Kolesov et al., 1968). Tanner and colleagues (1978) reported a febrile period lasting less than 24 hours in 12 of 49 vaccinated cows but no change in daily food consumption. In addition, decreased activity or decreased milk production has been noted and is presumed to be due to the presence of inflammation. Studies of live spore vaccine in veterinary use are primarily descriptive, so the actual incidence of adverse reactions to the vaccine is not known. The committee did not find any long-term studies (greater than a year) that monitored adverse effects from vaccination with the live spore vaccine.
Studies in laboratory animals. Studies with the live spore vaccine in laboratory animals have been conducted under better controlled conditions than those in veterinary practice. Many of these studies make no mention of adverse effects in guinea pigs, hamsters, rabbits, or mice (Klein et al., 1962; Jaiswal and Mittal, 1979; Ezzell and Abshire, 1988; Turnbull et al., 1988; Stepanov et al., 1996). Small laboratory animals such as rabbits, guinea pigs, and mice are more susceptible than larger animals to dying from administration of the live spore vaccine (Welkos, 1987; Welkos and Friedlander, 1988; Ivins et al., 1990). High doses of the live spore vaccine killed one-third of the guinea pigs studied by Turnbull and colleagues (1986, 1988) and up to 60 percent of the guinea pigs in a study by Klein and colleagues (1962).
A thorough study by Gusman and Migulina (1967) histologically examined rabbits and guinea pigs immunized with live anthrax spore vaccines by subcutaneous injection. They monitored tissue from internal organs as well as from the site of administration of the vaccine for up to 210 days after vaccination. Edema occurred at the site of the injection, sometimes with hemorrhage and abscess formation. Dilation of the blood vessels and infiltration of the site with segmented white blood cells also occurred. Edema and inflammation lasted for 14 days, followed by the formation of granulation tissue. Over a 2-month period, researchers noted changes in the lymphoid organs, consistent with a response to an antigen. In addition, histological changes were evident in the liver and heart muscle but resolved within 2 months.
Vaccination with live spore vaccine may also lead to complications of otherwise symptomless infections or to death from anthrax when the animal is subject to trauma. Kolesov and Gutiman (1968) and Stefanova (1968) noted that rabbits injected with live spore vaccine would sometimes die. They confirmed by autopsy and bacteriological examination that the rabbits died from pasteurellosis infection, not from anthrax. Thus, vaccination with the live spore anthrax vaccine may activate an underlying infection in a rabbit that was in satisfactory health prior to vaccination. In a similar manner, death from anthrax may occur more readily in an animal whose health is compromised. Stefanova (1968) found that rabbits subjected to the trauma of an ear biopsy after vaccination with the live spore vaccine were more likely to die than animals not subject to the trauma.
Guinea pigs vaccinated with the live spore vaccine have delayed-type hypersensitivity reactions 1 year after vaccination (Shlyakhov, 1970; Shlyakhov and Rubinstein, 1994b), indicating stimulation of the cellular immune response.