Experimental infection with Mycobacterium avium, serotype 2, 2. Oral infection with large doses of M. avium

Twelve pigs were inoculated orally with Mycobacterium avium. The doses used were 0.5, 2 or 10 mg daily for 5 days, or 10, 50 or 180 mg once (1 mg = 37 × 10⁶ viable units). Two pigs were used per dose, 1 of which was sacrificed 3 days, the other 28/31 days after the last inoculation (Table 1).Three days after inoculation, M. avium was found in the tonsils and in the intestinal mucosa of all 6 pigs, and in the mesenteric lymph nodes of 4. Viable unit counts for tonsils and intestinal mucosa were highest in pigs inoculated with 180 mg×1 and 10 mg×5. Histopathologically these pigs showed activation of the lymphoid tissue in the tonsils, Peyer patches and mesenteric lymph nodes. Twenty-eight/31 days after inoculation a spreading of the infection had taken place in all pigs, most often to the liver, less frequently to the spleen and the lungs. The kidneys and the musculature were not infected (Table 4). A correlation was apparent between the size of dose and the number of viable organisms in the tissues. Divided doses gave about 10 times higher viable counts than a single dose with the same total number of organisms (Table 5).No gross lesions were found 28/31 days after inoculation. Microscopic granulomatous lesions were found in the tonsils of 6 pigs, in the intestinal mucosa of 4 pigs, in the mandibular and mesenteric lymph nodes of 6 pigs, in the retropharyngeal lymph nodes of 3 pigs, and less frequently in the parotid and hepatic lymph nodes (Table 3).Five of 6 pigs were weakly sensitive to avian tuberculin PPD, 1000 t.u. per dose, when tested 22/25 days after inoculation; 1 of these pigs cross-reacted to human tuberculin (Table 2).     

Multiplication of attenuated and virulent porcine parvoviruses in colostrum-deprived, neonatal pigs

Colostrum-deprived, neonatal, 2 days old pigs were inoculated with the attenuated HT-/SK or the virulent 90HS strain of porcine parvovirus (PPV) by the oral or subcutaneous route and sacrificed 2, 4 or 6 days after inoculation. Then, comparison was made on viral multiplication in pigs between the two strains. Pigs inoculated with the HT-/SK strain showed no detectable viremia or HI antibody responses against PPV within 6 days after inoculation. Only in pigs inoculated by the subcutaneous route, a small amount of virus was recovered from the spleen, liver, or mesenteric lymph nodes. These viruses were distinguished from the parental virulent 90HS strain, as examined for rct maker in vitro. When pigs were inoculated with the virulent 90HS strain, viremia appeared in all of them 1 day after inoculation and continued for up to the sacrificed day. Moreover, a considerable amount of virus was also detected from all tissues, including brain, lung, liver, spleen, pancreas, small intestine, and lymph node tissues, in all pigs tested. HI antibodies were first detected 6 days after inoculation.     

Granulomatous lesions in lymph nodes of slaughter pigs bacteriologically negative for Mycobacterium avium subsp. avium and positive for Rhodococcus equi

The prevalence of granulomatous lesions in lymph nodes of pigs was studied. From January till August 2004 in two slaughterhouses in The Netherlands 2,116,536 pigs were examined for the presence of granulomatous lesions in the sub-maxillary lymph nodes. In 15,900 (0.75%) of these pigs, lesions could be detected. Nine farms with the highest incidence of lesions were selected for a more detailed pathological and bacteriological examination. On these farms, the prevalence of lesions in sub-maxillary lymph nodes ranged from 2.3 to 5.7% with a mean of 3.0%. From 1276 pigs that were sampled, 98 (7.7%) displayed granulomatous lesions in the sub-maxillary lymph nodes and one (0.1%) pig showed lesions in its mesenteric lymph node. Mycobacterium avium subsp. avium (MAA) could not be isolated from the lymph nodes of the 99 pigs with lesions and from a selection of lymph nodes (n = 61) of pigs without lesions. Rhodococcus equi was isolated from 44 out of 98 (44.9%) of the sub-maxillary lymph nodes with granulomatous lesions and from two mesenteric lymph nodes without lesions. A comparison of former studies and the current results indicate that the prevalence of MAA infections in slaughter pigs has strongly decreased over the last decade, whereas R. equi is highly prevalent. The high incidence of granulomatous lesions associated with the bacteriological presence of R. equi could be considered as a serious cause of misdiagnosis of MAA infections in cases where meat inspection is carried out by inspection for granulomatous changes of lymph nodes only.     

Granulomatous lymphadenitis associated with Actinobacillus pleuropneumoniae serotype 2 in slaughter barrows

This study evaluated the occurrence of granulomatous lymphadenitis and its association with Actinobacillus spp. in 151 653 slaughtered pigs. Markedly enlarged pulmonary hilar, mediastinal, mandibular or hepatic lymph nodes were detected in 6 castrated males. The cut surfaces showed multifocal yellow-white lesions. Histologically, gram-negative bacilli were visible in the centers of the lesions with asteroid bodies, epithelioid cells, and multinucleated giant cells. Dense fibrous connective tissue surrounded these granulomatous lesions. Immunohistochemically, the organisms reacted with polyclonal antibodies against Actinobacillus pleuropneumoniae serotype 2 in all 6 barrows. The organism was isolated from the lymph nodes of all 6 animals. The results indicate that the granulomatous lymphadenitis was associated with A. pleuropneumoniae serotype 2 and the disorder had a tendency to occur in slaughter barrows.     

Infection of pigs with transmissible gastroenteritis virus from contaminated carcases

Sixteen 6-month-old pigs were exposed to transmissible gastroenteritis (TGE) virus by placing them in close contact with piglets infected at 1 week of age. Fourteen of the older pigs were slaughtered between 1 and 5 d after exposure to infection and their carcases dressed in simulated abattoir conditions. Samples of muscle, bone marrow and carcase lymph nodes were stored at -25 degrees C for at least 30 d and then homogenised and fed to groups of 1-week-old and 3-week-old pigs. Four of 12 one-week-old pigs died and TGE virus was isolated from intestinal contents of one of these. All pigs of both age groups developed neutralising antibody to TGE virus over the ensuing 4 w. The results indicate that carcases from pigs infected with TGE virus can represent a source of infection for susceptible pigs given access to them.     

Manipulation of the type of fat consumed by growing pigs affects plasma and mononuclear cell fatty acid compositions and lymphocyte and phagocyte functions

To investigate the immunological effect of feeding pigs different dietary lipids, 3-wk-old, weaned pigs were fed for 40 d on one of five diets, which differed only in the type of oil present (the oil contributed 5% by weight of the diet and the total fat content of the diets was 8% by weight). The oils used were soybean (control diet), high-oleic sunflower oil (HOSO), sunflower oil (SO), canola oil (CO), and fish oil (FO; rich in long-chain [n-3] polyunsaturared fatty acids). There were no significant differences in initial or final animal weights, weight gains, or health scores among the groups. There were no significant differences in the concentration of anti-Escherichia coli vaccine antibodies in the gut lumens of pigs fed the different diets. The fatty acid composition of the diet markedly affected the fatty acid composition of the plasma and of mononuclear cells (a mixture of lymphocytes, monocytes, and macrophages) prepared from the blood, lymph nodes, or thymus. The FO feeding resulted in a significant increase in the number of circulating granulocytes. The FO feeding significantly decreased the proportion of phagocytes engaged in uptake of E. coli and decreased the activity of those phagocytes that were active. The proliferation of lymphocytes in cultures of whole blood from pigs fed the HOSO, SO, or FO diets was less than in those from pigs fed the CO diet. Proliferation of lymph node lymphocytes from SO- or FO-fed pigs was less than that from control, CO-, or HOSO-fed pigs. The natural killer cell activity of blood lymphocytes from pigs fed the FO diet was significantly reduced compared with those from pigs fed the CO diet. The concentration of PGE2 in the medium of cultured blood, lymph node, or thymic mononuclear cells was lower if the cells came from pigs fed the FO diet. Thus, the type of oil included in the diet of growing pigs affects the numbers and functional activities of immune cells in different body compartments.     

一例猪瘟与猪圆环病毒2型混合感染的诊治

在生猪养殖过程中,多种病原混合感染的情况较为常见,并这种混合感染也导致传统的临床诊断容易造成误诊或漏诊,继而延误诊断治疗从而造成经济损失。2020年8月初,孟连县某养猪场保育猪群零散发病,临床主要表现为发热、咳喘、打堆、被毛凌乱无光泽、局部皮肤发绀、消瘦、饮食欲下降、生长滞缓,个别猪只伴便秘和腹泻交替。病理剖检变化显示为肾脏点状出血,脾脏边缘梗死,胸腹腔淋巴结、肠系膜淋巴结、下颌淋巴结、腹股沟淋巴结肿大或伴有出血,肺炎伴局部肝变,回盲瓣或局部空回肠黏膜脱落、出血、坏死或溃疡。实验室诊断结果表明,该病由猪瘟病毒(CSFV)与猪圆环病毒2型(PCV2)混合感染所致,经过猪瘟及猪圆环病毒疫苗的加强免疫,辅助控制继发感染及对症治疗,该场保育猪群全部恢复健康。     

Activated carbon does not prevent the toxicity of culture material containing fumonisin B1 when fed to weanling piglets

Fumonisins are mycotoxins found primarily in corn and corn products that are produced by Fusarium verticillioides, F. proliferatum, and several other Fusarium species. The toxicity of fumonisin B1 (FB) from culture material with and without activated carbon was evaluated using weanling piglets. Fifty-six weanling pigs were assigned to one of four treatments diets based on BW. The treatment diets were 1) control = corn-soybean basal diet with < 2 ppm FB; 2) AC = control + activated carbon at 1% of the diet, as fed; 3) FB = control + culture material (formulated to contain 30 ppm FB, as-fed basis); and 4) AC + FB = control + activated carbon at 1% of the diet as fed + culture material (formulated to contain 30 ppm FB). A total of four replicates of four pigs per pen for the control and AC treatments and three piglets per pen for the FB and AC + FB treatments were used. Feed and water were offered ad libitum for the duration of the 42-d experiment. Compared with pigs fed the control or AC diets, pigs receiving the two FB-contaminated diets (FB or AC + FB) had lower G:F (P < 0.01), higher serum enzyme activities of gamma-glutamyltransferase and glutamic oxaloacetic transaminase (P < 0.05), and higher concentrations of cholesterol, free sphinganine, sphingosine-1-phosphate, and sphinganine 1-phosphate (P < 0.05). Although animals consuming FB diets showed no signs of respiratory distress, all pigs consuming either the FB or the AC + FB diets had marked pulmonary edema. Lesions were observed in the lungs, heart, and liver of pigs fed the FB or AC + FB diets, and treatment-associated changes also were seen in the pancreas, intestines, spleen, and lymph nodes. No lesions were observed in the brain. In liver, lung, heart, pancreas, spleen, intestines, and lymph nodes, the histopathological effects observed were more severe in the AC + FB group, suggesting that the AC treatment worsened the toxic effects of FB. Additionally, immunological measurements of macrophage function (CD14) were affected (P < 0.05) by the consumption of the FB diets. The consumption of FB diets containing 30 ppm fumonisin B1 from cultured material significantly affected performance, biochemical measurements, and organ pathology in weanling pigs. The addition of activated carbon at the rate of 1% to the diet was not effective in protecting against the detrimental effects of fumonisin consumption.     

Postweaning multisystemic wasting syndrome induced after experimental inoculation of cesarean-derived, colostrum-deprived piglets with type 2 porcine circovirus.

Cesarean-derived, colostrum-deprived pigs (n = 23) were inoculated intranasally and subcutaneously with a low cell culture passage of type 2 porcine circovirus. In 11 pigs, a persistent fever that lasted 7-17 days began 12-15 days after inoculation with virus. Additional signs of disease in those 11 pigs included depression (11 of 11 pigs), palpable enlargement of inguinal, prefemoral, and popliteal lymph nodes (11 of 11), icterus (6 of 11), and hyperpnea (2 of 11). The remaining 12 pigs had fever that occurred intermittently for 2-4 days between days 12 and 20 postinoculation. Overt signs of disease in those pigs were limited to palpable enlargement of inguinal and popliteal lymph nodes (9 of 12 pigs). When compared with control pigs of similar age, the average daily rate of weight gain for all pigs inoculated with virus was less over a 2-week period that began 2 weeks post inoculation. At postmortem examination, lymph node enlargement was seen in 14 of 14 pigs euthanized between days 20 and 28 postinoculation. Lymph node enlargement was especially prominent in pigs that developed a persistent fever. Microscopic lesions noted in pigs that developed a persistent fever included cellular depletion in lymphoid tissues; hepatic cell necrosis; and lymphogranulomatous inflammation of lymph nodes, Peyer's patches of the intestine, liver, kidney, and heart. Virus was isolated with varying frequency from nasal, rectal, or tonsil swab specimens, buffy coat, serum, urine, and lung lavage fluid obtained antemortem or postmortem. Virus was isolated from or viral DNA was detected in a variety of tissues obtained postmortem up to 125 days postinoculation. Antibody against type 2 porcine circovirus usually was detected in serum between 15 and 20 days postinoculation; however, antibody against virus was not detected in serum from 4 pigs euthanized 20-24 days postinoculation. Direct contact with pigs inoculated with virus 42 days previously resulted in transmission of virus to 3 of 3 control pigs.     

Effect of dietary copper and vitamin E supplementation, and extensive feeding with acorn and grass on longissimus muscle composition and susceptibility to oxidation in Iberian pigs

The objective of this study was to assess the effect of dietary copper and/or vitamin E supplementation on composition and oxidation of M. longissimus in Iberian pigs and to compare it with meat samples from pigs produced extensively and fed with acorn and grass. Grass had the highest α-tocopherol content (> 150 mg/kg DM), while acorns had the highest copper concentration (78.1 mg/kg DM). Dietary treatment did not affect copper composition in muscle and no interactions were detected between copper and α-tocopherol. The α-tocopherol content in muscle from pigs fed diets supplemented with α-tocopheryl acetate (100 mg/kg feed) was 1.5 times greater (p < 0.0001) than those from pigs receiving a basel diet. M. longisssimus dorsi from pigs fed extensively had a higher concentration of α-tocopherol than those fed in confinement with the basel level of α-tocopheryl acetate, but lower values than pigs fed supplemented levels. Total n -3 fatty acids (p < 0.02) and hematin (p < 0.0001) concentrations were significantly higher in muscle from pigs fed extensively than when fed in confinement. Muscle homogenates from Iberian pigs fed in extensive conditions showed significantly (p < 0.02) higher susceptibility to oxidation than those from pigs fed mixed diets. Dietary α-tocopheryl acetate supplementation (100 mg/kg feed) significantly (p < 0.05) reduced lipid oxidation of muscle, while dietary copper concentration did not modify susceptibility to lipid oxidation.     

Zoonotic risk of Toxocara canis infection through consumption of pig or poultry viscera

The potential zoonotic risk of Toxocara canis infections from consumption of swine or poultry viscera containing larvae was assessed using a pig model. Two groups of six pigs were fed either fresh swine viscera (group FS) or poultry viscera (FP) containing around 3500 Toxocara larvae. Another two groups of six pigs were fed swine viscera (PS) or poultry viscera (PP) preserved at 4 degrees C for 1 week. All pigs were necropsied 14 days after the exposure. Liver white spots were counted and T. canis specific IgG antibodies were measured by ELISA. Larval burdens were assessed in the mesenteric lymph nodes, liver, lungs, brain, tongue, and eyes. All recipient pigs exhibited several white spots on the liver surface and detectable antibody levels. Larvae were recovered predominantly from the lungs, but also from the mesenteric lymph nodes and the liver, a few larvae were found in the brain and tongue of the pigs. Two larvae were found in the eyes of two pigs in group FS. Mean percentages of total larval recoveries in groups FS, FP, PS, and PP were 75.3, 63.6, 42.6, and 18.8%, respectively. Significantly higher numbers of larvae were recovered from pigs given swine viscera than pigs given poultry viscera. The preservation at 4 degrees C for 1 week caused a significant reduction in the larval infectivity overall, nevertheless, the recoveries remained substantial. The fact that larvae migrating in swine or poultry organs and tissues have high infectivity in pigs even after preservation at 4 degrees C for 1 week, suggests that human infection with T. canis might easily occur following consumption of raw or undercooked dishes, either fresh or refrigerated, prepared from swine or poultry organs and tissues harbouring T. canis larvae.     

Experimentally induced Mycobacterium avium serotype 8 infection in swine.

Five of 6 swine experimentally inoculated with Mycobacterium avium serotype 8 had microgranulomas in the cervical or mesenteric lymph nodes at necropsy 92 days later. In vivo tuberculin skin reactivity and in vitro lymphocyte immunostimulation responses were evaluated at 10 and 12 weeks after the pigs were inoculated. Positive responses were obtained on both tests in inoculated pigs, whereas test results in noninoculated pigs and pigs given killed bacterial cells were negative. Mycobacterium avium serotype 8 was isolated at necropsy from the cervical or mesenteric lymph nodes of each of the pigs inoculated with viable microorganisms and from the 2 pigs kept in the pen with inoculated swine. Mycobacteria were not isolated from tissues of the noninoculated swine or those given killed cells.     

Typing of Rhodococcus equi isolated from submaxillary lymph nodes of pigs in Japan

Isolation of Rhodococcus equi from the submaxillary lymph nodes of pigs, with or without caseous lymphadenitis, and typing of the isolates by two serological methods were carried out. The rate of isolation of the organisms from the lymph nodes of pigs was 5 times higher in the lymph nodes with caseous lymphadenitis than in those without the lesion. Of 219 isolates, 146 (66.7%) were typable by the method of Prescott, while all the 219 isolates (100%) were typable by the method of Nakazawa et al. The most frequently isolated were serotype 2 of Prescott (identical to serogroup 16 of Nakazawa et al.), and serogroup 3 of Nakazawa et al., which did not correspond with any serotypes of Prescott. Serotypes/serogroups of R. equi from pigs were thus first clarified in Japan.     

Barley-derived β-glucans increases gut permeability, ex vivo epithelial cell binding to E. coli, and naive T-cell proportions in weanling pigs

Weaning in young animals is associated with an increased incidence of gastrointestinal infections. β-glucans exert numerous physiological effects, including altering immune function. The objective of this study was to determine the effects of feeding barley (Hordeum vulgare L.)-derived β-glucans on immune and intestinal function in weanling pigs (Sus scrofa). Thirty-one individually-housed Dutch Landrace pigs (21 d; initial BW, 6,298 ± 755 g) were weaned and fed a wheat-based diet (control) or a low (Lo-BG), medium (Med-BG), or high β-glucan-containing barley-based diet (Hi-BG) for 2 wk with 7 or 8 pigs/treatment. Intestinal segments were analyzed for permeability using Ussing chambers and K88 Escherichia coli adhesion to enterocytes was assessed ex vivo. Immune cells from mesenteric lymph nodes, peripheral blood, and Peyer's patches were analyzed for lymphocyte subsets by indirect immunofluorescence and the ability to respond ex vivo to mitogens by (3)H-thymidine incorporation. Hematology and neutrophil function were determined by flow cytometry. Neutrophil burst, size, and granularity, lymphocyte proliferation, and B-cell distribution in peripheral blood lymphocytes, Peyer's patches, and mesenteric lymph nodes were not affected by β-glucans content of the diet. The β-glucans content of the diet altered blood concentrations of erythrocytes and leukocytes, CD4, CD45RA, and CD8 blood cells (P < 0.05). In addition, feeding β-glucan resulted in increased (P < 0.05) percentage CD45RA positive cells in peripheral blood lymphocytes, Peyer's patches, and mesenteric lymph nodes. Mannitol permeability and tissue conductance were increased (P < 0.05) in Hi-BG fed pigs compared with control pigs. Percentage maximum K88-E.coli binding was increased in proportion to the β-glucan content of the diet (P < 0.05). Although β-glucan feeding during the weaning period increased blood lymphocytes and the proportion of na?ve T-cells, it also increased E. coli-enterocyte binding and intestinal permeability. β-glucan may alter immune and intestinal function of weaning pigs.     

Virulence genes and plasmid profiles in Rhodococcus equi isolates from domestic pigs and wild boars (Sus scrofa) in Brazil

The virulence genes and plasmid profiles of 23 Rhodococcus equi isolates from 258 lymph nodes from domestic pigs (129 nodes with lesions and 129 without lesions) and 120 lymph nodes from slaughtered wild boars (60 nodes with lesions and 60 without) were characterized. R. equi was obtained from 19 lymph nodes of domestic pigs, 17 with, and two without lesions, and from four lymph nodes with lesions, from wild boars. The 23 isolates were tested for the presence of vapA and vapB genes, responsible for the 15–17 and 20 kDa virulence-associated proteins, respectively, by PCR in order to characterize as virulent (VapA), intermediately virulent (VapB) and avirulent. Plasmid DNAs were isolated and analyzed by digestion with restriction endonucleases to estimate size and compare their polymorphisms. Of the 19 domestic pigs strains, seven (36.8%) were avirulent and 12 (63.2%) were intermediately virulent, with the intermediately virulent isolates being plasmid types 8 (8 isolates), 10 (2 isolates), 1 (1 isolate) and 29 (1 isolate). The plasmid type of four strains isolated from wild boars was also intermediately virulent type 8. None of the domestic pigs and wild boar isolates showed the vapA gene. These findings demonstrate a high occurrence of plasmid type 8 in isolates from pigs and wild boars, and the similarity of plasmid types in the domestic pigs, wild boars and human isolates in Brazil.     

An outbreak of tuberculosis in pigs and cattle caused by Mycobacterium africanum.

An outbreak of tuberculosis in pigs and cattle caused by Mycobacterium africanum produced lesions in the pigs similar to those caused by M tuberculosis, M bovis and M avium, with caseation in the lymph nodes of the head and in the jejunal lymph nodes. Bacteriological examination of the dysgonic mycobacteria isolated showed that they were M africanum I. The intradermal tuberculin test was very reliable in pigs, differentiating between mammalian and avian reactions, and the results of the test were in accordance with the lesions found at meat inspection. No clinical signs were observed during the outbreak, and the infection was neither serious nor progressive. There were no lesions in the tuberculin-positive cattle. The source of the infection remains unknown.     

ORIGINAL ARTICLE: Effects of herbage ingestion upon ileal digestibility of amino acids in heavy Iberian pigs fed on an acorn‐based diet

We conducted two experiments with heavy Iberian pigs to determine the ileal digestibility of amino acids (AA) in acorns and freshly cut herbage, and the effects of adding fresh herbage upon the supply of ileal digestible AA when pigs were fed on holm‐oak acorns. In Experiment 1, carried out in cannulated pigs of 107 kg bodyweight (BW), daily intake of acorns reached 44.9 g DM/kg^0.75 BW. Arg, His and Thr showed the lowest apparent ileal digestibility (AID) values, whereas Met, the branched‐chain AA and Phe had the highest coefficients. The AID of total EAA was 0.716 but only 0.222 for NEAA. Most of the digestive and absorptive processes of acorn protein occurred before the hindgut. Acorn provides (per kg DM) 2.27 g apparent ileal digestible Lys and 22.7 g apparent total digestible AA. Standardized ileal digestibility (SID) values for EAA, NEAA and total AA were 0.924 ± 0.020, 0.784 ± 0.041 and 0.860 ± 0.029. In Experiment 2 fresh herbage was given to six cannulated Iberian pigs of 140 kg either as a single feed (13.7 g DM/kg^0.75 BW) or as a supplement to acorns (28.4 g DM/kg^0.75 BW). When only freshly cut forage was offered the AID of the EAA, NEAA and total AA was close to 0.65 and supplied (per kg DM ingested) 5.61 g AID Lys and 91.7 g digestible AA. Standardized ileal values were 0.744 ± 0.023, 0.912 ± 0.038 and 0.831 ± 0.030 respectively. The addition of fresh forage to the acorns led to a significant decrease in AID of AA in acorn due to digesta transfer to the hindgut: His (p < 0.01), Met (p < 0.001), Phe (p = 0.092), Thr (p < 0.05) and Val (p < 0.05), but Arg, Lys and the branched‐chain AA remained unaffected. The main contribution of herbage to AA nutrition of the grazing Iberian pig relies mainly on increasing the supply of digestible AA for pig tissues.     

Branched Mycobacterium-like organisms from swine lymph nodes

Branched, weakly acid fast organisms were isolated from 5 of 112 caseous lymph nodes derived from slaughter-house pigs. In two cases they were associated with typical Mycobacterium avium strains. The bacteria differed from all other mycobacteria known at present. Limited experiments in pigs with one strain failed to disclose a possible pathogenic role in the host species although this strain was pathogenic for mice. Tests with this and three other strains showed that all four were apathogenic for chickens.     

Effect of infections with swine fever virus on immune functions II. Lymphocyte response to mitogens and enumeration of lymphocyte subpopulations

Peripheral blood and spleen lymphocytes from pigs infected with a low-virulent strain of swine fever virus (SFV) were transiently hyporesponsive to the mitogenic action of PHA, PWM and Con A. The mitogenic reactivity of lymphocytes from lymph nodes from such pigs appeared to be enhanced rather than depressed at that time. In addition, hyperresponsiveness of peripheral blood lymphocytes (PBL) to these mitogens occurred in some pigs.PBL from pigs lethally infected with virulent SFV showed a persistent depression of the response to these mitogens, whereas lymphocytes from lymph nodes had a high responding capacity.A lymphocyte response to SFV antigens could not be demonstrated in infected pigs.These SFV infections did not markedly affect the percentage of lymphocytes in the blood and most lymphoid organs rosetting with sheep red blood cells. On the other hand, surface immunoglobulin-bearing lymphocytes were markedly increased in lymph nodes from pigs exposed to virulent SFV. The sum of both lymphocyte subpopulations in the lymph nodes from these pigs often considerably exceeded the 100% value, which strongly suggests the presence of cells bearing both surface immunoglobulin and receptors for dextran-treated sheep red blood cells.Possible correlations between these findings are discussed. The results suggest that infections with SFV induce systemic alterations in the process of lymphocyte recirculation in the pig.     

THE ISOLATION OF SALMONELLA FROM JEJUNAL AND CAECAL LYMPH NODES OF SLAUGHTERED ANIMALS

One jejunal and one caecal lymph node were sampled from each of 50 cows, 40 yearling cattle, 25 sheep, 20 lambs and 45 pigs after slaughter. Salmonella, Clostridium perfringens and Staphylococcus aureus , all organisms which cause food poisoning in man, were sought by direct plating methods. The samples were also enriched and cultured for Salmonella. Organisms were cultured from 208 (58%) of the 360 lymph nodes; aerobic plate counts yielded up to 25,000 organisms per gram of tissue, although from most infected samples less than 1000 organisms per gram were cultured. Salmonella was isolated directly from 5% of samples, with counts up to 1,500 per gram. After enrichment Salmonella was isolated from nodes taken from 15 cows, 2 yearling cattle, one sheep and 8 pigs. Cl. perfringens was isolated from the caecal nodes of 2 yearling cattle and 2 pigs; S. aureus was not isolated from any sample. It was concluded that mesenteric lymph nodes may be a significant reservoir of Salmonella for transfer to meat and meat products.