Did hepatitis C virus originate in horses?

Dog and horseAbout 2% of the world’s population is chronically infected with hepatitis C virus (HCV). This enveloped, positive-strand RNA virus was discovered in 1989, but serological and phylogenetic evidence indicates that it has been infecting humans for hundreds of years, perhaps as long ago as the 14th century. All human viral infections most likely originated in non-human species, but the progenitor of HCV is not known. Recent evidence suggests that horses might have been the source of HCV in humans.

For many years there were no known non-human relatives of HCV until canine hepacivirus was discovered in dogs (we discussed this virus on TWiV #137). However two subsequent studies failed to reveal additional evidence for CHV infection of dogs. In one study, no antibodies to CHV were found in sera from 80 dogs in New York State, and in a second study, PCR failed to detect CHV nucleic acid sequences in 190 samples from dogs in Scotland. Samples from rabbits, deer, cows, cats, mice, and pigs were also negative for CHV. However both groups found evidence for infection of horses. These viruses have been called non-primate hepaciviruses (NPHV).

In one study carried out on horses in New York State, 8 of 103 samples were found to contain antibodies to NPHV. Complete viral genomes were identified from all 8 horses. Most are genetically distinct from CHV, but one viral sequence, obtained from a pool of sera from New Zealand horses, is nearly identical to CHV. NPHV was also detected by PCR in sera from 3 of 175 Scottish horses. Separate serum samples obtained from one horse 5 months apart were positive for viral RNA, indicating persistent infection. None of the horses had any evidence of clinical hepatitis or any other illness.

These results from geographically distinct areas suggest that horses are a reservoir of NPHV. It seems likely that dogs might acquire NPHV infection from horses, as there are opportunities for contact between the two animals on farms or in kennels. Additional NPHV isolates from horses must be studied to confirm this hypothesis.

It will be important to determine if horse NPHV was the source of human HCV. This is theoretically possible because horse products, such as serum containing antibodies to pathogens or toxins, have been injected into humans. There are six genotypes of HCV, each of which is believed to have emerged at different times and geographic locations. Whether their emergence represent different cross-species transmissions, as is the case with the different groups of HIV-1, remains to be determined.

I also wonder how horses originally acquired NPHV. Perhaps it was transmitted to them from another species via a vector bite, such as a mosquito – but from what species?

TWiV 219: Fauci pharmacy

Fauci PharmacyOn episode #219 of the science show This Week in Virology, Vincent and Rich meet up with Anthony S. Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases.

You can find TWiV #219 at www.microbe.tv/twiv.

TWiV 194: Five postdocs in North America

On episode #194 of the science show This Week in Virology, Vincent returns to Madison, Wisconsin and meets with postdocs to discuss their science and their careers.

You can find TWiV #194 at www.microbe.tv/twiv.

TWiV 189: Five postdocs in Glasgow

On episode #189 of the science show This Week in Virology, Vincent returns to the Centre for Virus Research at the University of Glasgow and meets with postdocs to discuss their science and their careers.

You can find TWiV #189 at www.microbe.tv/twiv.

TWiV 188: Haggis, single malt, and viruses

On episode #188 of the science show This Week in Virology, Vincent travels to Scotland to meet with members of the Centre for Virus Research at the University of Glasgow to discuss their work on hepatitis C virus and jaagsiekte sheep retrovirus.

You can find TWiV #188 at www.microbe.tv/twiv.

TWiV 166: Breaking and entering

npc1 ebolaHosts: Vincent Racaniello, Dickson DespommierRich Condit, and Alan Dove

Vincent, Dickson, Rich, and Alan review cell proteins essential for entry of hepatitis C, Ebola, and measles viruses.

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Click the arrow above to play, or right-click to download TWiV 166 (59 MB .mp3,  98 minutes).

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Links for this episode:

Weekly Science Picks

Dickson – What are you swimming with?
Rich –
Twelve monkeys
AlanKindle Touch
Vincent – Microbe news (thanks to Dave Winer)

Listener Pick of the Week

EricThe Nature of Things with David Suzuki
LanceTrials and Errors (Wired)

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TWiV 164: Six steps forward, four steps back

xmrvHosts: Vincent RacanielloRich Condit, and Alan Dove

Vincent, Alan, and Rich review ten compelling virology stories of 2011.

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Click the arrow above to play, or right-click to download TWiV 164 (60 MB .mp3, 99 minutes).

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Ten virology stories of 2011:

  1. XMRV, CFS, and prostate cancer (TWiV 119, 123, 136, 150)
  2. Influenza H5N1, ferrets, and the NSABB (TWiV 159)
  3. The Panic Virus (TWiV 117)
  4. Polio eradication (TWiV 127, 149)
  5. Viral oncotherapy (TWiV 124, 131, 142, 156)
  6. Hepatitis C virus (TWiV 130, 137, 141)
  7. Zinc finger nuclease and HIV therapy (TWiV 144)
  8. Bacteria help viruses (TWiV 154)
  9. Human papillomaviruses (TWiV 126)
  10. Combating dengue with Wolbachia (TWiV 115, 147)

Links for this episode:

Weekly Science Picks

Rich – Fundamentals of Molecular Virology by Nicholas H. Acheson
AlanFetch, with Ruff Ruffman
Vincent – Year end reviews at Rule of 6ix and Contagions

Listener Pick of the Week

GarrenTrillion-frame-per-second video
Judi – iBioMagazine
Ricardo –
Brain Picking’s 11 best science books of 2011

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv, or call them in to 908-312-0760. You can also post articles that you would like us to discuss at microbeworld.org and tag them with twiv.

TWiV 148: Retreating into Harvard virology

harvard virology retreatHosts: Vincent Racaniello, Philip Kranzusch, David Knipe, and Priscilla Yang

Vincent, Philip, David, and Priscilla recorded this episode before an audience at the Harvard Virology Program Annual Retreat, where they discussed negative strand RNA viruses, a vaccine against herpes simplex virus type 2, lipidomics of viral infection, and science communication.

The Keynote Speaker at the Harvard Virology retreat is usually an individual, but this year the honor went to TWiV as an example of science communication to the public. Many thanks to members of the Virology Program for a terrific retreat!

Artwork by Silvia Piccinotti, G4

Click the arrow above to play, or right-click to download TWiV 148 (56 MB .mp3, 77 minutes).

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Links for this episode:

Weekly Science Picks

Philip – AntWeb
David –
Herpes-like viruses in corals (PNAS and LiveScience)
Priscilla –
Science museums (Boston, Durham)
Vincent –
Contagion

Listener Pick of the Week

JennyEmerman’s review of Planet of Viruses (PLoS Biology)

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv, or call them in to 908-312-0760. You can also post articles that you would like us to discuss at microbeworld.org and tag them with twiv.

TWiV 141: Mickey gets HCV

hcv miceHosts: Vincent Racaniello, Rich ConditDickson DespommierAlan Dove, and Matt Evans

Matt Evans joins Vincent, Rich, Dickson, and Alan to deconstruct a mouse model for hepatitis C virus infection.

Click the arrow above to play, or right-click to download TWiV #141 (117 MB .mp3, 97 minutes).

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Links for this episode:

Weekly Science Picks

Matt – Benezra letter to NIH (pdf); (NIH response and Nature commentary)
Dickson –
The Big Thirst by Charles Fishman
Alan –
Earth’s First Steps by Jerry MacDonald
Rich – Final space shuttle launch and NIAID paylines
Vincent – Hertog Global Strategy Initiative

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv, or call them in to 908-312-0760. You can also post articles that you would like us to discuss at microbeworld.org and tag them with twiv.

TWiV 137: Look what the dog dragged in

dog_humanHosts: Vincent Racaniello, Alan Dove, Rich Condit, Dickson Despommier, Amit Kapoor, and Ian Lipkin

The TWiV team speaks with Amit Kapoor and Ian Lipkin about how they discovered canine hepacivirus, and its implications for the origin and evolution of hepatitis C virus.

Click the arrow above to play, or right-click to download TWiV #137 (69 MB .mp3, 96 minutes).

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Links for this episode:

Weekly Science Picks

Alan – What do marine mammals eat? (YouTube)
Rich
NIH rocket boys
Dickson – Cytomegalovirus needs an antiviral protein (Science)
Vincent – All pdfs free at National Academy of Science Press

Listener Pick of the Week

Adriana and Ye Jung  – The man who was cured of AIDS (article one and two)

Send your virology questions and comments (email or mp3 file) to twiv@microbe.tv, or call them in to 908-312-0760. You can also post articles that you would like us to discuss at microbeworld.org and tag them with twiv.