Complement resistance in Actinobacillus (Haemophilus) pleuropneumoniae infection of swine

The possible role of the complement-mediated bactericidal system in protection of swine against contagious pleuropneumonia was investigated. Strains of Actinobacillus (Haemophilus) pleuropneumoniae representing serotypes 2, 3 and 5 were found to be fully resistant to the bactericidal action of porcine serum from precolostral, clinically normal adult, and chronically infected pigs. All strains were also resistant to hyperimmune rabbit serum, but 3 of 4 strains were sensitive to normal human serum. This bactericidal effect was lost when human serum was previously absorbed with the homologous bacteria, indicating that antibody was necessary for killing. Addition of human serum to porcine serum or to absorbed human serum did not restore the bactericidal system. Pretreatment of the bacteria with undiluted heat-treated human serum also failed to sensitize the bacteria to the absorbed serum, indicating that a heat-labile, absorbable factor may have been required for killing of A pleuropneumoniae. None of the strains was sensitized to porcine serum by sublethal treatment with polymyxin B, a treatment that is known to disrupt the integrity of the outer membrane and induce serum sensitivity in gram-negative bacteria. The ability of A pleuropneumoniae to resist complement killing in vitro may reflect a virulence mechanism in vivo that assists bacteria in avoiding the pulmonary defenses of swine and promotes bacterial invasion of the lungs.     

Establishment of an attenuated strain of bovine respiratory syncytial virus for live virus vaccine

To develop a live virus vaccine for the prevention of bovine respiratory syncytial (BRS) virus infection in calves, an attempt was made to produce an attenuated virus. The RS-52 strain of BRS virus, isolated from the nasal secretions of a naturally infected calf, was subjected to serial passages in adult hamster lung established (HAL) cells at 30 degrees C and the attenuated rs-52 strain as a live virus vaccine was established. The rs-52 strain multiplied better at 30 degrees C than at 34 or 37 degrees C in HAL cells. The differences in the highest virus titers of this strain between the culture temperature of 30 degrees C and that of 34 or 37 degrees C were more than 2.25 log TCID50. Colostrum-deprived newborn calves and 2 approximately 4 months old calves inoculated with the rs-52 strain manifested no abnormal clinical sings at all. However, all inoculated calves produced serum neutralization antibody. When the colostrum-deprived newborn calves immunized with the rs-52 strain were challenged with the virulent NMK7 strain of BRS virus, they exhibited no pyrexia or other abnormal clinical signs at all. An attempt was made to recover the virus from nasal secretions of these calves, but in vain. On the other hand, a nonimmunized control colostrum-deprived newborn calf developed slight fever, mild cough, and slight serous nasal discharge after challenge exposure. The virus was recovered from nasal secretions of this calf. From these results, it was considered that the rs-52 strain could be used as an attenuated live virus vaccine for prevention of BRS virus infection.     

Comparative cell kinetics of avian growth plates

New data on the cell kinetics of the cartilage growth plates in the chicken, budgerigar and rhea derived from studies with tritiated thymidine labelling are given. Quantitative histological measurements on growth plates from leg bones (tibiotarsus, tarsometatarsus and a phalangeal bone) in a further five species of birds are presented. Counts of flat cells and measurements of the average diameter of hypertrophic cells were made for each growth plate. These data are compared with values for the overall growth rates of the bones. The variation in sizes of hypertrophic cells was small and it is concluded that the largest factor in determining the growth rate of an avian bone is the size of the zone of flat cells.     

Presence of Theileria annulata in Mauritania

A fatal case of bovine theileriosis by Theileria annulata is reported from Mauritania in a Friesian cow born in a dairy farm in Nouakchott. The farm was originally established with cattle imported from France. Specific diagnosis was based on piroplasm morphology and on high specific antibody titres in some of the animals. The only tick found in the herd was Hyalomma dromedarii. Four of 49 local zebus sampled at random in the south of the country had high specific antibody titres to T. annulata, while 14 had lower or doubtful titres. The infection therefore appears to be autochthonous.     

A Comparison of Xylazine–Diazepam–Ketamine and Xylazine–Guaifenesin–Ketamine in Equine Anesthesia

After sedation with xylazine (0.3 mg/kg intravenously [IV]), anesthesia was induced in six healthy horses with ketamine (2.0 mg/kg IV) and guaifenesin (100 mg/kg IV), diazepam (0.05 mg/kg IV), or diazepam (0.10 mg/kg IV). Anesthesia was maintained with halothane for 30 minutes. Heart rate, respiratory rate, direct arterial blood pressure, arterial blood gas, and pH measurements were made before, and at set intervals after, induction of anesthesia. Quality and characteristics of induction and recovery were evaluated objectively by an independent observer unaware of the protocol used. There were no significant differences among the three protocols from pre-induction values for arterial blood pressure, blood gas values, and pH. There was significantly greater ataxia at induction with the use of guaifenesin. The nature of induction, transition to and recovery from general anesthesia were comparable between guaifenesin and the higher dose of diazepam. Because of movements and difficulty with intubation, the lower dose of diazepam was considered unsatisfactory. It was concluded that diazepam (0.10 mg/kg) could be substituted for guaifenesin (100 mg/kg) to produce comparable quality of anesthesia in horses.     

Dietary fiber for dogs: II. Iso-total dietary fiber (TDF) additions of divergent fiber sources to dog diets and their effects on nutrient intake, digestibility, metabolizable energy and digesta mean retention time

The objectives of this study were to examine widely divergent fiber sources for their efficacy as ingredients in a meat-based dog diet and to determine the effects of these fibers on fecal excretion responses and mean retention time of marked fiber in the gastrointestinal tract of the dog. Fiber sources tested included beet pulp (BP), tomato pomace (TP), peanut hulls (PH), wheat bran (WB) and alkaline hydrogen peroxide-treated wheat straw (AHPWS). Diets were isonitrogenous (5.3% N) and iso-total dietary fiber (TDF; 12.5%). Thirty female English Pointers (five/treatment) were used in the experiment. Intakes of DM and OM were similar among treatments. The highest intakes of ether extract (EE) occurred on the TP, PH and WB treatments. Dogs fed PH ingested the most crude fiber (23.6 g/d), NDF (53.5 g/d), ADF (34.3 g/d) and TDF (59.7 g/d). Digestibilities of DM and OM for all fiber treatments were lower than the control (87.6 vs 81.8% for DM; 90.2 vs 85.4% for OM), but values were similar among fiber sources. The highest EE and N digestibilities occurred on the control and AHPWS treatments. No differences were noted among exogenous fiber-containing treatments in fiber component digestibility. Digestible energy and ME values generally were similar among treatments. Among fiber sources, BP resulted in the greatest amount of wet feces excreted (270 g/d) and the lowest fecal DM (30.3%). No differences among fiber sources were noted in frequency of defecation or mean retention time. Iso-TDF diets (containing, on average, 12.5% TDF) appear to be utilized similarly, regardless of the diversity in sources of fiber tested.     

Riems foot-and-mouth disease oil emulsion vaccines for swine. 2. Use of foot-and-mouth 2-component oil emulsion vaccines in practice

Riems FMD two-component oil emulsion vaccine was subcutaneously applied (5 ml) under field conditions to 855 store pigs of different age groups (trivalent--O1, A5, C). It produced early onset of lasting strong immunity against the three above FMD virus types. General condition of the animals and their body weight development were not adversely affected. Pea-size to walnut-size vaccination granulomas were recorded on slaughter as locally delimited reactions in 15 to 20 percent of vaccinated animals and were found to be morphologically correlated to adjuvant action. They were easily removed from the carcasses by excision of the vaccination point, with only minor loss of slaughter substance.     

Influence of antibody treatment of Campylobacter jejuni on the dose required to colonize chicks

This study was designed to clarify the role of antibodies in controlling chicken colonization by Campylobacter jejuni. Cecal colonization by C. jejuni was compared after the organism was exposed either to phosphate-buffered saline, normal rabbit serum, rabbit hyperimmune anti-C. jejuni serum, or anti-C. jejuni antibodies extracted from chicken bile. Antibodies from chicken bile were extracted by affinity absorption against outer-membrane proteins from the challenge organism. Sera were heated 1 hour at 56 C to destroy complement activity. Bacterial inoculum levels were enumerated after 1 hour exposure at 4 C to the various treatments. The heated sera and the bile antibodies were not bactericidal, and bacterial agglutination was not evident. Serial dilutions of the antibody-treated C. jejuni were given by gavage into 1-day-old chicks. Six days later, the ceca were removed from the chicks, and samples were cultured on Campylobacter-charcoal differential agar. The colonization dose-50% was increased by twofold to 160-fold when the organism was preincubated with hyperimmune antiserum or the bile antibodies as compared with preincubation with phosphate-buffered saline. We conclude that antibodies inhibit chicken cecal colonization by C. jejuni.