For intramuscular administration in domestic swine, the rabbit-origin live classical swine fever virus API is released as a freeze-dried cake intended for reconstitution in a phosphate-buffered saline diluent at 2–8 °C. The lyophilized matrix is compounded with sucrose, sorbitol, lactalbumin hydrolysate or gelatin hydrolysate to stabilize the viral envelope during freezing and primary drying; the ratio of amorphous to crystalline bulking agent is set so that the collapse temperature of the maximally freeze-concentrated solute remains above the primary drying shelf temperature. In sucrose-dominant cakes, product temperature is commonly held below −35 °C during primary drying at chamber pressures of 0.1–0.2 mbar; collapse or meltback is observed when the cake temperature crosses the collapse threshold and produces a translucent, shrunken cake with slow reconstitution and titre loss. Residual moisture determined by Karl Fischer titration per Ph. Eur. 2.5.12 is controlled to ≤ 2.5 % w/w, because moisture in the amorphous phase acts as a plasticizer and accelerates first-order inactivation of the live virus at 2–8 °C. The reconstituted solution is a suspension of fine cake fragments and should be withdrawn into a polypropylene syringe through a 21-gauge needle after gentle swirling, not shaking; vigorous shaking can shear the lyophilizate particles and generate foam that denatures the viral glycoprotein. Osmolality of the reconstituted injection is typically adjusted to 280–320 mOsmol/kg to reduce injection-site reactions. In-use hold time after reconstitution should not exceed 4 hours at 2–8 °C; published data for this specific configuration is limited, but general live-attenuated veterinary vaccine guidance identifies a 0.5 log10 TCID50 titre decline as the acceptable end-of-hold boundary. Diluents containing benzalkonium chloride, chlorhexidine or other cationic preservatives are incompatible with the live virus; if a transfer needle or syringe has been cleaned with disinfectant, trace residues below 0.01 % w/v can still reduce viable titre. The vaccine should not be mixed with killed vaccines or other adjuvanted preparations in the same syringe because aluminium hydroxide and oil emulsions can alter pH and ionic strength.

What Limits Compression Force in Live Virus Oral Baits for Wild Boar?

Compression of live rabbit-origin classical swine fever virus granulate into oral bait tablets requires a direct-compression process that minimizes mechanical shear and thermal load. The API is first blended with a cereal-based carrier, sodium bicarbonate buffer, and a lipid binder; the blend is then compacted on a rotary tablet press fitted with cooled die bores. A critical process limit is the relationship between compaction force and viral titre loss; direct compression forces above approximately 5 kN have been shown to generate localised temperature spikes and particle-particle friction that can reduce infectivity by more than 0.5 log10 TCID50 per compression step. Tablet hardness is maintained at 30–50 N to provide adequate handling strength in field bait distribution, while friability per Ph. Eur. 2.9.7 is held below 1.0 % w/w to avoid breakage during aerial or hand baiting. Disintegration time in water at 37 °C measured by Ph. Eur. 2.9.1 is controlled to 10–15 minutes, so that the wild boar does not reject the bait before the virus is released. The bait matrix contains an acid-buffering system because gastric pH in wild boar ranges from 2.5 to 4.5 post-prandially; without buffer, the acid-labile viral envelope loses infectivity within minutes. Lipid coating of the final tablets with hydrogenated vegetable fat melting at 42–45 °C provides a moisture barrier and delays humidity-driven titre loss in forest environments. Storage of finished oral baits at 2–8 °C is required; published data for this specific configuration is limited, but extended exposure above 25 °C causes measurable titre loss within 24 hours because the lipid coating begins to soften and water migration into the core accelerates.

In liquid administration via drinking water or drench, the lyophilized API is dispersed into chlorine-free potable water at 10–20 °C and administered within a short hold window. Free chlorine residuals above 0.1 ppm are destructive to the lipid-enveloped live virus; therefore, municipal water must be conditioned with sodium thiosulfate or aged in an open tank before API addition. The solution is not a true solution but a fine dispersion of lyophilizate particles; continuous gentle agitation is required to prevent sedimentation in header tanks and nipple lines. Metal ions such as iron and copper at concentrations commonly found in well water can also reduce infectivity, particularly if the water pH falls below 6.5. The pH of the drinking-water vehicle is adjusted to 7.0–7.4 with phosphate buffer before dispersion, and the hold time at 25 °C is limited to 2 hours; beyond this window, the absence of the protective amorphous cake matrix exposes the virus to aqueous-phase degradation. This route is used mainly for oral mass vaccination where individual injection is not feasible; however, the dose delivered per animal is subject to water consumption variability and is less reproducible than parenteral injection. Sanitizers such as citric acid or hydrogen peroxide must not be used in the water line during the administration period, because residual oxidising capacity will neutralise the live virus. After the dosing period, the water line should be flushed with plain water; disposal of unused medicated water must follow local biosecurity rules for live veterinary vaccines.

Live Virus Premix Homogeneity in Mineral-Rich Feed Matrices

Dry blending of the lyophilized API into a feed premix requires a carrier system that protects the live virus from moisture, pH excursions, and direct contact with reactive minerals. The API is first sieved through a 500 µm screen to break up soft agglomerates, then blended with lactose monohydrate or corn cob granules in a ribbon blender at 10–15 rpm for 10 minutes; longer mixing times can generate electrostatic charge and separate the low-density lyophilizate from the carrier. Carrier particle size is controlled between 200 µm and 500 µm to match the API particle size and prevent segregation during transport. Premix moisture content is held below 12 % w/w because free water accelerates virus inactivation and promotes mould growth. Feed ingredients containing high levels of calcium carbonate, copper sulfate, zinc oxide or choline chloride are incompatible with direct inclusion of the live virus API; a top-dress application over the finished feed at the point of use avoids prolonged contact with these reactive minerals. If pelleted feed is required, the premix should be applied after pelleting because steam conditioning at 65–85 °C for even 30–60 seconds is sufficient to reduce live virus titre by more than 1.0 log10 TCID50. The final top-dress powder should be consumed within 24 hours after application; uneaten medicated feed should be collected and inactivated with a suitable virucidal agent.

When a Capsule Shell Is Used for Targeted Oral Delivery of Live Virus

When the rabbit-origin live classical swine fever virus API is filled into hard capsules for oral vaccination, the capsule shell must function as a moisture barrier and, where enteric delivery is required, a pH-sensitive release mechanism. Hard gelatin capsules containing 13–16 % w/w moisture can transfer water into the lyophilized API and reduce glass transition stability; therefore, low-moisture hydroxypropyl methylcellulose capsules or pre-dried gelatin capsules are preferred. The fill is prepared by dry granulation of the lyophilized cake with a pregelatinized starch binder to improve flow, and the capsules are filled on a dosator machine at 15–25 °C and 20–30 % RH to prevent moisture uptake. Enteric coating with a methacrylic acid copolymer dispersion is applied to a weight gain of 6–8 % w/w; the coating dissolves at pH values above 6.8, which corresponds to the distal duodenum of swine and bypasses the gastric acid compartment. Dissolution testing per Ph. Eur. 2.9.3 in 0.1 M hydrochloric acid for 2 hours should show no virus release, followed by release within 45 minutes in phosphate buffer pH 6.8. The capsule route is used primarily for oral immunization of individual animals or small groups where bait distribution is impractical; however, published data for this specific configuration is limited, and the enteric coating process must be validated for live-virus titre recovery because the polymer dispersion spray-drying temperature above 30 °C can inactivate the virus.