Canine parvovirus in Africa: Explaining persistent disease despite vaccination

Canine parvovirus (CPV) remains one of the most important causes of infectious gastroenteritis and mortality in puppies worldwide despite the widespread availability of effective vaccines. Although vaccination has substantially reduced disease incidence since the introduction of modified-live vaccines, CPV continues to circulate globally, and cases of parvoviral enteritis are still reported in both vaccinated and unvaccinated dogs. These observations have generated ongoing debate regarding the relative contribution of viral, host, and management factors to vaccination failure. This narrative review provides an updated synthesis of CPV epidemiology, vaccination strategies, causes of vaccine failure, and recent advances in prevention and treatment. Particular attention is given to major controversies surrounding antigenic variation, maternally derived antibody (MDA) interference, host-related factors, and vaccination protocol compliance. The review examines the emergence and global spread of CPV-2a, CPV-2b, and CPV-2c and critically evaluates experimental and field evidence regarding their impact on vaccine efficacy. While concerns regarding antigenic mismatch have accompanied the emergence of CPV variants, current evidence indicates that commercially available modified-live vaccines provide substantial cross-protection against circulating strains, including CPV-2c. In contrast, MDA interference, incomplete vaccination schedules, inadequate population immunity, improper vaccine handling, and high environmental infectious pressure appear to account for most reported vaccination failures. The review also discusses the concept of the immunity gap and the evolution of international vaccination recommendations, including administration of repeated vaccine doses until at least 16 weeks of age and an additional booster at approximately 26 weeks in selected high-risk situations. Recent advances in passive immunotherapy, including CPV-specific monoclonal antibodies and hyperimmune plasma, are also reviewed. Particular emphasis is placed on African epidemiological settings, where limited surveillance systems, variable vaccination coverage, sustained environmental viral circulation, and frequent deviations from international vaccination guidelines may contribute to persistent disease burden. Morocco is presented as a representative example of these challenges because, despite the availability of effective vaccines, veterinarians continue to encounter frequent cases of parvoviral enteritis and apparent vaccination failure in the absence of structured surveillance and pharmacovigilance systems. By integrating recent experimental, clinical, and epidemiological evidence, this review aims to clarify the mechanisms underlying CPV vaccination failure and to identify priorities for improving disease prevention and control in Africa and other regions facing similar epidemiological constraints.