New Review Maps the Future of Vaccines Against Deadly Livestock Disease

Haemorrhagic septicemia, an acute and often fatal bacterial disease of cattle and buffalo caused by Pasteurella multocida serotypes B:2 and E:2, continues to defy decades of vaccination efforts across the endemic regions of Asia and Africa. A comprehensive new review, published in the journal Discover Animals, has undertaken the most detailed comparative assessment yet of every vaccine strategy deployed or proposed against the pathogen, from nineteenth-century antisera to genetically engineered mutants and mucosal delivery platforms. The authors, Rajneesh Raj and Ashwani Kumar Sharma of Guru Angad Dev Veterinary and Animal Sciences University in Ludhiana, India, conclude that the principal obstacle to controlling the disease is no longer a shortage of vaccine concepts but the translation of promising laboratory approaches into durable, field-applicable interventions.

The urgency of the problem is underscored by events beyond the farm gate. In 2015, an outbreak in Kazakhstan’s Betpak-Dala region killed nearly 200,000 Saiga antelopes within weeks, wiping out more than sixty percent of the regional population and pushing the species closer to extinction. The review notes that haemorrhagic septicemia, with its peracute course and capacity to trigger mass mortality events, bears an epidemiological resemblance to historical scourges such as plague and pneumococcal disease. Because the disease can kill susceptible animals within 24 to 72 hours, therapeutic intervention is rarely feasible, making vaccination the only realistic preventive strategy. The pathogen is also a central player in the bovine respiratory disease complex, the leading cause of morbidity and mortality in feedlot and dairy cattle, which further complicates disease management in production systems.

Conventional vaccines remain the backbone of control programs in endemic countries, and the review evaluates them in meticulous technical detail. Plain bacterins, the earliest whole-cell preparations, offered protection lasting only around six weeks and carried a risk of endotoxin-associated shock, and have now been largely abandoned. Alum-precipitated vaccines, produced by formalin inactivation followed by precipitation with potash alum, remain the most widely used formulations in Asia and Africa because of their simplicity and low cost; the electrostatic binding of antigens to alum promotes uptake by antigen-presenting cells and drives a strong Th2-polarized antibody response, but protective immunity typically lasts only four to six months and post-vaccination shock occurs in some animals. Aluminium hydroxide gel vaccines, which bind antigen ionically to the adjuvant, extend immunity to roughly six months, although one study found protection did not persist beyond 90 days even with immunomodulators such as levamisole and vitamin E.

Oil-adjuvanted vaccines emerge as the benchmark among conventional platforms. Formalin-inactivated organisms emulsified with mineral oil and lanolin induce higher and more sustained antibody titers than alum-based formulations, with field and experimental studies reporting protection lasting eight to twelve months and, in some cases, up to eighteen to twenty-six months. Their thermal stability is a major practical advantage in tropical settings, where cold-chain capacity is limited. Modern commercial adjuvants such as Montanide ISA-50, ISA-70 and ISA-206 reduce reactogenicity while preserving immunogenicity, and comparative field work has shown that formulation choice matters even within this class, with different emulsions performing better in calves than in adult animals. Yet even the best oil-adjuvanted products suffer from injection-site swelling, high viscosity, occasional shock reactions and a continuing dependence on booster doses. Multiple emulsion vaccines, created by re-emulsifying oil-adjuvanted preparations with Tween 80, were developed to ease these drawbacks and have protected buffalo calves for up to nine months and cross-bred calves for up to a year, but they have achieved limited commercial uptake and lack robust head-to-head field comparisons.

The review then turns to modified whole-cell approaches. Digested bacterial lysates, including potassium thiocyanate extracts and bacteriophage-lysed preparations of P. multocida B:2 grown under iron-limited conditions, broaden antigenic exposure and have elicited cross-protective responses in chickens, turkeys, mice and rabbits, with calves showing elevated antibody titers peaking at 90 days, but manufacturing heterogeneity has prevented standardization. Autogenous vaccines, formulated from isolates taken directly from infected herds, offer strain-specific outbreak control but only against homologous serovars and with a delayed onset of immunity. Live attenuated vaccines, which mimic natural infection, have been revitalized by molecular genetics: disruption of the aroA gene, which cripples aromatic amino acid biosynthesis, and of gdhA, which impairs glutamate dehydrogenase activity, produces strains that are attenuated yet immunogenic and protective in calves. Complementary defined mutants targeting lipopolysaccharide biosynthesis genes such as waaQ, capsule genes such as cexA and bcbH, and fimbrial genes including pfhaB1, pfhaB2 and pfhaC have all shown protective potential in experimental models. A recent finding by the lead author adds a novel target: field isolates of P. multocida produce hyaluronidase and can utilize host hyaluronic acid as a nutrient, implicating this metabolic pathway in virulence and opening a new avenue for rational attenuation. Chemically altered live vaccines, such as streptomycin-dependent mutants, have shown variable results across serotypes, underscoring the unpredictability of the approach.

Immunostimulatory and adjuvant-based strategies occupy a middle ground between whole-cell and defined-antigen vaccines. Bacterial DNA enriched with immunostimulatory CpG motifs, when used as an adjuvant for iron-inactivated P. multocida preparations, protected chickens against lethal challenge and raised antibody levels in mice above those achieved with conventional alum-adjuvanted vaccines. Dietary supplementation offers a surprising complementary lever: mice fed arginine-enriched diets alongside a formalin-inactivated vaccine achieved complete protection against challenge, while L-proline and L-glutamine similarly fortified vaccine-induced immunity. The authors stress that such nutritional immunomodulators should be viewed as adjuncts rather than substitutes for antigen-specific vaccination, and that their mechanisms and field efficacy in livestock remain uncharacterized.

Acellular and subunit vaccines represent the shift toward precision design. Candidates focus on the capsule, fimbriae, lipopolysaccharides and outer membrane proteins, whose surface-exposed loops drive antigenic diversity yet also carry conserved epitopes. Immunization with outer membrane proteins, particularly from bacteria cultured under iron-restricted conditions, has elicited cross-protective antibodies across serotypes, and buffalo calves vaccinated intramuscularly with B:2 outer membrane proteins reached peak ELISA antibody titers 21 days after vaccination. Recombinant subunit candidates under investigation include the type 4 fimbrial protein PtfA, the porin OmpH, outer membrane protein OMP87, the lipoprotein PlpE, which induced 80 to 100 percent protection in mice, and iron-regulated heme-binding proteins such as HasR, HemR and HgbA. Synthetic peptides derived from OmpH loop structures have also protected against homologous challenge. Bacterial ghosts, empty envelopes generated through controlled expression of the PhiX174 lysis gene E that preserve native surface architecture without cytoplasmic content, achieved complete protection in laboratory models, while anti-idiotype vaccines mimicking lipopolysaccharide or outer membrane protein epitopes have produced strong protective responses in mice and rabbits. None of these platforms has yet reached commercial application, however, because no universally cross-protective antigen has been identified and most efficacy data come from laboratory animals rather than cattle and buffalo.

Delivery technology emerges as a decisive frontier. Because P. multocida enters through the respiratory tract, intranasal vaccination targeting nasopharyngeal and bronchus-associated lymphoid tissue can stimulate mucosal IgA alongside systemic IgG, placing immunity at the site of pathogen entry. Evidence is compelling: intranasal potassium thiocyanate extract outperformed intramuscular administration, and intranasal delivery of a live attenuated B:2 derivative in buffalo raised antibody levels even in non-vaccinated in-contact animals through secondary transmission, suggesting herd-level protection. A live intranasal aerosol vaccine based on P. multocida B:3,4 was deployed at scale in Myanmar between 1992 and 1995, reaching nearly one million cattle and buffalo. Intradermal vaccination, exploiting the dense antigen-presenting cell network of the skin, offers dose-sparing potential demonstrated for influenza, rabies, poliovirus, yellow fever and hepatitis A vaccines, though some adjuvants provoke unacceptable local reactogenicity by this route. Formulation matters too: particulate carriers and mucosal adjuvants such as MF59, chitosan, Toll-like receptor agonists and mutant enterotoxins can amplify nasal responses, but toxin-based adjuvants have been linked to Bell’s palsy in human intranasal use, demanding caution.

The review’s final assessment is that the deepest unresolved gap is immunological: no validated correlate of protection exists for haemorrhagic septicemia in cattle or buffalo. Serum IgG titers are widely used as surrogate markers, yet no protective threshold has ever been established, and the roles of mucosal IgA, T cells, memory B cells and innate activation remain unmapped in target species. The authors call for standardized endpoints, including serum bactericidal and opsonophagocytic killing assays and IFN-γ ELISpot, harmonized challenge protocols and longitudinal field validation. They further argue that wildlife must enter the equation: no current vaccine has been evaluated in wild ruminants, and the remoteness of outbreak sites, cold-chain limits and the impossibility of repeated handling demand thermostable, oral-bait or aerosol formulations for free-ranging populations. Bridging these translational gaps, the authors conclude, will require coordinated work among immunologists, molecular biologists, veterinarians, wildlife specialists and regulators to convert a century and a half of vaccine innovation into durable, broad-spectrum and economically sustainable control of one of livestock’s most devastating diseases.

Subject of Research: Vaccine development against haemorrhagic septicemia caused by Pasteurella multocida in livestock and wildlife

Article Title: Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia

Article References: Raj, R., & Sharma, A. K. (2026). Current challenges emerging strategies and future directions in vaccine development for haemorrhagic septicemia. Discover Animals, 3(1), Article 86. https://doi.org/10.1007/s44338-026-00244-5

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00244-5

Keywords: haemorrhagic septicemia, Pasteurella multocida, vaccine development, livestock, mucosal vaccination, outer membrane proteins, oil-adjuvanted vaccines, recombinant subunit vaccines, intranasal delivery, wildlife, correlates of protection, cattle and buffalo