Efficacies of erythromycin and chloramphenicol in extinguishing fecal shedding of Campylobacter jejuni in dogs.

Oral treatment regimens of erythromycin stearate and chloramphenicol were evaluated in naturally infected laboratory colony dogs for their efficacies in extinguishing fecal shedding of Campylobacter jejuni. Of the 25 Campylobacter-infected English Foxhounds in the study, 9 were assigned to erythromycin treatment, 9 to chloramphenicol treatment, and 7 to no treatment. Antimicrobials were administered for 12 days. All of the dogs that received erythromycin stearate ceased shedding C jejuni by the fourth day of treatment and remained negative throughout the treatment period. Chloramphenicol was associated with a reduction in shedding from 100% to 57% by the ninth day of treatment. Within 9 days of the discontinuation of antimicrobial treatment, C jejuni was isolated from all chloramphenicol-treated dogs and 89% erythromycin-treated dogs.

Characterization of herpesvirus of turkeys. Replication using recombinant DNA.

DNA has been isolated from herpesvirus of turkeys (HVT) virions and used to construct a partial gene library in pBR-322. The recombinants have been characterized and shown to contain HVT DNA inserts. A representative recombinant containing a 5.9-kilobase HindIII fragment was used as a probe to quantitate the yields of HVT DNA in vitro and to follow the kinetics of viral DNA replication. The data shown that in chicken fibroblasts, viral DNA synthesis initiates by about 12-14 hr postinfection and that the yield of progeny virus plateaus at 28-30 hr postinfection. Based upon quantitative hybridization to cloned DNA probes, we estimate that approximately 2000 HVT genomes are produced per infected cell in vitro; however, in vivo in persistently infected turkeys, the number of viral genomes was below the level of detection by Southern blotting.

Distribution of selenium in chicken tissues as affected by bursectomy.

An experiment was designed to determine if surgical bursectomy (Bx) of day-old chicks would alter the distribution or amount of selenium (Se) in chicken tissues. Sham-operated chicks and Bx chicks were fed a practical corn-soy diet with either no supplemented Se, selenite to supply .1 ppm Se, or selenomethionine to supply .1 ppm Se. Several chicks were killed at 10 and 21 days of age to determine tissue Se levels. At each time the remaining chicks were injected with sheep red blood cells (SRBC). The remaining chickens were killed at 56 days. Serum from Bx chicks caused no agglutination with SRBC, and the immunoglobulin content was decreased as compared to levels in serum of sham-operated chicks. The Se level of tissues increased as a result of time and Se supplementation (P less than .01). The Bx caused a small but significant (P less than .01) decrease in spleen Se level, but other tissue Se levels were not affected. The results suggest that the serum lymphocytes and immunoglobulins have only a passive function in Se metabolism and distribution in chickens.

In vivo function tests of the effect of tilorone and niridazole on cell-mediated immunity in chickens.

The need for effective, safe, specific cellular immune suppression in avian research led to the study of effects of tilorone and niridazole on cell-mediated immunity of chickens. Two in vivo tests for cell-mediated immunity function were used--the graft-vs-host (GvH) test and the delayed hypersensitivity (DH) test. Humoral immunity was evaluated by measuring natural hemagglutination (HA) titers against rabbit red blood cells. Intraperitoneal administration of tilorone to young chickens appeared to have severe toxic side effects and was of little value as an immune suppressant. Oral administration of tilorone to 6-week-old chickens caused DH suppression, but no marked effect was seen on GvH reactions or HA titers. Toxicosis appeared less severe. Oral administration of niridazole to 6-week-old birds caused nearly complete loss of GvH and DH reactivity but caused an increase in HA titers. General toxic effects of niridazole were not apparent.

Efficacy of herpesvirus of turkeys vaccine against challenge with Marek's disease tumor cells.

Tests were made of the effectiveness of herpesvirus of turkeys (HVT) vaccine in preventing tumorigenesis following challenge with a neoplastically transformed Marek's disease tumor cell line (MSB-1). HVT vaccine prevented tumors due to MSB-1 inoculation whereas 21.4% of unvaccinated controls had tumors. The results support, but do not prove, the theory that HVT acts through enhancement of cell-mediated immunity against MDV-transformed cells. The drawbacks of using MSB-1 cells in this experiment and the need for true Marek's transplantable tumor cells are discussed.

Specific suppression of the bursa-dependent immune system of chicks with infectious bursal disease virus.

Chicks which had been inoculated with infectious bursal disease virus (IBDV) at 1 day of age had a severe depression of bursa-dependent humoral immune functions by day 42. Antibody responses against rabbit red blood cells or to immunization with bovine serum albumin were significantly suppressed. In contrast, chicks inoculated with IBDV at 21 days of age produced near normal antibody responses as compared with the responses in noninfected control chicks. The IBDV had no significant effect on the thymus-dependent cellular responses as measured by skin graft rejection or delayed type hypersensitivity reactions to tuberculin.