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793.e2 Pneumocystosis

Pneumocystosis Client Education
Sheet
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transmission is by airborne droplets, typically
BASIC INFORMATION
• Serum protein electrophoresis: hypogam-
from asymptomatic bitch to pup soon after • Urinalysis: usually normal
Definition birth. maglobulinemia (IgM, IgG, IgA)
Rare infectious opportunistic disease of the • Pneumocystosis is caused by P. carinii, a • Thoracic radiographs
lungs; associated with immune incompetence saprophyte of the mammalian respiratory ○ Diffuse, symmetrical, mixed interstitial to
tract whose life cycle is completed within alveolar pattern
Synonym alveolar spaces. ○ Bronchial pattern
Pneumocystis carinii pneumonia • Five species of Pneumocystis, which appear to ○ Less commonly, cavitary lesions, solitary
be highly host specific, have been described: lesions, and asymmetrical changes are seen.
Epidemiology two species that infect dogs and rats, P. carinii ■ Single case report of pneumomedias-
SPECIES, AGE, SEX and Pneumocystis wakefieldiae; one species tinum in a whippet with P. carinii
• Young dogs of either sex that infects mice, Pneumocystis murina; a ○ Emphysema in severe chronic cases
• Miniature dachshunds develop disease at < species that infects rabbits, Pneumocystis ○ Right-sided cardiomegaly (cor pulmonale)
1 year of age; Cavalier King Charles spaniels oryctolagi; and Pneumocystis jirovecii, which • Pulmonary hypertension sometimes con-
tend to develop disease as young adults. infects humans. For purposes of this chapter, firmed on echocardiogram
• Not reported in cats the organism that infects dogs is referred to
as P. carinii. Advanced or Confirmatory Testing
GENETICS, BREED PREDISPOSITION • Based on polymerase chain reaction (PCR) • Definitive antemortem diagnosis of P. carinii
Most infected dogs are miniature dachshunds, analysis, the organism is classified as an is established by direct visualization of the
Shetland sheepdogs, or Cavalier King Charles atypical fungal organism. trophozoite or cyst in respiratory washes
spaniels. Also reported in a beagle, Yorkshire • P. carinii can be found in low numbers in collected by transtracheal aspiration or
terrier, Pomeranian, and whippet cross. the pulmonary alveoli of healthy animals and bronchoalveolar lavage, fine-needle aspirates
is associated with pneumonia and respira- of lung (p. 1113), or lung biopsies obtained
RISK FACTORS tory distress only when there is immune by thoracotomy or thoracoscopy (pp. 1073
• Congenital or acquired immune-suppressive compromise. and 1074).
diseases • With immune compromise, the organism ○ Histochemical stains and diagnostic
• Syndrome of common variable immunodefi- proliferates within the alveoli, resulting in immunohistochemistry tests may facilitate
ciency reported in the miniature dachshund alveolar capillary blockage and ventilation- observation of organisms.
and Pomeranian (single case report). perfusion mismatch. Thickening of alveolar ○ PCR on respiratory samples can establish a
• Cavaliers may have defects in lymphocyte septa occurs, but there is rarely extension of diagnosis and identify the species. Current
function and immunoglobulin deficiencies the infection into the pulmonary interstitium. data suggest sensitivity of PCR is superior
similar to miniature dachshunds. to direct visualization due to potentially
DIAGNOSIS low organism numbers in airway samples.
ASSOCIATED DISORDERS • Serologic tests: available for humans but of
Those supporting concurrent immune dysfunc- Diagnostic Overview uncertain value in dogs
tion (e.g., generalized demodicosis) The diagnosis is suspected in young dogs of • Thoracic CT: compatible with diffuse inter-
susceptible breed with described signs and stitial lung disease (ground-glass attenuation)
CONTAGION AND ZOONOSIS pulmonary infiltrates. Fever is frequently absent • Arterial blood gas (ABG) analysis: hypox-
Zoonotic transmission to an HIV-infected despite significant disease. Definitive diagnosis emia, normocapnia to hypocapnia, increased
person may be possible but is as yet unreported. requires direct visualization of the organism or alveolar-arterial (A-a) oxygen gradient
confirmation by PCR on airway washes.
Clinical Presentation
HISTORY, CHIEF COMPLAINT Differential Diagnosis TREATMENT
Some or all of the following may prompt an • Other infectious pneumonias Treatment Overview
owner to seek veterinary consultation: ○ Bacterial (p. 795) Eradicate infection while providing symptom-
• Tachypnea/respiratory distress ○ Viral atic and supportive care.
• Exercise intolerance ○ Protozoal (e.g., Neospora caninum, Toxo-
• Weight loss plasma gondii) Acute General Treatment
○ Mycotic (e.g., Histoplasma capsulatum, • Oxygen administration as needed (p. 1146)
PHYSICAL EXAM FINDINGS Blastomyces dermatitidis, Coccidioides • Mucolytics
• Tachypnea immitis) ○ Acetylcysteine (10% or 20% solution)
• Respiratory distress/increased effort • Pulmonary fibrosis (p. 553) 50 mL/h for 30-60 minutes q 12h by
• Poor body condition • Congestive heart failure (p. 408) nebulization
• Marked increase in respiratory sounds on • Ciliary dyskinesia ○ Bromhexine 1 mg/kg PO q 12h
thoracic auscultation ○ Administration of bronchodilators
• Cyanosis with severe infections. Initial Database beforehand is recommended.
• ± Cough • CBC may demonstrate • Bronchodilator: aminophylline 10 mg/kg PO
• ± Fever (often low grade or absent) ○ Erythrocytosis q 8h or terbutaline 0.625-2.5 mg PO total
○ Thrombocytosis dose q 8-12h
Etiology and Pathophysiology ○ Neutrophilic leukocytosis • Saline nebulization and coupage to liquefy
• Pneumocystis spp are commensal organisms ○ ± Eosinophilia and monocytosis hyperviscous mucus and promote the
of the respiratory tract. Disease occurs in • Serum biochemistry profile removal of secretions from the respiratory
immunocompromised subjects. In dogs, ○ ± Low to low-normal globulins tree

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