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© The Author(s) 2021
K. De Baets, J. W. Huntley (eds.), The Evolution and Fossil Record of Parasitism,
Topics in Geobiology 49, https://doi.org/10.1007/978-3-030-42484-8_2
Chapter 2
Fossil Record of Viruses, Parasitic Bacteria
and Parasitic Protozoa
George Poinar
Abstract Fossil evidence of ancient pathogens is rare and limited mostly to
specimens associated with arthropod vectors in amber. In various fossil vectors is
evidence of cytoplasmic and nuclear polyhedrosis viruses, pathogenic spirochetes,
rickettsia, actinomycetes and protozoa. Also present in amber are examples of fossil
virus-like tumors and indirect evidence of iridoviruses, polydnaviruses, pathogenic
bacteria and protozoans. Many of these pathogens resemble those being transmitted
today to a range of vertebrate hosts by arthropod vectors. Based on these findings,
it is clear that invertebrate and vertebrate viruses, as well as a range of pathogenic
bacteria and protozoa, were well established by the mid-Cretaceous.
Keywords Fossils · Polyhedrosis viruses · Iridoviridae · Polydnaviruses ·
Pathogenic bacteria · Pathogenic protozoa · Cretaceous · Cenozoic
2.1 Introduction
Insects evolved some 400 million years ago and probably became infected with
viruses bacteria and protozoa soon after. Over time, these microbes developed various symbiotic associations with invertebrates and vertebrates (De Baets and
Littlewood 2015). One phase of the evolution of microbes was their association
with hematophagous arthropods which resulted in the introduction of viral, bacterial and protozoan parasites into vertebrates. In searching for records of fossil
microbial parasites, it is useful to carefully examine fossils in amber, especially
hematophagous arthropods. Due to the excellent preservation qualities of amber, it
is one of the most suitable fossil sources for studying pathogenic microbes. This is
due to the ability of resin to infiltrate, fix, and dehydrate the inclusions. During these
processes, oxygen is restricted and associated decay-causing microorganisms are
destroyed. Terpenoids and resin acids are responsible for tissue fixation, while
G. Poinar ()
Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
e-mail: poinarg@science.oregonstate.edu
© The Author(s) 2021
K. De Baets, J. W. Huntley (eds.), The Evolution and Fossil Record of Parasitism,
Topics in Geobiology 49, https://doi.org/10.1007/978-3-030-42484-8_2
Chapter 2
Fossil Record of Viruses, Parasitic Bacteria
and Parasitic Protozoa
George Poinar
Abstract Fossil evidence of ancient pathogens is rare and limited mostly to
specimens associated with arthropod vectors in amber. In various fossil vectors is
evidence of cytoplasmic and nuclear polyhedrosis viruses, pathogenic spirochetes,
rickettsia, actinomycetes and protozoa. Also present in amber are examples of fossil
virus-like tumors and indirect evidence of iridoviruses, polydnaviruses, pathogenic
bacteria and protozoans. Many of these pathogens resemble those being transmitted
today to a range of vertebrate hosts by arthropod vectors. Based on these findings,
it is clear that invertebrate and vertebrate viruses, as well as a range of pathogenic
bacteria and protozoa, were well established by the mid-Cretaceous.
Keywords Fossils · Polyhedrosis viruses · Iridoviridae · Polydnaviruses ·
Pathogenic bacteria · Pathogenic protozoa · Cretaceous · Cenozoic
2.1 Introduction
Insects evolved some 400 million years ago and probably became infected with
viruses bacteria and protozoa soon after. Over time, these microbes developed various symbiotic associations with invertebrates and vertebrates (De Baets and
Littlewood 2015). One phase of the evolution of microbes was their association
with hematophagous arthropods which resulted in the introduction of viral, bacterial and protozoan parasites into vertebrates. In searching for records of fossil
microbial parasites, it is useful to carefully examine fossils in amber, especially
hematophagous arthropods. Due to the excellent preservation qualities of amber, it
is one of the most suitable fossil sources for studying pathogenic microbes. This is
due to the ability of resin to infiltrate, fix, and dehydrate the inclusions. During these
processes, oxygen is restricted and associated decay-causing microorganisms are
destroyed. Terpenoids and resin acids are responsible for tissue fixation, while
G. Poinar ()
Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
e-mail: poinarg@science.oregonstate.edu