Catastrophic declines in wild populations of
African gorilla and chimpanzees due to disease outbreaks have been reported in
recent years, yet similar disease impacts are rarely identified for the more
solitary Asian great apes, or for smaller primates. Researchers led by Sadie
Ryan, Assistant Professor at the State University of New York College of
Environmental Science and Forestry has recently published a study centered on
the interaction between the social system and demographics of different primate
species to determine if any of these behaviors or realities predispose them to
potentially lethal pathogens. Through this study the researchers have identified
interactions between social structure, demography, and disease transmission
modes that create “dynamic constraints” on the pathogens that can
establish and persist in primate host species with different social systems.
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Intragroup contact structure – the social network
– creates different constraints for different transmission modes, and the model
underscores the importance of intragroup contacts on infection prior to
intergroup movement in a structured population. When alpha males dominate
sexual encounters, the resulting disease transmission dynamics differ from when
social interactions are dominated by mother-infant grooming events, for
example.
The study included the identification of five
major primate social systems including solitary, monogamous, unimale,
multi-male, and fission-fusion. They developed matrices, for five disease
transmission modes including sexual, fecal-oral or local contamination,
aggressive interactions such as biting and scratching, direct aerosol and
vector transmitted disease. Pathogen transmission is highly dependent upon the
rate of contact, which is naturally different from one primate species to the
next.
In general, infections, which lead to immunity,
require higher rates of transmission, which in turn roughly scales with the
duration of immunity. This can also create complex epidemic dynamics such as
those seen in classic studies of human diseases. Ryan’s team focused on the
constraints that social system and body size place on the initial establishment
and impact of a non-immunizing infection.
“This has important repercussions for
pathogen spread across populations,” said the lead author, Dr. Sadie Ryan. “Our framework reveals essential social and demographic characteristics of
primates that predispose them to different disease risks that will be important
for disease management and conservation planning for protected primate
populations.”
Read more at SUNY ESF.
Orangutan
image via Shutterstock.