Are there lessons from the TB investigation for cow-calf producers?

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Source: Ontario Ministry of Agriculture, Food and Rural Affairs

The follow-up on the initial tuberculosis (TB) positive cow from Canada detected at slaughter in the United States has been complicated and expensive, but the rapid response reduced the overall impact by short-circuiting further disease spread.

Recently the Canadian Food Inspection Agency (CFIA) reported that the testing of cattle after the discovery in the fall of 2016 was completed. About 11,500 animals have been destroyed and about 30,000 head have now been released from quarantine. All cows from the original herd, plus those in 18 other herds deemed to be high-risk because of direct contact with the original herd, were included in the humanely slaughtered group. A high profile disease occurrence like this one should encourage everyone to take a look at infectious disease control programs on their own farms and areas.

Cattle are at risk of many infectious diseases that can cause varying levels and degrees of impact. Fortunately TB in cattle in Canada is rare and has occurred only very sporadically, but when it does occur, it is one of the most impactful. To protect human health and the health of our country’s cattle herd, routine screening for TB at slaughter occurs to detect a mainly subclinical disease and provides the greatest opportunity for preventing further spread. Unfortunately we don’t have this level of surveillance on farms for other less dramatic infectious diseases of cattle, although some of these can have a very significant negative impact on the individual herds they infect.

There is a perception that cow-calf herds are at a lower risk of infectious diseases compared to other commodities, perhaps because of the extensive and predominantly outdoor manner of rearing beef cattle. This may give producers a false sense of confidence in the level of biosecurity they currently practice. The TB investigation reminds us that cow-calf herds too can face significant infectious disease problems. The extent of the TB investigation was greatly increased because cattle from 18 herds were commingled on community pastures. Returning cattle or new cattle added to the cow-calf herd, such as bulls, potentially puts many herds at a higher risk of infectious diseases than they may suspect. By reviewing current herd biosecurity programs we can evaluate if the programs we have in place can protect our cattle herds from the risks they confront. TB is a “headline” disease, but other less news worthy diseases may commonly be present in Ontario herds and have a negative impact on productivity and health.

A basic starting point for developing a good specific herd biosecurity program is to know which diseases a herd owner should be concerned about. These could be diseases that are known to be present in the herd already and/or diseases that could be newly introduced.

To monitor the occurrence of disease, routinely conducting post-mortems on all animals that die should be a core component of a cow-calf herd’s biosecurity program. Often why cattle die is not apparent or the cause of death is something different than what was suspected when the animal was alive. A post-mortem can be conducted on the farm or at a dead stock operation depending on the farm’s location. Many times the post-mortem itself will provide answers, or laboratory testing of samples can be done if recommended by the herd vet and desired by the owner.

The recently completed Calf Health Surveillance Project highlighted the value of post-mortems on calves for more accurately pin-pointing the causes of infectious diseases that beef producers and their veterinarians did not always know were occurring. For example, calves were detected with underlying White Muscle Disease that had looked like cases of infectious diarrhea. Some were found to have died acutely from pneumonia, and other calves found dead were diagnosed as having septicemia due to undetected umbilical infections. About a third of all the calves that were post-mortemed had diarrhea as a suspected cause of death. On follow-up lab testing, six different diarrhea-causing infectious agents, including viruses, bacteria and/or protozoans, were identified. Many of the infectious disease conditions diagnosed by the post-mortems pointed at specific actions a producer could take to prevent future calf sickness and death in their herd. The use of vitamin E/selenium injections, more targeted vaccination programs for respiratory disease and calf diarrhea, management of the calving area and a heightened awareness of umbilical infections to allow early treatment are all practical actions producers could undertake to improve calf health and survivability, based on the post-mortem results.

Having post-mortems done on cattle that die, particularly calves, can prevent future losses and should be a part of any basic biosecurity program, yet it appears this is an under-utilized service that veterinarians can provide. Working on an animal that has already died may not sound like “preventive medicine” but it can be if infectious disease conditions are accurately identified and the diagnosis leads to constructive management changes.

As we approach spring calving, consider talking to your vet about what conducting post-mortems on cattle that die would entail. Calves may be the easiest way to start and probably give the most immediately rewarding and timely information for instituting management changes.

Surveillance at slaughter for TB has been a very effective monitor for an important national disease; surveillance by post-mortem of calves that die may go a long way towards improving your herd’s biosecurity program by enabling you to implement cost-effective and herd-specific infectious disease preventive practices.

Author: Dr. Ann Godkin, Veterinary Science, OMAFRA

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