Aspergillus spp. Infection

There have been isolated reports of outbreaks and spo­radic cases of upper respiratory tract infections in labo­ratory rats due to Aspergillus fumigatus or Aspergillus niger. On microscopic examination, the changes are consistent with a chronic rhinitis with epithelial changes varying from hyperplasia to squamous metaplasia. Pulmonary aspergillosis has also been reported in laboratory rats. Fungal hyphae are readily demonstrated on epithelial surfaces of affected nasal passages or lung lesions with PAS or silver stains. Possible predisposing factors include contaminated bedding, air quality, the presence of con­current infections, and immune status of the host.