Malevolent Design - How A Chicken Virus Got More Deadly - Malice Or Evolution?

Ancient DNA reveals how a chicken virus evolved to become more deadly | University of Oxford

Marek's Disease Virus (MDV) is a serious infection in chickens that costs th4e poultry industry over $1 billion annually. Now an international group of virologists and archaeologists led by researchers from Oxford University, Ludwig-Maximilians-Universitat, Munich, Germany, have discovered how it has evolved over time to become more virulent and deadly, or, as creationists insist, has been intelligently redesigned.

The team reached this conclusion from an analysis of the virus in modern and ancient chickens going back over the past 1000 years. The ancient samples were obtained from DNA extracted from chicken bones recovered from 140 archaeological sites in Europe and the Near East. This analysis showed that MDV was widespread in European chickens for at least 1000 year before being first described in 1907.

Tell me all about Marek's Disease Virus and what it does to chickens. Marek's Disease Virus (MDV) is a highly contagious herpesvirus that primarily affects chickens. It is named after Jozef Marek, a Hungarian veterinarian who first described the disease in 1907. Marek's disease primarily affects domestic chickens and, to a lesser extent, turkeys and quails. Here are key aspects of Marek's Disease:

1. Causative Agent: Marek's Disease Virus is a member of the family Herpesviridae, subfamily Alphaherpesvirinae, genus Mardivirus. There are three serotypes of MDV, with serotype 1 (MDV-1) being the most important and commonly associated with clinical disease.
2. Transmission: The virus is highly contagious and spreads through the inhalation of airborne dust particles contaminated with the virus shed by infected birds. It can also be transmitted vertically from an infected hen to its chicks through the egg.
3. Pathogenesis: Marek's Disease primarily affects lymphoid tissues, causing T-cell lymphomas. The virus targets and transforms T-lymphocytes, leading to the development of tumors in various organs, including the nerves, skin, liver, spleen, and muscles.
4. Clinical Signs:
   • Classical Marek's Disease: Chickens may exhibit paralysis, particularly in the legs and wings.
   • Ocular Marek's Disease: Tumors can develop in the eyes, leading to irregularly shaped pupils and blindness.
   • Cutaneous Marek's Disease: Tumors can develop in the skin, causing raised nodules and lesions.
   • Internal Organs: Tumors may affect internal organs, leading to a range of symptoms depending on the affected organ.
5. Diagnosis: Diagnosis is often based on clinical signs, post-mortem examination, and laboratory tests such as histopathology, PCR, and virus isolation.
6. Prevention and Control:
   • Vaccination: Vaccination is a common and effective strategy to control Marek's Disease. Vaccines are typically administered to chicks at the hatchery.
   • Biosecurity: Strict biosecurity measures are crucial to prevent the introduction and spread of the virus within poultry flocks.
7. Economic Impact: Marek's Disease can have a significant economic impact on the poultry industry due to increased mortality, reduced growth rates, and poor production performance.
8. Evolution of Virulence: MDV has evolved over time, and there have been reports of more virulent strains emerging. This evolution poses challenges for disease control and necessitates ongoing research and surveillance.

It's important for poultry farmers to work closely with veterinarians to implement appropriate biosecurity measures and vaccination protocols to control and prevent Marek's Disease in their flocks.

When first described, this disease only led to mild symptoms in older chickens. As chicken consumption dramatically increased in the 1950s and 1960s, MDV has continued to evolve and has become increasingly aggressive despite the development of several vaccines.

Dr Steven Fiddaman, first author
Department of Biology
University of Oxford, Oxford, UK.

Ancient DNA has provided us with a unique perspective on the emergence of MDV as a deadly chicken virus and may teach us lessons that are applicable to the control of other viral infections of medical and veterinary importance.

Professor Adrian Smith, co-senior author
Department of Biology
University of Oxford, Oxford, UK.

We have seen how mitigating diseases often creates a selection pressure that increases the virulence of the virus. Being able to watch this process take place by sequencing ancient virus genomes shows just how dramatically the virulence of MDV has increased in the past century.

Professor Greger Larson, co-senior author
The Palaeogenomics and Bio-Archaeology Research Network
Research Laboratory for Archaeology and History of Art
University of Oxford, Oxford, UK.

One of the ancient chicken bones used in the study.

Credit: Olaf Thalmann.

The team have shown that one of the genes in the virus, Meq, which causes the characteristic tumors, was incapable of doing so in the earlier forms of the virus but has since evolved to do so (or as creationists insist, has been intelligently redesigned to cause tumors). The team's findings are published in science, sadly behind a paywall, to which, as a member of the American Association for the Advancement of Science, I have access but not permission to reprint here. They identified two factors which in combination, probably drove this evolution of increased virulence:

1. rapid growth in the world chicken population, increasing the likelihood of novel mutations arising.
2. The use of 'leaky' vaccines (i.e., vaccines that prevent symptomatic disease but not the transmission of the virus) creating selection pressure which accelerated the virulence of the virus.

Brief details of their findings are given in the abstract:

Abstract

The pronounced growth in livestock populations since the 1950s has altered the epidemiological and evolutionary trajectory of their associated pathogens. For example, Marek’s disease virus (MDV), which causes lymphoid tumors in chickens, has experienced a marked increase in virulence over the past century. Today, MDV infections kill >90% of unvaccinated birds, and controlling it costs more than US$1 billion annually. By sequencing MDV genomes derived from archeological chickens, we demonstrate that it has been circulating for at least 1000 years. We functionally tested the Meq oncogene, one of 49 viral genes positively selected in modern strains, demonstrating that ancient MDV was likely incapable of driving tumor formation. Our results demonstrate the power of ancient DNA approaches to trace the molecular basis of virulence in economically relevant pathogens.

Steven R. Fiddaman et al.
Ancient chicken remains reveal the origins of virulence in Marek’s disease virus. Science 382, 1276-1281 (2023). DOI:10.1126/science.adg2238

Copyright © 2023 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Reprinted with kind permission under licence #5690470719130

This neatly exposes several creationist lies:

Firstly, it is an example of how mutations are not always detrimental (or as some argue, invariably fatal) but, under appropriate selection pressure, can be highly beneficial to the organism, in this case the virus, which is now present in the chicken population in vastly greater numbers that in earlier times before the mutations arose and is more infectious.

Secondly, it shows how a changing environment is the driver of evolution turning the randomness of mutations into a highly directional process leading to greater reproductive success.

Thirdly, there is the dependence of biologists on the Theory of Evolution by natural selection to explain and make sense of the facts, with no hint that the theory is being replaced by magic and superstition, as creationist frauds tell their credulous dupes.

And of course, as with all parasites, it gives creationists the problem of choosing between malevolence, incompetence or evolution as the explanation for these organisms and how they changed over time.

And we can all enjoy the spectacle of watching a creationist, who will earlier have been waving their ignorant incredulity and intellectual bankruptcy around by arguing the something too complex for them to understand (like DNA) must have been designed by their favourite god (with that false dichotomy fallacy for which creationism and religious apologetics is infamous), now having to argue that their god wouldn't have done something like this, so something else must have done it (but it definitely wasn't evolution!)

---

Thank you for sharing!

Tweet Link