Every year cow herds in some areas are hit by the blood-borne disease anaplasmosis. Severe anemia caused by the disease can lead to sudden death, with mature cows especially at risk.
Biosecurity measures should be heightened as new adult cattle are brought into existing herds. These animals may be anaplasmosis carriers, or they may be clean but lack herd immunity the home herd (which may carry anaplasmosis) has developed. Either way, results can be devastating. Initial infection periods are especially dangerous and most often result in sudden death. Once an animal is infected, if it survives, it carries the illness and can pass it on for the rest of its life.
Texas has historically been a prime area for anaplasmosis due to environmental conditions that allow a common carrier, the tick, to thrive. Thomas Hairgrove, Extension veterinarian and professor at Texas A&M University, has researched and written about anaplasmosis for many years. He explains that the blood-borne disease is most often spread by ticks, biting flies and use of contaminated instruments to work cattle, including needles and ear taggers.
Hairgrove notes carrier cattle rarely show symptoms but are persistently infected and generally live with the disease.
"In carriers, we can't find anything to support the idea that there are more abortions or lower conception rates," he says, adding that bulls may also be infected, and research is continuing to look at whether this could impact their fertility.
ANAPLASMOSIS CAUTION FLAG
Kansas State University's (KSU) website follows positive diagnostic test submissions for anaplasmosis, allowing veterinarians and researchers to track instances of the disease each year.
Bob Weaber, Extension cattle specialist for KSU, explains that clinical signs appear as the red blood cell count falls, and animals become anemic. Watch for weight loss, abortions, respiratory distress, yellow mucus membranes (gum tissue, around eyes, vulvar tissue), dark yellow urine and constipation with hard, dry, shaded green feces. Behavior may become aggressive, or animals may act in a stupor as oxygen levels decline. The specialist urges producers to handle animals they suspect might be infected carefully, trying not to excite or agitate them.
"If you think you're dealing with an anaplasmosis situation, be very gentle in animal movement. You don't want them running. Keep them as quiet as you can as you move them," he says.
Treatment options should always be dictated by the herd veterinarian, but Weaber notes there are antibiotics to help infected animals get past critical time periods. Some producers will feed antibiotics in a daily supplement, and some antibiotics are approved for use in a mineral mix, he explains. These are only available with a Veterinary Feed Directive (VFD).
"Self-feeding is an issue," Weaber adds. "Not all of the animals will eat minerals at a dose we want them to every day. So, there are challenges when it comes to controlling the disease."
In some cases, veterinarians in endemic areas have recommended use of an anaplasmosis vaccine as a type of control program. This is a multi-vaccine approach, which some producers limit by first testing for anaplasmosis and then only treating animals with positive test reactions.
Developed by Louisiana veterinarian Gene Luther in 2000, the University Products LLC (UP) vaccine has FDA approval for experimental use. Based on literature from UP available at presstime, the vaccine is a 1-cc dose administered subcutaneously in the neck. The first year, two doses are required (four weeks apart), with annual boosters each year thereafter. Protective immunity, according to UP, occurs "in a week to 10 days after the second injection of vaccine."
This is a killed vaccine and is stable at environmental temperatures. The vaccine is reported safe in pregnancy. Luther produces it at Louisiana State University.
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