Lumpy Skin Disease Virus Infected Calves Showing Multisystemic Vasculitis on Postmortem Examination: A Summary of Six Cases.

Lumpy skin disease (LSD) is a rapidly spreading transboundary viral disease of cattle and water buffalo that poses a significant threat to livestock health and economies of Bangladesh. Calf mortality is steadily increasing over time. This study documented fatal calf mortality with vasculitis-driven multisystemic pathology, which has been rarely reported in Bangladesh. To investigate the rising incidence of calf mortality in Bangladesh, this study conducted a pathological investigation of six deceased calves and molecular analyses of the viruses. Clinically affected calves in north-central Bangladesh exhibited high fever, skin nodules, lymphadenopathy, joint swelling, respiratory distress, ocular and nasal discharge, and edema. Cutaneous nodules often sloughed off, leaving deep ulcerative lesions. Gross pathology of six deceased calves revealed multisystemic lesions, including congestion and edema of the nasal passages, tracheitis, pulmonary consolidation, renal congestion and necrosis, hepatomegaly with multifocal necrosis, splenic atrophy, and lymphadenopathy. Histopathology demonstrated necrotizing inflammation, severe broncho-interstitial pneumonia, hepatic centrilobular necrosis, myocardial infarction, interstitial nephritis with vasculitis, and marked lymphoid depletion. Molecular detection confirmed moderate to high viral loads in the skin and internal organs, consistent with the pathological findings. Whole-genome phylogenetic analysis placed the isolates within cluster 1.2 (classical African/Kenyan sheep and goat pox [KSGP]-like lineage), with one strain clustering closely with isolates from India, Serbia, and Russia, indicating possible cross-border viral movement and genetic evolution. These findings confirm the continued circulation of classical cluster 1.2 LSD virus (LSDV) in Bangladesh, with accumulating genetic variation possibly enhancing virulence in calves. The study underscores the need for sustained genomic surveillance, expanded vaccination, and improved biosecurity to mitigate future LSD outbreaks.