Rapid transmission of respiratory infections within but not between mountain gorilla groups

Abstract

Minimizing disease transmission between humans and wild apes and controlling outbreaks in ape populations is vital to both ape conservation and human health, but information on the transmission of real infections in wild populations is rare. We analyzed respiratory outbreaks in a subpopulation of wild mountain gorillas (Gorilla beringei beringei) between 2004 and 2020. We investigated transmission within groups during 7 outbreaks using social networks based on contact and proximity, and transmission between groups during 15 outbreaks using inter-group encounters, transfers and home range overlap. Patterns of contact and proximity within groups were highly predictable based on gorillas’ age and sex. Disease transmission within groups was rapid with a median estimated basic reproductive number (R0) of 4.18 (min = 1.74, max = 9.42), and transmission was not predicted by the social network. Between groups, encounters and transfers did not appear to have enabled disease transmission and the overlap of groups’ ranges did not predict concurrent outbreaks. Our findings suggest that gorilla social structure, with many strong connections within groups and weak ties between groups, may enable rapid transmission within a group once an infection is present, but limit the transmission of infections between groups.

RETRACTED ARTICLE: Exploring the potential effect of COVID-19 on an endangered great ape

“…For example, increased group density is associated with increased intergroup interactions 42 , 43 , which presumably would enhance the opportunity for COVID-19 to pass from one group to another, thus increasing R 0 . The potential transmission of diseases like COVID-19 between social groups is an important area of future study (for respiratory diseases on this population see 44 . Nonetheless, our finding that there is a threshold value of R 0 = 1.05 above which the subpopulations start declining highlights the current risk of an outbreak on the subpopulation.…”

“…In the longer term, minimizing R 0 in mountain gorillas could involve decreasing the frequency of group interactions 44 , by minimizing any risk of human disturbance to existing habitat allowing groups to spread out to the maximum extent and also expanding the park.…”

Respiratory Disease Risk of Zoo-Housed Bonobos Is Associated with Sex and Betweenness Centrality in the Proximity Network

“…Bonobos that never exhibited symptoms were considered to be healthy and non-infected during the study period (cf. [ 57 , 58 ]; see Supplementary Table S1 ).…”

“…Nevertheless, respiratory disease is a major cause of morbidity and mortality in both captive and wild primate populations and thus a prominent threat to general primate welfare [ 40 , 42 , 43 , 54 , 55 , 56 ]. To date, only two studies have investigated the link between SNA measures and the occurrence of respiratory disease in primates [ 57 , 58 ]. One study found no association between the social network and respiratory disease in mountain gorillas ( Gorilla beringei beringei ) [ 57 ], while another study showed that in chimpanzees, males with higher strength in a proximity network had a higher chance of showing symptoms of respiratory disease, indicating the vital role of the social-proximity network in the spread of the pathogen in the group [ 58 ].…”

“…To date, only two studies have investigated the link between SNA measures and the occurrence of respiratory disease in primates [ 57 , 58 ]. One study found no association between the social network and respiratory disease in mountain gorillas ( Gorilla beringei beringei ) [ 57 ], while another study showed that in chimpanzees, males with higher strength in a proximity network had a higher chance of showing symptoms of respiratory disease, indicating the vital role of the social-proximity network in the spread of the pathogen in the group [ 58 ]. However, this study focused solely on adult males and did not investigate the role of females and juveniles, which can also be important mediators of the spread of pathogens throughout the group [ 58 ].…”