Gastrointestinal parasites in a Polish flock of various sheep breeds kept in confinement

Abstract

The infection of sheep with gastrointestinal nematodes and coccidia was studied in a flock of 900 animals kept in confinement. Between May and November 2024, a total of 509 individual faecal samples were collected bimonthly from randomly selected sheep of various ages and analysed using the McMaster method. Additionally, pooled faecal samples were used for coproculture to identify infective third-stage (L3) nematode larvae, and for sporulation to determine coccidia species. Overall, 66.4% of the examined sheep were infected with coccidia of the Eimeria genus, with a mean oocyst count of 2,238 (range 20–158,400) OPG (oocysts per gram of faeces), and 18.9% of sheep were infected with nematodes of the order Strongylida, with a mean egg output of 728 (range 20–12,000) EPG (eggs per gram of faeces). The prevalence of strongylid nematode infection gradually increased in the subsequent months, whereas the infection intensity was highest in May, prior to deworming. Especially lambs aged 6–12 months, and ewes, exhibited high infection levels. Identification of 150 Strongylida L3 larvae revealed a predominance of pathogenic species Teladorsagia circumcincta (61%), followed by Trichostrongylus sp. (27%), Bunostomum trigonocephalum (9%), and Haemonchus contortus (3%). Regarding coccidia, the highly pathogenic E. ovinoidalis and E. crandalis were identified among the detected Eimeria species. Following the necessary administration of a coccidiostat to heavily infected lambs, a slight decline in overall Eimeria infection was observed in the months subsequent to the May peak. In conclusion, despite regular deworming twice a year and the use of coccidiostats in lambs, gastrointestinal parasites, particularly coccidia, remained a significant threat to confined sheep. Therefore, continuous monitoring is recommended, particularly during periods of expected peak infection, to enable timely intervention and prevent parasitic problems within the herd.