A Disease Most People Have Never Heard Of Is Costing the Cattle Industry Million a Year
It doesn’t make national headlines. It doesn’t shut down borders or trigger federal disaster declarations. But bovine anaplasmosis — a tick-borne bacterial disease — quietly works its way through American cattle herds every season, destroying red blood cells, causing miscarriages and weight loss, and killing animals that represent years of investment for the families who raise them.
The numbers are significant. According to researchers at the University of Missouri, anaplasmosis costs the U.S. cattle industry an estimated million annually. Worldwide, losses approach billion per year. And in Missouri alone — home to a cattle industry valued at billion — a 2025 study found that nearly 50% of cattle had already been exposed to the disease.
Those are not numbers from a new or emerging threat. Anaplasmosis has been present in American cattle for well over a century. What has changed is the scale of the problem — and, finally, the science being deployed to confront it.
What Bovine Anaplasmosis Is and What It Does
Bovine anaplasmosis is caused by the bacterium Anaplasma marginale, which is transmitted primarily through tick bites. Once inside a cow’s bloodstream, the bacteria infect red blood cells and begin multiplying. The immune system destroys the infected cells — but in doing so, it triggers a cascade of symptoms that can rapidly become severe.
How the Disease Progresses
Affected cattle typically show a recognizable pattern of decline:
- Lethargy and loss of appetite
- Rapid weight loss
- Pale or yellow mucous membranes from severe anemia
- Labored breathing as red blood cell counts drop
- Miscarriage in pregnant cows
- Death, in acute cases — particularly in older cattle, which are more vulnerable than calves
Animals that survive an acute infection often become chronic carriers, harboring the bacteria without showing symptoms but remaining capable of spreading it to others. There is no cure. Until recently, there was no effective vaccine.
According to Mizzou’s College of Veterinary Medicine, the primary tool farmers have relied on since the 1940s is chlortetracycline — an antibiotic first discovered at Mizzou in 1945 — which can suppress the disease but does not fully eliminate infection. For decades, that imperfect solution was the best available option.
How It Spreads — and Why the Answer Surprised Researchers
Understanding how anaplasmosis spreads is central to controlling it. The conventional assumption has long been that ticks are the primary vector — and that addressing tick populations would go a long way toward reducing transmission. Mizzou researchers set out to test that assumption directly.
The 29,000-Tick Study
A team led by Rosalie Ierardi, assistant clinical professor in the College of Veterinary Medicine, conducted systematic tick surveillance across cattle pastures in five Missouri counties. Researchers used a technique called drag sampling — dragging a cloth across the ground and through vegetation to collect ticks — and gathered more than 29,000 ticks in total. Of those, approximately 1,500 were American dog ticks (Dermacentor variabilis), which prior research had identified as the primary carrier of Anaplasma marginale in the region.
The finding was striking: fewer than 1% of the male American dog ticks collected actually carried the bacterium.
That low rate of infection in the tick population creates an important scientific question. If only a fraction of ticks carry the disease, how is nearly half of Missouri’s cattle herd getting exposed? The answer, Ierardi and her colleagues suggest, may involve direct transmission between animals — cow-to-cow spread through shared equipment, blood-contaminated needles, or biting flies — rather than tick bites alone.
“By better understanding where certain ticks are located and how diseases spread, we can inform public health strategies.” — Rosalie Ierardi, assistant clinical professor, Mizzou College of Veterinary Medicine
That distinction matters enormously for farmers and veterinarians trying to reduce exposure. Tick control is one set of practices. Preventing blood-to-blood transmission between animals is an entirely different set — and both may need to be happening simultaneously.
A New Vaccine — and Why It’s a Breakthrough
While Ierardi’s team was mapping how the disease moves through tick populations, another Mizzou researcher was working on the most significant development in anaplasmosis management in decades: the first effective vaccine.
How the Vaccine Works
Roman Ganta, McKee endowed professor at Mizzou’s College of Veterinary Medicine, developed the vaccine by genetically modifying Anaplasma marginale itself. By deleting a specific gene from the pathogen, researchers created a weakened version of the bacterium that could be safely injected into cattle. The immune system responds by building defenses against the real thing — without the animal suffering the effects of a full infection.
According to KCUR, which covered the vaccine’s development, the approach represents the first proven effective vaccine for the disease. Early results show protection lasting at least one month, with ongoing research to determine how long immunity holds. Ganta is working with industry partners on the path toward commercial distribution.
As Ganta noted in describing the gap this vaccine fills: “There is currently no effective, widely available vaccine for the disease, and cattle farmers are very worried about the disease harming or killing their cattle.”
The vaccine is patented. If it reaches commercial scale, it would give farmers a preventive tool they have never had — moving anaplasmosis management from reactive treatment to proactive protection.
Why the Threat Is Growing
The research comes at a moment when the conditions that support tick populations are actively improving — for the ticks.
Warmer winters and earlier springs across Missouri and much of the central and southern United States are allowing tick populations to expand beyond historical ranges. Ticks that once died off during cold months are surviving longer. Breeding seasons are extending. The geographic reach of established tick species is growing northward.
The American dog tick, lone star tick, and blacklegged tick are all present in Missouri. Each carries its own set of disease risks for both livestock and humans. As research published in Frontiers in Veterinary Science tracking anaplasmosis seroprevalence in Missouri from 2010 to 2021 shows, the disease is not static — its distribution and intensity shift over time with environmental conditions.
The combination of a warming climate and a cattle industry with limited preventive tools creates a vulnerability that researchers are working urgently to address.
What This Means for Missouri’s Billion Cattle Industry
Missouri consistently ranks among the top cattle-producing states in the country. The industry supports thousands of farm families, feeding into processing, retail, and export supply chains that extend well beyond the state’s borders.
A disease that has exposed half the herd and costs hundreds of millions annually is not a background concern — it is an active drag on an industry that operates on thin margins and cannot easily absorb unexpected losses. Every animal that dies from anaplasmosis represents not just that animal’s value, but the years of breeding, feeding, and care that went into it. Every miscarriage is a calf that will never enter the herd.
The research coming out of Mizzou — the tick surveillance data, the transmission insights, and now a first-of-its-kind vaccine — represents the kind of scientific investment that has real consequences for real farm families. As the USDA’s Animal and Plant Health Inspection Service has demonstrated repeatedly with programs like the screwworm eradication effort, targeted, science-driven pest control can protect entire industries and the communities that depend on them.
The tools, for the first time in decades, are getting better. The question now is how quickly they can be deployed at scale.
