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Downer Cow Syndrome opinions
Database aims to send Mad Cow Disease packing
U.S. Ruffles EU Feathers in Meat Trade Deal
Trade Panel Set to Fault EU on Hormone Ban
Hogg finally relieved at MAFF
UK Department of Health: May 1997 CJD figures
Epidemiology of BSE in Northern Ireland
Epidemiology of CJD in Canada

Downer Cow Syndrome [DCS]

Barrett Slenning , MS, DVM, MPVM
Coordinator, Population Medicine Program
FAE Dept / College of Vet Med   Box 8401
NC State Univ
Raleigh, NC 27606   USA
[ph] 919.829.4324
[fax] 919.829.4317
2 May 97. As soon as we start talking about 'syndromes' people need to realize we are talking about complex, multi-cause, usually multi-symptom events. Unfortunately, we then immediately name them for their major/most obvious sign. Then, people logically take the major sign in the name as being the entire story. So it is very understandable that something called "downer cow syndrome" seems very similar to a central nervous system disease like a TSE. It certainly isn't the fault of the general public; it is the fault of those of us who perpetuate misnomers for disease entities.

I would think the USDA/APHIS program is doing just what it should. In part the DCS animal is difficult to confuse with a TSE animal. In addition, the DCS animal is very unlikely to enter the system, in part this is due to the nature of how testing programs work.

It has been US law for years that non-ambulatory animals are not allowed to be picked up by an abattoir truck, let alone be put into the food chain. The non-ambulatory ban was developed in response, not so much as a food safety concern, but as an animal welfare issue, prior to the BSE blow-up. Because of this, DCS animals will not be presented to USDA inspectors to screw up the program. I, as a practicing vet, will see her on the farm. And if I cannot explain her problem, she will be sent to the lab.

What the pre-slaughter screen is developed for is to capture animals showing signs that could be ascribed to central nervous system disorders that are not explainable by some of the more common problems. So, if a cow that walked onto a truck but went down in the abattoir truck during transit, and had no diagnosable reason for being down, she would be caught by the screen. But then, she would not be a true DCS cow either.

However, if a steer suffered from a bacterial meningitis (something that is not obvious without microscopy), and showed behavioral, postural, or ambulatory deficits, this animal would be captured by the screen for TSE evaluation. That seems infinitely reasonable to me; they are targeting animals with unexplained signs -- just the population in which the first TSE's will show up in.

So, the USDA/APHIS screen seems to me to be well designed as a surveillance tool to determine if a TSE exists in the US. By its design, it will concentrate the clinically affected animals into a small population. That raises the prevalence of the disease from what it would be in the larger population. Any test, whether it is a blood test or a histopathological test, has a higher positive predictive value (that is, a lower false positive rate) when the disease prevalence is high. Hence, it is much more likely to actually be able to identify an exceedingly rare disease. And that is what a good surveillance tool should do.

So, though it will not prevent a non-clinical animal from passing through, it has a very good chance of correctly detecting the disease when it is still at a much lower prevalence than would a system that cast a wider net. A random sampling procedure would cost much, much more, and would create major unwarranted perturbations to both consumers and the industry alike. The screening system designed by USDA should end up giving greater protection with less potential for the downsides of huge testing programs.

The USDA rules are aimed at animals showing symptoms attributable to central nervous system signs that cannot be explained by more common etiologies. DCS, because we can demonstrate site-specific muscle atrophy, enzyme level changes, and post-mortem changes in the affected areas does not qualify as a _central_ nervous system disorder. Peripheral nerves (those in the limbs) are certainly affected, so it is a _nervous_ disorder, but not a _central_ nervous system disorder. A _neurological_ disease is one in which a primary, or even inciting, event is damage to structure or function of nervous tissue. Rabies infects nerves and damages them. Muscular dystrophy is essentially a short-circuiting of nerves due to loss of insulation. TSE's destroy nervous tissues at the cellular and organ level. All of these are neurological diseases. In DCS the nerve damage is a _result_ of an underlying physiological event: pressure causes anoxia which results in cell death of nerves, muscles, fibroblasts, blood cells, etc., etc.. It is _not_ a neurological disease. A true DCS animal will not be submitted to a slaughter house, so she will not be available for a slaughter house examination. However, a DCS animal showing abnormal signs or an unclear history will be submitted by a private practitioner. Different process, same result.

A US TSE will/will not 'look' like BSE

I fully agree that there is no guarantee that a TSE showing up in the USA will show the same signs as the TSE we refer to as BSE. Of course, then, it will not be BSE; so your comment about "... when BSE is finally found in the US ..." is probably inaccurate. I would have said "... If a bovine TSE is found in the US ...". Then we would agree. As my other postings have already stated, there is no guarantee one way or the other about how TSE's will be demonstrated.

One thing to remember: If Dr. Gibbs' assumption that _all_ mammals have endemic, sporadic TSE's at around the 1 per million rate, then the prevalence may be below our ability to find it in a few years' time, even with the USDA's concentrating strategy of the CNS screen. My guess (and that's all it is) is that _if_ there is a sporadic bovine TSE, it must be at a level below even the 1 per million, otherwise shouldn't the UK have identified at least one such case in all the examinations they have performed? So far as I can tell, they describe only one case type.

Another way of looking at it, though, is that BSE _is_ the sporadic disease in regards to its pathogenesis (how it acts once it gets into the brain), and only its ability to be transmitted from animal to animal has been augmented in the UK situation. If this is the true case, then, we should expect any sporadic US TSE to look like BSE, and we are incorrect in predicting a US TSE will 'look' different from BSE.

The common feature, whether a US TSE did or did not emulate BSE, is that either will be unexplainable, using normal diagnostics for the common diseases of the bovine. That characteristic is what the sampling program is aimed at, not specific signs. So, it should still be on target, despite the uncertainties.

It means that the signs of classical Downer Cow Syndrome make a TSE less likely. Do _some_ TSE's show similar signs? It would seem so, but my reading of the literature is that they are in the minority. Do many other diseases show similar signs? This also is true. You can neither rule-in nor rule-out such diseases based on general signs, but you can say one is more or less likely, based on the signs.

Be careful with "Downer Cows", which most in the field equate with the term "down cow". To be precise, all Downer Cow Syndrome cows cannot rise, but not all cows that are unable to rise are true Downer Cow Syndrome cases.

Again, DCS is a syndrome that occurs _secondary_ to an animal going down. It is not a diagnosis for what _caused_ the initial problem, it is an explanation why the animal's condition continues to deteriorate even when the initiating cause is removed. A 'down cow' is merely an animal that is unable to rise.

It may seem like a picky differentiation that I am insisting on here, but in working with my clients, a diagnosis of DCS has a very poor prognosis, whereas a 'down cow' may only need a single treatment with calcium to be up and about. So, in the field, the differentiation between DCS and 'down cow' describes a true chasm in treatment success rates. Also, remember that my initial definition of DCS stated that "... , the classical DCS cow is usually bright and alert right up to the end. She is usually quite aware of your presence, and can find food and water without any difficulty. This is quite different from the clinical signs of TSE's. ...". I stand corrected on the last statement: I should have said "... This is quite different from the _classical_ clinical signs of TSE's...", allowing for the occurence of animals who will show different signs. My point, however, is that my description of the DCS cow was that she is _usually_ bright and alert, and _usually_ aware of your presence. Let me throw another confounder in the list of problems we are facing: Just because an animal has a TSE does not mean that TSE is guaranteed to be the prime factor in its demise. How many 'BSE' cows died from other unrelated diseases prior to going clinical with BSE? I don't know, and probably nobody else does either. So some animals who are bright and alert while down, yet test positive for BSE, could be animals who went down for a non-BSE related problem. We see this kind of thing often with organ systems, skeletal abnormalities, etc. -- in the profession we call these 'incidental findings on necropsy', meaning they were not involved with the death of the animal. Neither a TSE nor a DCS is so cut and dried in demonstrating signs that we can confidently diagnose them based on those signs. _Most_ TSE cases in the bovine (using BSE as the example) do not fit the definition of a DCS cow. Likewise, _most_ DCS cows will not fit the definition of non-experimentally occuring TSE's (using BSE as the example). Some animals in both categories, however, will look sufficiently similar to animals in the other category to cause us trouble. If there are other, as yet undiscovered, TSE diseases in the bovine, they may well show signs different from either BSE or DCS. That is why the slaughter rules and the recommendations to private practitioners say that _any_ animal with unexplained central nervous system signs should be examined for TSEs. Is it perfect? Of course not. Does it guarantee we will find it if it exists? Of course not. However, it appears very likely to find a TSE in the US even if it is a rare event. We can ask no better a definition of a well designed surveillance system.

Bart M. Govenal responds:

In your original posting, you wrote:

As far as for the difference between DCS and BSE, the classical DCS cow is usually bright and alert right up to the end. She is usually quite aware of your presence, and can find food and water without any difficulty. This is quite different from the clinical signs of TSE's. That alertness, alone, would cause one to discount the _likelihood_ of BSE in such an animal.
This is true, however, there is no reason to expect that _all_ TSEs produce the behavioral changes characteristic of BSE. In fact, Richard Marsh's experimental transmissions of transmissible mink encephalopathy to bulls produced no behavioral changes at all prior to the animals suddenly becoming nonambulatory. This is part of the reason for Marsh's warning that surveillance measures are not enough to prevent a TSE outbreak in U.S. cattle. You need to end the practice of feeding rendered animal protein back to animals of their own species. Rachel Shepherd comments:

If we look at human animals we find that there is more than one TSE and that each TSE has a different effect on the brain (nv CJD can be distinguished from classical CJD on the basis of brain florets and some other characteristics). I think it is not unreasonable that there may also be more than one type of TSE in cows. If a second strain is involved and the USA is looking for classical BSE florets then they will not find it.

Personally I am not happy with the argument that we can tell if a down cow has BSE just by looking at it. Wild eyed cow = BSE. Alert cow = something else. Comments from people actually working with BSE suggest that this is unwise.

Also in the real world there is a very large number of down cows in the USA and it is my understanding that many are not examined by a vet at all. I would be very surprised if there were no bovine TSE in the USA (sporadic at the very least). So long as they do not make the same mistakes as the UK it should not be a major problem.

One of the biggest mistakes was covering up and distorting the facts so that the consumers lost faith in official reassurances and stopped beleiving anything the government said.

4 May 1997 Michael Worrall has been there:

I reply as a simple toiler at the coal face, however I have diagnosed and dealt with 536 cases of BSE since 1 January 1990. My experience is that a number of cases of BSE present as "Downer Cows" and are alert and eating. You can only rule out BSE on histology - not on clinical grounds.

I work for the Veterinary Field Service of MAFF in the UK, based on the Isle of Wight. My experience is about average. A detailed epidemiological report is written on every case. BSE is notifiable, and all cases investigated. Farmers here do seem to be honest in reporting. Incidentally, BSE is not always as easy to diagnose as it may seem. Policy here is to slaughter suspect down/downer cows on welfare grounds, incinerate the carcase and carry out histology. If positive (and some are) the farmer is paid compensation.

VMOs reminded to "cooperate" with APHIS slaughter surveillance

April 7, 1997 FSNET
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HERD ON THE HILL: NATIONAL MEAT ASSOCIATION The Food Safety and Inspection Service issued Notice NC 97-11 on March 31, 1997 to "remind Veterinary Medical Officers (VMOs) of their obligation to cooperate with the Animal and Plant Health Inspection Service (APHIS) in conducting slaughter surveillance for Bovine Spongiform Encephalopathy (BSE)" in the U.S. Making reference to a memo issued in April of 1996 by Deputy Administrator of Field Operations Dr. Craig Reed, all FSIS VMOs in plants slaughtering adult cattle were requested to be especially aware of cattle showing signs of central nervous systems (CNS) disorders. "The collection and submission of brain samples for the surveillance of BSE needs to improve," states the Notice. "Samples sent to NVSL (National Veterinary Services Laboratories) should equal the number of animals condemned on ante-mortem for CNS disorders." The notice instructs VMOs to assure that proper communication is achieved with APHIS by logging each call with the date and name of the person notified and that any animal reported to APHIS but not sampled should be reported immediately.

Hogg gone, Cunningham in at MAFF

Will the cover-ups and disinformation continue at MAFF under the Labor Government? Yes, says our UK correspondent: they may blame previous government for the backlog and then go for the economics of renewed exports.

New Minister of Agriculture, Fisheries and Food: Jack Cunningham - overall responsibility for all aspects of policy.

Minister of State: Jeffrey Rooker - food safety, animal health.

Minister for Farming and the Food Industry: Lord Donoughue - ministry's representative in House of Lords, reform of European Union common agricultural policy.

Parliamentary Secretary: Elliot Morley - fisheries, countryside. In-tray: setting up new independent Food Standards Agency. Early shake-up of the ministry, involving name and structure changes to reflect new emphasis on food and consumer interests. Will work with Foreign Secretary at European Union's summit in June to seek solution to problem of "quota-hopping" foreign fishing vessels. Make "fresh start" on getting beef ban eased by "positive dialogue" with EU Will go to Brussels on Monday to meet senior Commission officials. Longer-term goal is reform of EU's common agricultural policy.

Our English correspondent explains the system:

The way it works is that we elect a political party into power and the leader becomes Prime Minister. The allocation of all other ministerial posts is entirely his choice. Hogg was the Minister for Agriculture and Fisheries from the Conservative administration and when Labour got elected he effectively disappeared in a puff of votes. Blair can't fire him because he has already gone.

The Conservatives concealed a lot of information when they were in power, including lots of stuff on BSE and the real unemployment figures. The most sensible thing for the Labour government (with Blair as prime Minister) to do is to reveal most everything and blame it of the previous Conservative administration! However, they will wish to minimise the economic costs of BSE and its a toss-up whether they reveal all and start with a clean slate with the EU or continue to hide some stuff. As they intend to separate food out from MAFF hopefully they will reveal all.

The new administration will have access to all the info in MAFF and will probably evolve a new strategy for dealing with the problem. If MAFF can convince them that it is all a storm in a tea cup and it is all over then they will keep quiet in order to try and get British beef back into Europe and reduce the economic cost. On the other hand if it seems that an epidemic will occur they may try to blame the Conservatives by publicising it. The natural tendency of undemocratic governments is secrecy I'm afraid. By the way, you may be interested to know that the huge Labour majority was achieved with just 45% of the votes, thats right - less than half!

Remember that we are only an illusory democracy over here, we have no freedom of information act, no civil rights guaranteed by a constitution, an unelected second house populated by the descendants of Royal bastards and political has-beens, and not even a secret ballot for elections. They used to say that the Conservative Party is the party of the establishment - the ruling elite. Don't be fooled by the new Labour government into thinking that things will change, the establishment has simply taken over the Labour party! What used to be a workers socialist party is now run by people who went to private schools and Oxford or Cambridge University, the same people who were in the Conservative Government. Don't expect any sudden shift to democracy and openness. It's not how competent or bright you are that matters in the UK, it's whether you speak with the right accent. Nothing much changes over here.

We shall just have to watch the nvCJD figures and look for trends. It's probably worth keeping an eye on Germany, they eat lots of beef there and use to import quantities of ours so if anything is going to happen we should see an increase in cases there. The same for Europe as a whole really. I anticipate that most of the news will now come from the scientific community so we must keep an eye on the learned journals.

Database Aims to Send Mad Cow Disease Packing

by Wendy Grossman 10.Mar.97 Wired Ventures, Inc.

Mad cow disease may finally be on the run in the United Kingdom, thanks to a combination of plastic tags and a distributed database. The new system may end the export ban on beef in the wake of the disease that has crippled the British beef industry.

The system - currently in use in Northern Ireland - involves a uniquely numbered plastic tag that is placed inside each newly born calf's ear. The number is registered with the Department of Agriculture Northern Ireland (DANI), along with the animal's sex and breed. Each time the cow moves through a market or is seen by a vet, the details are entered into a dumb terminal that connects directly to a database maintained by DANI and supplied by Unisys.

The development of a tracking system is a requirement for lifting the export ban imposed by the European Community, which is currently slated to last until 1999 despite UK governments' orders to cull herds to eliminate infected cows.

The disease, also known as bovine spongiform encephalopathy (BSE), has caused grief for British cattle farmers. Until now, farmers have had no universal way to prove their cattle were disease-free.

All information about a cow's history was exchanged among farmers but not centralized. Calves born in the UK have been tagged since June 1996, but records of the newborn calf's health, ownership history, and veterinary treatment have been made into a paper "passport" by the Ministry of Agriculture, Fisheries and Food (MAFF). When a cow is sold, the seller hands on the passport to its new owner.

Database records can be made universally available and help pinpoint smaller areas of infestation in the event of BSE outbreaks. For example, if a cow is found to be infected with the disease, all the cows that have been in close proximity to it can be traced because the information about owners and farm locations is also tracked in the database.

In addition, cows that are not in the database can't be sold. So the system forces registration and tracking of all cattle if farmers are to participate in the market. Unisys is prototyping a similar system for use in tracking the 10 million cows in England, Scotland, and Wales.

Department of Health: May 1997 CJD figures

Tuesday 6th May 1997 release covers to end March 1997
The next table will be published on 2 June 1997.

       Deaths of definite and probable cases in the UK
         Referrals    Sporadic  Iatrogenic Familial   GSS    nvCJD   Total
 

  1985       -          26       1       1       0       -      28
  1986       -          26       0       0       0       -      26
  1987       -          23       0       0       1       -      24
  1988       -          21       1       1       0       -      23
  1989       -          28       2       2       0       -      32
  1990       53         27       5       0       0       -      32
  1991       75         32       1       3       0       -      36
  1992       96         44       2       4       1       -      51
  1993       78         38       4       2       2       -      46
  1994      116         53       1       2       3       -      59
  1995       86         34       4       2       3       3      46
  1996      129         38       4       2       3       10     57
  1997       31          5       0       0       0       1       6
 
Two cases of definite nvCJD still alive.
Total number of definite and probable cases of nvCJD = 16

For comparison: the previous month's data:
  1996      128         34       3       2       3       10     52
  1997       21          3        0       0       0       0      3

Epidemiology of BSE in Northern Ireland 1988 to 1995

Vet Rec 140 (12): 302-306 (Mar 1997) 
Denny GO, Hueston WD
The epidemiology of bovine spongiform encephalopathy (BSE) in Northern Ireland from 1988, when it was first confirmed, to the end of 1995 is described. All cases of BSE were subjected to a detailed epidemiological investigation, complemented by data from the national animal health records on every bovine animal. Data are presented on 1680 cases. Many of the epidemiological features of the disease were similar to those reported in Great Britain, but the incidence in Northern Ireland was approximately one-tenth that in Great Britain.

The epidemic increased to a peak of 56 cases per month in January 1994, and decreased to nine cases in December 1995. Statutory intervention banning the use of meat and bone meal in ruminant feed in January 1989 has produced a marked and continuing reduction in the incidence. The majority of the cases were in Northern Ireland cattle, but 83 cases were imported from Great Britain and five from the Republic of Ireland. Many of the key epidemiological features have remained constant throughout the epidemic: the greater incidence of BSE in dairy herds than in beef suckler herds, the low within-herd incidence, the variation in incidence with herd size, the breed distribution, the distribution of the reported clinical signs and the proportion of purchased cases. Although the source of the BSE epidemic in Northern Ireland has not been established conclusively, the evidence suggests that the importation of meat and bone meal and protein concentrates from Great Britain may have been responsible.

Epidemiology of CJD in Canada

Elizabeth Stratton, Maura N. Ricketts, and Paul R. Gully,
Laboratory Centre for Disease Control, Health Canada,Ottawa, Ontario, Canada Creutzfeldt-Jakob disease (CJD), and particularly its transmissibility through blood and blood products, has become a focus of concern in Canada. The recent identification of new variant CJD led to a review of the Canadian mortality database to identify any clustering of CJD by age, sex, or geographic location. [Emerging Infectious Diseases 3(1):63-64, 1997. Centers for Disease Control]

The study by Holman and colleagues [1], which uses mortality data and active surveillance methods, has provided further information on the epidemiology of Creutzfeldt-Jacob disease (CJD). The study concluded that the incidence of the disease in the United States has remained stable and is similar to crude incidence worldwide at about one case per million annually. In addition, the study found no evidence that new variant CJD is present in the U.S. population. These findings are of interest because the epidemiology of CJD in Canada is not well described, and concerns have been raised there about the transmissibility of CJD through transfusion of blood and blood products or through tissue and organ transplants. In addition, many Canadians travel to and from the United Kingdom, where new variant CJD was first identified and linked to the bovine spongiform encephalopathy epidemic [2].

We report here our findings on the epidemiology of CJD in Canada, which are derived from published mortality data (underlying cause of death by standard 5-year age group and sex, for all Canadian residents). The Statistics Canada mortality reports for the years 1979 to 1993 were reviewed for CJD deaths by sex and age group for each province and territory. Reports before 1979 were not used because CJD (ICD-9 code 46.1) was not listed as a cause of death before this time.

Overall, 334 deaths attributed to CJD were recorded in Canada in the 15-year period from 1979 to 1993, ranging from 14 to 34 deaths per year, with a 1.1:1 male-to-female ratio (Figure 1). Eighty-five percent of the deaths were among persons at least 60 years of age and 50% among the 60- to 69-year-old age group, which corresponds to the peak age of onset of sporadic-type CJD [3-5]. Eleven deaths (3%) were reported among persons 30 to 44 years of age. Of these, one death was reported in the 30- to 34-year-old age group, four in the 35- to 39-year-old group, and the remaining six in the 40- to 44-year old age group. No more than one CJD-attributed death was reported per year in the 30- to 44-year-old age groups, with the exception of two deaths reported in 1993. No CJD deaths have been reported among persons under 30 years of age.

thumbnail Figure 1. (click here to zoom image) Age and sex distribution for Creutzfeldt-Jakob disease in Canada, 1979-1993.
Figure 2 shows the mortality rate for CJD in Canada, standardized to the 1979 population. The age-adjusted mortality rate increases from a low of 1.1 deaths per million population in 1979 to a high of 2.1 per million in 1992, dropping to 1.8 per million in 1993. The increase is most marked from 1986 onward. This may be related to increased case recognition following publication of the discovery that CJD was linked to human growth hormone of pituitary origin. A real increase in incidence may also be present, but this graph must be interpreted with caution as the absolute numbers are small and the validity of CJD on death certificates has not been determined in Canada.

thumbnail Figure 2. (click here to zoom image) Age-adjusted mortality rate for Creutzfeldt-Jakob disease in Canada, 1979-1993.
Familial-type CJD has been documented in Canada [6,7]. As in other countries, most cases of CJD in Canada are of the sporadic type [3-5]. One case of iatrogenic CJD was reported in Canada, in a dura mater recipient [8]. A review of the Canadian growth hormone recipient database, containing information on the 800 patients who received human growth hormone shows no cases of CJD (Dr. Heather Dean, pers. comm., 1996). Human growth hormone was used in Canada from 1965 until April 1985 [9].

There is one report of a possible cluster of CJD cases in Canada; between April 1989 and October 1990, six cases were reported in the province of Ontario, from a population of 9.5 million (1986 census figure). Two of the patients had come from areas of Czechoslovakia with a high incidence of familial-type disease, but no other risk factors were associated with these cases [7].

In conclusion, the epidemiology of CJD in Canada is not well defined, as current data sources are limited to aggregated mortality data and the annual total case numbers are small. However, several projects have been initiated to provide further information on the transmission of the disease, including an examination of death certificates to identify space/time clustering, active surveillance for CJD and new variant CJD, and a case control study of CJD and blood transfusion.