Studies on failure of T strain live Babesia bovis vaccine

SUMMARY Field investigations of the protection afforded by the Australian live Babesia bovis vaccine used in the early 1990s (T strain) revealed inadequate vaccine-induced protection in certain herds. Vaccination/challenge trials using 207 experimental cattle were conducted to evaluate the protection afforded by T strain B bovis against field isolates from these herds. The trials investigated whether isolates that could ‘break-through’ T strain immunity were present in the field, the ability or inability of specific cattle to develop protective immunity after vaccination with T strain and the effect of attenuation and maintenance procedures on the immunogenicity of T strain. The results showed that B bovis parasites present early in the process of attenuation of T strain were more protective than those remaining late in the process. They also showed that cattle from properties experiencing vaccine failures were less protected by T strain vaccination than Bos taurus cattle randomly selected from the general population if vaccinated with highly attenuated T strain. A hypothesis is offered to explain these findings .     

New infection with Corynebacterium pseudotuberculosis reduces wool production

SUMMARY The effect of natural Corynebacterium pseudotuberculosis infection on wool production and quality in sheep was examined in light of evidence that artificial C pseudotuberculosis infection causes wool production loss. A toxin ELISA was used to identify sheep that had been infected with C pseudo tuberculosis. Greasy and clean fleece weights and fibre diameter were compared in infected and uninfected sheep. C pseudotuberculosis infection caused a 3.8 to 4.8% decrease in greasy wool production and a 4.1 to 6.6% decrease in clean wool production. C pseudotuberculosis infection did not affect fibre diameter. The effects of caseous lymphadenitis (the disease caused by C pseudotuberculosis infection) cause an annual loss of about $17 million in wool production to the Australian wool industry.     

Development of a Johne's disease infection model in laboratory rabbits following oral administration of Mycobacterium avium subspecies paratuberculosis

To assess the rabbit as a model for the study of Johne's disease pathogenesis, a breeding group of adult and juvenile New Zealand white rabbits were orally challenged with three doses of the Mycobacterium avium subspecies paratuberculosis wildtype bovine strain, CLIJ623, on three occasions. Faecal culture, post-mortem tissue bacteriological culture and histopathology were used to monitor the disease progression in the rabbits for more than 2 years. Of 4 adult and 16 juvenile orally dosed rabbits M. paratuberculosis organisms were recovered bacteriologically from two and three animals, respectively, using the BACTECtrade mark radiometric culture system. Tissue sites from which the bacteria were recovered included the mesenteric lymph nodes, ileocaecal valve, vermiform appendix, caecum, proximal colon and jejunum. Body weight loss, reduced abdominal fat and mild lesions were observed at necropsy in four infected rabbits. Diarrhoea and persistent faecal shedding of bacteria were not observed. Faecal culture did not yield any cultivable mycobacterial organisms on solid media.     

The prevalence of serum antibodies to Toxoplasma gondii in Ontario mammals.

The prevalence of seropositive reactions to Toxoplasma gondii was studied in farm animals, companion animals, wild rodents and birds. Of the animals tested, 17% of cattle, 65% of sheep, 45% of pigs, 9% of horses, 33% of dogs and 20% of cats were seropositive by the Sabin-Feldman dye test. In addition 11% of mice (Mus musculus), 5% of deer mice (Peromyscus), 3% of rats (Rattus norvegicus) and less than 2% of sparrows (Passer domestcus) were seropositive. All samples from short-tailed field mice (Microtus pennsylvanicus), squirrels (Sciurus carolinensis), chipmunks (Tamias striatus), meadow jumping mice (Zapus hudsonius) and starlings (Sturnus vulgaris) were seronegative. The significance of these findings in relation to the epizootiology of toxoplasmosis in Ontario is discussed.     

Uromodulin (Tamm-Horsfall glycoprotein): a renal ligand for lymphokines

The protein portion of the immunosuppressive glycoprotein uromodulin is identical to the Tamm-Horsfall urinary glycoprotein and is synthesized in the kidney. Evidence that the glycoproteins are the same is based on amino acid sequence identity, immunologic cross-reactivity, and tissue localization to the thick ascending limb of Henle's loop. Nucleic acid sequencing of clones for uromodulin isolated from a complementary DNA bank from human kidney predicts a protein 639 amino acids in length, including a 24--amino acid leader sequence and a cysteine-rich mature protein with eight potential glycosylation sites. Uromodulin and preparations of Tamm-Horsfall glycoprotein bind to recombinant murine interleukin-1 (rIL-1) and human rIL-1 alpha, rIL-1 beta, and recombinant tumor necrosis factor (rTNF). Uromodulin isolated from urine of pregnant women by lectin adherence is more immunosuppressive than material isolated by the original salt-precipitation protocol of Tamm and Horsfall. Immunohistologic studies demonstrate that rIL-1 and rTNF bind to the same area of the human kidney that binds to antiserum specific for uromodulin. Thus, uromodulin (Tamm-Horsfall glycoprotein) may function as a unique renal regulatory glycoprotein that specifically binds to and regulates the circulating activity of a number of potent cytokines, including IL-1 and TNF.     

A long-term study in Merino sheep experimentally infected with Mycobacterium avium subsp. paratuberculosis: clinical disease, faecal culture and immunological studies

Two longitudinal experiments involving Merino sheep challenged with either bovine or ovine strains of Mycobacterium avium subsp. paratuberculosis (Map) have been conducted over a period of 54 and 35 months, respectively. Blood samples for the interferon-gamma test, the absorbed ELISA and faecal samples for bacteriological culture were taken pre-challenge and monthly post-challenge. Infections were induced with either a bovine or ovine strain of Map in separate experiments with infections being more easily established, in terms of faecal bacterial shedding and clinical disease when the challenge inoculum was prepared from gut mucosal tissue than cultured bacteria. The patterns of response for shedding and clinical disease were similar. Cell-mediated immune responses were proportionally elevated by at least an order of magnitude in all sheep dosed with either a bovine or ovine strain of Map. Conversely, antibody responses were only elevated in a relatively small proportion of infected sheep. Neither of the clinically affected tissue challenged sheep developed an antibody response despite the presence of persistent shedding and the development and decline in cell-mediated immunity. The results indicated that for sheep the interferon-gamma test may be useful for determining if a flock has been exposed to ovine Johne's disease.