Pneumocystis Colonization in Dogs Is as in Humans

Abstract

Pneumocystis is an atypical fungus that resides in the pulmonary parenchyma of many mammals, including humans and dogs. Immunocompetent human hosts are usually asymptomatically colonised or show subtle clinical signs, but some immunocompromised people can develop florid life-threatening Pneumocystis pneumonia (PCP). Since much less is known concerning Pneumocystis in dogs, we posit the question: can Pneumocystis colonization be present in dogs with inflammatory airway or lung disease caused by other pathogens or disease processes? In this study, Pneumocystis DNA was detected in bronchoalveolar lavage fluid (BALF) of 22/255 dogs (9%) with respiratory distress and/or chronic cough. Although young dogs (<1 year-of-age) and pedigree breeds were more often Pneumocystis-qPCR positive than older dogs and crossbreds, adult dogs with other infectious conditions and/or a history of therapy-resistant pulmonary disease could also be qPCR-positive, including two patients with suppression of the immune system. Absence of pathognomonic clinical or radiographic signs render it impossible to convincingly discriminate between overt PCP versus other lung/airway disease processes colonised by P. canis. It is possible that colonisation with P. canis might play a certain role as a co-pathogen in some canine patients with lower respiratory disease.

Oculosystemic pneumocystosis in 2 sibling Chihuahuas

“…For this reason and because history was unavailable on the parents and siblings of the 2 dogs, it was impossible to identify the original source of Pneumocystis . Potential sources include transplacental transmission or colonization by aerosolization between dogs housed in the same environment 2,3 . It is unclear if pneumocystosis was the cause of tachypnea noted initially in the dogs described here or if the organism disseminated after chronic corticosteroid administration.…”

“…In dogs, Pneumocystis carinii formae speciales “ canis ” ( P. canis ) recently has been identified using quantitative PCR and genetic sequencing 1 . Pneumocystis pneumonia in the dog appears to be similar to that in humans, where low numbers of organisms, presumed to be commensal in healthy immunocompetent individuals, proliferate in immunocompromised individuals and cause severe pneumonia 1‐3 . Use of quantitative PCR to document low cycle thresholds (CT) in dogs with pneumonia has allowed elucidation of this disease process, 1 and rRNA sequencing confirms infection 2 …”

“…1 Pneumocystis pneumonia in the dog appears to be similar to that in humans, where low numbers of organisms, presumed to be commensal in healthy immunocompetent individuals, proliferate in immunocompromised individuals and cause severe pneumonia. [1][2][3] Use of quantitative PCR to document low cycle thresholds (CT) in dogs with pneumonia has allowed elucidation of this disease process, 1 and rRNA sequencing confirms infection. 2 Approximately 50 cases of Pneumocystis pneumonia have been reported in the veterinary literature, most cases in miniature dachshunds with immunodeficiency involving T and B cells 4 and in Cavalier King Charles spaniels, 5 in which immune deficits are also suspected.…”

“…[1][2][3] Use of quantitative PCR to document low cycle thresholds (CT) in dogs with pneumonia has allowed elucidation of this disease process, 1 and rRNA sequencing confirms infection. 2 Approximately 50 cases of Pneumocystis pneumonia have been reported in the veterinary literature, most cases in miniature dachshunds with immunodeficiency involving T and B cells 4 and in Cavalier King Charles spaniels, 5 in which immune deficits are also suspected. An X-linked mutation of a protein involved in both humoral and cell-mediated immunity also has been reported.…”

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

“…In those cases, previous illnesses and chronic co-infections such as demodicosis [ 51 , 62 , 68 , 69 ] or canine distemper [ 70 ] may have caused the underlying immunodeficiency. In breeds with described congenital immunosuppression, the dogs with PCP are generally young [ 64 , 65 , 72 ], while there are reports that age is not a crucial factor in dogs with immunosuppression caused by other factors [ 70 , 73 ]. Nevertheless, little information is available for many mammalian species regarding congenital immunosuppression.…”