Preliminary analysis of cattle deaths suspected to be an adverse reaction of vaccination against lumpy skin disease in Croatia

Vaccination against lumpy skin disease was carried out in Croatia during 2016 and 2017 to prevent this emerging viral disease from causing significant damage to the cattle population. Two unauthorised live vaccines were used for immunoprophylaxis, and adverse reactions in cattle were expected. Adverse events were monitored and 14 selected reported cases of deaths were analysed using the available necropsy results. The cases analysed were classified as probable, possible, inconclusive, or unlikely to be caused by vaccination, primarily based on results of post-mortem examination, taking into consideration factors that contributed to or resulted in death or euthanasia. Most cases were classified as possibly caused by vaccination due to subcutaneous oedema of varying consistency (at the injection site) and intramuscular haemorrhage, in some cases leading to purulent and necrotic processes. These processes eventually led to fatal purulent bronchopneumonia, pulmonary emphysema, septic conditions, or euthanasia. In the remaining cases, necropsy results were unable to be linked to vaccination or the findings were inconclusive due to the presence of other factors, such as Klebsiella infection. It can be assumed that neither vaccine had a direct connection with animal deaths, but they may have contributed to the fatal outcomes due to the complications of severe local reactions and general impact on the immune system.