Mad Cow Disease

Mad Cow Disease (Transmissible Spongiform Encephalopathy):
DO ALPACAS OR LLAMAS HAVE ANYTHING TO FEAR?

David E Anderson, DVM, MS, Diplomate ACVS
Associate Professor, Ohio State University
December, 2003


     This communication is a very preliminary discussion about the relevance of concerns regarding transmissible spongiform encephalopathy (TSE) in alpacas. This issue has been raised recently because of the Canada-USA border closing to movement of all ruminanting species after the diagnosis of BSE in a single cow in Alberta, Canada.

TSE's are the prion particle diseases of animals and humans. Prions are similar to viruses, but much smaller and act to cause abnormal function or metabolism in the cells. In the case of TSE's, the prion particle
causes a change in the form of an intracellular protein. Cell proteinases can no longer breakdown this protein causing a buildup of the protein until cell function degrades. Eventually, enough cells are involved to cause clinical signs of disease. 

To date, we have found no published research on TSE's in South American Camelids. There has been one published study that looked at the prion protein characteristics in a Dromedary Camel. Sheep and cattle have
approximately 97% homology (identical sequences) in the prion protein.  This homology may have some bearing on the fact that cattle and sheep suffer from a similar prion disease (sheep = scrapie; cattle = BSE or
bovine spongiform encephalopathy). The dromedary camel examined had only 92 to 93% homology to cattle and sheep. At this time, we have no idea what the significance of this finding is. The differences in alleles may
or may not be indicative of a species barrier to TSE's in camelids. 

To date and to our knowledge, no camelid has been diagnosed with a TSE.  At Ohio State University, our pathologists examine over 100 llamas and alpacas each year. Brains are routinely inspected because of the common meningeal worm infection in the Northeast to the Midwest USA. Our pathologists have never seen any lesions similar to a spongiform encephalopathy. 

The current state of knowledge of TSE in camelids is severely lacking.  Scientific study will be needed to answer questions regarding species susceptibility of camelids to TSE's. TSE's are not directly contagious.
The principle risk that an infected animal might pose to other humans or animals is in the event the animal is eaten. Eating prion infected tissues may result in infection in the exposed animal. Thus, all meat and bone derived proteins have been banned from ruminants feeds in the USA. Thus, alpacas would only become infected if they have consumed feedstuffs containing tissues from infected animals (e.g. sheep or cattle with TSE). Affected alpacas would only transmit the disease to their offspring or to other animals if they themselves or contaminated tissues were eaten. 

This is strictly preliminary and is in response to questions we have been asked. We will continue to update and modify this report as more information is obtained.

REFERENCE:
Sequencing analysis of prion genes from red deer and camel.

Kaluz S, Kaluzova M, Flint AP.

University of Nottingham, Sutton Bonington Campus, Loughborough, UK.
virukalu@savba.sk

An abnormal isoform of the prion protein (PrP) appears to be the agent responsible for transmissible spongiform encephalopathies (TSE). The normal isoform of PrP is host-encoded and expressed in the central nervous system. The recent bovine spongiform encephalopathy (BSE) epidemic in the UK and the incidence of prion-related diseases in other animals could indicate that ruminants are highly susceptible to infection via ingestion of prion-contaminated food. Sequence analysis of PrP gene open reading frames from red deer and camel was carried out to investigate sequence variability of these genes among ruminants.

PMID: 9358067 [PubMed - indexed for MEDLINE] 


 David E Anderson, DVM, MS
Diplomate, American College of Veterinary Surgeons
Associate Professor of Surgery, Food Animal
601 Vernon L Tharp Street
College of Veterinary Medicine
The Ohio State University
Columbus, Ohio 43210

Current Information From Washington State Can Be Found Here.

 


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