Mizzou on the front lines of tracking tick-borne diseases in Missouri

By Brian Consiglio

July 15, 2026
Contact: Brian Consiglio, [email protected]
Photo by Abbie Lankitus

As tick-borne diseases threaten Missouri cattle, the University of Missouri's College of Veterinary Medicine is leading the charge to protect producers and the state's livestock economy. At the Veterinary Medical Diagnostic Laboratory (VMDL), experts are providing timely testing services to gain much-needed insights and help researchers and agricultural professionals track the spread of tick-borne diseases across the state.

Rosalie Ierardi and Tirth Uprety, researchers at the VMDL, are monitoring the increase in tick-borne diseases affecting cattle. Below, they offer practical advice to Missouri livestock producers looking to protect their herds.

What are the most common diseases that ticks spread to cattle in Missouri, and have any new threats emerged in recent years?

Ierardi: Bovine anaplasmosis has long been the most common tick-borne disease impacting Missouri cattle, and the American dog tick carries the bacterium Anaplasma marginale, which causes it. A 2025 Mizzou study found that nearly half of all Missouri cattle have been exposed to the disease. The economic consequences can be devastating for producers, as the disease kills red blood cells in cattle, causing lethargy, weight loss and sometimes pregnancy loss or death.

In recent years, bovine theileriosis has emerged as another tick-borne disease affecting many Missouri cattle. Bovine theileriosis is spread by the invasive Asian longhorned tick, which carries the Theileria orientalis parasite. This tick was first identified in Missouri in 2021, and researchers have since documented it in additional counties across the state. As the tick expands its range, livestock producers are increasingly concerned about the economic consequences. Similar to bovine anaplasmosis, bovine theileriosis kills red blood cells in cattle, causing weight loss and potentially pregnancy loss.

What makes the Asian longhorned tick different from other ticks?

Ierardi: One reason the species has attracted attention is its ability to reproduce without mating. Since the ticks don't waste time looking for a mate, their population can explode very quickly.

How has the VMDL supported cattle producers in recent years?

Uprety: We have met the rising demand for testing in recent years, especially for bovine theileriosis. In 2024, the VMDL tested 263 samples for Theileria orientalis, with roughly 34% testing positive. That increased to 421 samples in 2025 with roughly 53% testing positive. By May 15, 2026, we have already tested more than 651 samples with nearly 65% testing positive. So, not only are we receiving more samples for testing, but the positivity rates are increasing as well, suggesting both growing awareness among producers and continued concern about the spread of disease.

How can producers know if their cattle have been infected with bovine anaplasmosis or bovine theileriosis?

Uprety: Since the symptoms - anemia, weakness and reduced weight gain - for both diseases look very similar clinically, sending samples for testing at the VMDL is crucial. The VMDL offers polymerase chain reaction testing that can detect both Anaplasma marginale and Theileria orientalis from the same blood sample.

Once producers know the specific problem, are there treatment options?

Ierardi:While tetracyclines are the most common antibiotics for treating bovine anaplasmosis, there are currently no approved treatments for bovine theileriosis.

How quickly can Missouri producers expect to hear back after submitting samples to the VMDL?

Uprety: Having in-state diagnostic capabilities allows producers and veterinarians to receive results more quickly than they might from some out-of-state laboratories. Most samples received early in the day can often be processed with results available by the next business day. Producers looking to submit samples for testing can find more information on the VMDL website.

Are there particular herd management practices producers should keep in mind?

Ierardi: We recommend testing cattle for both diseases before introducing them into a herd. Problems can arise when infected animals are mixed with uninfected animals or when cattle with no prior exposure are introduced into herds where the disease is already present. Understanding the infection status of incoming animals can help reduce risk.

Why is early detection important?

Ierardi: Previous research has shown that by the time the first visibly sick animal is identified, much of the herd may already be infected with disease, especially in the case of bovine theileriosis. That means producers and veterinarians should think proactively about surveillance, testing and management rather than waiting until multiple animals become ill.

How does the VMDL reinforce Mizzou's status as a land-grant university?

Ierardi: The work we do here at the VMDL directly impacts Missourians, especially those in rural areas of the state where agriculture and livestock production are extremely important drivers to the state's economy. Our efforts help producers and veterinarians make better-informed decisions related to herd management. We are proud of the relationships we have built with producers and veterinarians throughout the state who know they can count on Mizzou to provide timely testing results as the state's flagship university.