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| Liver flukes, Fasciola hepatica. |
Scientists working at the University of Córdoba, Spain, have discovered just how devious any intelligent designer would have to have been when it designed the liver fluke, Fasciola hepatica.
Creationists who advocate intelligent design as the best explanation for organisms and the diversity of living things need to believe several key things about their purported designer:
- It knows exactly what it's designs will do when it designs them.
- It designs them for a purpose.
- That purpose is exactly what the designs do, nothing more and nothing less.
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| Liver fluke, Fasciola hepatica. Life cycle. |
Liver Fluke (Fasciola hepatica)
The liver fluke is a parasite on herbivores such as cattle and sheep and humans. It has a complex life cycle which begins when a female migrates from the liver of the host to the biliary duct where she can lay up to 25,000 eggs per day. Like the lancet fluke, the eggs are discharged into the intestine of the host and are discharged in faeces. If they land in water they hatch into a larval form known as a miracidia. The miracidia seek out and infect a water snail.
In the snail it goes through three stages, turning from a sporocyst to a redia and finally a large–tailed cercaria which exits the snail and finds aquatic vegetation in which it forms a cyst called metacercaria. If the vegetation is eaten by cattle, sheep or humans, the metacaercaria, having been protected against the stomach acids by its hard case, emerges from the cyst in the duodenum and burrows through the intestinal wall into the peritoneal cavity. From there, if migrates to the liver and spends time eating liver cells until ready to breed and repeat the cycle.
What the scientists at the University of Córdoba discovered is how the parasitic liver fluke immediately sets about defending itself from attack by its host's immune system by basically fooling it into thinking everything is just fine and dandy, so no need for any response. Move along now - nothing to see here. From the first day of infection, the parasite stimulates an over-activity of the gene FOXP3, that codes for a protein present in the regulatory lymphocyte that acts as a signal in the immune system, and effectively erases any immune response.
The team also identified other genetic markers that mean it will be easier to detect and treat infections in sheep in future. Their results were published open access in Scientific Reports last February.
Abstract
The aim of this study was to validate reference genes for gene normalisation using qRT-PCR in hepatic lymph nodes (HLN) and livers from sheep infected with Fasciola hepatica during early and late stages of infection. To this end, a comprehensive statistical approach (RefFinder) encompassing four different methods of analysis (geNorm, BestKeeper, ΔCt method and NormFinder) was used to validate ten candidate reference genes. Stability analysis of gene expression followed by pairwise variation (Vn/Vn + 1) analysis revealed that PGK1, HSP90AA1 and GYPC were the most stable reference genes and suitable for qRT-PCR normalisation in both HLN and liver tissues. These three genes were validated against FoxP3, IL-10, TGF-β, TNF-α and IL-1β genes in the HLN tissue of sheep vaccinated with Cathepsin L1 from F. hepatica and unvaccinated infected and uninfected controls during early stages of infection. In the liver, the three reference genes were validated against TNF-α and IL-1β during chronic stages of infection with F. hepatica and in uninfected controls. Our study is the first to evaluate and validate sheep reference genes in order to provide tools for monitoring cytokines in Fasciola hepatica infected sheep target organs. Our results present an approach to elucidate the role of different cytokines in F. hepatica vaccinated and infected sheep.
Pacheco, I. L., Abril, N., Zafra, R., Morales-Prieto, N., Hernández, V. M., Ruiz, M. T., … Pérez, J. (2019).
Identification of reference genes for real-time PCR cytokine gene expression studies in sheep experimentally infected with Fasciola hepatica.
Scientific Reports, 9(1). doi: 10.1038/s41598-018-37672-7
Copyright: © The authors.
Published open access by Scientific Reports.
Reprinted under the terms of a Creative Commons Attribution 4.0 International License (CC BY 4.0).
As the press release from the University of Córdoba points out:
This research on sheep, one of the main victims of Fasciola hepatica, could mean an important step toward improving the effectiveness of vaccines in the future. Although some of them have had promising results in the laboratory, none have attained enough protection to be developed commercially. For this reason, current control of this disease is based on using drugs, meaning high costs and what is more, they make the parasite more resistant, as well as adding residues in products such as milk and meat.
Once again we see that creationism's supposed intelligent (sic) designer has tried to circumvent human attempts to control the parasite by making it resistant to drugs so, if we accept for a moment that this putative designer actually exists, it is impossible to conclude that it is intentionally trying to harm our cattle and us with liver flukes. Not only has it designed them to fool our immune systems but it has also make them resistant to the drugs we use to protect sheep.
The curious thing, and something you can never get a creationist to address, is that this supposedly intelligent designer almost seems to be fighting with itself. It designed an immune system then saw that as a problem for the liver fluke to overcome; it supposedly designed humans with the intelligence to make anti-helminthic drugs then saw the anti-helminthic drugs they made as a problem to be overcome.
The only explanation, if you believe there is an intelligent designer, is that this intelligent designer is malevolent and wants to harm humans and their livestock. Tweet
Mindless, amoral evolution, of course, perfectly well explains and predicts these evolutionary arms races without needing magic. Tweet
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