A University of Missouri researcher hopes his work may help prevent ticks from transmitting anaplasmosis to cattle, other animals and people.
Dr. Roger (Bill) Stich, an associate professor in the department of veterinary pathobiology at MU’s College of Veterinary Medicine, is following two tracks of research. In one of those, he told Ozarks Farm & Neighbor, he’s focusing on understanding how ticks acquire the pathogens that they then transmit to vertebrate hosts; the pathogen he’s studying Anaplasma marginale, the agent of bovine anaplasmosis. “By understanding how it infects the tick or the mechanisms – the adaptations of these organisms for the ticks,” he said, “our hope is that we’ll be able to develop novel approaches to prevent the ticks from becoming infected. One of the biggest problems we have out there, for example, is when a clinically silent carrier animal is moved into a herd of previously unexposed, naive hosts; theoretically, ticks are capably of acquiring the pathogen off of that carrier, and transmitting it to the other host.”
Stich’s other work involves dogs, which can be hosts to a number of pathogens transmitted by ticks. He said, “Dogs are potential sentinels as well as models and, for some agents, possibly reservoirs of zoonotic or tick-borne pathogens that are capable of infecting humans.” Although the anaplasma species that infects dogs, A. phagocytophilum is capable of infecting cattle, it’s not known to be a problem in cattle in the United States, but affects horses and sheep as well as dogs and humans.
Anaplasmosis is commonly seen in cattle in this region of the country. Dr. Jeremy Powell, University of Arkansas Extension veterinarian, told OFN it’s found in western and central Arkansas. “It can cause fairly acute problems in mature cows, and producers can have death loss in cows that have been affected by anaplasmosis,” he said. Powell said producers should watch for engorged ticks. “They’re easy to see, and oftentimes would be on the lower part of the animals or sometimes under the tail head,” he said. He recommended producers monitor on a monthly basis starting in May, and through the warm months of the year until the first frost occurs around the middle of October.
He said several ticks are known to cause problems for Arkansas cattle raisers. “One would be the lone star tick (Amblyomma americanum), and we commonly observe that one in summertime in cattle in Arkansas,” he said. “The American dog tick (Dermacentor variabilis) does feed on dogs, but it can also feed on cattle and other livestock. We can have problems upon occasion with the spinose ear tick (Otobius megnini); that seems to be more of a problem in some parts of the state and is somewhat sporadic,” and is mostly confined to the southwest part of the state.
Stich said there are a number of other pathogens that can be passed from ticks to cattle, but most of them are not a problem in the U.S. “As one time,” he said, “we had a huge problem with a protozoan pathogen related to the protozoan that caused malaria in people; it’s called babesia. Babesia was the agent of Texas cattle fever, which almost wiped out the U.S. cattle industry in the first part of the 20th Century; by about the middle of the 20th Century through efforts across the southern United States, the tick that transmitted the pathogen was eradicated,” although it still pops up occasionally in southwest Texas.
Livestock epidemiologists are also worried about another pathogen related to the one that causes bovine anaplasmosis; it’s called Ehrlichia ruminantium (formerly Cowdria ruminantium), and causes a disease called heartwater. Stich said it’s in the Caribbean, and there is concern that it could find its way eventually into the United States. “There’s been surveillance for that, vigilance looking for that particular pathogen and the ticks that may transmit it, for decades,” he said. “So far we’ve managed to keep it out of the country, as far as I know, but if that pathogen were to come into the United States, then there are ticks capable of transmitting it.” One of those is known as the Gulf Coast tick; despite its name, it ranges fairly far north, and tends to feed in the ears of cattle, and if E. ruminantium ever shows up here, “these ticks are potential vectors of it, as well.”
