Livestock fatalities attributed to a massive attack of Psorophora columbiae following Hurricane Laura

The objective of this case report is to characterize the sudden fatality of livestock associated with a massive attack of dark rice field mosquitoes (Psorophora columbiae) after the passage of Hurricane Laura in southwest Louisiana late August 2020. In 3 days, approximately 30 deer, 600 beef cattle, 100 sheep and 30 horses died following a brief history of weakness or, in most cases, no clinical signs prior to death. Several on-site visits were performed by veterinarians to evaluate animals and perform necropsies. Two deer were received for necropsy, and tissue samples from 1 bull and 1 horse were evaluated at the Louisiana Animal Diagnostic Disease Laboratory. In addition, postmortem examination was performed on another 15 animals by veterinarians. Similar gross alterations were observed in all necropsies. Lesions included multifocal petechiae and ecchymoses in the skin and the subcutaneous tissues. Both deer also had pale discoloration and accentuated lobular patterns in their livers. Histologically, the livers of the deer and the bull exhibited centrilobular degeneration and hepatocyte dissociation suggestive of severe anemia. The description of this animal fatality event associated with Psorophora colum- biae attack demonstrates the need to establish prevention and/or intervention protocols in areas prone to hurricanes and tropical depressions.