New World Screwworm Detected in Texas, What Does this Mean for Kansas?

Cassandra Olds, extension livestock entomologist

New World screwworm (NWS) infestations were detected in Texas and New Mexico in early June. Following the USDA NWS response playbook, infested animals are treated, surveillance efforts are being carried out, and sterile flies are released over infested zones. You can view the current status of the outbreak here.

Prior to eradication efforts in the 1960’s, NWS were present in Kansas. Annual reports from Extension entomologist E. G. Kelly describe years where no infestations occurred and other years where screwworm infestations impacted 2% of cattle within a herd. Two scenarios were described in outbreak years. Scenario one occurred through natural annual northward movement of fly populations from overwintering sites in southern states (Figure 1). In these years, populations of NWS were found in Southwest Kansas and were strongly influenced by climate conditions.

Scenario two occurred through the movement of already infested cattle into the Flint Hills in the spring, followed by local spread within the Flint Hills, spreading to western Kansas later in summer. Then-as well as now- winter temperatures were too cold for the fly to survive and all infestations were eliminated.

Currently, the primary risk of introduction into Kansas is through the movement of infested animals from outbreak regions during the spring and summer months. To mitigate risk, inspect any animals arriving from out of state for wounds infested with maggots. If maggots are found infesting a wound of any animal, contact the Kansas Animal Health Commissioner and APHIS Area Veterinary Office to co-ordinate sample collection and identification. As the NWS is attracted to the smell of wounds, inspect and clean any wounds to reduce the risk of an infestation. Detailed information on the fly life cycle can be found here and reporting suspected infestations here.

Additionally, Kansas State University is hosting a webinar series with a variety of experts which you can register for here and submit any questions you have. Recordings are made of all webinars for those who are unable to attend live.