Abstract
Background:
Parasite infestations of poultry kept in organic production systems are re-emerging, but case reports of Ascaridia dissimilis infections in turkeys reared under organic conditions are limited.

Case Description:
A flock of organic B.U.T. six turkeys at the age of 12 weeks experienced an acute increase in mortality in spring. Necropsy of affected turkeys revealed severe intestinal lesions with necrotic enteritis. Histopathology confirmed the presence of ascarid larvae within intestinal lesions, establishing the definitive diagnosis: ascaridiasis caused by A. dissimilis, the turkey roundworm. The remaining turkeys in the flock were immediately treated with fenbendazole in the drinking water. Within a week after treatment, the daily mortality rate dropped dramatically and returned to normal. The warm and humid spring weather, wet litter, and the use of gas heaters likely accelerated parasite egg development and led to an early, overwhelming infestation.

Conclusion:
This outbreak points out that A. dissimilis, typically a subclinical parasite, can cause fatal enteritis in young turkeys under certain conditions. Prompt diagnosis via necropsy and histology was critical, as routine fecal exams can miss prepatent infestations. A targeted parasite monitoring strategy is crucial to detect and manage Ascaridia infestations before losses occur. Effective control of A. dissimilis in turkeys requires vigilant monitoring and timely intervention, alongside good husbandry practices, to prevent severe disease and economic loss in poultry production.

Key words: Ascarid infestation; Enteritis; Mortality; Organic farming; Turkeys.