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Sometimes there are no answers to troubling questions

Animal Health with Dr. Ron Clarke

Life is unpredictable. The hinterland between known and unknown is often blurred. Despite our techno-ability to scrutinize things at a molecular level, the ability to provide answers to troubling questions is sometimes beyond reach.

Take, for example, the year-long investigation into TB discovered in an Alberta cow shipped to the U.S. for slaughter. The discovery and investigation became a nightmare for southeastern Alberta ranches. About 11,500 mature cattle and most of the calves from 18 farming operations were killed and tested. Evidence suggests that the risk of cattle from the infected farming operation commingled with other cattle in a community pasture situation failed to transmit the disease. The investigation involved quarantine of over 90 herds. Compensation amounted to $37.2 million plus another $5.2 million in costs to cover feed and care for quarantined animals, cleaning and disinfection and interest on outstanding loans. Communication problems between CFIA, producers directly involved and the industry in general hampered progress. Despite Canada’s traceability efforts over two decades, the inability to track cattle movement in and out of herds impeded the ability to make sound decisions. The caudal fold test, the 100-year-old standard backed up with culture methods, proved troublesome in that it involves handling cattle twice, and lacks accuracy in terms of diagnostic sensitivity and specificity despite new diagnostic technology sitting on the shelf waiting to be adopted. In the end, and after a huge investment in time and money, the public is told the origin of infection remains a question and probably will never be known.

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The public worries about the spread of Lyme disease and the ticks responsible for transmitting it. Estimates from the U.S. Center for Disease Control and Prevention (CDC) indicate the number of diagnosed cases of Lyme disease in the United States may be 10 times that of cases actually reported through routine surveillance.

Lyme disease is the most commonly reported tick-borne illness in the United States. About 30,000 cases are reported each year in the U.S. The CDC estimates total annual diagnosed cases may be up to 300,000. In Canada, cases of Lyme disease are on the increase in every province. Prevalence estimates vary widely. Prevalence of the black-legged tick, the species of tick typically associated as a vector of Borrelia burgdorferi, is showing up in all Canadian provinces.

Though dogs and humans represent the majority of Lyme disease cases, antibodies to B. burgdorferi have been demonstrated in cattle in Europe, Australia, the U.K. and the United States. Spirochetes have been detected from the blood and urine of cows in Wisconsin. At the present time, there seems no set pattern of symptoms, diagnosis or treatment of the disease in cattle. Typically, in the acute stage of the disease, cattle may develop fever, stiffness and swollen joints, lameness, and decreased milk production. Chronic weight loss, laminitis, and abortion have also been reported.

Another species of tick mysteriously arrived in North America. The longhorn tick, native to East Asia, has been discovered in five U.S. states. No one can say for sure how it got here or how to get rid of it. It is an aggressive biter and can spread pathogens among a diverse range of hosts. The females reproduce without a male, which means a single female can create a colony of severe infestations on animals.

As of June 27, 2018, 210 people from 36 U.S. states and Canada were infected with the E. coli strain O157:H7 traced to romaine lettuce grown in the Yuma growing region of Arizona. Forty-eight per cent of ill people required hospitalization including 27 people who developed hemolytic uremic syndrome, a type of kidney failure. Five people died. DNA fingerprinting techniques known as pulse gel electrophoresis and whole genome sequencing and aided by sophisticated surveillance systems provided no definitive answers. Contamination occurred throughout the growing season. Investigators pointed to irrigation canal water as the likely source of contamination, but experts remain puzzled how E. coli entered the water. Internalization of food-borne bacteria into edible parts of fresh produce beyond simple surface contamination has been identified as a potential issue in this outbreak. Although the outbreak appears to be over, the source of bacterial contamination may never be identified.

Thalidomide, first marketed in the late 1950s as a sedative and used by pregnant women to help overcome morning sickness, damaged a generation of babies in the womb by interfering with the growth of arms and legs. About 10,000 thalidomide babies were born worldwide until the drug was withdrawn in the early 1960s. Brazil re-licensed thalidomide in 1965 as a treatment for skin lesions caused by leprosy. Millions of thalidomide pills are distributed annually. The toll taken on developing fetuses is not known.

A&W’s new plant-derived burger is being advertised internationally. The same company successfully introduced a “no hormone, no antibiotic label” several years ago that is now recognized as a brilliant marketing effort that sold more burgers everywhere. Should the industry be concerned about the new protein burger when consumers recognize that burgers are much more than a patty, a slice of cheese and a bun? Today’s burger has a wide variety of flavours and toppings. It seems North Americans have fallen in love with burgers of every description. The “better burger” sector continues to thrive in the overall burger category and that trend shows no signs of stopping. No one seems to know for sure what will catch on!

About the author

Columnist

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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