The Potential Long-Term Infectivity of Oxyspirura petrowi Eggs to Insect Intermediate Hosts Over Different Seasons

Oxyspirura (O.) petrowi is a parasitic eyeworm that infects a wide range of avian hosts across North America at high prevalences, including species undergoing significant population declines. Despite growing concern over its ecological impact, the epidemiology of O. petrowi eggs remains poorly understood. This study is the first to assess the potential long-term infectivity of larvated O. petrowi eggs across seasonal exposure periods, aiming to identify environmental thresholds affecting larval survival. Eggs were placed in mesh bags with soil and placed in an outdoor plot where O. petrowi are naturally found. Bags were collected after 1, 3, and 6 mo, once over winter and once over summer. The eggs were extracted from the soil, and the total eggs recovered and the number of eggs that remained larvated were counted. Egg inactivity was calculated by comparing these numbers to control bags. Across both seasons, total egg recovery declined steadily over time, with 69.7% inactivation occurring over winter and 67.9% inactivation occurring over summer. A sharp drop in larvated eggs between 1- and 3-mo winter exposures corresponded with a cold snap, suggesting extreme cold may significantly impact egg infectivity. Conversely, summer exposures showed a more gradual decline in the number of eggs recovered, with high temperatures and natural membrane degradation likely the contributing factors. A near-consistent percentage of larvated eggs was recovered from each timeframe. Despite these declines, approximately one-third of eggs remained larvated after both seasons, indicating strong resilience and a persistent transmission risk. These findings underscore the resilience of O. petrowi and highlight the importance of integrated management strategies. Targeted interventions may be necessary to disrupt reinfection cycles and support the conservation of vulnerable host species.