The latest Parasitology Paper of the Month is “Origin of a major infectious disease in vertebrates: The timing of Cryptosporidium evolution and its hosts” by Juan C. Garcia-R and David T. S. Hayman.

Cryptosporidium species are parasites that have been found in all vertebrate groups although most of their diversity is associated with mammal and bird species. They are increasingly known as major contributors to diarrhoea morbidity and mortality in humans, mainly in children and AIDS patients, and economic losses in agriculture and medical care.

There is a lack of information about the time of origin of this group of parasites and the reciprocally effect with their hosts. However, current tools in biology can help to infer major evolutionary events and interactions between parasites and their hosts. In a new paper published in Parasitology (doi: 10.1017/S0031182016001323) we used molecular sequences, calibrated molecular clocks, Bayesian inferences and cophylogenetic analysis in order to better understand the timing and pattern of diversification in Cryptosporidium. We estimated that the origin of Cryptosporidium is concordant with the rise of vertebrates about 600 million years ago. Furthermore, our divergence time inferences showed that the formation of several species in Cryptosporidium occurred after the bolide impact of an asteroid resulted in the extinction of numerous animal groups (Dinosaurs among the most known), which left major ecological opportunities for terrestrial mammals and birds to flourish (the Cretaceous-Paleogene extinction event).

Despite the evidence that some species of Cryptosporidium are shifting to infect new hosts there is also evidence of co-evolution with vertebrate species. These results provide a framework for addressing new questions about the evolution of Cryptosporidium and other unresolved parasitic lineages that have practical importance for humans in different research fields.

The paper outlines that future taxonomic and phylogenetic work will impact our understanding of Cryptosporidium evolution and will stimulate comparative studies to assess important traits that generate variability and might help to overcome barriers to infect potential new hosts. We expect to open new avenues of research in the ecology, dynamics and epidemiology of cryptosporidiosis disease and integrate the knowledge from many areas of research to contribute in our understanding of the origin of major infectious diseases in humans and other animals.

In particular, we hope that this research leads to advances and future research in the biological constraints around parasites’ ability to expand their host range by exploiting novel host species, because this work will be interesting from an evolutionary perspective but also potentially useful for public health purposes.

Read the paper “Origin of a major infectious disease in vertebrates: The timing of Cryptosporidium evolution and its hosts” in full for free until 31st December 2016.

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