Melioidosis in Cynomolgus Macaques ( Macaca Fascicularis ) Imported to the United States from Cambodia

Abstract

Melioidosis, a potentially fatal infectious disease of humans and animals, including nonhuman primates (NHPs), is caused by the high-consequence pathogen Burkholderia pseudomallei. This environmental bacterium is found in the soil and water of tropical regions, such as Southeast Asia, where melioidosis is endemic. The global movement of humans and animals can introduce B. pseudomallei into nonendemic regions of the United States, where environmental conditions could allow establishment of the organism. Approximately 60% of NHPs imported into the United States originate in countries considered endemic for melioidosis. To prevent the introduction of infectious agents to the United States, the Centers for Disease Control and Prevention (CDC) requires newly imported NHPs to be quarantined for at least 31 d, during which time their health is closely monitored. Most diseases of public health concern that are transmissible from imported NHPs have relatively short incubation periods that fall within the 31-d quarantine period. However, animals infected with B. pseudomallei may appear healthy for months to years before showing signs of illness, during which time they can shed the organism into the environment. Melioidosis presents diagnostic challenges because it causes nonspecific clinical signs, serologic screening can produce unreliable results, and culture isolates are often misidentified on rapid commercial testing systems. Here, we present a case of melioidosis in a cynomolgus macaque (Macaca fascicularis) that developed a subcutaneous abscess after importation from Cambodia to the United States. The bacterial isolate from the abscess was initially misidentified on a commercial test. This case emphasizes the possibility of melioidosis in NHPs imported from endemic countries and its associated diagnostic challenges. If melioidosis is suspected, diagnostic samples and culture isolates should be submitted to a laboratory in the CDC Laboratory Response Network for conclusive identification and characterization of the pathogen.

Figure 1.

Phylogenomic single nucleotide polymorphism (SNP) tree of Burkholderia pseudomallei strains throughout the world (n = 1,695). The geographic origin of each strain, collected from the NCBI BioSample database, is colored at the tree leaves. Each of 3 strains isolated from individual Cambodian NHPs imported to the United States are shown with red branches and emphasized with black arrows to indicate phylogenetic placements in the large tree. BpTX2021NHP_Alpha was isolated from the NHP described in this report; BPTX2014NHP_Alpha and BPTX2015NHP_Alpha were imported in 2014 and 2015, respectively. All 3 NHP strains occur within East Asia; however, each is clearly distant from the others. Scale bar and substitutions are per core SNP site.

Figure 2.

(A) Gross liver lesions (arrows; scale is cm). (B) Gross splenic lesion (arrow; scale is cm). (C) Gross lung lesion, right caudal lung lobe (arrow; scale is cm). (D). Gross spinal cord lesion (arrow; longitudinal section; left is cranial; scale is cm).

Figure 3.

Histopathologic and immunohistochemical findings in in a cynomolgus macaque (Macaca fascicularis) case of B. pseudomallei infection: (A) Low magnification of lung shows microabscess. Hematoxylin and eosin (H and E), 5× original magnification. (B) Low magnification of liver shows abscess with necrosis (*) surrounded by neutrophils, macrophage, and fibrosis. Hematoxylin and eosin (H and E), 5× original magnification. (C) High magnification of liver abscess wall shows inflammatory infiltrate composed predominantly by neutrophils and macrophages. Hematoxylin and eosin (H and E), 20× original magnification, (D) Immunostaining by using anti–Burkholderia pseudomallei antibody.