Origin of a major infectious disease in vertebrates: The timing ofCryptosporidiumevolution and its hosts

Abstract

Protozoan parasites of the genus Cryptosporidium infect all vertebrate groups and display some host specificity in their infections. It is therefore possible to assume that Cryptosporidium parasites evolved intimately aside with vertebrate lineages. Here we propose a scenario of Cryptosporidium-Vertebrata coevolution testing the hypothesis that the origin of Cryptosporidium parasites follows that of the origin of modern vertebrates. We use calibrated molecular clocks and cophylogeny analyses to provide and compare age estimates and patterns of association between these clades. Our study provides strong support for the evolution of parasitism of Cryptosporidium with the rise of the vertebrates about 600 million years ago (Mya). Interestingly, periods of increased diversification in Cryptosporidium coincides with diversification of crown mammalian and avian orders after the Cretaceous-Palaeogene (K-Pg) boundary, suggesting that adaptive radiation to new mammalian and avian hosts triggered the diversification of this parasite lineage. Despite evidence for ongoing host shifts we also found significant correlation between protozoan parasites and vertebrate hosts trees in the cophylogenetic analysis. These results help us to understand the underlying macroevolutionary mechanisms driving evolution in Cryptosporidium and may have important implications for the ecology, dynamics and epidemiology of cryptosporidiosis disease in humans and other animals.

Local and global genetic diversity of protozoan parasites: Spatial distribution of Cryptosporidium and Giardia genotypes

“…More systematic sampling of local and introduced fauna along with whole genome sequences over short timescales will allow us to identify major functional loci involved in host specificity, proliferation and host shifting. This information will provide insights into the zoonotic potential of different genotypes, host range, cross-species transmission and risks for host shifts to humans [67]. …”

“…These recombinant events are associated to the high probability of finding new genotypes (S4 Fig). Cryptosporidium parvum displayed a large genotypic variation as a result of gene combinations and host range shift [67]. Similarly, genetic recombination has been shown to occur commonly in C .…”

Diverse single-amino-acid repeat profiles in the genusCryptosporidium

“…The evolutionary process which leads to speciation in the genus Cryptosporidium is unknown. The parasitic life style of these species and the observation that certain Cryptosporidium species or genotypes appear to have a narrow host range, has led to the assumption that parasite populations infecting different host species have evolved separately and differentiated into genetically distinct populations and/or have co-evolved with the host (Garcia & Hayman, 2016). The existence of Cryptosporidium species with distinct organ tropism, together with the recent expansion of good quality Cryptosporidium genome sequences, provides new opportunities to query genomes for polymorphisms which may reflect adaptation.…”

Prevalence and Genotypes of Cryptosporidium in Wildlife Populations Co-Located in a Protected Watershed in the Pacific Northwest, 2013 to 2016

“…Parasites of the genus of Cryptosporidium infect virtually all vertebrate groups, with some species exhibiting host specificity [1,2]. Currently, approximately 31 valid species of Cryptosporidium have been described [3][4][5].…”