Epidemiological, pathological and microbiological investigation of neonatal lamb mortality in the region of Constantine, Algeria

Abstract

Background: Neonatal lamb mortality affects the sheep flock's productivity. In Algeria, data are very limited, making investigations quite relevant. This study aimed to determine risk factors associated with neonatal lamb mortality, describe gross and histopathological lesions on affected organs, and identify bacterial pathogens involved. Design: Thirty-five sheep farms located in Constantine participated in this survey between February and December 2022. An epidemiological questionnaire was used to describe monitoring practices and to identify associated risk factors. Twenty-two collected lamb corpses (immediate postmortem changes) underwent detailed postmortem examinations, including anatomopathological, histopathological and microbiological analyses. Results: The recorded neonatal mortality rate was 5.74%. Statistical analysis revealed significant associations between mortality and factors such as soil and livestock building hygiene, as well as the breeding system used (p < 0.05). The lungs, liver, kidneys and heart were the most affected organs. Causes of death included respiratory disorders, omphalitis with septicaemia, stillbirth, trauma and starvation-hypothermia syndrome. From these organs, 218 bacterial strains were isolated, mainly Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Providencia spp., Citrobacter spp.), causing primary infections, alongside non-fermenting Gram-negative bacilli (Pseudomonas aeruginosa, Comamonas spp., Acinetobacter spp.), responsible for the associated septicaemic evolution. According to the EUCAST breakpoints, isolates were resistant to commonly used antibiotics: amoxicillin, amoxicillin/clavulanic acid, trimethoprim/sulfamethoxazole and tetracycline. Notably, only Klebsiella spp. strains harboured blaSHV genes. Conclusion: This study concluded that improved sanitary protocols, early diagnosis and antimicrobial testing are crucial to prevent neonatal mortality. It also recommended larger studies and farmer training programmes to enhance lambing and neonatal care practices.