The observation of reactive thrombocytosis in New Zealand white rabbits in response to experimental Pasteurella multocida infection.

Reactive thrombocytosis is an increase in the circulating thrombocyte count secondary to a physiologic process within the body, often an infection. Reactive thrombocytosis is different than primary or essential thrombocytosis which is usually related to myeloproliferative neoplasia. Essential thrombocytosis is most common in adults, whereas reactive thrombocytosis is most frequently observed in children. Reactive thrombocytosis has been occasionally reported in cats, dogs and horses but has not been previously reported in the rabbit. Rabbits were challenged with virulent Pasteurella multocida. Hematologic, clinical, and culture assessments were performed prior to challenge, enabling each animal to serve as its own control. The questions asked were whether reactive thrombocytosis was a consistent phenomena and whether its presence and/or intensity was related to disease severity. All challenged rabbits demonstrated some degree of thrombocytosis in response to the infection, but individual rabbits were varied in their pattern of thrombocytosis. Elevations varied from intense to mild to undulating with durations of 1 to 11 days above 500 x 10(9)/L and 0 to 5 days above 650 x 10(9)/L. Correlation analysis was unable to demonstrate significant association between thrombocytosis, body temperature, leukocyte count, or the granulocyte lymphocyte ratio (all r < 0.2). No significant association between intensity of thrombocytosis and degree or type of pathologic lesions was observed. Thrombocytosis does not appear predictive of disease intensity or outcome. The data indicate that in the rabbit thrombocytosis is a consistent response to infection with P. multocida. Rabbits may serve as a model for the study of reactive thrombocytosis, in humans especially in children infected with Haemophilus sp., which are also a members of the bacterial family Pasteurellaceae.

Evaluation of commercially available Escherichia coli J5 bacterin as protection against experimental challenge with Pasteurella multocida in rabbits.

OBJECTIVE: To evaluate the ability of commercially available Escherichia coli J5 bacterin to protect rabbits from experimental challenge with Pasteurella multocida. ANIMALS: 40 P multocida-free New Zealand White rabbits. PROCEDURES: Rabbits were assigned to 1 of 4 groups of 10 rabbits each. Three of the groups were inoculated SC with J5 bacterin at 8 weeks old. Inoculation was repeated 3 and 6 weeks later. The fourth group was not inoculated and served as controls. Groups 1, 2, and 3 were given 10(9), 10(8), and 10(7) colony forming units (CFU), respectively. Response was monitored by titer assessment, using an E coli J5 antigen capture ELISA. Five weeks after the last inoculation, all rabbits were challenged with P multocida and observed for an additional 5 weeks. Clinical, hematologic, serologic, culture, and necropsy data were collected. RESULTS: Inoculation of rabbits with 10(9) CFU of E coli J5 bacterin-induced titers that were significantly greater than titers of rabbits vaccinated with 10(8) or 10(7) CFU or those in controls. The incidence of acute bacteremia was lower in rabbits with high titers. At necropsy, prevalence of lesions typical of P multocida was not significantly different among groups. Prevalence of histologic lesions was also not significantly different among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Although the bacterin induced considerable antibody response and possibly reduced the rate of bacteremia, antibodies were not protective against long-term colonization or infection of the frontal sinuses or tympanic bullae by the challenge strain of P multocida. This bacterin in its currently available form is unlikely to aid in reducing the prevalence of pasteurellosis in rabbits.

Seroprevalence of antibodies against gram-negative core antigens in rabbits, using an Escherichia coli J5 antigen-capture enzyme-linked immunosorbent assay.

OBJECTIVE: To determine the seroprevalence of antibodies to gram-negative core antigens (GNCA) in specific-pathogen-free (SPF) rabbits (ie, free of Pasteurella multocida) and rabbits of undefined bacterial status (conventional). SAMPLE POPULATION: Serum samples were obtained from 7 groups of rabbits. The SPF rabbits comprised 2 adult groups and 1 immature group, whereas the 4 groups of conventional rabbits were all adults. PROCEDURE: A seroprevalence survey was conducted on rabbit sera for antibodies against GNCA, using an Escherichia coli J5 antigen-capture ELISA. RESULTS: Collective geometric mean titer (GMT) of adult rabbits was 1:6,463. The GMT of each of the 6 groups of adult rabbits was 1:956, 1:1,133, 1:4,525, 1:5,338, 1:7,669, and 1:25,600. Titers of populations differed significantly. CONCLUSION: Data analysis revealed there were anti-GNCA antibodies in rabbits. Similar to other species, the prevalence of IgM and IgG anti-GNCA antibodies increased with age. The IgG response was more marked than the IgM response. The SPF rabbits had lower IgG anti-GNCA titers than conventional rabbits, indicating possible cross-reactive epitopes between P multocida and Enterobacteriaceae. Rabbits with the highest anti-GNCA titers were those used in polyclonal antibody production, possibly stemming from endotoxin contamination of antigen or adjuvant. CLINICAL RELEVANCE: The possible cross-reactive antibodies directed at homologous wall components of Pasteurellaceae and Enterobacteriaceae could prove to be a possible heterotypic vaccination strategy for the protection of rabbits against pasteurellosis. Investigators should determine whether antigen impurity (endotoxin contamination) influences epitope focus during polyclonal antibody production and whether it affects sera variability among rabbits.

Comparative cancer potency for silica from extrapolations of human and animal findings.

The International Agency for Research on Cancer has judged that the evidence for the carcinogenicity of silica in animals is sufficient, and for humans it is limited. With the use of the Global 86 computer model, animal and human cancer potency data were extrapolated and the findings compared. The animal findings were based on inhalation rat studies. The cancer slope factors ranged from 2.3 x 10(-5) to 6.0 x 10(-3) for (1 mu g center dot m(-3)-1 among three experimental studies. The epidemiologic findings were from gold workers exposed to quartz and diatomaceous earth workers exposed to cristobalite. The cancer slope factors ranged from 6.8 x 10(-7) to 1.85 x 10(-5) for lifetime exposure to 1 (mu g center dot m-3)-1 of silica dust. Because of the many uncertainties involved in extrapolating to humans from animal data, more rational risk assessments are achieved when data from silica-exposed workers are used than when laboratory findings are relied on.

Congenital abnormalities in immature dogs from a pet store: 253 cases (1987-1988).

In a pet store, 6- to 18-week-old dogs were examined for congenital abnormalities. Of those pups offered for sale over a 2-year period (1987 and 1988), 15% (253/1,679) had at least 1 congenital defect, and 1.5% (26/1,679) had multiple congenital abnormalities. Defects observed and their respective rates were patellar luxation, 7.2% (121/1,679); cardiac abnormalities characterized by murmurs, 0.7% (11/1,679); palpebral abnormalities, 3.0% (50/1,679); inguinal hernia, 1.3% (22/1,679); umbilical hernia, 0.6% (10/1,679); faciodental malformations, 1.3% (21/1,679); and cryptorchidism, 2.6% (44/1,679). Rates of congenital abnormalities in pups from this study were higher than published rates in adult dogs.

Morbidity and mortality in pups from pet stores and private sources: 968 cases (1987-1988).

Morbidity (greater than or equal to 1 disease condition) for pups sold from 3 pet stores from January 1987 through December 1988 ranged from 54 to 68%. In 1 store, morbidity was higher for store pups, compared with pups originating from private parties, for such disease conditions as "kennel cough," diarrhea, and several species of gastrointestinal parasites. In-store mortality ranged from 5 to 9.5% of pups arriving for sale.