Case study: Pneumonia in a Ringtail Lemur

From the June 2020 Newsletter:

The first case is a 2-week-old female Ringtail lemur (Lemur catta) that was found dead after three other neonatal lemurs from the same cohort died the previous week. Grossly, lung lobes were mottled red and pink and were heavy, wet and congested – lesions consistent with pneumonia.Under the microscope, large airways were packed with cellular debris (necrosis) and acute inflammatory cells (Figure A). Smaller airways also were filled with inflammatory cells. Respiratory epithelial cells rarely contained one enlarged smudged nuclei, suggestive of adenovirus infection (Figure B, arrows).

Airways are filled with cellular debris (necrosis) and acute inflammatory cells in a neonatal Ring-tailed lemur with Bordetella bronchiseptica pneumonia (A). Inflammatory cells are primarily degenerate neutrophils (B) and rare enlarged nuclei are in respiratory cells, suggestive of adenovirus infection (arrows).

Other features denoting underlying viral infection also were observed. Bacterial cultures were positive for Bordetella bronchiseptica and Escherichia coli. Pneumonia associated with B. bronchiseptica (one of the etiologic agents associated with canine infectious respiratory disease complex or “kennel cough”) has been described in nonhuman primates (NHP), including marmosets, tiki monkeys and bushbabies. The latter are prosimians, a subgroup of NHPs that also includes lemurs.

The organism is a known commensal (normal bacterium) in the nasopharynx of several NHPs, but disease can be associated with stressful conditions, such as overcrowding, recent shipping, being quarantined and poor husbandry. E. coli also can cause septicemia and death in neonates of many species.PCR for common human adenoviruses was negative. However, lemurs are known to harbor their own species-specific adenoviruses that would not have been detected by the assay performed. Adenovirus infection is not uncommon in NHP neonates that have concurrent respiratory or systemic infections.

Another differential for neonatal pneumonia in lemurs is disseminated Toxoplasma gondii infection, which can be acquired in utero. Immunohistochemical stain was negative for this protozoan parasite. Thus, the cause of death was determined to be B. bronchiseptica pneumonia with likely underlying adenovirus infection.

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