Current Parasite News

New World Screwworm:

New World Screwworm (NWS) is a fly that can impact livestock, pets, wildlife, and rarely, people. This fly causes significant damage because its larvae feed on the living flesh, as opposed to other blow flies, that feed on the dead tissue in wounds or carcasses. If left untreated, these larvae will continue to consume flesh and eventually kill the host.

Maggots in wounds are not uncommon this time of year and are commonly blowfly larvae that only feed on dead tissue. However, if you suspect NWS in an animal, you should reach out to us at Apogee for diagnostic testing. Cases have only been found in Texas, with one case identified in a dog in New Mexico, but it could move to other locations in the US through movement of infested animals. It is important that USDA is aware of all possible and confirmed cases, so they know where to release sterile flies, which is the method of eradicating this pest.

Historically, this fly caused losses to US livestock industries through the 1970’s but through extensive eradication efforts, was pushed South, out of the US and Central America. However, in 2023, the NWS started moving back North through Central America and was found in Texas in June of 2026. The sterile insect technique was used to eradicate this pest from the US previously and is currently being deployed in Texas to reduce the fly population. The female flies only mate one time in their life, so if the female mates with a male that is sterile, the eggs she lays will not hatch and the population will slowly decrease over time.

The state of Texas has strict inspection and treatment requirements for cattle coming out of infested areas to ensure cattle being shipped out of these areas don’t unknowingly transport larvae. If you are importing animals from Texas currently, we would be happy to discuss the situation in Texas and how to mitigate the risk of bringing this pest further North.

Theileriosis:

 Theileriosis is a parasitic, blood-borne disease that has been found in over 30 states including Kansas. It is caused by the protozoa Theileria orientalis ikeda and spread most commonly by the Asian Long-Horned Tick. There have been numerous cases of this disease in Kansas in both feeder cattle and cow/calf herds. Many of these cases are in cattle imported to Kansas from Eastern states, but some have been in Kansa native cattle.

The Asian Long-Horned tick was first identified in the United States in 2017 and was first found in Kansas in 2025. This tick replicates asexually, so a single female tick can produce thousands of offspring. Theileria is like Anaplasmosis in that the parasite infects red blood cells causing anemia. However, Anaplasmosis typically causes disease in cattle over 2 years of age, while Theileria can cause disease and death in young animals as well. Anaplasmosis is bacterial and can be treated with antibiotics, whereas Theileria is protozoal and currently has no treatment options.  

Initial clinical signs are seen 1 to 8 weeks after exposure with anemia being the most common. You may notice pale or yellow mucous membranes, labored breathing or lethargy. Late term abortions and even death loss can occur. However, many infected cattle never show any clinical signs. The majority of animals survive and become asymptomatic. Once an animal is infected, it will have the organism in its bloodstream for the rest of its life. Theileria can be spread by anything that spreads blood such as shared needles between animals and biting flies such as horn and stable flies.

To test for Theileria, the preferred sample is a blood sample from live animals and a spleen sample from deceased animals. There is a conditionally licensed vaccine that recently became available in the US, but it is important to note that there has been no studies to show if this vaccine is effective at reducing infection or clinical signs of Theileria. Currently, treatment only involves treating the clinical signs associated with the disease course. Stress exacerbates disease, so stressful events should be minimized during this acute infection period if known. There is still research that needs done on this disease, but please be aware of this threat that is continuing to spread.