Miniature dachshunds are the most commonly reported breed to be affected, although the condition has also been documented in standard dachshunds ...
The Veterinary Record, April 5, 1997
Pneumocystis carinii pneumonia in two Cavalier King Charles spaniels I.
K. Ramsey, A. Foster, J. McKay, M. E. Herrtage
Veterinary Record (1997) 140, 372-373
Pneumocystis carinii is a ubiquitous parasite of animals and man. It was originally thought to be a protozoan but has since been classified as a fungus (Edman and others 1988). It can cause severe respiratory disease in susceptible animals and man, although infections are usually subclinical. In man, the parasite is a major cause of mortality in immunocompromised individuals, for example AIDS patients. In dogs, the parasite seems to be associated with particular breeds. Miniature dachshunds are the most commonly reported breed to be affected, although the condition has also been documented in standard dachshunds (Copland 1974, Botha and van Rensberg 1979, McCully and others 1979, Lobetti and others 1996). Three Cavalier King Charles spaniels have been reported with the condition (Brownlie 1990, Canfield and others 1993, Sukura and others 1996). 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 (Fig 1). 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
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-
I. K. Ramsey, A. Foster, J. McKay, M. E. Herrtage, Department of Clinical Veterinary Science, University of Cambridge, Madingley Road,
Cambridge CB3 OES A. Foster's present address is Oakley Veterinary Clinic, 65 Oakley Road,
Caversham, Berkshire RG4 7RN
FIG 1: Lateral thoracic radiograph of a Cavalier King Charles spaniel with interstitial pneumonia due to P carinii which shows the severe generalised interstitial lung pattern that was a feature of both cases
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. On sections stained with haematoxylin and eosin there was a severe interstitial pneumonia with infiltration of lymphocytes and macrophages into the interstitium. The alveolar luminae were filled with a weakly eosinophilic foamy substance. Sloughing of the alveolar lining cells was noted in some luminae. Type II pneumocyte proliferation with syncitial formation was noted (suggesting destruction of type I pneumocytes). Smooth muscle hyperplasia was present in some bronchiolar walls. Grocott-Gomori methanamine silver and periodic acid-Schiff staining (PAS) demonstrated that the foamy substance in the alveolar luminae was made of large numbers of cystic structures consistent with P carinii. The cysts were oval or round in shape and varied in diameter from 2 to 6 ,um. Electron microscopy demonstrated both the thin-walled trophozoite forms of the parasite and the thickwalled pneumocysts containing the daughter cells (Fig 2). The diagnosis of pneumocystic pneumonia was confirmed by Dr K. Whitwell (Animal Health Trust) by performing immunohistochemistry using a monoclonal anti-P carinii antibody (Dako). These two cases were similar in many respects to those previously reported. 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 (Lobetti and others 1996). 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
The Veterinary Record, April 5, 1997
373 LOBET1TI, R. G., LEISEWITZ, A. L. & SPENCER, J. A. (1966) Journal of Small Animal Practice 37, 280 McCULLY, R. M., LLOYD, J., KUYS, D. & SCHNEIDER, D. J. (1979) Journal of the South African Veterinary Association 50, 207 SUKURA, A., SAARI, S., JARVINEN, A., OLSSON, M., KARKKAINEN, M. & ILVESNIEMI, T. (1996) Joumal of Veterinary Diagnostic Investigation 8, 124 TESKE, E., STOKHOF, A. A., VAN DEN INGH, T. S. G. A. M., WOLVEKAMP, W. T. C., SLAPPENDEL, R. J. & DE VRIES, H. W. (1991) Journal of the American Animal Hospital Association 27, 289
Prevention of entry of avian influenza and paramyxoviruses into an ornithological collection K. F. Shortridge, D. Burrows Veterinary Record (1997) 140, 373-374 FIG 2: Electron micrograph showing a thick walled pneumocyst containing three daughter cells (d) with remnants of the membranous strands (arrowed) that attached the cells to the cyst wall in vivo. x 20,000
in animals whose respiratory function is already severely compromised (Teske and others 1991). 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 (Lobetti and others 1996). Short-term improvements have also been seen in response to glucocorticoid therapy (Botha and van Rensberg 1979). Given the role of immunosuppression in the pathogenesis of the disease in humans this therapeutic approach is not recommended in confirmed cases. A search of the postmortem and radiological records at Cambridge University veterinary school over the past 10 years failed to reveal any other confirmed cases of pneumocystic pneumonia. This suggests that it is a rare condition in dogs. The expanding use of immunosuppressive therapy in veterinary medicine may increase the prevalence of this condition. A preponderance of cases of pneumocystic pneumonia in miniature dachshunds has been noted over several years, although no cases have been reported in miniature dachshunds of UK origin. 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 (Lobetti and others 1996). Five cases (including these two) have now been reported in Cavalier King Charles spaniels, three of whom originated in the UK. It is possible that there is a breedspecific factor that predisposes Cavalier King Charles spaniels in the UK to the development of this condition.
Acknowledgements.- The authors would like to acknowledge the assistance of Dr K. Whitwell, Miss E. McInnes and Mr A. Jefferies with these cases.
References BOTHA, W. S. & VAN RENSBERG, I. B. J. (1979) Journal of the South African Veterinary Association 50, 173 BROWNLIE, S. E. (1990) Journal of Small Animal Practice 31, 371 CANFIELD, P. J., CHURCH, D. B. & MALIK, R. (1993) Australian Veterinary Practitioner 23, 150 COPLAND, J. W. (1974) Australian Veterinary Journal 50, 515 EDMAN, J. C., KOVACS, J. A., MASUR, H., SANTI, D. V., ELWOOD, H. J. & SOGIN, M. L. (1988) Nature 334, 519 FARROW, B. R. H., WATSON, A. D. J. & HARTLEY, W. J. (1972) Comparative Pathology 82, 447
THE potential importance of avian paramyxoviruses (APMV) as a cause of mortality in captive bird collections under conditions of stress was highlighted in a previous report (Shortridge and others 1991). In that study, APMV-3 was associated with the death of two red-headed tits (Aegithalos concinnus) in a collection in Hong Kong during a preseasonal cold spell. Subsequently a new, separate collection was established in a walk-through aviary of 3000 m2 with vegetation, and the opportunity was taken to screen the birds for myxoviruses (influenza) and APMV before placing them in the collection. The study lasted three and three quarter years from the time of receipt of the first batch of birds into quarantine in September 1991 to the end of the observation of birds in the aviary in June 1995. To stock the collection, 971 birds of species indigenous to the Malesian region were acquired in 31 batches from zoos, breeders and suppliers in southeast Asia, Europe and the USA and was 90 per cent complete within one year. The birds comprised 25 families from eight orders: Passeriformes (65 per cent), Columbiformes (15 per cent), Psittaformes (9 per cent), Piciformes (3 per cent), Galliformes (3 per cent), Gruiformes (2 per cent), Anseriformes (2 per cent) and Pelicaniformes (1 per cent). All birds were quarantined and clinically monitored for 30 days or longer and faecal samples collected on arrival. Birds that died were subjected to postmortem examination and postmortem specimens of brain, lung, trachea and intestine were collected for virological examination. Faecal and tissue samples were collected in transport medium containing double strength penicillin, streptomycin, gentamicin and nystatin. Faecal specimens were agitated in a vortex mixer and tissue specimens homogenised in a Ten Brock homogeniser before inoculation into the allantoic cavities of 10day-old embryonated hen eggs. Two to four eggs were used for each sample depending on availability. Samples that could not be inoculated immediately were stored at -70°C. Haemagglutinating agents that were isolated were identified in haemagglutination inhibition (HI) and in neuraminidase inhibition (NI) tests as required. Influenza A viruses were isolated from the faeces of four birds from two batches acquired at the outset: three hill mynahs (Gracula religiosa) from one batch yielded H4N8 viruses, and a long-tailed broadbill (Psarisomus dalhousiae) from the other yielded an isolate of the H4 subtype that reacted in NI with both N6 and N7 monospecific antisera suggestive of a mixed population of viruses (Table 1). Mixed populations of influenza A virusK. F. Shortridge, Department of Microbiology, The University of Hong Kong, University Pathology Building, Queen Mary Hospital, Pokfulam
Road, Hong Kong D. Burrows, Veterinary Services Section, Urban Services Department, 42/F, 66 Queensway, Hong Kong