Non-lethal infection parameters in mice separate sheep Type II Toxoplasma gondii isolates by virulence

The zoonotic protozoan parasite Toxoplasma gondii can infect all warm-blooded animals, but virulence of isolates has previously been characterised mainly by the ability to kill mice after experimental infections. In the present study, 15 Type II strains of T. gondii, isolated from five adult sheep, six sheep abortions, two pigs, one cat and one fox were examined for their virulence to young mice by less dramatic parameters. Clinical disease of inoculated mice, directly evidenced by reduced weight gain, was correlated to increase in serum level of haptoglobin and level of specific antibodies. Although Type II T. gondii strains are non-virulent to mice by lethality studies, significant differences in mouse virulence were observed between the strains of T. gondii isolated either from adult sheep or from sheep abortions. It was not possible to characterise strains isolated from sheep abortions as being more or less virulent than strains isolated from adult slaughter sheep.     

Studies on Erysipelothrix insidiosa S. rhusiopathiae. 1. Morphology, cultural features, biochemical reactions and virulence

Sixty-two E. insidiosa strains isolated from joints or regional lymph nodes of pigs were examined from the point of view of morphology, cultural aspects, biochemical activity and virulence. All the strains consisted of gram-positive, short rods, which were similar on solid and fluid media. All strains formed H₂S. Otherwise the biochemical activity was rather low except in 1 strain (no. 18), which was very active. One strain (no. 36) was rather inactive, since it showed no other activity than H₂S formation. This latter strain was the only one that was avirulent for mice. The rest of the strains (61) were strongly virulent for mice (LD50 0.5 × 10^−4.17 to 0.5 × 10^−8.5).Of 7 strains examined for virulence for pigs by intracutaneous injection of 0.1 ml broth culture, 6 were virulent. The 7th, which was avirulent, was the one that was also avirulent for mice.     

Comparison of inoculation regimes for the experimental production of swine erysipelas arthritis: I Clinical, pathological and bacteriological findings

The arthritic form of swine erysipelas was induced in pigs by multiple intravenous inoculation of 2 strains of Erysipelothrix rhusiopathiae. The strains differed significantly in their arthritogenicity but not in the number of cases of lameness induced. The use of 3 intravenous inoculations instead of 5 did not significantly affect the outcome. In a second trial, the more arthritogenic strain was injected in ten-fold dilutions from 5 x 10(9) to 5 x 10(4) organisms. Pigs receiving the lower doses showed high variability in their arthritic responses that precluded sensitive analysis of the dose effects on the number of arthritic and infected joints. However, slaughter weights showed a significant negative correlation with dose. Mean slaughter weights in treatment groups varied by 14.6 kg per pig, an average weight loss of 3 kg per pig for each ten-fold rise in dose of the highly virulent strain, and significantly correlated with the number of arthritic and infected joints. Culture of homogenised synovial membrane through selective horse meat-serum broth containing kanamycin, neomycin and vancomycin identified 66% and 59% more infected joints than primary blood agar culture of synovial fluid or synovial membrane homogenate, respectively.     

Classical swine fever virus infection modulates serum levels of INF-α, IL-8 and TNF-α in 6-month-old pigs

Several studies have highlighted the important role of cytokines in disease development of classical swine fever virus (CSFV) infection. In the present study, we examined the kinetics of 7 porcine cytokines in serum from pigs infected with 3 different CSFV strains. Based on the clinical picture in 6-month-old Danish pigs, the strains used for inoculation were classified as being of low (Bergen), low to moderate (Eystrup) and moderate to high (Lithuania) virulence. The cytokines interferon-alpha (INF-α), interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) showed increased levels after CSFV infection with more or less comparable course in the 3 groups. However, the cytokine level peaked with a 2–3 days delay in pigs infected with the low virulent strain compared to those infected with a moderately or highly virulent strain. These findings may indicate that INF-α, IL-8 and TNF-α are involved in the immune response during CSFV infection with strains of different virulence.     

The virulence of Dichelobacter nodosus,measured by the elastase test,is an important predictor for virulent footrot diagnosis in New South Wales sheep flocks

Ovine footrot is a contagious bacterial disease that causes foot lesions, and depending on the virulence of the causative strains, may lead to severe underrunning of the hoof and lameness. Virulent footrot can be identified, treated and controlled more effectively than less virulent benign forms. The in vitro elastase test for virulence of the causative bacteria, Dichelobacter nodosus, has been used to support clinical diagnosis. However, not all laboratory-designated virulent D. nodosus strains cause clinical signs of virulent footrot. This study evaluated retrospectively how well the elastase test supported clinical footrot diagnosis in 150 sheep flocks examined for suspect footrot in New South Wales between August 2020 and December 2021. Flocks were included if measures of clinical disease, environmental conditions and the virulence of D. nodosus isolates were available. Variation in the elastase activity result between D. nodosus isolated from the same flock made bacterial virulence hard to interpret, but calculating the mean elastase rate for all isolates from the same flock made correlations between bacterial virulence and flock footrot diagnosis possible. Simplifying bacterial virulence into whether there were any elastase-positive D. nodosus isolates before 12 days increased the predictive value of elastase results for virulent diagnosis, compared with using the first day that any isolate was elastase positive or the percentage of elastase-positive isolates by 12 days, but not all clinically virulent flocks had isolates with elastase activity before 12 days. Logistic regression models were fitted to identify the minimum number of predictors for virulent footrot diagnosis, with models suggesting that virulent footrot diagnosis was best predicted by adding the elastase test result and environmental conditions to the prevalence of severe foot lesions (score 4 and 5). However, performing the same analysis with different breeds, ages of sheep and seasons might highlight other factors important in the diagnosis of virulent footrot.     

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.     

Experimental infections of mice and pigs with Streptococcus suis type 2.

Five inbred strains of mice were tested for their susceptibility to Streptococcus suis type 2 including the type strain, two isolates from meningitis in pigs and two isolates from tonsils of clinically healthy pigs. C57BL/6, ICR and ddY strain mice showed lower susceptibility to all strains of S. suis type 2 than BALB/c and SS strain mice. The type strain and the isolates from diseased pigs produced septicaemia and meningitis in BALB/c and SS mice inoculated with 10(8) colony forming unit of the bacteria and 60 to 100% of these infected mice died. On the other hand, mice inoculated with the isolates from healthy pigs showed mild clinical signs but none of them died. In BALB/c mice which died or developed nervous signs, the purulent meningo-encephalitis, myocarditis, ophthalmitis, labyrinthitis and otitis media were observed. S. suis type 2 antigen was demonstrated in these lesions by immunoperoxidase staining using rabbit S. suis type 2 antiserum. These results were similar to those in the experimentally infected pigs with these virulent and avirulent strains against mice. These results indicate that BALB/c and SS strains of mice are useful as an experimental model of S. suis type 2 infections in pigs, and that there are virulent and avirulent strains against mice and pigs among the strains of S. suis type 2.     

Involvement of trauma in the pathogenesis of osteochondritis dissecans in swine.

Limb joint soundness was examined in 40 pigs loaded into a wooden box cart and 40 control pigs not subjected to loading. On postmortem examination, eight loaded pigs showed osteochondritis dissecans in their medial humeral condyles, suggesting that porcine joints are vulnerable to osteochondral lesions when mechanically overloaded. Prevention of trauma by careful handling of pigs during penning and transportation should help to control joint lesions and lameness.     

Relationship between serotype, virulence and SDS-PAGE protein patterns of Haemophilus parasuis

141 Haemophilus (H.) parasuis and 8 H. parasuis-like strains from different farms were serotyped according to Morozumi and Nicolet (1986 b) as well as to Bakos et al. (1952). It was possible to classify 72.8% of the investigated strains. 7 out of 12 serotypes have been described for the first time. The high specificity in the agar gel precipitation test was not reproducible in the more sensitive dot-blot procedure. The dot-blot results point to a participation of non-immunogenic polysaccharides in the detection reaction. The serotypes SV 1, SV 5, SV Jena 6 and SV Jena 10 proved to be highly virulent in SPF pigs, SV 2 and SV 4 were of medium virulence. The other serotypes were found to be nonvirulent. Unencapsulated strains and isolates of serotype SV 5 prevailed in animals with Glasser's disease. 23 H. parasuis and 3 H. parasuis-like strains were examined in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). On the basis of protein profiles of whole-cell lysates, 23 of them could be assigned to 5 groups. Apart from the highly virulent strains of serovar 1, which belonged to PAGE type III, all other highly virulent strains of the serovars SV 5, SV Jena 6 and SV Jena 10 were grouped into PAGE type I. No correlation could be found between PAGE type on the one hand and virulence or origin of isolates on the other hand.     

High tissue burden of Toxoplasma gondii is the hallmark of acute virulence in mice

Toxoplasma gondii virulence is commonly determined by mortality rate of infected mice. Limited data showed that virulent T. gondii strains had increased parasite growth in mice compared to that of less virulent strains. To determine if this is a common phenomenon for a variety of strains and to develop an alternative assay to test acute virulence in mice, we measured parasite burdens in experimentally infected outbred CD-1 mice for 19 T. gondii isolates, in which the virulence phenotypes had previously been determined by mortality assay. Our results showed that parasite concentrations in spleen tissues were two orders of magnitude higher in the virulent than the intermediately and non-virulent isolates at day 7 post infection. In competition assays, mice inoculated with mixed tachyzoites of virulent and intermediately virulent strains or virulent and non-virulent strains showed that the former always reached a higher concentration at day 7 post infection. In mixed infection of intermediate and non-virulent strains, both strains were detectable in mice at day 7 post infection. In conclusion, our data showed that the virulence of T. gondii can be predicted by parasite load in the spleen tissue of infected mice at 7 days post infection, providing an alternative method to determine virulence of Toxoplasma.     

猪多杀性巴氏杆菌对HeLa细胞附着能力的研究

本研究通过猪肺疫的活菌疫苗和死菌疫苗多杀性巴氏杆菌菌株(Pasteurella multocida,Pm)对小鼠的毒力试验测定它们的毒力性。结果表明,死菌疫苗Pm的毒力性比活菌疫苗Pm的强,即死亡率分别为10 0 %和0 %。通过两菌株对He L a细胞的附着试验测定它们的附着能力,结果证明强毒菌的附着能力明显地比弱毒菌强(P<0 .0 1) ,平均附着数分别为11.96和2 .4 4 ;从上述菌株细胞荚膜中分别提取荚膜蛋白,用SDS- PAGE分离测定两菌株荚膜蛋白质结构,结果表明39k Da荚膜蛋白是强毒菌的特异性蛋白。以上研究结果证明Pm的毒力与He L a细胞的附着能力是密切相关的,同时暗示本菌39k Da荚膜蛋白可能与它们的毒力和He L a细胞的附着能力有关     

副猪嗜血杆菌小鼠毒力和仔猪毒力的相关性分析

旨在对我国最为流行的血清4、5、12和13型副猪嗜血杆菌（Haemophilus parasuis， HPS）（共36株）进行BALB/c小鼠和仔猪毒力试验的比较研究。小鼠毒力试验结果表明，4种血清型菌株的LD₅₀分别介于9.80×10⁷~4.60×10⁹、2.10×10⁸~8.85×10⁹、4.81×10⁷~7.01×10⁹和1.75×10⁸~8.45×10⁸ CFU；整体毒力表现强弱依次是13、4、12、5型，但仅在5型与13型菌株之间毒力具有显著差异（P<0.05）。仔猪毒力试验结果表明，同一血清型中不同菌株的毒力具有明显差异，均存在强毒和弱毒菌株；整体毒力表现强弱依次是5、13、4、12型；但5型与4型（P=0.039）和12型（P=0.033）之间具有显著差异（P<0.05），与13型差异不显著（P=0.241）。综合对比分析HPS的小鼠和仔猪毒力试验结果，可以得出3个结论：1）4种国内流行性血清型菌株的整体毒力由强到弱依次是5、13、4和12型；2）但同一血清型中均存在强毒和弱毒菌株，HPS的血清型与其毒力之间不具有相关性；3） HPS虽能致死BALB/c小鼠，但其毒力结果与仔猪毒力试验结果并不一致，表明其作为替代模型具有一定的缺陷。     

Arthroscopic findings in horses with subtle radiographic evidence of osteochondral lesions of the medial femoral condyle: 15 cases (1995-2002)

OBJECTIVE: To determine arthroscopic findings in lame horses with subtle radiographic lesions of the medial femoral condyle. DESIGN: Retrospective study. ANIMALS: 15 horses examined because of lameness that had subtle radiographic evidence of osteochondral lesions involving the medial femoral condyle in at least 1 joint. PROCEDURE: Medical records were reviewed, and results of physical examination, radiography, and arthroscopy were recorded. Follow-up information was obtained through reexamination of the horses or telephone conversations with the referring veterinarians, owners, or trainers. RESULTS: Lameness severity ranged from grade 1 to 3 on a scale from 0 to 5. Radiography and arthroscopy were performed on 28 stifle joints. The 4 unaffected joints in 4 horses with unilateral hind limb lameness that underwent bilateral arthroscopy had no radiographic lesions, but 2 of the 4 had arthroscopic lesions. Of the remaining 24 joints, 20 had radiographic evidence of flattening of the apex of the medial femoral condyle and 4 had minimal subchondral lucency. Lesions were identified arthroscopically in 18 of the 20 joints with flattening of the condyle and in all 4 joints with subchondral lucency. Treatment consisted of abrasion arthroplasty or microfracture. Seven of the 9 horses with focal cartilage lesions and 2 of the 6 horses with generalized cartilage lesions were reportedly sound without any evidence of joint effusion at the time of final follow-up. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that horses with hind limb lameness and subtle radiographic lesions of the medial femoral condyle are likely to have arthroscopically apparent cartilage lesions and subchondral bone defects.     

Evaluation of virulence of Mycoplasma hyopneumoniae field isolates

The course of enzootic pneumonia, caused by Mycoplasma hyopneumoniae, is strongly influenced by management and housing conditions. Other factors, including differences in virulence between M. hyopneumoniae strains, may also be involved. The aim of this study was to evaluate the virulence of six M. hyopneumoniae field isolates and link it to genetic differences as determined by randomly amplified polymorphic DNA (RAPD) analysis. Ninety, conventional M. hyopneumoniae-free piglets were inoculated intratracheally with the field isolates, a virulent reference strain or sterile culture medium. Animals were examined daily for the presence of disease signs and a respiratory disease score (RDS) was assessed per pig. Twenty-eight days post infection, pigs were euthanized, blood sampled and a lung lesion score was given. Lung samples were processed for histopathology, immunofluorescence testing for M. hyopneumoniae and isolation of M. hyopneumoniae. RAPD analysis was performed on all M. hyopneumoniae strains. Significant differences between isolates were found for the RDS, lung lesion score, histopathology, immunofluorescence and serology. Based on the results of the different parameters, isolates were divided into three "virulence" groups: low, moderately and highly virulent strains. Typically, a 5000 bp RAPD fragment was associated with the highly and moderately virulent strains whereas it was absent in low virulent strains. It was concluded that high variation in virulence exists between M. hyopneumoniae strains isolated from different swine herds. Further studies are required to determine whether the 5000 bp fragment obtained in the RAPD analysis can be used as a virulence marker.     

Effects of 0.05% Chlorhexidine Lavage on the Tarsocrural Joints of Horses

In six horses, a 0.05% solution of chlorhexidine diacetate was used to lavage one tarsocrural joint; the contralateral control joint was lavaged with lactated Ringer's solution. Horses were evaluated daily for lameness. Synovial fluid samples were collected on days 1, 4, and 8 for determination of protein concentration, total and differential leukocyte counts, and mucin clot formation. After death on day 8, synovium and osteochondral samples were collected from the tarsocrural joints for examination of morphology and proteoglycan staining. Lavage with chlorhexidine solution caused lameness that was reduced but still evident at day 8. Synovial protein concentration was significantly increased by chlorhexidine lavage; the greatest increase occurred on day 1. Joint lavage increased synovial leukocyte counts on day 1, primarily by increasing polymorphonuclear (PMN) cell counts. Although total synovial leukocyte counts returned to normal by day 4, PMN cell counts remained elevated through day 8; PMN cell counts for chlorhexidine-lavaged joints were typically twice that of control joints. Chlorhexidine lavage caused synovial ulceration, inflammation, and abundant fibrin accumulation. Consistent differences in proteoglycan staining were not detected between control and chlorhexidine-lavaged joints. Joint lavage with 0.05% chlorhexidine diacetate, the lowest known bactericidal concentration, is not recommended for equine joints.     

Virulence of Salmonella enteritidis phagetypes 4, 8 and 13 and other Salmonella spp. for day-old chicks, hens and mice.

Virulence of three Canadian poultry strains of Salmonella enteritidis, namely phagetypes (PT) 4, 8 and 13, and one Salmonella heidelberg strain was assessed in orally and intraperitoneally inoculated one-day old chickens and compared to the virulence of a human S. enteritidis PT 4 strain from the United Kingdom (UK). The two PT 4 strains were also compared in orally inoculated adult laying hens. In addition, orally inoculated Balb/c mice were used to evaluate virulence of the above strains and two strains of Salmonella typhimurium containing different plasmids. In orally inoculated one-day old chickens, the UK S. enteritidis PT 4 strain was more virulent than the Canadian PT 4 strain. The UK PT 4 strain was also more virulent and invasive in adult laying hens than the Canadian PT 4 strain. The S. enteritidis PT 8 strain and one S. typhimurium strain isolated from a chicken hatchery were the most virulent for orally inoculated Balb/c mice. This strain of S. typhimurium contained the 60 megadalton plasmid associated with virulence for Balb/c mice which was not present in the S. typhimurium strain isolated from a pig with septicemic disease.     

新疆不同地区奶牛乳房炎β溶血性金黄色葡萄球菌毒力与基因相关性分析

从新疆5个地区8个奶牛场乳房炎奶样中分离的101株β溶血性金黄色葡萄球菌中随机选64株用小鼠进行毒力测定,同时用随机引物扩增多态性(RAPD)技术分别以3个随机引物进行基因相关性分析,建立种系进化树。结果表明,55%的菌株对小鼠具有较强毒力(可致小鼠2/3死亡),且在乌鲁木齐、奎屯和伊犁地区占据优势。基因相关性分析表明,当相对基因相关性为0.35时,被检测菌株主要分布于6个进化群,86.5%的菌株分布在A、B、C和E4个进化群。其中,50%菌株属于A群,13.5%属于B群,5.8%属于C群,17.3%属于E群。从地区分布可见,乌鲁木齐、伊犁和奎屯地区分离的菌株分别有69.6%、61.1%和71.4%分布在A群;昌吉3个牛场48%、24%的分离菌株分布在B群和C群;库尔勒牛场35.7%、57.1%的分离菌株分布在A群和E群。26株对小鼠具有致死性的菌株分布在A群,这些菌株占致死小鼠菌株的74.3%。     

Attenuated properties of thymidine kinase-negative deletion mutant of pseudorabies virus

A thymidine kinase (TK)-negative (TK-) deletion mutant of the Bucharest (BUK) strain of pseudorabies virus (PRV) was isolated. The mutant, designated as PRV (BUK d13), did not revert to TK-positive (TK+), even when propagated in medium that selected for TK+ viruses. The mutant also replicated equally well at 39.1 C and 34.5 C, and was easily distinguished from other PRV strains by molecular hybridization experiments, restriction nuclease fingerprints, and plaque autoradiography or other assays for the TK phenotype. The PRV (BUK d13) had greatly reduced virulence for mice and rabbits, compared with parental TK+ strains, PRV (BUK-5) and PRV (BUK-5A-R1), and provided mice with solid protection against the TK+ BUK and Aujeszky strains of PRV. Experiments were done in 5- to 6-week-old pigs to assess the safety and efficacy of PRV (BUK d13) in the natural host. In one experiment, pigs were vaccinated IM with 7.5 X 10(8) plaque-forming units of TK- PRV (BUK d13), and were then challenge exposed intranasally (IN) with 4.3 X 10(8) TCID50 of virulent PRV [Indiana-Funkhauser (IND-F)]. Vaccinated pigs did not have clinical signs of illness after vaccination or after challenge exposure. One nonvaccinated control pig died on postchallenge day 4; a 2nd nonvaccinated control pig became moribund, but eventually recovered. Pigs developed virus-neutralizing antibodies after vaccination, and had a secondary immunologic response after challenge exposure; however, PRV was not isolated from the tonsils or trigeminal ganglia of vaccinated pigs at postchallenge exposure day 11.(ABSTRACT TRUNCATED AT 250 WORDS)     

Virulence of Mycoplasma synoviae strains in experimentally infected broiler chickens

Seven field isolates of German origin and the type strain WVU 1853 of Mycoplasma synoviae (MS) were experimentally investigated for their virulence in mycoplasma-free broiler chickens. Two groups of birds were inoculated at 6 days of age with each isolate, one group into the thoracic air sac and the other group intravenously and all surviving birds were examined at necropsy 17 days post inoculation (pi). Groups of negative control birds received sterile Frey's broth medium by intravenous and intra-air sac inoculation, respectively. Variation in virulence was evaluated on the basis of significant differences in incidence, severity and extend of MS-induced airsacculitis and synovitis as well as isolation rates of MS especially from parenchymous organs. All the strains tested were pathogenic but varied in their virulence for broiler chickens. Based on differences of the virulence, the isolates were classified to the categories: (1.) highly virulent, (2.) virulent, (3.) moderately virulent and (4.) slightly virulent. (1) Strains WVU 1853 and 246-91 induced a systemic disease associated with multiple synovitis and bilateral airsacculitis (2) Strains 93-92 and 151-77 induced bilateral airsacculitis similar to WVU 1853 and 246-91 but rarely a systemic disease after exposure by intra-thoracic airsac inoculation. (3) In comparison, strains 27-79, 76-93 and 513-83 caused less frequently airsacculitis and even if, then only at the side of intra-airsac exposure. (4) Strain 91-93 has been found to differ significantly from all the other isolates in its capacity to produce disease independently from the inoculation route. After intravenous inoculation, findings gave no indications for strains with selective tropism to the epithelial membranes of the lower respiratory tract or to those of the joints, tendon sheaths and bursae. However, the presented data of the experiments suggest that the MS strains tested differ in their potential capacity to invade systemically and produce acute septicaemia.     

鸡传染性法氏囊病病毒12个野毒株的毒力比较

对3－7周龄SPF鸡人工感染的致病性比较试验表明，从不同地区收集的12个鸡传染性法氏囊病病毒（IBDV）野毒株的毒力差异甚大，致病性最强的GX8／99株可引起易感年龄的SPF鸡70％－92％的死亡率，属超强毒，而人工接种YN2／99株的SPF鸡死亡率几乎为零。其余毒株对SPF鸡的致死率介于20％－60％，它们的毒力介于IBDV的标准毒与超强毒之间。