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New Council of Europe regulations mandate housing of two rabbits in the same cage space currently used to house one, provided the animals are socially compatible. This study was designed to assess changes in growth and selected serum chemistry parameters due to pair housing or single housing of rabbits. Six sets of four female siblings of Crl:KBL(NZW)BR rabbits were used. The animals were seven weeks old on arrival. Two siblings of each set were allocated to pair housing, two to single housing. The animals were housed in stainless steel cages (120 cm x 60 cm x 60 cm) with a perforated floor, including a shelf (60 cm x 30 cm) at 30 cm height from the floor. The rabbits were provided with an aspen cube (5 cm x 5 cm x 5 cm), one item per animal. The rabbits were weighed and blood samples were taken from the auricular central artery at four different times during the study. Blood sera were assayed for a set of routinely assayed clinical chemistry parameters: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (APHOS), blood urea nitrogen (BUN), cholesterol (CHOL) and protein (PROT). Mean and variance profiles over the study period were statistically analysed by multivariate analysis of variance. No differences in mean profiles were detected; however, weight (P = 0.0002) and APHOS (P = 0.017) variances were significantly lower in pair-housed animals. The reduction in variance on growth and APHOS attributable to pair housing appears to be rather large. During the 21-week study, occasional fighting was seen between the pair-housed rabbits. After sexual maturity, further major fighting bouts resulted in significant trauma that necessitated the cessation of the study. In conclusion, pair housing appears to have a decreasing effect on growth and APHOS variance, but antisocial behaviour such as fighting remains a serious problem.

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A small animal model of localised candidiasis is needed for the evaluation of new antifungal compounds. Mammary glands of immunocompetent (BALB/cJ) and immunodeficient (SCID and athymic nude) mice were infected with a wild-type of Candida albicans. Some of the animals were treated with amphotericin B (AmB) while others were treated with saline and acted as controls. The histologic changes of infected mammary gland tissues and a number of other organs were evaluated. Complement (C) activation was analysed by immunoelectrophoretic quantification of molecules with C3c epitopes (C3, C3b, iC3b, and C3c) in serum. In all animals the organisms were confined to the mammary glands. Serum C3c levels were significantly higher (P<0.05) in infected untreated BALB/cJ and SCID mice, which also had severe mammary gland tissue inflammation, compared with control mice treated with AmB (4 mg kg(-1) i.p. once daily for 4 days). Both treated and control nude mice showed less tissue inflammation compared to BALB/cJ and SCID mice, and revealed insignificant activation of the complement system. It is concluded that innate immune response is important in the control of candidiasis and that the murine mastitis model is useful for immunopathological studies as well as evaluation of potential antifungal compounds.

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The murine model of mycotic mastitis was used to study the efficacy of amphotericin B (AmB). Twenty-four BALB/cJ mice at the fifth day of lactation were anesthetized and inoculated through the teat canal (two glands) with 50 microl suspension containing 5.0 x 10(7) cfu ml(-1) Candida albicans blastospores. Mice were randomly divided into two groups: untreated controls and AmB treated. Animals were euthanized 3 and 6 days after infection and treatment (4 mg kg(-1) per day intraperitoneally). The fungal burden of the mammary gland was determined by quantitative cultures. The number of C. albicans cells recovered from mammary gland homogenates were significantly lower in the AmB treated animals (both 3 and 6 days post-infection) than in the untreated controls (P<0.007 and P<0.003, respectively). The mammary glands of all untreated control animals showed marked neutrophilic infiltration, severe necrosis, and presence of blastospores, hyphae and pseudohyphae. In contrast, 10 of 12 animals treated with AmB showed only a mild neutrophilic infiltration which was restricted to alveoli and excretory ducts. All extra-mammary organs were free of infection in both groups. The results demonstrate that the murine mycotic mastitis model is suitable for investigations of new antifungal compounds. In addition, this model is more lenient than the systemic candidiasis models.

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Candida albicans strains with a deletion of the mitogen-activated protein kinase CEK1 gene are defective in the yeast to hyphal transition on solid surfaces in vitro. The virulence of a cek1 delta/cek1 delta null mutant strain was compared with its wild-type parent strain (WT) in a novel model of localized candidiasis. The mammary glands of lactating mice (at day 5 postpartum) were infected for 2, 4 and 6 days with 50 microliter suspension containing 1 x 10(5), 1 x 10(6) and 1 x 10(7) blastopores before death. Infected and non-infected control glands were evaluated pathologically. All animals infected with cek1 delta/cek1 delta null mutant strains showed no lesions while 65% of animals infected with the WT strain had severe lesions characterized by widespread heterophilic infiltration, necrosis, and abscess formation. As an additional control, animals infected with the disrupted strain complemented with the WT CEK1, on a replicating plasmid, also showed severe pathological changes similar to the WT strain. These results clearly demonstrate that the CEK1 gene codes for a virulence determinant of C. albicans and that the mouse mastitis model is well suited for the discriminative study of the pathogenicity of different C. albicans strains.

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Candida albicans strains with a deletion of the mitogen-activated protein kinase tyrosine phosphatase gene (CPP1) are derepressed in the yeast-to-hyphal transition on solid surfaces in vitro at ambient temperatures and this gene is therefore required for repression of the yeast-to-hyphal switch. The pathology caused by a CPP1 null mutant strain was compared with that of the null mutant into which the wild-type CPP1 gene was introduced by homologous recombination and with the wild-type parent strain in a murine mycotic mastitis model. The mammary glands of lactating mice (at day 5 postpartum) were infected for 2, 4 and 6 days with 1 x 10(5), 1 x 10(6) and 1 x 10(7) cell-forming units before euthanasia. Infected and non-infected control glands were evaluated histopathologically. The null mutant strains showed less severe pathology than the two control strains. The Cpplp tyrosine phosphatase may thus be considered a virulence determinant during localized infection in C. albicans.

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Secretory immunoglobulin A (sIgA) has been suggested to be a potential marker of stress in the human and the dog. We describe a simple method of saliva collection from rats for quantification of salivary sIgA in the first study of sIgA as a possible stress marker in the rat. Three groups of adult male rats were housed under different conditions (singly housed, paired with a female, and group housed). The animals were conditioned for the saliva collection by presenting a chocolate reward after every session and saliva was collected by soaking filter paper discs (5 mm in diameter) with saliva directly in the rats' oral cavity. The levels of salivary sIgA were determined by a novel paper disc rocket immunoelectrophoresis using sheep anti rat IgA antiserum. The resulting rockets had similar morphology as rockets in a standard rocket immunoelectrophoresis. Males housed singly showed stable sIgA levels with little variation while those housed singly with a female showed an initial decrease in sIgA followed by a steady increase. Males housed in a group (n = 6) showed a steady decline in sIgA levels. This indicates that sIgA levels are reduced by social stress and that this molecule may be a useful marker for well-being in the rat.

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This study established a murine model for the study of mycotic mastitis. The mammary glands of BALB/c mice were inoculated on the fifth day of lactation with graded doses (10(4), 10(5) and 10(6) cells) of a pathogenic strain of Candida krusei isolated from bovine mastitis. The animals were killed 1, 2, 3, 4 or 5 days after inoculation. In the infected mammary glands, the pathological reaction consisted of primary infiltration with heterophils and mononuclear cells, focal necrosis, formation of microabscesses, epithelial hyperplasia and some fibrosis. The severity of the changes was dose-dependent and increased with time after infection. An increase in the plasma concentrations of complement factors C1, C3c, C4 and C5, factor B and alpha-2-macroglobulin suggested that an acute phase response and activation of the complement system had occurred as a result of the infection.

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