Pneumocystis Pneumonia and
Cavalier King Charles Spaniels

Cavalier King Charles spaniels are predisposed to develop pneumocystis pneumonia (also referred to as pneumocystis carinii pneumonia [PCP], and pneumocystosis) a form of pneumonia caused by a fungus, commonly found in the lungs of most all dogs but which can infect the lungs of dogs with weak immune systems. It was first reported about in a CKCS in a 1996 article, and several veterinary research articles have been written about it since then. See Veterinary Resources. Dachshunds also are known to be predisposed to pneumocystis pneumonia as a breed-specific immune system disorder, and Yorkshire terriers to a lesser extent.

This form of pneumonia can be life-threatening if not diagnosed and treated at an early stage.


What It Is

Pneumocystis pneumonia is caused by a fungus, pneumocystis jirovecii, which is commonly found in the lungs of dogs but which can cause infection of the lungs of dogs which have immune system deficiencies.

Inherited immune system deficiency is suspected as a cause in the CKCS breed, in part, because in a 2009 Australian study, a pair of cavalier littermates were diagnosed with pneumocystis pneumonia. In the cavalier, this infection has been diagnosed in young and older dogs.

In a 2001 UK study of the DNA of pneunocystis cysts taken from a cavalier, the researchers reported detecting a unique form of pneumocystis, stating:

"We have therefore shown that this dog was infected with a genetically distinct form of Pneumocystis and propose that Pneumocystis infecting a canine host be referred to as Pneumocystis canis. It is also proposed that the two forms be temporarily designated Type A and Type B while awaiting further clarification of their relationship."


The most common early symptoms of pneumocystis pneumonia are a non-productive cough, very rapid breathing, shortness of breath, and possibly rapid heart rate. As the disorder progresses, the dog may develop inflammation in the mouth, including lesions, poor appetite, and exercise intolerance, but with a normal body temperature. Also, the dog's breathing becomes more and more labored.

Note that mouth lesions also are symptomatic of eosinophilic stomatitis, another immune-related disorder to which the CKCS is predisposed. Also, chronic ulcerative paradental stomatitis (CUPS), to which cavaliers are "over-represented", includes mouth inflammation and ulcers as symptoms.



Pneumocystis x-rayThere are several options available for diagnosis of pneumocystis pneumonia. An x-ray should reveal a fine, net-like pattern of matter in the lungs, referred to as a "generalized interstitial lung pattern" (see at left). High resolution computed tomography (HRCT) will be more effective in providing an accurate diagnosis than a plain radiograph.

The examining veterinarian should perform a bronchoalveolar lavage (BAL) under anestheseia, a procedure in which a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then recollected for microscopic examination of the cellular make-up of the fluid. If successful, the Pneumocystisexam should show the presence of pneumocystis jirovecii organisms. However, definitive diagnosis can be difficult, and BALs may be unhelpful. A more reliable alternative to the BAL is to perform a fine needle biopsy or aspirate, by inserting a needle into the lung to collect a sample of the affected lung tissue. But, this procedure may increase risk of complications, especially in dogs whose respiratory function is already severely compromised. Also, as with the BAL, this diagnostic procedure does not always detect the fungus.  (The photo at the right shows pneumocystis jirovecii cysts as the round dark purple spots.)

Blood should be collected to determine the serum concentrations of immunoglobulin G (IgG), IgM, and IgA IgG concentrations may be expected to be significantly low in pneumocystis-affected dogs, and IgM concentrations may be significantly high in affected dogs. See this 2006 study report. Decreased arterial oxygen tension is a recognized feature of the disease. See this 1997 report.

Identification of pneumocystis by DNA analysis may also be performed. See this 2001 report.

Given the possible inconclusive diagnosis by either BAL or needle biopsy, if the x-ray shows a generalized interstitial lung pattern and there is no obvious signs of cardiac failure (which otherwise could explain the rapid breathing and rapid heart rate), the examining veterinarian should be alert to the possibility of pneumocystis pneumonia. See this 1997 report.



If the pneumocystis pneumonia is diagnosed at an early-enough stage, certain antibiotics have been effective in eliminating the spread of the fungus. A combination of trimethoprim and sulfamethoxazole (Tribrissen, Di-Biotic, Borgal) has been a successful treatment, as has pentamidine isethionate (pentam 300).

Amphotericin B can be effective in killing the fungus, but is quite toxic and must be administered while the dog is on IV fluids to flush the kidneys. Other drugs that have been used include carbutamide, trimetrexate, and combinations of clindamycin, primaquine, dapsone, and trimethoprim.

Imidazole antifungal agents (itraconazole, fluconazole, ketoconazole, miconazole) have not proven effective in laboratory tests.

Additional therapies may include oxygen, mucolytics, bronchodilators, nebulization, and discontinuation of immunosuppressive medications.

Immunosuppression therapy (i.e., glucocorticoids) is not recommended. The use of immunosuppressive therapy in veterinary medicine may increase the prevalence of this condition. See this 1997 report.



Research News

Dr. Christiane Weissenbacher-LangNovember 2017: Austrian researchers suspect cavaliers may have an impaired immunity to Pneumocystis infection. In a November 2017 article in which a team of Austrian veterinarians (Christiane Weissenbacher-Lang [right], Andrea Fuchs-Baumgartinger, Abigail Guija-De-Arespacochaga, Andrea Klang, Herbert Weissenböck, Frank Künzel) studied the case histories of 43 dogs with Pneumocystis infection, including 16 cavalier King Charles spaniels, they concluded that a breed predisposition for cavaliers is evident and that an underlying heritable immunodeficiency in the breed is suspected.

October 2012: UK/South African veterinary pathologist finds pneumocystis infection in a cavalier. In an October 2012 study, UK/South African veterinary pathologist Emma Scurrell reported identifying pneumocytis pneumonia in a 1-year-old cavalier King Charles spaniel showing symptoms of tachypnoea and dyspnoea.

April 2012: UK diagnostic lab identifies pneumocystis carinii pneumonia in a CKCS. In an April 2012 study, UK's Carmichael Torrance Veterinary Diagnostic Lab reported diagnosing pneumocystis carinii pneumonia in a 4 year old cavalier with symptoms of recurrent dyspnoea and tachypnoea and showed a generalized interstitial pattern on x-ray.

February 2012: UK diagnostic veterinary lab pneumocystis carinii pneumonia in a CKCS. In a February 2012 study, Richard Fox, veterinary pathologist at Abbey Veterinary Services, a UK diagnostic veterinary laboratory, diagnosed pneumocystis carinii pneumonia in a 6 year old cavalier King Charles spaniel with a recent history of increased respiration and a marked bilateral and diffuse interstitial pattern on its lung x-ray.


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Veterinary Resources

Pneumocystis Carinii Pneumonia in Dogs -- a Diagnostic Challenge. Antti Sukura, Seppo Saari, Anna-Kaisa Järvinen, Mats Olsson, Marjatta Kärkkäinen and Timo Ilvesniemi. J.Vet.Diagn.Invest. 1996;8:124. Quote: "A Cavalier Ring Charles Spaniel (1.5 years, male) with respiratory signs unresponsive to therapy ... had suffered many problems during its first year, including tibial fracture, a large abscess in the stifle region, gastroenteritis, and erosive inflammation in the mouth and tongue. Erosive lesions were detected also at the beginning of the respiratory disease. The examination for canine distemper virus by immunofluorescence testing of cytological specimens had been negative. The dog had been vaccinated twice against distemper. Progressive respiratory signs had appeared 2 months prior to referral and included cough and dyspnea. The dog exhibited poor appetite and exercise intolerance. Therapy with antibiotics (amoxicillin clavulanic acid, tetracycline, cephalexin) produced no response. Some relief, especially at night, was obtained with low-dose corticosteroids (2.5 mg prednisolone/day for 1 month). The dog was afebrile and dyspneic with increased abdominal effort in respiration. Cyanosis became evident after slight exercise. Lung auscultation revealed respiratory crackles and wheezes. A soft murmur was auscultated on the left and right thorax. In thoracic radiographs diffuse interstitial and peribronchial densities were seen throughout the lungs, giving the impression of a reticular structure with micronodule formations. Chronic alveolar densities could be seen in all parts of the lungs. ... A diagnosis of P. carinii pneumonia was made on the basis of the preliminary results, and specific therapy with high dose (60 mg/kg/day) trimethoprim sulfonamide and folinic acid (1 mg/kg/day)11 was initiated, but the dog died on the same day the medication was instituted, and was sent to necropsy. A thorough necropsy showed the dog to be slightly emaciated, with all visible mucosal membranes cyanotic. All lymph nodes were atrophic and difficult to find; histopathologically they lacked germinal centers as well as paracortical lymphoid tissue. The architecture of the remaining structures was loose. The spleen was small and firm, showing histopathologically only a few follicular structures and periarterial lymphoid sheaths. The splenic trabeculae were prominent. In the heart, mild changes typical of endocardiosis were seen in the atrioventricular valves. The main gross lesions were associated with the lungs. The lungs were diffusely edematous, firm, and rubbery. The general color was brownish red, with diffuse yellowish-brown granular and patchy foci. The trachea and main bronchi were clean. A serous exudate in the distal bronchioli and interstitial tissue was easily detected on the cut surface of the lung. Formalin -fixed and paraffin-embedded lung-tissue specimens were stained with hematoxylin and eosin (HE), van Gieson, Gomori’s modification of Grocott’s methenamine silver staining (GMS), and immunohistochemically with the avidin-biotin peroxidase method, with the primary antibody being P. carinii-specific monoclonal antibody (DMo).h This antibody is known to stain both cyst and trophozoite stages of human-origin organisms.30 The lung showed changes typical for diffuse interstitial pneumonia; in some areas only minimal inflammation was present, with the number of inflammatory cells generally low, consisting mainly of macrophages with a smaller number of polymorphonuclear neutrophils and lymphocytes."

Pneumocystis carinii pneumonia in two Cavalier King Charles spaniels. Ramsey IK, Foster A, McKay J, Herrtage ME. Vet Rec. 1997 Apr 5;140(14):372-373. Quote: "This report describes two clinical cases of pneumonia in Cavalier King Charles spaniels in which large numbers of P carinii cysts were identified at postmortem examination. The first dog was a three-year-old neutered female that presented with a six week history of increasing respiratory distress. Treatment with various antibiotics, etamiphylline and glucocorticoids by the referring veterinary surgeon had been unsuccessful. On clinical examination the dog was found to be thin and tachypnoeic (100 to 160 breaths/minute). Despite this severe respiratory distress the dog was only slightly depressed. Rectal temperature was normal and the submandibular lymph nodes were slightly enlarged. On thoracic auscultation the lung sounds were diffusely increased and there was no cardiac murmur. Haematology demonstrated increased numbers of neutrophils, monocytes, eosinophils and a mild thrombocytopenia. Routine biochemistry was normal. Arterial blood gas analysis demonstrated reduced oxygen tension (59 mmHg) and haemoglobin saturation (91 per cent). Thoracic radiography showed a severe generalised interstitial lung pattern with patches of a superimposed alveolar pattern. The cardiac silhouette was of normal size and shape. Bronchoscopy under general anaesthesia was unremarkable. Cytology and bacterial culture of a bronchoalveolar lavage were unhelpful. The dog's condition progressively deteriorated and it was euthanased two months after first developing signs of respiratory disease. The second case was a 17-month-old entire female Cavalier King Charles spaniel that was presented with a two week history of progressive dyspnoea and occasional cyanosis. Clinical examination revealed tachypnoea (160 breaths/minute), tachycardia (170 beats/minute), slight cyanosis, a normal rectal temperature and harsh lung sounds over all lung fields. The dog was not depressed despite the severe clinical signs and no heart murmur was heard. Haematology demonstrated neutrophilia, monocytosis and eosinophilia. Routine biochemistry was normal. Arterial blood gas analysis demonstrated reduced oxygen tension (46.5 mmHg) and haemoglobin saturation (81 per cent). No antibodies to Toxoplasma gondii or Aspergillus species were detected on serological examination. Faecal examination did not demonstrate any lungworm larvae. A thoracic radiograph demonstrated an increased interstitial pattern and a pneumomediastinum. A prominent pulmonary artery segment was noted on the dorsoventral projection. Treatment with frusemide, enrofloxacin and anti-inflammatory doses of prednisolone was initially successful in reducing the respiratory rate. Bronchoscopy and bronchoalveolar lavage were then performed under general anaesthesia. Cytological examination of the lavage fluid did not identify a cause for the dog's respiratory distress. A fine needle aspirate of the right lung was non-diagnostic. Following this procedure the dog developed a pneumothorax which resolved following drainage. The dog's clinical condition remained stable for a few weeks but she died at home 10 weeks after the initial development of clinical signs. On postmortem examination both dogs had diffuse consolidation of the lungs which exuded foam from their cut surfaces. In the first case there were also multiple white foci, which were 1 to 2 mm in diameter, present over all the lobes and the bronchial lymph nodes were enlarged. Both cases showed similar histological changes, but the changes were more pronounced in the first case. ... The clinical signs of tachypnoea without pyrexia in a young dog with a generalised interstitial lung pattern and without obvious signs suggestive of cardiac failure should alert the clinician to the possibility of pneumocystic pneumonia. The decreased arterial oxygen tension seen in both cases is a recognised feature of the disease in humans and has been reported in other canine patients. Definitive diagnosis in the live patient can be difficult as bronchoalveolar lavages may be unhelpful (Farrow and others 1972). Fine needle lung aspirates are more reliable but there is an increased risk of complications, especially in animals whose respiratory function is already severely compromised. More invasive techniques, such as percutaneous lung biopsies and open lung biopsies, would be expected to carry even more risks. Data from human studies suggest that untreated pneumocystic pneumonia is uniformly fatal; however, the mortality rate in treated humans is 25 per cent. Trimethoprim-sulphamethoxazole appears to be the treatment of choice in canine patients. Short-term improvements have also been seen in response to glucocorticoid therapy. Given the role of immunosuppression in the pathogenesis of the disease in humans this therapeutic approach is not recommended in confirmed cases. ... The expanding use of immunosuppressive therapy in veterinary medicine may increase the prevalence of this condition. ... This has led to speculation that there may be an inherited immunodeficiency in this breed, although the affected dogs can make a full recovery and do not show clinical signs of other opportunistic infections. ... It is possible that there is a breedspecific factor that predisposes Cavalier King Charles spaniels in the UK to the development of this condition."

Case II - PM91-067 (AFIP 2642601). AFIP Wednesday Slide Conference - No. 27. April 21, 1999. Conference Moderator: LTC A. Peter Vogel. Contributor: Department of Veterinary Pathology, University of Liverpool. Quote: "Signalment: Two-year-old, male, Cavalier King Charles Spaniel, canine. History: There was tachypnea of two months duration and occasional diarrhea. The referring veterinarian treated the dog with antibiotics and steroids, but there was no response. The dog was referred to the Small Animal Hospital, University of Liverpool. On clinical examination, the dog was non-febrile, cyanotic, tachypneic, tachycardic, and had prominent mesenteric lymph nodes. Radiographs demonstrated marked interstitial pattern in lungs, an enlarged liver, and possibly enlarged sublumbar lymph nodes. The other lymph nodes were unremarkable. Gross Pathology: Respiratory System: The external nares, frontal sinuses and pharynx were unremarkable. The larynx, and especially trachea and bronchi, contained pale, stable foam and were lined by pale epithelium. The lungs collapsed partially on opening the chest. The cut surfaces of all lobes were grey-pink, firm, poorly-aerated, and exuded abundant fluid. The pleural surfaces were smooth and glistening without excess fluid. The macroscopic diagnosis was pulmonary consolidation. ... Contributor's Diagnosis and Comments: Lung: Chronic active interstitial pneumonia with myriad ring-shaped organisms typical of cyst forms of Pneumocystis carinii, Cavalier King Charles Spaniel, canine. Autolytic changes include detachment of airway epithelial cells. There is abundant eosinophilic, foamy, granular contents in airway lumina in which a few cells and faintly stained ring structures are also present. There are inflammatory cells (mostly lymphocytes and plasma cells) and patchy fibroplasia in alveolar septa. There is variable hyperplasia of type II pneumocytes. Methenamine silver staining reveals myriad ring-shaped organisms typical of cyst forms of Pneumocystis carinii in airway and alveolar lumina. This Cavalier King Charles Spaniel had advanced chronic active interstitial pneumonia in which organisms with morphological and staining characteristics of cyst forms of Pneumocystis carinii are identified. ... AFIP Diagnosis: Lung: Pneumonia, interstitial, chronic, diffuse, mild, with abundant alveolar and intra-airway eosinophilic flocculent material (atypical fungi), Cavalier King Charles Spaniel, etiology consistent with Pneumocystis carinii."

Pneumocystis carinii pneumonia in a Cavalier King Charles Spaniel. Hagiwara Y, Fujiwara S, Takai H, Ohno K, Masuda K, Furuta T, Nakayama H, Doi K, Tsujimoto H. J Vet Med Sci. 2001 Mar;63(3):349-51. Quote: "Pneumocystis carinii pneumonia was diagnosed by postmortem examination of a one-year-old Cavalier King Charles Spaniel with four-week history of dyspnea. Cytologic and histologic examination of lung tissues revealed numerous P. carinii trophozoites and cysts, and P. carinii specific DNA was detected by polymerase chain reaction. The dog showed hypogammagloblinemia and extremely low levels of serum IgG. It was considered that P. carinii pneumonia in this case was associated with an immunodeficient condition which has already been reported in Miniature Dachshunds."

DNA Analysis of Pneumocystis Infecting a Cavalier King Charles Spaniel. Kate English, Sarah E. Peters, Duncan J. Maskell, Margaret E. Collins. J. Eukaryotic Microbiology; June 2001;48(s1):106s. Quote: "Lung tissue was obtained from a 20-month old entire female Cavalier King Charles Spaniel which had been diagnosed with PCP post mortem by identification of Pneumocystis cysts. ... RESULTS AND DISCUSSION: The product of the PCR reaction was approximately 350 base pairs, similar in size to the PCR product generated from a positive control P. carinii from rat, and was consistent with amplification of a Pneumocystis-specific product. On sequencing seven clones of the PCR products two distinct DNA sequences were observed. Five clones gave Type A, and two Type B. A representative of each sequence type was sequenced on both strands to verify the data. The two sequences were shown to have 86.9% identity when compared to each other ... A FASTA search of the European Molecular Biology Laboratory Database found greatest identity with mt LSU rRNA Pneumocystis sequences derived from other host species. The identity with the sequence of Pneunocystis derived from other host species ranged from 87%-73% in the region compared. We have therefore shown that this dog was infected with a genetically distinct form of Pneumocystis and propose that Pneumocystis infecting a canine host be referred to as Pneumocystis canis. It is also proposed that the two forms be temporarily designated Type A and Type B while awaiting furthcr clarification of their relationship."

Immunoglobulin Deficiency in Cavalier King Charles Spaniels with Pneumocystis Pneumonia. P.J. Watson, P. Wotton, J. Eastwood, S.T. Swift, B. Jones, and M.J. Day. J Vet Intern Med 2006;20:523–527. Quote: "Serum concentrations of immunoglobulin G (IgG), IgM, and IgA were measured in 9 Cavalier King Charles Spaniels with pneumonia caused by Pneumocystis sp that were examined at 4 veterinary surgeries in the United Kingdom (UK) between September 2001 and November 2002. Pneumocystis pneumonia was confirmed in all dogs by visualization of the organism in bronchoalveolar lavage fluid or a transthoracic lung aspirate. Two dogs had a history of demodicosis. Immunoglobulin concentrations also were measured in breed-and age-matched dogs sampled over the same period. IgG concentrations were significantly (P 5 .000) lower in the affected dogs (median 3.2 mg/mL) than in the control dogs (median 8.5 mg/mL). IgM concentrations were significantly (P 5 .002) higher in the affected dogs (median 1.95 mg/mL) than in the control dogs (median 1.12 mg/mL). One affected dog had no change in IgG concentration more than 3 months after resolution of infection or vaccination, but did have reduction in IgM concentration after resolution of infection and vaccination. Control dogs had low serum IgG and IgM concentrations, compared with the reference interval for all dogs. Lymphocyte count in blood was normal or high in 7 of 8 affected dogs. The results of this study suggest that there is a defect in immunity in Cavalier King Charles Spaniels that underlies the susceptibility of these dogs to pneumocystosis. Further studies are indicated to elucidate the mechanisms behind the defect, the prevalence within the breed, and the potential mode of inheritance of the problem."

Pneumocystis pneumonia in two Cavalier King Charles Spaniel littermates. Meffert, F. J.  Australian Vet. Practitioner 2009; 39(1):2-2...9. Quote: "Pneumocystis pneumonia was diagnosed in two Cavalier King Charles Spaniel littermates with a chronic history of intermittent respiratory signs including tachypnoea, coughing and dyspnoea. Thoracic radiographs showed a diffuse interstitial pattern. Pneumocystis organisms were identified on cytological and histopathological examination of lung tissue at necropsy (of the first dog) and on pre mortem cytological examination of bronchial secretions from a second dog. The first dog was euthanised due to rapid deterioration prior to diagnosis. The second dog developed megaoesophagus two months after diagnosis of pneumocystis pneumonia and was euthanised due to persistent regurgitation. To the author's knowledge, this is the first report of pneumocystis pneumonia in Cavalier King Charles Spaniel littermates and provides further support for an underlying inheritable immunodeficiency in this breed."

A Case of Suspected Pneumocystis carinii Pneumonia in a Cavalier King Charles Spaniel. Richard Fox. Abbey Vet. Serv. Feb. 2012. Quote: "A male neutered 6-years-old Cavalier King Charles Spaniel presented with a 5 day history of increased respiratory effort. Radiographic examination revealed a marked bilateral and diffuse interstitial pattern. The dog was anaethetised and a bronchoalveolar lavage was performed from both the right and left lung fields. The sample was sent for Fox, Figure 1cytological examination. Cytospin and direct preparations were made of both samples and stained with a Rapid Romanowsky Stain. Degenerate neutrophils , small lymphocytes and infrequent erythrocytes (see photo at right) were prevelant. There were also several extracellular colonies of monomorphic short bacilliary bacteria exhibiting bipolar staining. Occasional neutrophils appeared to contain similar bacteria within their cytoplasm. The smear of BAL fluid from the right side revealed a more cellular harvest than that of the left side but its cellularity was qualitatively similar. However, there were multiple organisms present dissimilar to the bacteria previously noted. A few extracellular basophilic bodies were present. Most were approximately 3-4 um in diameter, homogenous basophilic staining associated with a background of flocculant basophilic material. Infrequently however there were similarly sized organisms with 8 spindle shaped deeply basophilic structures (8-10 um diameter). These organisms, given the breed and presence of numerous foamy macrophages were considered compatible with Pneumocystis trophozoites. Also a few septate fungal hyphae and pleomorphic bacteria were noted in the BAL from the right side. ... Numerous darkly staining spherical organisms (in addition to the fungal hyphae) were noted. Closer examination of less darkly stained structures reveiled a typical yeast like structure. Pneumocystoisis was then suspected but identifying a convenient laboratory which would perform PCR testing was not possible at the time of diagnosis. ... CKCS and Miniature Dachshunds appear to be predisposed to infection due to a suspected immunodeficient condition. ... The diagnosis is made by identifying the fungi in histologic sections. ... Pneumocystis cannot be cultured using conventional techniques, but novel cell culture systems have recently been described. A PCR test has been developed however."

A case of Pneumocystis carinii pneumonia in a 4 year old Cavalier King Charles Spaniel. Carmichael Torrance Vet. Diagnostic Lab. April 2012. Quote: "The dog had presented with recurrent dyspnoea and tachypnoea and showed a generalized interstitial pattern on radiographs. A few small round granular structures are found in a cytospin preparation from a BAL, consistent with Pneumocystis Carinii. This may be associated with an immunodeficient condition which has already been reported in Miniature Dachshunds, and assessment of the immunoglobulins (IgA, IgM and IgG) is advisable in these cases. PCR is also available, although this is usually carried out on lung tissue rather than washing fluid and false negative results may be possible."

Pneumocystis in CKCS Figure 1Pneumocystis infection in a Cavalier King Charles Spaniel. Emma Scurrell. CytoPath Vet. Path. Lab. Oct. 2012. Quote: "A 1-year-old male CKCS presented for tachypnoea and dyspnoea. Radiographs revealed an interstitial lung pattern. The rectal temperature was normal. A bronchoalveolar lavage (BAL) was performed. Fig 1 (right). Cytological findings revealed low numbers of neutrophils and macrophages and large numbers of extra- and intracellular 4-5um organisms typical of Pneumocystis spp. The red arrows point to two macrophages which are distended by the small fungal bodies (stained with modified Wrights-Giemsa). Final Diagnosis: Pneumocytis pneumonia. Discussion: Pneumocystis is an opportunistic fungal pathogen affecting humans and animals with impaired immunity. The entire life cycle is in the lungs and lesions are usually limited to the lungs. Any breed of dog can potentially be affected however Miniature Dachshunds and Cavalier King Charles Spaniels are predisposed, suspected to be associated with underlying immunodeficiency. Affected CKCSs have been shown to have decreased levels of IgG compared to control dogs. Diagnosis is usually made on direct visualisation of the organisms in BAL fluid or in a transthoracic lung aspirate. The organism will not culture using conventional techniques."

Finding your Way Through Pneumocystis Sequences in the NCBI Gene Database. Christiane Weissenbacher-Lang, Nora Nedorost, Herbert Weissenböck. J. Eukaryotic Microbiology. Sept. 2014;61(5):537-555. Quote: "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."

Pneumocystis canis pneumonia in dogs. Elizabeth Ralph, George Reppas, Catriona Halliday, Mark Krockenberger, Richard Malik. Microbiology Australia. March 2015; 10.1071/MA15026:A-D. Quote: Pneumocystis canis is a potential cause of life-threatening interstitial fungal pneumonia in dogs. It is seen almost exclusively in two canine breeds, miniature Dachshunds and Cavalier King Charles Spaniels (CKCS). Historically, Australian veterinarians had a key role in the documentation of this entity and its conspicuous breed associations. Affected Dachshunds and CKCS are likely to have an inherited immunodeficiency that predisposes them to infection with this commensal organism of the respiratory tract and pharynx. A high index of suspicion is required to make a timely diagnosis and save affected patients, as these dogs cope poorly with anaesthesia and other measures to procure the specimens required to make a definitive diagnosis. Possible co-infection with Bordetella bronchiseptica must be considered when determining antimicrobial strategies. Affected dogs occasionally have a previous or concurrent history of generalised demodicosis. With early intervention, affected dogs can be saved, although some require life-long therapy to prevent recurrence. The future challenge is to develop fast molecular techniques to diagnose P. canis pneumonia (PCP) and to determine the underlying immune defect in over-represented breeds through the rapidly advancing field of canine genomics.

Molecular diagnosis of Pneumocystis pneumonia in dogs. Patrizia Danesi, Silvia Ravagnan, Lynelle R. Johnson, Tommaso Furlanello, Adelaide Milani, Patricia Martin, Susan Boyd, Matthew Best, Bradley Galgut, Peter Irwin, Paul J. Canfield, Mark B. Krockenberger, Catriona Halliday, Wieland Meyer, Richard Malik. Med. Mycology. February 2017. Quote: Pneumocystis pneumonia (PCP) is a life-threatening fungal disease that can occur in dogs. The aim of this study was to provide a preliminary genetic characterisation of Pneumocystis carinii f.sp.‘canis’ (P. canis) in dogs and thereby develop a reliable molecular protocol to definitively diagnose canine PCP. We investigated P. canis in a variety of lung specimens from dogs with confirmed or strongly suspected PCP (Group 1, n = 16), dogs with non-PCP lower respiratory tract problems (Group 2, n = 65) and dogs not suspected of having PCP or other lower respiratory diseases (Group 3, n = 11). Presence of Pneumocystis DNA was determined by nested PCR of the large and small mitochondrial subunit rRNA loci and by a real-time quantitative polymerase chain reaction (qPCR) assay developed using a new set of primers. Molecular results were correlated with the presence of Pneumocystis morphotypes detected in cytological/histological preparations. Pneumocystis DNA was amplified from 13/16 PCP-suspected dogs (Group 1) and from 4/76 dogs of control Groups 2 and 3 (combined). The latter four dogs were thought to have been colonized by P. canis. Comparison of CT values in ‘infected’ versus ‘colonized’ dogs was consistent with this notion, with a distinct difference in molecular burden between groups (CT ≤ 26 versus CT range (26 <CT < 35), respectively). Phylogenetic analyses showed that P. canis is specifically ‘canine’ associated, being separated from other mammalian Pneumocystis species, thereby confirming the accuracy of qPCR amplicon for Pneumocystis in dogs. Using qPCR, Pneumocystis DNA can be detected in specimens from the respiratory tract and a CT value can be interpreted to distinguish infection versus colonization.

Pneumocystosis in dogs: meta-analysis of 43 published cases including clinical signs, diagnostic procedures, and treatment. Christiane Weissenbacher-Lang, Andrea Fuchs-Baumgartinger, Abigail Guija-De-Arespacochaga, Andrea Klang, Herbert Weissenböck, Frank Künzel. J. Vet. Diagn. Investig. November 2017. doi: 10.1177/1040638717742429. Quote: We evaluated 43 published cases of dogs with confirmed Pneumocystis infection [including 16 cavalier King Charles spaniels and 17 miniature Dachshunds] 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. ... A breed predisposition for Miniature Dachshunds and Cavalier King Charles Spaniels is evident. Dachshunds are reported to have a predisposition for combined B- and T-cell immunodeficiency, and typical clinical after-effects, such as severe respiratory tract infections, are documented. Given that Cavalier King Charles Spaniels were more susceptible to pneumocystosis than other breeds, a similar impairment of immunity was also assumed, but has not yet been confirmed. In a 2009 study, 2 King Charles Cavalier Spaniel littermates were affected by pneumocystosis, which also supports suspicions of an underlying heritable immunodeficiency in this breed. ... 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. ... The administration of an immunosuppressive dose of prednisolone of 15 mg q12h has only been described once in a Cavalier King Charles Spaniel. Because pneumocystosis occurs only rarely in dogs, there is little experience with the regulation of corticosteroid concentrations and the balance between immunosuppression and proliferation of the fungus. Additionally, predisposition for Pneumocystis infections of dog breeds with inherited immunodeficiency should be considered in the choice of an appropriate therapy.