This work was an attempt to develop an in vitro adherence model for Mycoplasma hyopneumoniae, using monolayers of human and porcine lung fibroblasts and porcine kidney cells. Mycoplasma hyopneumoniae grown in Friis mycoplasma broth was radiolabeled with 35[S]-methionine, washed, concentrated, and inoculated on the monolayers. After 15 minutes of centrifugation to facilitate adherence, monolayers were washed 3 times, dissolved with 0.1N NaOH, and suspended in scintillation liquid, and the radioactivity was determined in a liquid scintillation counter. Adherence, measured as a percentage of counts added, varied according to the mycoplasma strain and the cell line used. Comparison of strains J, 144L, and 232 of M hyopneumoniae revealed 7.5 +/- 5.9, 31.9 +/- 13, and 9.6 +/- 5% adherence to porcine kidney cells, respectively. Slightly different, but proportionally the same relationships were obtained with swine or human fibroblasts. Adherence was decreased slightly by repeated washings of the mycoplasma-treated cell monolayers; however, a plateau was reached, indicating irreversibility of the adherence process. Pretreatment of cell monolayers with nonlabeled organisms substantially blocked adherence by labeled organisms. Dilution of labeled organisms resulted in an increased proportion adhering. Therefore, it appears that the adherence was a receptor-dependent event. Treatment of the mycoplasmas with trypsin prior to the inoculation of monolayers resulted in a marked reduction in adherence. Treatment of the mycoplasmas with hyperimmune swine serum against M hyopneumoniae or normal swine serum resulted in 80 to 90% reduction of adherence; however, no inhibition occurred when mycoplasmas were treated with purified IgG from the hyperimmune serum.

A prospective cohort study was undertaken in a farrow-to-farrow swine herd to describe patterns of pneumonia, and to identify host risk factors associated with the extent of pneumonic lesions in 2 weight groups of slaughter swine. The risk of coughing and pneumonic lesions increased with increasing age of pigs within the herd (P < 0.0001). The age-specific prevalence of pneumonic lesions was low (2.7%) in pigs < 16 weeks old at slaughter, but increased rapidly when pigs were between 16 and 22 weeks old (8.6 to 67.9%). After 22 weeks, the prevalence remained relatively constant at about 80%. Associations between possible risk factors and pneumonia were investigated by use of multiple-regression models. Age at weaning (< 24 days) and birth weight (< 1 kg) exerted small, but significant (P < 0.002), effects on the extent of pneumonic lesions in pigs slaughtered at 30 to 50 kg live weight. For pigs slaughtered at 90 to 110 kg, pneumonic lesions were more extensive (P = 0.007) in pigs sired by Yorkshire boars than pigs sired by non-Yorkshire sires (Duroc, Hampshire, Chester White, or American Spotted). Other host factor variables including weaning weight and clinical diseases (atrophic rhinitis, diarrhea, and arthritis) were not associated with pneumonia extent in either weight group. Higher pneumonia percentages were also associated with reduced growth rates in the grower/finisher phase. Pigs sired by Yorkshire boars grew significantly (P < 0.0001) more slowly from entry into shed 2 (mean, 38 kg) until about the time of exit (mean, 92 kg) than pigs sired by other breeds (747 g/d and 795 g/d, respectively).

Seventeen sows were fed 1,000 Toxoplasma gondii oocysts of isolates GT-1 or PT-1 at 32 to 92 days of gestation, and the products of conception were examined for T gondii antibodies and parasites. Twelve of these sows were euthanatized near term between 21 and 62 days after being fed T gondii; fetal body fluids or fetal sera were examined for agglutinating T gondii antibodies, and tissues were bioassayed in mice for T gondii parasites. Six sows produced pigs that had been transplacentally infected with T gondii; one of them aborted a T gondii-infected fetus 17 days after ingesting oocytes. Agglutinating antibodies were detected in fetuses infected in utero, but transplacental transfer of T gondii antibodies was not observed in noninfected fetuses. Transcolostrally acquired T gondii antibodies disappeared by 3 months of age. Diagnosis of transplacental toxoplasmosis was confirmed on the basis of detection of T gondii organisms in fetal tissues by use of histologic examination and bioassay in mice. In conclusion, finding of T gondii antibodies in body fluids could serve as a rapid screening test for transplacental T gondii infection in pigs.

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (MH) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calcium was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 +/- 40 and 370 +/- 216 nmol/L; P < 0.01) and slower rates of calcium accumulation (39 +/- 16 and 127 +/- 52 nmol/L/min) in untreated lymphocytes from MH-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of MH-susceptible swine (154 +/- 36 and 408 +/- 47 nmol/L/min at 175 nmol/L; 972 +/- 111 and 1,690 +/- 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of MH-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.

High-performance liquid chromatography (HPLC) was used to determine the phospholipid (PL) composition of ovine, equine, bovine, porcine, and canine RBC membranes. Procedural modifications of established techniques provided for separation of 7 PL within a 15- to 20-minute sample run. Significant (P < 0.05) differences were detected in RBC membrane PL composition among the various species. The concern for physiologic properties associated with hemolysis and/or sedimentation rate must include evaluation of differences in the PL bilayer structure.

Logistic regression was used to develop models predicting preweaning survival in 334 neonatal swine. Measured risk factors included birth weight, litter size (live born), dam parity, serum IgG concentration, serum ELISA titers recognizing common gram-negative core antigens, and serum concentrations of the third component of complement. Larger birth weights were associated with increased probability of preweaning survival. The highest mortality was observed in litters with more than 12 pigs. Pigs with serum concentration of the third component of complement (C3) in the lowest stratum, < 20% adult pooled C3 standard (APC3), had reduced mortality, compared with high (> 38% APC3) and middle (20 to 38% APC3) groups. Associations between all other variables, including total serum IgG concentration and preweaning survival were not significant. Few pigs had hypogammaglobulinemia, < 3% of the study population had serum IgG concentrations < 1 g/dl. Of all measured variables, only birth weight and dam parity were significant predictors of preweaning gain. Larger pigs and pigs born to third or greater parity dams had more preweaning gain than other pigs.

A fully age-structured deterministic model of the population biology of a pseudorabies epizootic in a farrow-to-finish operation was used to examine the disease-related change in productivity following the initial disease episode. A strategy involving continual sow vaccination was compared with various strategies involving the vaccination of growing pigs, as well as sows. The model suggests that vaccinating growing pigs, in addition to the breeding herd, results in only a relatively small improvement in long-term productivity following a pseudorabies epizootic.

The disposition of doxycycline hyclate after IV administration of 20 mg/kg of body weight was studied in 6 pigs. Median elimination half-life, estimated in 4 pigs, was 3.92 hours. Mean (+/- SEM) total body clearance was 1.67 +/- 0.18 ml/min/kg, and mean apparent volume of distribution at steady state was 0.53 +/- 0.04 L/kg. In 2 pigs, secondary peaks in the logarithmic serum concentration-time profile suggested discontinuous enterohepatic cycling, and precluded using these pigs in the pharmacokinetic analysis. The extent of doxycycline binding to serum protein was 93.1 +/- 0.2%. Serum or urine from 3 of the pigs was analyzed by use of photodiode array detection and mass spectrometry of a high-performance liquid chromatographic column effluent. These procedures documented lack of doxycycline biotransformation in pigs. It is concluded that, despite an elimination half-life shorter than that reported in other species, doxycycline may be a valuable antimicrobial drug for use in swine practice, pending the development of appropriate formulations.

Fifty-six samples of feces and intestinal contents from nonvaccinated diarrheal pigs with rotavirus infections were tested, using a subgroup (SGP)-specific ELISA, to determine rotavirus SGP classification. Forty-one percent (23/56) were SGP 1, 25% (14/56) were SGP 2, and 34% (19/56) were not classifiable. For classifiable samples, the geographic distribution for SGP 1 and SGP 2, respectively was: 60%/40% from Ohio (n = 15), 63%/37% from other midwestern states (Iowa, Minnesota, Nebraska, South Dakota: n = 16), and 67%/33% from Canada (n = 6). Thirty-seven SGP-classifiable samples were categorized according to age of pigs. Of pigs less than or equal to 1 week old, 22% of samples were SGP 1 (n = 8), and 14% (n = 5) were SGP 2. Of samples from 1- to 2-week-old pigs, 8% were SGP 1 (n = 3), and 5% were SGP 2 (n = 2). Of samples from 2- to 3-week-old pigs, 5% were SGP 1 (n = 2), and 8% were SGP 2 (n = 3). Of samples from 3- to 4-week-old pigs, 5% were SGP 1 (n = 2), and 3% were SGP 2 (n = 1). Of samples from pigs > 4 weeks old, 22% were SGP 1 (n = 8) and 8% were SGP 2 (n = 3). Double-stranded RNA extracted from positive controls and from 10 selected field samples (5 from SGP 1 and 5 from SGP 2) was electrophoresed in polyacrylamide gels to detect correlation between subgroup classification by ELISA and long or short double-stranded RNA electrophoretic-migration patterns. All SGP-1 and -2 rotavirus samples tested had typical long double-stranded RNA electrophoretic-migration patterns.

A deterministic mathematical model of the population biology of pseudorabies in swine was used to clarify some of the basic features of the host-virus relationship and to inquire into the circumstances that promote or impede virus persistence in a single herd. When the basic reproductive rate of the infection (ie, the number of secondary infections resulting from the introduction of a single infective animal into a wholly susceptible herd) is greater than unity, the model suggests that the number of infective individuals in the herd will undergo highly damped oscillations to a final equilibrium level. The most important determinants of virus persistence are herd size and the density at which sows are maintained. There is a threshold density of susceptible individuals below which the virus will eventually be eliminated from the herd, even when specific control measures are lacking. Test and removal strategies hasten virus elimination when herd density is already below threshold, but are otherwise likely to succeed only when the removal of latent infections reduces the basic reproductive rate of the infection below unity. Vaccination strategies may also result in virus elimination, but only in relatively small herds.