Throughout the summer grazing season, Midwest beef producers are plagued with a host of insect-related issues.
Ticks and flies can be difficult pests for producers to control and, in addition to the economic hits the insects impose in the form of lost pounds and control methods, the diseases the insects carry and spread are of paramount concern for producers.
“The transmission of anaplasmosis is always something that producers should keep in mind,” said University of Missouri Extension veterinarian Craig Payne. “Somewhere in Missouri, anaplasmosis is always problematic, and we don’t really have any idea of which areas will be worse than others until the outbreak occurs.”
Payne said many producers have referred to the disease as the “horsefly disease,” however, research conducted over the past decade shows that ticks — which are actually not insects but small arachnids — also contribute to the spread of the disease, often at a much faster rate than the fly species.
In research conducted at Kansas State University in 2018, 520 American dog ticks were sampled. Of the ticks sampled, more than 35% tested positive for anaplasmosis.
Greg Hanzlicek shared with producers who attended the 2019 Kansas, Oklahoma, Missouri and Arkansas Beef Conference that when an American dog tick takes a meal from an infected animal, the tick may take in 1,000 red blood cells. In a short time, those 1,000 red blood cells will become millions of red blood cells, and as the bacteria progresses into the tick’s salivary glands, each new meal the tick takes can infect its bovine host.
The male ticks present the greatest risk due to their feeding pattern — taking a meal from a host and then dropping from the animal to look for a female, attaching to several hosts within the tick’s lifespan.
“The Anaplasma marginale bacteria will complete part of the lifecycle in the tick’s gut, which is what makes the number of organisms the tick can transmit greater,” said Payne. “That’s why when I’m talking to a beef producer about anaplasmosis, I am always talking about tick control; they are by far the most efficient living transmitter of the bacteria.”
Bill Stich, University of Missouri professor of parasitology, said the greatest threat to a herd likely comes when ticks infect a herd and the spread of the disease is exacerbated by above-average fly populations.
“The epidemiology (of anaplasmosis) can be complex, sometimes with ticks introducing the A. marginale to a herd, followed by horseflies or blood-contaminated needles spreading the pathogen throughout the herd,” Stich said.
He said all producers can best control the effects of anaplasmosis by working with a veterinarian who has experience with the costly disease.
Not to be overlooked, few years pass without producers feeling the effects of the Moraxella bovis bacteria, the primary causative agent in bovine pinkeye, Payne said.
“Face flies can cause irritation of the cornea on the eye itself,” Payne said. “The insect tends to feed on the eye secretions of cattle and are known to carry the M. bovis bacteria on their body parts.”
Aside from the diseases, the mere presence of insects can be costly to an operation.
“Research suggests that 200 horn flies per animal is the economic threshold for cattle,” said Payne. “The irritation caused by the biting of the horn flies will cause cattle to group up and a producer will see decreased performance because of decreased grazing and increased stress. That isn’t necessarily related to disease transmission, but it is definitely a performance consideration.”
Many insect control options are readily available through both local veterinary offices and farm stores, and prevention can provide a much more cost effective approach than treating the diseases’ symptoms.