Clinical Manifestations of an Outbreak of Monkeypox Virus in Captive Chimpanzees in Cameroon, 2016

Abstract

Monkeypox virus (MPXV) is a reemerging virus of global concern. An outbreak of clade I MPXV affected 20 captive chimpanzees in Cameroon in 2016. We describe the epidemiology, virology, phylogenetics, and clinical progression of this outbreak. Clinical signs included exanthema, facial swelling, perilaryngeal swelling, and eschar. Mpox can be lethal in captive chimpanzees, with death likely resulting from respiratory complications. We advise avoiding anesthesia in animals with respiratory signs to reduce the likelihood of death. This outbreak presented a risk to animal care staff. There is a need for increased awareness and a One Health approach to preparation for outbreaks in wildlife rescue centers in primate range states where MPXV occurs. Control measures should include quarantining affected animals, limiting human contacts, surveillance of humans and animals, use of personal protective equipment, and regular decontamination of enclosures.

Keywords: One Health; epidemiology; mpox; outbreak; zoonosis.

Figure 1.

A, Map showing the location of Mefou Primate Sanctuary in the Centre Region of Cameroon, the affected chimpanzee enclosure, and small mammal trapping locations. For the country map (inset), Health Districts are divided by thin, light grey lines, whilst thicker, darker grey lines denote regional boundaries. Health Districts in Cameroon where mpox cases have been reported in humans and NHPs up to the end of 2021 [, –20] are shaded. Single human cases of CI MPXV have been documented in the Centre region of Cameroon in 1979 [21] and 1989 [22], with more widespread outbreaks recorded since 2019 [1, 17, 19, 20]. Cases of CII MPXV were reported in the Southwest and Northwest Regions of Cameroon in 2018 and 2022–23 [1, 15, 17, 19]. The virus circulating in 2018 was closely related to strains circulating in neighboring Nigeria [15]. The primate enclosures typically comprise a covered night shelter connected to an open-air, forested area (Supplementary Figure 1). The sanctuary is within the 1044ha proposed Mefou National Park which is a mixture of intact and disturbed forest. Adjoining farmlands are cultivated on a rotating basis, with forest allowed to regenerate during the fallow period. The animals at the sanctuary were typically removed from the wild by poachers as infants and arrived in the sanctuary following confiscation or voluntary handovers from hunters, traders or people keeping them as pets. B, Epidemic curve shows incident cases of mpox by subgroup against date of onset. Subgroup A moved between a daytime forested enclosure and a caged night shelter, but subgroup B were confined to cages throughout (Supplementary Figure 1). Likely exposure dates and latest onset date for a point source outbreak were calculated by extrapolation of the IQR for human incubation periods for clade I mpox to the onset date in the index case. Labelled dashed lines: A = earliest likely exposure date, B = latest likely exposure date, C = latest expected onset date from a point source exposure. Unlabelled dashed line (17 Aug): last date with percutaneous direct contact between the subgroups. Index case: *date of onset, **death. Other fatality: +date of onset, +death.