Nematode Parasites in Poultry: Their Prevalence, Species Diversity, and Control Strategies

Abstract

Gastrointestinal nematode infections are an important parasitic constraint to poultry production, particularly in low- and middle-income countries where diverse production systems and variable biosecurity measures may facilitate parasite transmission. In Pakistan, large-scale multicenter data on the prevalence, species diversity, and management-related determinants of poultry nematodiasis remain limited. Objective: To determine the prevalence, species diversity, and risk factors associated with gastrointestinal nematode infections in chickens reared under different production systems in Pakistan, and to evaluate the relationship of parasite burden with deworming practices and production performance. Methods: This cross-sectional epidemiological study was conducted across four provinces of Pakistan, including Punjab, Sindh, Khyber Pakhtunkhwa, and Balochistan. A total of 60 farms were selected using stratified sampling, representing commercial broiler, commercial layer, and backyard poultry systems. Twenty chickens were randomly sampled from each farm, yielding 1,200 birds. Individual fresh fecal samples were examined using standard flotation techniques, and eggs per gram (EPG) were quantified by the McMaster method. Nematode species were identified morphologically. Species diversity was assessed using species richness, Shannon diversity index, and Simpson’s diversity index. Associations were analyzed using the chi-square test, logistic regression, analysis of variance, and Pearson correlation. Results: Of 1,200 examined birds, 497 were positive for gastrointestinal nematodes, giving an overall prevalence of 41.4%. Prevalence varied significantly by region, ranging from 35.3% in Punjab to 47.0% in Balochistan (p=0.021). Infection prevalence was strongly associated with farm type and was highest in backyard flocks (63.8%), followed by commercial layer farms (37.2%) and commercial broiler farms (24.5%) (p<0.001). Four nematode taxa were identified: Ascaridia galli, Heterakis gallinarum, Capillaria spp., and Syngamus trachea. Species richness was similar across provinces, with moderate diversity indices. Mean EPG was significantly lower in routinely dewormed flocks than in non-dewormed flocks (210±165 vs 465±188; p<0.001). Parasite burden was negatively correlated with body weight (r=−0.42, p<0.001) and positively correlated with feed conversion ratio (r=0.37, p<0.001). Conclusion: Gastrointestinal nematode infection is highly prevalent in poultry in Pakistan, particularly in backyard production systems. Routine deworming appears to reduce parasite burden, while heavier infections are associated with poorer production performance. Integrated parasite control strategies may improve poultry health and productivity.