Sequential development of esophagogastric ulcers induced in swine by infections with Ascaris suum goeze, 1782

Twenty-five experimental and five control hysterectomy derived pigs were raised colostrum free under specific pathogen-free conditions. The experimental pigs were first inoculated with A. suum eggs at 8 weeks of age, and a second dose of infective eggs was given 15 days later. They were necropsied from 4 to 10 days post second infection.The ulcers found in the stomach of these pigs were confined to the esophagogastric area. A sequence of epithelial changes, erosions, and ulceration was seen in the stratified squamous epithelium. Edema and hemorrhage were noted in the lamina propria and submucosa. Vascular changes in the area were characterized by thickening of the wall and presence of thrombi in arteries as well as cellular degeneration and vacuolization of the media and intima of the veins.Changes in the muscularis were characterized by edema and degeneration of the muscle cells, which later were replaced by fibroblasts and heavy infiltration by eosinophils.Three of the control pigs received one dose of A. suum eggs, and were killed one on each of the 8th, 9th, and 10th days post infection. The remaining two pigs received no infective material and were killed when they were 11 weeks of age. Neither the uninoculated pigs nor the once-inoculated animals developed ulcerations in their stomachs.The possible mechanisms by which esophagogastric lesions are produced following A. suum larval migrations are discussed.     

Culture requirements of Ascaris suum larvae using a stationary multi-well system: Increased survival,development and growth with cholesterol

Ascaris suum third-stage larvae (L₃) were converted from infected rabbits and cultured in a stationary multi-well plate system. Several different culture media including Mediuim 199, NCTC-135, Minimum Essential Medium-Eagle, Dulbecco's Modified Eagle's Medium, RPMI 1640, McCoy's 5A and Neuman-Tytell mdium were tested to determine which was best for overall larval survival, development and growth. Larvae developed from L₃ to fourth-stage (L₄) in all media tested, but larval survival and the yield and growth of L. were superior in RPMI 1640. Pyruvate is an important medium component because its addition to RPMI 1640 enhanced the yield and growth of L₄ while its removal from DMEM reduced larval survival and the yield and growth of L₄. Cholesterol markedly enhanced larval survival and the yield and growth of L₄ when added to RPMI 1640 as either a soluble supplement in Tween 80 or to a lesser degree, as a component of liposomes. The multi-well culture plate system is a convenient method for determining the effects of different media and changes in media composition on larvae in vitro.     

Ecological studies of Yersinia enterocolitica. II. Experimental infection with Y. enterocolitica in pigs

Fattening pigs were inoculated with the human pathogenic strains of Yersinia enterocolitica, biovar 4 serovar 3 phagovar 8 and biovar 2 serovar 5.27. Each pig received 2.6 × 10⁹ organisms by catheter into the stomach and thereafter 10% sodium bicarbonate solution, by the same route. The serovar 3 strain became established in the intestines of four out of six 11-week-old pigs and in all three 24-week-old pigs. Serovar 5.27 established in the intestines of all four 10-week-old pigs. In these pigs, both serovars were excreted in the feces at 10²?10⁶ cells g^?1 for a few weeks. However, the serovar 5.27 was excreted in the feces at less than 10^3·3 cells g^?1 for 2 weeks by 24-week-old pigs. Horizontal transmission with the serovar 5.27 strain was observed on the 5th–11th day, and the bacteria were present in the intestines during the 2nd week. However, the serum titers to O-agglutinin were 1/10 and less, but in one pig, the titer was 1/40 against serovar 5.27 strain.     

Establishment of Ascaris suum in the pig: development of immunity following a single primary infection

Development of immunity after a single primary infection of Ascaris suum in pigs was investigated with regard to the worm population dynamics of a superimposed A. suum infection, host immune response and gross liver pathological changes. Group A was given a primary infection of 60,000 infective A. suum eggs and group B was left uninfected. Four weeks later both groups A and B were inoculated with 1,000 A. suum eggs, and subgroups were slaughtered 7, 14 and 21 days post challenge infection (p.c.i.). An uninfected control group C was slaughtered on day 21 p.c.i. The challenge worm recovery in group A was reduced compared to group B by 12%, 50% and 75% on day 7, 14 and 21 days p.c.i., respectively. In both groups was the expulsion of worms initiated between day 14 and 21 p.c.i. However, in group A the worms were recovered more posteriorly in the small intestine and 21 days p.c.i. the mean worm length was significantly shorter than in group B (p = 0.01). The results above were associated with significantly higher (p < 0.05) antibody response and higher eosinophil counts in group A compared to group B. The present results suggest that the larval growth and survival of a challenge infection are decreased, probably due to higher antibody and eosinophil attack during the migratory phase.     

Experimental immunization of calves against Anaplasma marginale infection: observations on the use of living A. centrale and A. marginale

Groups of Bos indicus cross calves aged 6 months were immunized with Anaplasma centrale or A. marginale. All animals were challenged with 10¹⁰A. marginale 7 months later. Groups immunized with A. marginale were refractory to challenge, whereas only a portion of the animals vaccinated with A. centrale were immune. Following immunization, animals that had experienced a good primary antibody response as measured by a complement fixation test, a marked reduction in packed cell volume, and a high parasitaemia, resisted a subsequent challenge with A. marginale. Resistance was characterised by a weak secondary antibody response and the absence of A. marginale in blood films     

Protection against and establishment of Dictyocaulus viviparus following primary infection at different dose levels

In two experiments, calves were primary infected with 1 of 12 (Experiment 1) or 6 (Experiment 2) different dose levels of Dictyocaulus viviparus infective larvae (L3), ranging from 5 to 2000 L3. To study the level of protection induced by the primary infection a challenge infection with 2000 L3 was given on day 10 (Experiment 1) or day 35 (Experiment 2). In both experiments, challenge control calves were included. Eleven days later, the challenge calves were necropsied for worm counts. Results were compared with predictions from a simulation model. Establishment of the primary infection was dose independent, lying on average in the range of 20-30%. The ratio female:male worms in the counts from the primary or from the challenge infection was consistently close to 1:1 irrespective of primary infection dose level or protection having developed in some of the calves. Level of early protection (10 days after a primary infection-Experiment 1) against establishment of the challenge infection depended significantly on primary infection dose level (P<0.01). At 10 days, after a primary infection, low dose levels did not result in protection against a challenge infection. In contrast, similarly low dose levels did result in partial protection, 35 days after the primary infection. Results confirmed that our provisional simulation model satisfactorily predicts primary infection outcomes, but that it does not accurately predict levels of protection and immunity against re-infections.     

高低蛋白乳清粉对保育仔猪生产性能的对比试验

试验选用35日龄约9 kg保育仔猪为试验动物,随机分为2个处理组,分别含4%高、低蛋白乳清粉;每个处理设3个重复,每组10头仔猪。经过21 d饲养试验,研究高、低蛋白乳清粉对35日龄至56日龄保育仔猪生产性能的饲养效果。结果表明:使用高蛋白乳清粉提高了平均日增重,降低了料肉比和单位增重成本,且改善了毛皮外观。     

Seroprevalence and risk factors of Mycoplasma suis infection in pig farms in central China

Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1–ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR = 0.24; 95% CI: 0.07, 0.88; P = 0.031) and frequency of disinfection (OR = 0.23; 95% CI: 0.06, 0.90; P = 0.035) were protective factors, and the presence of mosquitoes and flies (OR = 5.994; 95% CI: 1.56, 23.00; P = 0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.     

Disease patterns and immune responses in the offspring to sows with high or low antibody levels to Actinobacillus pleuropneumoniae serotype 2

The serum antibody responses to Actinobacillus pleuropneumoniae and the secondary invader Pasteurella multocida were monitored from birth until slaughter in the offspring to sows with high or low levels of serum antibodies to A. pleuropneumoniae.Serum antibody concentrations to A. pleuropneumoniae were higher from birth to the age of 9 weeks in piglets delivered by high responding sows. In contrast, antibody levels to P. multocida were similar in both groups during this period. From the age of 20 and 15 weeks, antibody levels to A. pleuropneumoniae and P. multocida, respectively, were higher in the offspring to high responding sows.This implies that the offspring to sows with high levels of antibodies may be better protected during the first period of life because of a higher level of passively derived immunity. These piglets will also mount a higher antibody response when later infected, indicating a heritability of the humoral immune response.     

Assessment of the long-term shedding pattern of Salmonella serovar choleraesuis following experimental infection of neonatal piglets.

In the United States, swine salmonellosis is most often attributed to infections by Salmonella serovar choleraesuis. As a host-adapted pathogen rarely found in nonswine sources, S. choleraesuis is thought to be spread primarily via horizontal transmission, with carrier animals playing an important role. Little has been reported regarding infection of neonatal piglets, particularly regarding their potential to become carriers. Evidence reported herein demonstrates that piglets experimentally infected by S. choleraesuis at 2 days of age were capable of shedding the pathogen for up to 85 days postinfection, at which time the study was concluded. This study also presents findings supporting the use of GN-Hajna as a preenrichment medium for the isolation of S. choleraesuis.     

Life cycle of Isospora suis in gnotobiotic and conventionalized piglets

Isospora suis had 3 asexual and 1 sexual intra-intestinal conventional life cycle. The first asexual generation was most prominent at 2 days p.i. (post inoculation) and produced 2–7 merozoites. The second-generation meronts were prevalent at 3–4 days p.i. and produced 2–12 large merozoites. At 4–5 days p.i. the third generation meronts were prominent and produced 4–24 small crescent shaped merozoites. Mature sexual stages were most prominent at 5–6 days p.i. The stages were most numeroous in the distal half of the small intestine. At 8–9 days p.i. stages morphologically similar to the second generation of meronts reappeared, followed by the further development into third generation merozoites and sexual stages. This was reflected in a prepatent period of 5 days and a biphasic patent period of 5–8 or 9, and 11–14 days p.i.Intraperitoneal injection of liver/spleen and intestinal lymph node homogenates, respectively, from piglets infected 24 and 48 h, previously with high doses of oocysts, resulted in a patent infection 10–12 days post inoculation of the donor piglets. No differences in the life cycle of I. suis were observed between conventionalized and germ-free piglets. An extra-intestinal life cycle of I. suis related to the second patent period was postulated.     

Experimental Ostertagia spp. infection of sheep: Populations and lesions in previously worm-free and previously exposed animals

Sheep raised and maintained under worm-free conditions were subjected to one heavy exposure and several low-level exposures of infective Ostertagia spp. larvae. The infections were terminated by treatment with thiabendazole. These sheep and not previously exposed controls were then challenged with 400 000 or 20 000 Ostertagia spp. larvae and killed after a further 8 days. In the previously exposed sheep, worm numbers, rate of worm development, and pathological effect, were greatly reduced. No significant differences were seen between sheep aged 6 and 18 months at the time of challenge.     

仔猪大肠杆菌病的病原分离鉴定

仔猪大肠杆菌病是危害仔猪较严重的传染性疾病之一 ,特别是仔猪黄痢和白痢常引起仔猪发育不良 ,饲养成本增高 ,严重时导致大量死亡[1,2 ] 。目前在一些大型和个体养猪场中 ,由于饲养管理不良 ,卫生条件差 ,消毒不严 ,常暴发大肠杆菌病。在临床上由于缺乏化验条件 ,加之生产上盲目滥用药物 ,导致大肠杆菌的耐药菌株不断产生 ,致使该病的控制越来越难 ,给养猪业带来严重经济损失。生产实践中 ,我们接触到许多疑为该病的病猪 ,为了进一步确诊 ,并给该病防治上提供可靠依据 ,从而指导生产 ,减少该病带来的经济损失 ,因此进行了以下试验 ,报告如…     

Mycobacterium bovis infection in the brush-tailed possum (Trichosurus vulpecula): I. Preliminary observations on experimental infection

An Australian cattle strain of Mycobacterium bovis was injected intramuscularly into 10 brush-tailed possums (Trichosurus vulpecula) which were shown to be highly sensitive to experimental infection with this organism. The possums were killed and examined throughout the course of infection. At necropsy, gross and microscopic lesions were recorded and several tissues cultured for recovery of M. bovis. Infection spread rapidly via the lymphatic system from the injection site to the lumbar lymph nodes, then to the spleen. There was a bacteraemia after 2 week and by 6 weeks lesions were present in spleen, lymph nodes, lungs and kidneys; M. bovis proliferated rapidly and host response was minimal. Few organisms were detected in the liver where miliary lesions were found. M. bovis was excreted in large numbers in urine, faeces and discharging sinuses from subcutaneous abscesses. In two possums that died early in the infection, stress had rendered then more susceptible; infection spread more rapidly than in other possums and liver involvement was more severe. Although aerosol transmission was considered to be a possible means of spreading M. bovis, three in-contact possums did not acquire infection.     

Experimental Actinobacillus pleuropneumoniae infection in piglets with different types and levels of specific protection: immunophenotypic analysis of lymphocyte subsets in the circulation and respiratory mucosal lymphoid tissue

Actinobacillus pleuropneumoniae (APP) infection in piglets results in severe and fatal fibrinous hemorrhagic necrotizing pneumoniae. The aim of our study was to analyze changes in lymphocyte subset distribution in peripheral blood, bronchoalveolar lavage fluid (BALF) and tracheobronchal lymph nodes (TLN) in non-immune piglets upon a challenge with a high dose of APP and to compare the quality of such changes in unprotected piglets with counterparts exhibiting specific immunity mediated by high titers of colostrum-derived APP-specific antibodies and/or a low dose APP infection in the early postnatal period. Challenge with APP resulted in a massive increase in CD8-negative gammadelta T-cells in parallel with a reduction in numbers of CD3-CD8low cells in BALF independent of the type and level of immunity and this seems to be a general phenomenon associated with experimental infection. An increase in B-lymphocyte numbers in TLN was another characteristic feature accompanying APP infection in all experimental groups. In piglets with colostrum-derived APP-specific antibodies, this was associated with higher relative numbers of IgM+CD2+ lymphocytes in TLN, while B-cells with the CD2- surface phenotype apparently expanded in the absence of passive humoral immunity.     

Experimental studies on the pathogenesis of Coli-enterotoxemia in swine. 4. Effect of lipopolysaccharide endotoxin on weaned piglets following parenteral administration]

Ten clinically intact weaned piglets were experimentally intoxicated by intravenous injection of lipoproteide-free lipopolysaccharide endotoxin according to Westphal of E. coli O 127:B8. Severe endotoxin shock with all clinical manifestations of experimental coli-enterotoxaemia was induced in all animals and included circulatory disorder with tachycardia, intermittent pallor and/or cyanosis, symptoms of severe systemic intoxication, neurological symptoms, such as lack of coordination, hindleg staggering, spasm, paresis, paralysis, changes in respiration, such as rise in respiratory frequency and deepened breathing premortal deceleration of respiration and gasping for breath, temperature, variation, including hyperthermia and aggravating hypothermia, gastro-intestinal symptoms, such as temporary vomiting and persistent diarrhoea, leucopenia, eosinopenia, variation of haematocrit, edematisation, increased transudation, congestion, and gastro-intestinal shock lesions. Eight animals died. These experiments quite obviously have confirmed that endotoxin shock is the common pathogenetic principle behind all forms of coli-entertoxaemia (i.e, the forms of edematisation, cardiovascular failure, and gastro-intestinal processes.) Lipopolysaccharide endotoxin alone may be responsible for the development of both edemas and neurotoxic symptoms (edema disease) and diarrhoea (gastro-intestinal form of coli-enterotoxaemia). The pathogenetic relevance of additional toxins (neurotoxin and enterotoxin) is discussed under this aspect.