver, heart, kidneys, spleen, gastrointestinal tract and pancreas. In the lungs, the organisms were present in the alveolar space and interstitial tissue, and calcified foci containing P. carinii were observed. The presence of the organism in non-thoracic lymph nodes provided evidence of lymphogenous spread. A definitive diagnosis of disseminated pneumocystosis was achieved through the use of Grocott methenamine silver staining, immunohistochemistry (IHC) and polymerase chain reaction for P. carinii. Depletion of cells expressing immunoglobulin (Ig)A and IgG was confirmed by IHC of lymphoid tissue, suggesting possible underlying immunodeficiency.

Molecular detection of Pneumocystis in the lungs of cats

The genus Pneumocystis comprises potential pathogens that reside normally in the lungs of a wide range of mammals. Although they generally behave as transient or permanent commensals, they can occasionally cause life-threatening pneumonia (Pneumocystis pneumonia; PCP) in immunosuppressed individuals. Several decades ago, the presence of Pneumocystis morphotypes (trophic forms and cysts) was described in the lungs of normal cats and cats with experimentally induced symptomatic PCP (after immunosuppression by corticosteroids); yet to date spontaneous or drug-induced PCP has not been described in the clinical feline literature, despite immunosuppression of cats by long-standing retrovirus infections or after kidney transplantation. In this study, we describe the presence of Pneumocystis DNA in the lungs of normal cats (that died of various unrelated causes; n = 84) using polymerase chain reactions (PCRs) targeting the mitochondrial small and large subunit ribosomal RNA gene (mtSSU rRNA and mtLSU rRNA). The presence of Pneumocystis DNA was confirmed by sequencing in 24/84 (29%) cats, with evidence of two different sequence types (or lineages). Phylogenetically, lineage1 (L1; 19 cats) and lineage 2 (L2; 5 cats) formed separate clades, clustering with Pneumocystis from domestic pigs (L1) and carnivores (L2), respectively. Results of the present study support the notion that cats can be colonized or subclinically infected by Pneumocystis, without histological evidence of damage to the pulmonary parenchyma referable to pneumocystosis. Pneumocystis seems most likely an innocuous pathogen of cats’ lungs, but its possible role in the exacerbation of chronic pulmonary disorders or viral/bacterial coinfections should be considered further in a clinical setting.

CT findings in Pneumocystis carinii pneumonia in five dogs

Pneumocystis carinii pneumonia is a rare disease in dogs. It is primarily reported in cavalier King Charles spaniels and miniature dachshunds with suspected underlying immunodeficiency. This case series reports the findings in five dogs (four cavalier King Charles spaniels and one Bedlington terrier) with confirmed P. carinii pneumonia. Thoracic (CT) revealed ground glass opacity of the pulmonary parenchyma with a diffuse or multifocal distribution. The severity of this pattern was variable. Less consistent imaging findings included parenchymal bands, bronchial dilation and signs consistent with pulmonary hypertension. Four dogs recovered well with treatment and there was resolution of CT abnormalities in all dogs with follow-up.

Pneumocystosis in dogs: meta-analysis of 43 published cases including clinical signs, diagnostic procedures, and treatment

We evaluated 43 published cases of dogs with confirmed Pneumocystis infection regarding the value of clinical parameters indicating the presence of the disease as well as tools for the detection of the pathogen. The assessed parameters included clinical signs, laboratory findings, results of thoracic radiography, autopsy, histopathology, methods for the detection of Pneumocystis, as well as medical therapy. Pneumocystosis was diagnosed most often in certain breeds (Cavalier King Charles Spaniel, Miniature Dachshund) with a predisposition for impaired immunity. The median age of the dogs was 1 y. Chronic therapy-resistant respiratory signs, such as tachypnea, dyspnea, and cough, along with leukocytosis, neutrophilia, and hypogammaglobulinemia, were the most frequently described clinical and clinicopathologic abnormalities. Pneumocystosis can be masked by coinfections with other respiratory pathogens, and the successful detection of Pneumocystis organisms is of major relevance. Several detection methods have been used in the past, but only a few provide reliable results. In 2017, the cytologic evaluation of Giemsa-stained bronchoalveolar lavage samples is generally used, even if sensitivity is only moderate. More reliable results can be achieved using special stains or sensitive molecular techniques. Fast and reliable detection of Pneumocystis is the essential basis for appropriate treatment and higher survival chances for dogs.

Finding your way through Pneumocystis sequences in the NCBI gene database

Pneumocystis sequences can be downloaded from GenBank for purposes as primer/probe design or phylogenetic studies. Due to changes in nomenclature and assignment, available sequences are presented with a variety of inhomogeneous information, which renders practical utilization difficult. The aim of this study was the descriptive evaluation of different parameters of 532 Pneumocystis sequences of mitochondrial and ribosomal origin downloaded from GenBank with regard to completeness and information content. Pneumocystis sequences were characterized by up to four different names. Official changes in nomenclature have only been partly implemented and the usage of the "forma specialis", a special feature of Pneumocystis, has only been established fragmentary in the database. Hints for a mitochondrial or ribosomal genomic origin could be found, but can easily be overlooked, which renders the download of wrong reference material possible. The specification of the host was either not available or variable regarding the used language and the localization of this information in the title or several subtitles, which limits their applicability in phylogenetic studies. Declaration of products and geographic origin was incomplete. The print version of this manuscript is completed by an online database which contains detailed information to every accession number included in the meta-analysis.

A review of the pathology and treatment of canine respiratory infections

Numerous infectious agents are responsible for causing primary or secondary respiratory disease in dogs. These agents can cause upper or lower respiratory infections commonly observed in veterinary practices. Clinical signs might vary from mild dyspnea, sneezing, and coughing to severe pneumonia with systemic manifestations. Depending on the etiologic agent, the gross and microscopic changes observed during these infections can be rather unspecific or have highly characteristic patterns. While histopathology and cytology are not always required for diagnosis of respiratory infections, they are often useful for establishing a definitive diagnosis and identifying specific etiologic agents. Research regarding epidemiology, pathogenesis, diagnostics, and clinical manifestations related to these infectious pathogens provides valuable information that has improved treatments and management of the diseases they cause. This review discusses the epidemiology, general clinical characteristics, and pathologic lesions for some of the important viral, bacterial, fungal, and parasitic etiologies of canine respiratory disease.

Primary immunodeficiencies of dogs and cats

Primary immunodeficiencies are congenital defects that affect formation or function of the immune system. Congenital immunodeficiency should be considered as a differential diagnosis for repeated infections in a young animal. Defects in the immune system may lead to complete or partial loss of immunity. Some animals with mild immunodeficiency can be managed with long-term antibiotic therapy.

Respiratory defenses in health and disease

Every breath holds the potential to introduce infectious organisms and irritating particulates into the respiratory tract. Despite this continuous exposure, the lungs usually remain sterile. Further, potential pathogens are distinguished from innocuous particulates, thus sparing the respiratory tract from damaging inflammation. The article reviews the complex defenses used to protect the respiratory tract and also discusses the implications of failed defense systems.

Pneumocystis carinii pneumonia in a Yorkshire terrier dog

A 14-month-old male Yorkshire terrier was presented to the Autonomous University of Barcelona Veterinary Teaching Hospital because of a history of chronic non-productive cough and acute dyspnea. A follow-up radiograph revealed a diffuse, bilaterally interstitial-alveolar lung disease with presence of air bronchograms. The dog died 5 h after admission with severe dyspnea. Histological sections of the necropsy specimens revealed the presence of characteristic Pneumocystis carinii cysts within alveolar spaces. A diagnosis of P. carinii pneumonia (PCP) was made on the basis of these results. To our knowledge, PCP has not been described in a Yorkshire terrier dog.

Common variable immunodeficiency in miniature dachshunds affected with Pneumonocystis carinii pneumonia

Seven miniature dachshunds, all under the age of 1 year, were presented with polypnea, tachypnea, and exercise intolerance as a result of Pneumocystis carinii pneumonia, which was diagnosed on transtracheal aspirate cytology. In all of the dogs, historical and clinical signs were suggestive of immune incompetence. Immunological studies undertaken were leukogram parameters, serum immunoglobulin fraction quantification, lymphocyte transformation assay. CD3 and CD79a lymphocyte markers on lymphoid tissue, and anti-canine immunoglobulin G immunoperoxidase staining. The immunological studies showed hypogammaglobulinemia, deficiency of serum immunoglobulins A, G, and M, decreased lymphocyte transformation response to phytohemagglutinin and pokeweed mitogens and absence of B lymphocytes with presence of T lymphocytes in the lymphoid tissue stained with CD3 and CD79a lymphocyte markers. The preceding findings suggest that P. carinii pneumonia occurring in the miniature dachshund is a result of both a T- and B-cell deficiency. This presentation is not the classic primary severe combined immunodeficiency syndrome but rather combined variable immunodeficiency, which has been well documented in humans but never in the dog.

A review of immunologic diseases of the dog

The following review is based on notes used in the teaching of clinical immunology to veterinary students. Immune diseases of the dog are placed into six different categories: (1) type I or allergic conditions; (2) type II or auto- and allo-antibody diseases; (3) type III or immune complex disorders; (4) type IV or cell-mediated immune diseases; (5) type V conditions or gammopathies; and (6) type VI or immunodeficiency disorders. Separate discussions of transplantation immunology and the use of drugs to regulate unwanted immune responses are also included.

Radiographic aspects of Pneumocystis carinii pneumonia in the miniature Dachshund

The thoracic radiographic changes of Pneumocystis carinii in 7 miniature Dachshunds were reviewed. The dogs were 7-12 months old and presented with polypnea, exercise intolerance and clinical signs suggestive of immune-incompetence. P. carinii pneumonia was diagnosed in all the dogs using transtracheal aspirate cytology and confirmed at postmortem in 3 dogs that died. Radiographically, diffuse pulmonary changes were present and varied from a mild interstitial and bronchial pattern to an alveolar pattern. Radiographic evidence of cor pulmonale was present in 1 dog. The most severe radiographic changes were seen in 2 of the dogs that died.

Low serum immunoglobulin concentrations in related Weimaraner dogs

Chronic, recurrent disease involving the alimentary tract, joints, skin and peripheral lymph nodes, central nervous system and conjunctivae was recorded over a 229 day period in a young Weimaraner dog, first presented at 15 weeks of age. The dog had a left shift neutrophilia during periods of active disease and persistently subnormal levels of serum immunoglobulin G (IgG; 2.8 to 9.2 mg/ml) and IgA (< 0.1 to 0.26 mg/ml) in the absence of circulating immune complexes. One littermate died suddenly at 27 weeks of age and a second littermate had an episode of pyoderma. Both of these dogs had low serum IgG (3.5 to 7.2 mg/ml) and the second littermate also had reduced serum IgA (< 0.1 to 0.15 mg/ml). The dam of the litter and three other related dogs had reduced serum IgA (0.22 to 0.31 mg/ml); circulating immune complexes were not recorded in any of the related dogs. This case is the first of putative immunodeficiency of Weimaraners in the UK. Inability to synthesise adequate concentrations of serum immunoglobulins should be considered a primary defect in this disorder.