Transsplenic portal catheterization combined with a jugular double-lumen catheter for pharmacokinetic and presystemic metabolization studies in pigs

The reliability of a silicone double-lumen catheter implanted into the external jugular vein and tunnelled towards the neck region was investigated in eight pigs. Surgery was uneventful without interference with the normal homoeostasis during 8 days. After injection of amoxicillin/clavulanic acid through the distal port of the catheter, analysis of drug components in the simultaneous blood samples obtained by the proximal port and a Venoject^® system were comparable in one pig. Histological control of the catheterized jugular veins pointed to an acceptable tissue reaction while bacteriological examination of the tip of the catheters was negative in only three animals. A moulding of the intestinal veins was made in a pig cadaver to determine the optimal length of insertion of a silicone portal catheter from the splenic vein towards the portal vein. Surgery was straightforward in four pigs whereby the catheter was exteriorized towards the back region. No complications were encountered during and after surgery for 9 days. The technique of a double-lumen catheter placed into the jugular vein and a transsplenic portal catheter is a useful tool for the study of the pharmacokinetics and also the first-pass effect of drugs in experimental pigs.     

Bile acid metabolism in the pig

To study bile acid metabolism in the pig, indwelling catheters were surgically placed in the hepatic portal vein and the anterior vena cava of 12-17 kg crossbred pigs. The pigs were fed ad libitum for one hr at 0800 and 1600 hrs daily. Two weeks after the surgery, 50 microCi of 24[14C] chenodeoxycholic acid were infused into the hepatic portal vein. The radioactivity in plasma from the two veins was monitored hourly for six hrs following each of six consecutive meals over a 3-day period. Fecal and urine radioactivity were determined for 14 days. It was found that the peak levels of radioactivity in the plasma of both veins were reached within two hrs post-feeding. The biological half-life of chenodeoxycholic acid was determined to be 6.4 days.     

半乳甘露寡糖对猪门静脉血流速率、氨基酸和葡萄糖的净吸收量及耗氧量的影响

通过对10头15kg体重试验猪实施门静脉血管插管等外科手术,并结合回肠肠系膜静脉灌注对氨基马尿酸(PAH)技术,探讨半乳甘露寡糖对生长猪门静脉血浆流率(PVPF)和血液流率(PVBF)、氨基酸和葡萄糖的净吸收量及耗氧量的影响。10头杜长大阉公猪随机分为2个处理,每个处理5头,单笼饲养于可调节不锈钢代谢笼内,经过14d适应期后,在门静脉、肠系膜静脉、颈动脉安装插管,开始15d正式试验。对照组饲喂玉米-豆粕型基础饲粮,试验组饲喂基础饲粮 0.20%半乳甘露寡糖。结果表明,经过15d饲喂期后,与对照组相比,饲粮添加半乳甘露寡糖可显著降低试猪食后8h内门静脉的平均血浆流率和血液流率,显著提高食后8h内门静脉对氨基酸和葡萄糖的净吸收量,显著降低食后8h内门静脉的耗氧量,也就是说半乳甘露寡糖可通过减少生长猪小肠黏膜对氨基酸和葡萄糖的氧化而增加肠外组织对其吸收。     

Influence of carbadox on fasting oxygen consumption by portal vein-drained organs and by the whole animal in growing pigs.

Fasting O2 consumption by the whole animal (W) and by portal vein-drained organs (PVDO) during the 24- to 30-h postprandial period were measured in seven growing pigs (36.1 +/- 2.3 kg) with catheters chronically placed in the hepatic portal vein, ileal vein, and carotid artery trained to consume 1.2 kg of a 16% CP corn soybean meal basal diet (B) once daily. The pigs were placed individually into an open-circuit, indirect calorimeter and connected to an arteriovenous (A-V) O2 difference analyzer for hourly simultaneous measurements of O2 consumption by W and PVDO. The PVDO O2 consumption was calculated by multiplying the A-V O2 difference by the portal vein blood flow rate derived from constant infusion of a p-aminohippuric acid solution into the ileal vein. After the initial series of hourly measurements, four pigs remained on the B diet and three pigs were fed a B + 55 ppm carbadox diet. Seven days later, the second series of measurements was made. In pigs fed the diet with carbadox added, the hourly W O2 consumptions were not different (P greater than .05) between the initial and second series and averaged 7.5 mL.min-1.kg of BW-1. However, the A-V O2 differences (mL/dL) were reduced (P less than .05) from 4.6 to 4.0 at 24 h, 4.8 to 4.0 at 25 h, and 4.6 to 4.0 at 29 h postprandial and the fractions of W O2 consumption used by PVDO (percentage) were reduced (P less than .05) from 28.6 to 21.6 at 26 h and 25.2 to 18.2 at 27 h postprandial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of the subcutaneous abdominal vein for blood sampling and intravenous catheterization in potbellied pigs

The subcutaneous abdominal vein was used successfully to deliver fluids IV after catheterization and as a means of blood collection in 6 potbellied pigs of various body sizes and types. Because a 16-gauge catheter could be easily introduced into the vein, a large volume of fluid could be administered rapidly. Most pigs were highly tolerant of blood collection from this vein, and little restraint was required. The catheters remained in place for as long as 1 week, and no serious sequelae resulted from catheterization of the subcutaneous abdominal vein.     

The pathogenesis of persistent turbinate atrophy induced by toxigenic Pasteurella multocida in pigs

Six one-week-old piglets were pretreated with a 1% acetic acid solution for two days in one or both nostrils. Three piglets were not treated with acetic acid. Three days after treatment all nine piglets were inoculated in both nostrils with a toxigenic type D strain of Pasteurella multocida. Three piglets were killed seven days after inoculation; one died spontaneously 13 days after inoculation and the remaining pigs were killed at approximately 90 kg body weight, i.e., five to six months of age. All acetic acid-treated animals developed severe atrophy of the turbinates in the treated nostrils. Untreated nostrils were normal. The present results showed that toxigenic P. multocida can induce turbinate atrophy that persisted until 90 kg body weight when the lesions were similar to spontaneous atrophic rhinitis in pigs. The turbinate atrophy was not accompanied by inflammatory reaction, atrophy of other bone structures, or lesions in other organs. The experiment showed furthermore that toxigenic P. multocida may be present in the tonsils of control animals without causing turbinate atrophy. A pathogenesis for atrophic rhinitis in pigs is proposed.     

Effects of sodium dichloroacetate in awake, healthy, Yucatan miniature swine

Four healthy, fully conscious, 50- to 80-kg Yucatan miniature swine were fitted with carotid artery and jugular, portal, and hepatic vein catheters and hepatic artery and portal vein flow cuffs to determine transhepatic kinetics and insulin secretion. Three days later, after a 3-hour control period, the pigs were given IV sodium dichloroacetate (30 mg/kg of body weight as a bolus and 30 mg/kg/hr, as an infusion) for 6 hours. Arterial lactate concentrations decreased during the dichloroacetate infusion, but pyruvate concentrations were unaltered. The whole body rate of appearance and disappearance of glucose decreased, but plasma glucose concentrations did not change markedly. Limb skin surface temperatures increased, indicating a peripheral vasodilatory effect. Dichloroacetate had little effect on mean arterial pressure and hepatosplanchnic blood flow. Dichloroacetate may be effective as a hypolactatemic agent for lactic acidosis in pigs.     

Mycoplasma hyopneumoniae increases the susceptibility of pigs to experimental Pasteurella multocida pneumonia.

The interaction between Mycoplasma hyopneumoniae and Pasteurella multocida in experimental pneumonia was investigated in conventional pigs. The experimental animals were 49 days old when inoculated with M. hyopneumoniae; they were inoculated with P. multocida after 23 days, and killed 13 days later. In pigs inoculated only with P. multocida, clinical signs and lung lesions were not observed, and the agent was not recovered. Pigs inoculated with M. hyopneumoniae developed fever, moderate cough and dyspnea which tended to disappear, and small proliferative lung lesions from which M. hyopneumoniae was isolated. Pigs inoculated with both agents had higher fever, severe cough and dyspnea which tended to aggravate, and extensive exudative lung lesions from which organisms were isolated. All animals had similar growth rates, but the group infected with both agents consumed 60% more food. Therefore, M. hyopneumoniae causes mild pneumonia, whereas P. multocida is not pathogenic alone but aggravates the pneumonia initiated by M. hyopneumoniae.     

The effect of continuous in-feed medication with thiophanate on Ascaris suum and Oesophagostomum spp. egg output in young pigs

The full potential of anthelmintics now available for single dose treatment is not achieved because the devising system for worm control in piglets/weaners is not efficiently applicable in practice. Therefore an in-feed medication programme for growing young pigs, allowing only one feed lot to be handled by the farmer, was tested in two studies. Study A Feed containing 0.0225% thiophanate was continuously fed almost ad lib. to piglets from birth right up to about 25 kg body weight when ready for fattening. This control measure effectively prevented A. suum and Oesophagostomum from becoming established during the whole pre-fattening period, thus allowing "worm-free" weaners to be produced. -33% of animals receiving unmedicated feed harboured mature Oesophagostomum already at an age of 63 days when first examined. Three out of 97 unmedicated pigs were then A. suum egg-count positive. At the same time all medicated pigs, except one with a low Oesophagostomum egg output, were egg-count negative. All medicated were still egg-count negative at 23-29 days after the withdrawal of the feed. About 30% of unmedicated pigs were then shedding eggs of A. suum and Oesophagostomum respectively. At 45-49 days after the withdrawal of the medicated feed 8% of previously medicated pigs and 43% of unmedicated pigs were A. suum egg-count positive. The corresponding figures for Oesophagostomum egg-count positive pigs were 6% and 40% respectively. The acquisition of worm infections by previously medicated pigs most probably was made in the fattening unit after the withdrawal of the thiophanate medicated feed. Study B In this study it was further substantiated that in-feed medication of pigs with thiophanate prevents A. suum from becoming established. All treated pigs were A. suum egg-count negative at Day 43 and 46 after the withdrawal of the medicated feed whereas about 62% of untreated control pigs were shedding A. suum eggs at the same time. This finding justify the proposal that the in-feed medication performed prevented larval migration. Furthermore it was shown that the in-feed medication must proceed right up to the transfer of piglets to the fattening unit in order to achieve its full potential. Farrowing pens may be heavily contaminated with infective Oesophagostomum larvae at the end of the pre-fattening period resulting in sudden and heavy nodular worm infections after the withdrawal of the medicated feed.     

Progesterone secretion by the bovine fetoplacental unit and responsiveness of corpora lutea to steroidogenic stimuli at two stages of gestation

To evaluate the response of luteal cells to in vitro stimulation with luteinizing hormone (LH) or dibutyryl cyclic adenosine monophosphate (dbcAMP) and determine the secretion of progesterone by the fetoplacental unit, the corpora lutea were removed surgically in 10 cows (luteectomy) at 250 days (5 cows) or 270 days (5 cows) of gestation. During surgery, but before luteectomy, catheters were placed in the middle uterine artery and vein, carotid artery, and jugular vein. Blood samples were collected from all catheters just before luteectomy and at 8-hour intervals after luteectomy for 72 hours or until calving, whichever occurred first. Luteal tissue was prepared as a dispersed cell preparation and incubated with 0, 0.1, 1.0, 10, or 100 ng of LH/ml of medium or was incubated with 0, 0.5, or 2 mM dbcAMP. Synthesis of progesterone in response to LH by dispersed cells prepared from corpora lutea at 270 days was less (P less than 0.01; analysis of variance) than that by similar preparations at 250 days because a dose-response relationship was not observed for incubations of luteal tissue with LH at 270 days of gestation. Progesterone synthesis in response to the addition of dbcAMP also was less (P less than 0.01) at 270 than at 250 days of gestation. This difference in responsiveness to LH and dbcAMP between the 2 stages of gestation was not reflected by a significant difference between stages of gestation in systemic concentrations of progesterone before luteectomy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Occlusion of the External Carotid and Maxillary Arteries in the Horse to Prevent Hemorrhage from Guttural Pouch Mycosis

Balloon-tipped catheters were used to occlude the external carotid artery and its branches in nine horses with hemorrhage caused by guttural pouch mycosis. The internal carotid artery on the affected side was occluded simultaneously in four horses and had been occluded previously in two others. In three horses, a single balloon-tipped catheter was inserted in the external carotid artery beneath the floor of the guttural pouch and its tip was advanced blindly into distal branches. In one horse, the superficial temporal artery was occluded briefly during surgery by a balloon-tipped catheter so a catheter inserted into the external carotid artery could be diverted into the maxillary artery. In the other five horses, the external carotid artery was occluded proximally and the maxillary artery was occluded immediately caudal to the alar canal by a balloon-tipped catheter inserted into the major palatine artery. Serious postoperative hemorrhage did not occur in eight horses, but one horse that had a single balloon-tipped catheter inserted into the external carotid artery had profuse hemorrhage 11 days after surgery and was euthanatized. One horse was euthanatized because of persistent dysphagia. The only complication related to use of balloon catheters was a mild incisional infection in one horse. It was concluded that the external carotid and maxillary arteries must be occluded on both sides of the eroded segment to prevent hemorrhage from normograde and retrograde flow.     

The effects of body composition on the pharmacokinetics of subcutaneously injected ivermectin and moxidectin in pigs

Macrocyclic lactones are characterized by their long persistence in animals because of their extensive distribution into fat. This study examined the influence of body condition on the disposition of ivermectin (IVM) and moxidectin (MXD) in blood and fat following subcutaneous (s.c.) drug administration. 'Fat' and 'thin' lines of pigs were established using two different diets. All animals were then injected with either MXD or IVM at 300 microg/kg and blood samples were taken at regular intervals until slaughter. Two IVM-treated animals from each diet group were slaughtered at either 3 days or 3 weeks posttreatment. Two MXD-treated animals from each diet group were slaughtered at 3 days, 3, 6 or 9 weeks after treatment. Samples of backfat were taken from all animals at slaughter. Fluorescence HPLC was used to determine the concentrations of MXD or IVM in the plasma and fat samples. The plasma IVM concentration peaked more rapidly in the thin IVM treated pigs compared with the fat pigs. The concentration of IVM in backfat was significantly lower in the thin animals slaughtered 3 weeks after treatment. The MXD plasma concentration peaked within the first hour in both the thin and fat groups, but from 12 h posttreatment there was a higher MXD concentration in the plasma of the fat pigs resulting in MXD being detectable in these pigs for 28 days compared with only 17 days in the thin pigs. Despite this difference in plasma persistence no differences were seen in the MXD concentration of backfat between fat and thin animals. Body condition influenced the kinetic disposition of IVM and MXD following s.c. drug administration with both drugs being less persistent in thin compared with fat animals.     

Difference in rates of net portal absorption between crystalline and protein-bound lysine and threonine in growing pigs fed once daily

Net portal absorption of AA during the 6-h postprandial period was measured in eight gilts (48.5 +/- 1.6 kg BW) in a crossover design. The pigs had chronic catheters placed in the portal vein, carotid artery, and ileal vein, and were trained to consume 1.2 kg of a standard grower diet once daily. Blood samples were taken every 30 min for 4 h and then hourly until 6 h after feeding. The first set of blood samples was taken after pigs were fed a meal of the test 16% CP corn-soybean meal diet (16% CP) or the test 12% CP corn-soybean meal diet supplemented with crystalline lysine, threonine, and tryptophan (12% CP + AA) to equal the three AA levels in the 16% CP diet. Pigs were then fed the standard diet for 2 d. Following that, blood samples were again taken after the pigs were fed a meal of the test diet that was not given to them at the first sampling period. Net portal AA absorption was calculated by multiplying porto-arterial plasma AA concentration difference by portal vein plasma flow rate (PVPF), estimated by an indicator-dilution technique employing p-aminohippuric acid as the indicator infused into the ileal vein. Plasma concentrations of lysine and threonine of pigs were affected by the diet x time interaction (P < 0.01). Portal and arterial plasma lysine and threonine concentrations in pigs attained the maximal level by 1 h postprandial when the 12% CP + AA diet was fed, but reached the peak level at 2.5 h postprandial when the 16% CP diet was given. The PVPF of pigs over the 6 h postprandial was less (P < 0.01) when the 12% CP + AA diet was given than when the 16% CP diet was fed. Net portal absorptions of lysine and threonine also were affected (P < 0.05) by time x diet interaction. The peak portal absorption of both lysine and threonine in pigs appeared at 0.5 h postprandial when the 12% CP + AA diet was given, but at 2.5 h postprandial with the feeding of the 16% CP diet. The early appearance of peak portal absorption of lysine and threonine from feeding the 12% CP + AA compared with the 16% CP diet indicates that crystalline lysine and threonine are absorbed more rapidly than protein-bound lysine and threonine in pigs fed once daily.     

Combined rotavirus and K99 Escherichia coli infection in gnotobiotic pigs

Fifty nine 3-day-old gnotobiotic pigs were randomly assigned to 4 experimental groups: 14 pigs were orally inoculated with rotavirus (RV), 14 were orally inoculated with enterotoxigenic Escherichia coli (ETEC), 18 were orally inoculated with both agents, and 13 were controls. Pigs inoculated with RV plus ETEC were given the RV inoculum at 3 days of age and then, 24 hours later, were given the ETEC inoculum. Three pigs inoculated only with RV, 3 pigs inoculated only with ETEC, 4 pigs inoculated with RV plus ETEC, and 3 pigs in the control group were euthanatized at 5 and 7 days of age. Two pigs in each of the 4 experimental groups also were euthanatized at 9 days of age. Intestinal segments from 6 sites in the small intestine were examined by virologic, bacteriologic, and histologic procedures. For 10 days after inoculation, the remaining pigs in each group were observed clinically to monitor severity and duration of diarrhea, mortality, and shedding of RV or ETEC. Pigs inoculated with the combined RV plus ETEC inoculum developed more severe diarrhea, compared with pigs inoculated with the single agents; all dually inoculated pigs died between 3 and 6 days after inoculation. There was no mortality in pigs inoculated with either RV or ETEC. Lesions were restricted to the small intestine in pigs inoculated with RV plus ETEC and in pigs inoculated with RV or ETEC. There was no difference in the severity of the villus atrophy between the dually inoculated pigs and pigs inoculated only with RV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term lack of transmission of Aujeszky's disease virus (ADV) in a chronically infected Swedish weaner pig producing herd

A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation.     

The efficacy of a leptospirosis vaccine in preventing leptospiruria in pigs

A commercially manufactured leptospirosis vaccine containing serovars pomona and hardjo and licensed for use in cattle and sheep was investigated to determine if it would prevent leptospiruria in pigs exposed to serovar pomona. Twenty piglets were each vaccinated twice at an interval of three weeks. Twenty other piglets were unvaccinated and served as controls. Three weeks after the second dose of vaccine all animals were exposed for 64 to 89 days to a natural infection with pomona. During the investigation blood samples were examined serologically and urine samples were examined by dark ground microscopy and cultured for the presence of leptospirae. Attempts were made to culture leptospirae from kidneys at slaughter. Kidneys were also examined histologically for evidence of leptospira infection. One vaccinated animal developed a respiratory disease. It was treated with antibiotics and removed from the trial. Leptosphuria was demonstrated in six of the remaining 19 vaccinated pigs and leptospirae were found in nine of 578 (1.5%) urine samples examined from these animals during the period of exposure. In contrast leptospiruria occurred in 19 of 20 unvaccinated pigs and leptospirae were found in 253 of 642 (39.4%) urine samples examined from these animals. Histopathological lesions consistent with leptospirosis were found in kidneys examined from two of 16 vaccinates and 17 of 18 non-vaccinates. Antibodies to serovar pomona were detected in 12 of 19 vaccinated pigs examined three weeks after the second dose of vaccine and before exposure to infection, and in all of 18 unvaccinated pigs examined after exposure to infection. It was concluded that use of this vaccine in pigs resulted in a significant degree of protection against leptospiruria.     

Metabolic and microbial responses in western crossbred and Meishan growing pigs fed a high-fiber diet

Four Duroc x White composite crossbred (21.8 +/- 1.0 kg BW) and four 12-wk-old Meishan purebred (20.7 +/- 1.6 kg BW) growing barrows were used to determine the relative breed differences in metabolic and microbial responses to a high-fiber diet. The pigs were trained to consume 700 g of a diet containing 35% (as-fed basis) dehydrated alfalfa meal once daily. The pigs' daily intakes of DM, N, GE, NDF, and ADF were 610 g, 16.6 g, 2.64 Mcal, 150 g, and 88 g, respectively. On d 12 after surgical catheterization of the portal vein, ileal vein, and carotid artery, a 3-d total urine and feces collection was conducted. On d 24 after surgery, each pig was placed in an open-circuit calorimeter, and its catheters were connected to a system for simultaneous measurements of oxygen consumption by portal-drained viscera and by whole body, and the net portal absorption of VFA after a 24-h fasting and during a 5-h postprandial period. The VFA measured included acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids. A second 3-d total urine and feces collection was conducted on d 30 after surgery. There were no differences (P = 0.13) between the first and second collections in apparent total-tract digestibility coefficients for nutrients and N retention of pigs. Compared with Duroc x White composite crossbred pigs, Meishan pigs had lower (P = 0.05) apparent digestibility coefficients for DM, N, NDF, hemicellulose, and N retention, but their portal-drained viscera used a greater (P = 0.05) fraction of whole-body oxygen consumption. No differences (P = 0.12) were found between Duroc x White composite crossbred and Meishan pigs in total viable bacteria and cellulolytic bacteria from fecal samples, in vitro digestibility of alfalfa NDF fractions by fecal inocula, whole-body oxygen consumption, net portal absorption of VFA, total energy of absorbed VFA, and the potential of absorbed VFA for meeting the energy needs for whole-body heat production. These results indicate that, in contrast to previous beliefs, the ability of Meishan growing pigs to utilize a high-fiber diet is not superior to that of Duroc x White composite crossbred growing pigs.     

Studies on the secretion of amino acids and of urea into the gastrointestinal tract of pigs. 3. Secretion of urea determined by continuous intravenous infusion of 15N-urea

Three pigs, of 34 kg live weight, were each fitted with re-entrant cannulas both in the duodenum and terminal ileum and catheters in the jugular vein and in the carotid artery. Pigs received a diet based on wheat and dried skimmed milk in equal amounts at 12 h intervals. During the preliminary period the digesta flowing from both duodenal and ileal cannulas were collected over 12 h after feeding on two consecutive days and half of them were reintroduced into the gut and half were stored at -20 degrees C. During the experimental period 15N-urea was infused into the jugular vein for 12 hours starting with the morning meal. Total amount of urea infused was 5 g containing 1.22 g 15N-excess. The digesta from both proximal duodenal and ileal cannulas were collected and stored, while the digesta from the preliminary period were reintroduced into the respective distal cannulas. Blood samples were taken at different time of infusion. At the end of infusion period the animals were sacrificed and samples of the contents of the digestive tract and tissues were taken. Urea flux calculated according to atom-% 15N-excess of urea N in plasma was 1.23 to 2.37 g/kg body weight/day. In the duodenal digesta 94.5 +/- 0.2 and in ileal digesta 57.1 +/- 7.39 per cent of 15N were in the TCA soluble fraction. The total amount of 15N in the duodenal digesta was 1.7 to 6.3 times greater than in the ileal digesta. Only small amount of 15N was found in the caecum and almost none in the contents of colon and rectum. It is concluded that urea is secreted into all parts of the digestive tract, the main sites of urea secretion being pancreatic juice and/or bile as well as the small intestine. The total amount of urea secreted is assumed to be similar to the daily urea excretion.     

Guinea pig protection test as indicator of potency of oil emulsion foot-and-mouth disease vaccines

A vaccine potency test is described involving virus challenge to six groups of 10 guinea pigs at five weeks after vaccination. Sixteen oil emulsion foot-and-mouth disease vaccines were so tested and nine retested after storage at 4 degrees C for up to 28.3 months. The results were compared with those of the routinely used oil emulsion vaccine potency test (protection afforded to eight pigs challenged 21 days after vaccination). When guinea pig estimates of 3 log2 PD50 or more were obtained, then, with one exception, the batches protected all or almost all pigs from challenge, but when the guinea pig estimates were less than 1 log2 PD50, the vaccines failed to protect five out of eight pigs. The sensitivity and reproducibility of the guinea pig method, established by repeated tests on two vaccine batches, seemed acceptable. The results suggested that guinea pig estimates might provide a suitable substitute for pig challenge potency tests because they reflected the potency of the vaccines, were likely to involve smaller standard errors and caused less discomfort to animals.     

An experimentally induced Chlamydia suis infection in pigs results in severe lung function disorders and pulmonary inflammation

This study was aimed at evaluating the pathophysiology of pulmonary dysfunctions and inflammatory consequences of an acute respiratory chlamydial infection induced experimentally in conventionally raised pigs (aged 39-44 days). Eight animals were exposed to Chlamydia suis (C. suis) and four non-infected animals served as controls. The total observation period was from seven days before challenge to seven days post exposure. While non-infected control pigs did not exhibit any clinical symptoms, animals exposed to C. suis developed fever and were severely respiratory distressed within the first week after exposure. After C. suis infection, pulmonary dysfunctions were characterised by a significant decrease in the diffusion capacity of the lung (i.e. transfer factor of the lung for carbon monoxide; TL CO), a significant increase in the functional residual capacity (FRC), and significant changes in the pattern of ventilation (respiratory rate increased while the tidal volume decreased). In exhaled breath condensate (EBC), leukotriene B(4) (LTB(4)) and interleukin 6 (IL-6) showed a tendency to increase after infection. In the broncho-alveolar lavage fluid (BALF) of C. suis infected pigs, the activity of matrix metalloprotease 9 (MMP-9) was found to be increased compared to controls. BALF cytology was characterised by increased numbers of granulocytes and activated lymphocytes. Pulmonary inflammation in infected pigs was confirmed by post mortem histology. A prominent dissemination of chlamydial bodies in the lung was accompanied by an influx of macrophages, granulocytes and activated T-cells. Data obtained in this study provide new insight into the pathogenesis of acute respiratory chlamydial infections in pigs.