CALF_News_June_July_2020

18 CALF News • June | July 2020 • www.calfnews.net CALF ANIMAL HEALTH Chuteside Manner EXPLORING THE FRONTIER OF ANIMAL HEALTH Little Monsters By Patti Wilson Contributing Editor D uring the heat of the summer, there’s an abundance of concern over health issues and per- sistent annoyance. I am not talking about our grandchildren; I’m referring to flies. Agricultural scientists have put flies under close scrutiny, determining spe- cific bacteria, viruses and new threats the insects carry on their various body parts. Even their means of attacking livestock with specialized biting, sucking and abrasive features are examined. Flies carry diseases too numerous to dis- cuss in one sitting. This Chuteside column will whittle the list to only a few interesting or important maladies and pathogens. Bovine leukemia virus (BLV) There are few beef producers who are aware that cows can carry their own brand of leukemia, bovine leukosis. Although not well known, it is common in the United States, infecting 44 percent of dairy and 10 percent of beef cows. According to the Merck Veterinary Manual , the prevalence of this virus increases with age. Cattle are infected with BLV“through transfer of blood and blood products that contain infected lymphocytes.” Common farm practices like tattooing, dehorning or rectal palpa- tion can transmit BLV; however, flies are a guilty party as well. About 65 percent of infected animals show no outward symptoms. There is likely a silent loss of production that is impossible to measure, and these cattle become a reservoir of BLV for future transmission. About a third of infected cows have a stepped-up version called persistent lymphocytosis. They definitely show production loss and have a greater risk of passing along infection. The remaining 5 percent of BLV-positive cows are generally four years or older, and have outward symptoms of illness. This is called lymphosarcoma and is one of the main causes of condemnation of adult cows at harvest. There is no treatment for BLV. In case beef cattle producers are brushing off this problem as insignificant, just remember the speed at which Johne’s disease and hairy heel wart jumped from dairy into the beef industry. Warbles Anyone over the age of 55 can remem- ber the awful warbles or grubs that infested bovines back when LBJ was president. Otherwise perfectly good cattle developed painful bumps on their tops. Each bump had an air hole, and in the hole was a large and most disgusting larvae. Innumerable hides and loins were damaged or destroyed by warbles infes- tation, and calves and yearlings, the most susceptible, suffered immeasurable pain. Monetary loss followed these cattle to the packing plant. According to an article written by Jenny Halstead of Kansas State Uni- versity, warble flies live for only a week, only to reproduce. They are large and hairy, resembling bumble bees. Females have rudimentary, degenerate mouth parts that are useless for eating; their only function is to lay approximately 600 eggs before dying. The eggs are laid on the lower legs of cattle, and hatch within six days (only 3 percent to 5 percent will survive to maturity). The larvae pierce the skin and migrate through muscle and connective tissue on their way to the esophagus, a trek that takes four months. There they overwinter. In the spring, migration continues to the backs of cattle, a trip that takes a total of nine months after hatching. After arriving in the loin area, larvae get busy, cutting a breathing hole in the skin to molt twice, doubling in size. This final process takes 30 to 90 days. Finally, the grubs work their way out of the breath- ing holes in April and May to fall to the ground and pupate. There are two varieties of grubs, they are found on all continents in the North- ern Hemisphere. Thankfully, there are have been effec- tive treatments available to stop this parasite for several decades, drugs that are indispensable to the cattle industry. Most younger cattle producers have never seen a grub; good management has stopped them cold and warble flies have A few flies will escape even the best insect-control methods. Use the best products you can find, they pay great dividends in health and comfort of your cattle.