Competition of a sporidesmin-producing Pithomyces strain with a non-toxigenic Pithomyces strain

Sporidesmin, a mycotoxin produced by some strains of Pithomyces chartarum, is responsible for the hepatogenous photosensitisation disease facial eczema, which causes severe losses in agricultural revenue in New Zealand. A sporidesmin-producing strain of P. chartarum, isolated in New Zealand, was grown in co-culture with a South African strain that does not produce the mycotoxin. Competition occurred between the two strains when grown both on agar plates and on dried ryegrass, with a significant decrease in the total amount of sporidesmin produced. Biological control of toxkenic P. chartarum can thus occur under laboratory conditions, raising the possibility of similar control in the field situation.     

Lack of toxicity of a nonsporidesmin-producing strain of Pithomyces chartarum in cell culture and when dosed to lambs

In New Zealand the fungus Pithomyces charturum normally produces sporidesmin, a mycotoxin, which is responsible for the hepatogenous photosensitisation disease known as facial eczema. Cultures from an isolate of P. charturum, which does not produce sporidesmin, were examined by cell culture and by dosing to lambs to determine whether other toxic metabolites were produced. Acute and long term toxicity studies were conducted with the toxic response being assessed by weight changes, postmortem and histological examination of tissues, blood biochemistry and haematology tests.

An extract from a sporidesmin-producing isolate was highly toxic in cell culture, while extracts of the nonsporidesmin-producing isolate did not cause a cytotoxic response to HEp 2 cells.

After dosing with a sporidesmin-producing isolate, lambs developed liver lesions and clinical signs of facial eczema. Serum biochemistry changes occurred which were consistent with sporidesmin poisoning.

Lambs dosed with the nonsporidesmin-producing isolate, at the rate of thirty times the number of spores of the sporidesmin-producing isolate, showed no observable toxic effects. All organs were of normal appearance, and histological examination of tissues, blood biochemistry and haematology results showed no abnormal changes. Similarly, long term dosing of extracts of the nonsporidesmin-producing isolate, at a rate equivalent to 100 000 spores/g of grass, produced no indication of a toxic response. It was concluded that the nonsporidesmin-producing isolate of P. churtarum contained no toxic metabolites in significant concentration.     

Lack of toxicity of a non-sporidesmin-producing strain of Pithomyces chartarum in cell culture and when dosed to lambs

In New Zealand the fungus Pithomyces charturum normally produces sporidesmin, a mycotoxin, which is responsible for the hepatogenous photosensitisation disease known as facial eczema. Cultures from an isolate of P. charturum, which does not produce sporidesmin, were examined by cell culture and by dosing to lambs to determine whether other toxic metabolites were produced. Acute and long term toxicity studies were conducted with the toxic response being assessed by weight changes, postmortem and histological examination of tissues, blood biochemistry and haematology tests. An extract from a sporidesmin-producing isolate was highly toxic in cell culture, while extracts of the nonsporidesmin-producing isolate did not cause a cytotoxic response to HEp 2 cells. After dosing with a sporidesmin-producing isolate, lambs developed liver lesions and clinical signs of facial eczema. Serum biochemistry changes occurred which were consistent with sporidesmin poisoning. Lambs dosed with the nonsporidesmin-producing isolate, at the rate of thirty times the number of spores of the sporidesmin-producing isolate, showed no observable toxic effects. All organs were of normal appearance, and histological examination of tissues, blood biochemistry and haematology results showed no abnormal changes. Similarly, long term dosing of extracts of the nonsporidesmin-producing isolate, at a rate equivalent to 100,000 spores/g of grass, produced no indication of a toxic response. It was concluded that the nonsporidesmin-producing isolate of P. churtarum contained no toxic metabolites in significant concentration.     

禽呼肠孤病毒鸡源分离株的鉴定与人工感染试验

从临床患病鸡关节病料中分离到一株病毒，在电镜下观察到病毒粒子无囊膜，有双层衣壳，外衣壳直径约75nm，内核约50nm；分离病毒株对酸、热有较强的抵抗力，对乙醚不敏感；病毒感染鸡胚成纤维细胞上能产生以融合细胞为特征的CPE；爪垫接种1日龄雏鸡表现出明显的病毒性关节炎临床症状，并伴有吸收障碍型和坏死型的病理变化；血清中和交叉试验表明，该病毒分离株与国内的2株番鸭源呼肠孤病毒（YH和YB）分离株和国外S1133呈不同程度的交叉反应。通过对分离病毒株进行电镜观察、理化特性试验、病毒感染力测定、致病性试验、血清学试验，可以确定该分离病毒为禽呼肠孤病毒。     

An Argentine equine herpesvirus strain with special restriction patterns protect mice challenged with a pathogenic strain

Equine herpesvirus 1 (EHV-1) was first isolated in Argentina in 1979. This strain SPv has special restriction patterns, but a previous study demonstrated that SPv did not modify its growth in cell culture. In addition, it showed low virulence in the mouse respiratory model consistently with results found in female BALB/C at different state of gestation. This study evaluates in a mouse respiratory model, if primary infection with SPv strain protects animals from subsequent challenge with a pathogenic strain. Body weight loss was not observed in mice intranasally inoculated with SPv strain and challenged with HH1 Japanese strain. The SPv primary infection does not completely prevent clinical presentation by HH1 infection but the SPv inoculated animals recovered more quickly, with less intense and less persistent histological lesions. The challenge infection caused a rapid and prolonged increase in anti-EHV-1 antibodies in the mice previously infected with SPv, along with a more rapid reduction of viral titres in lungs. In this work it was demonstrated that this EHV-1 strain constitute a good immunogen. These results show that this SPv strain could be considered to produce an EHV-1 vaccine.     

Subtypes of intimin among non-toxigenic Escherichia coli from diarrheic calves in Brazil.

One hundred and five strains of Escherichia coli that were isolated from calves with diarrhea in the state of São Paulo, Brazil, and were negative for enterotoxins and cytotoxins, were examined for the eae gene. Four (3.8%) strains were positive by polymerase chain reaction (PCR) and were shown to produce intimin by using Western blot with specific antiserum against the conserved N-terminal region of intimin. Subtyping of the intimins was done by PCR with specific primers and by Western blot with specific antisera against the C-terminal variable region of the protein. Three of these isolates (O?:H11, O26:H-, O123:H1) produced the beta subtype of intimin, and the 4th (0103:H2) produced intimin that was not typable. The 0103:H2 and the O26:H-isolates adhered to HEp-2 cells with diffuse adherence and localized-like adherence patterns, respectively. The other strains did not adhere to HEp-2 cells. To our knowledge, this is the first report of the occurrence of a subtype of intimin described for human enteropathogenic E. coli among bovine diarrheogenic E. coli. It is also the first report from Brazil demonstrating the presence of bovine E. coli harboring the eae gene.     

Immunisation of cattle with a recombinant togavirus-vaccinia virus strain

Genetic engineering techniques have been used to construct a vaccinia virus recombinant which contains and expresses togavirus (Sindbis) genetic information. Intradermal inoculation of this recombinant strain into calves caused a transient pock-type lesion at the site of inoculation and elicited the production of substantial levels of anti-Sindbis virus neutralising antibodies. These results suggest that recombinant vaccinia virus vaccines may have potential for use in veterinary medicine.     

The influence of lime and nitrogen fertilisers on spore counts of Pithomyces chartarum in pasture

AIMS: To determine whether the application of lime or nitrogen to pasture affected the spore counts of Pithomyces chartarum.

MATERIALS AND METHODS: The lime application studies were undertaken on a spring-calving, pasture-based, commercial dairy farm near Te Awamutu, New Zealand. On 6 November 2012, five randomly selected paddocks were split into three equal sections. In two of the sections, lime was applied at either 1.5 or 2.5?t/ha, and the central section was left as an untreated control. Each section was sampled for spore counting weekly from 16 January to 15 May 2013.

Starting in January 2013, five other randomly selected paddocks were monitored for spore counts. On 20 March 2013 the average spore counts in three paddocks were >100,000 spores/g of pasture. These paddocks were then divided into three equal sections and lime was applied as described above. Spore counting in each section continued weekly until 15 May 2013.

The nitrogen application study was carried out on three commercial dairy farms near Te Awamutu, New Zealand. Two randomly selected paddocks on each farm were divided into three equal sections and, on 20 December 2012, nitrogen in the form of urea was applied at either 50 or 80?kg urea/ha to two of the sections; the central section remained as an untreated control. Each section was sampled for spore counting weekly from 16 January to 15 May 2013.

RESULTS: Following pre-summer lime application, treatment at 1.5 or 2.5?t/ha did not affect spore counts over time compared with the control section (p>0.26). Similarly following autumn lime application, treatment at 1.5 or 2.5?t/ha did not affect spore counts over time compared with the control section (p>0.11). Following nitrogen application median spore counts remained <20,000 spores/g pasture throughout the trial period and there was no effect of treatment on spore counts over time (p>0.49).

CONCLUSION: This study found that application of lime before the risk period for facial eczema, in November, application of lime after a spore count rise, in March, or urea application in December did not affect changes in number of spores produced by P. chartarum.

CLINICAL RELEVANCE: This study does not support previous suggestions that fertilising pasture with lime or urea could alter the spore counts of P. chartarum. Fertiliser use does not provide an alternative to, or support, conventional methods of facial eczema control such as zinc prophylaxis or treatment of pasture with fungicides.     

非典型性猪瘟病毒云南株/石门株嵌合病毒的构建和拯救

为研究猪瘟病毒(CSFV)云南株(YN株)突变位点在致非典型性猪瘟中的作用,本研究在CSFV石门株全长感染性克隆的基础上,利用分子克隆技术,将CSFV YN株的1 510位～1 532位、2 471位～2 658位、3 152位～3 176位和11 785位～11 816位突变位点基因序列替换CSFV石门株的相应基因序列,构建出嵌合的CSFV感染性克隆质粒pAC-SM-YN。全基因测序鉴定后,体外转录得到病毒RNA,经脂质体转染PK-15细胞方法拯救出了嵌合病毒vSM-YN。经直接荧光染色、对突变位点RT-PCR以及ELISA检测表明拯救嵌合病毒vSM-YN传代稳定。本研究为研究CSFV结构蛋白、病毒致病机理、新型疫苗,尤其是非典型猪瘟的致病机理奠定了基础。     

Apparent cross-infection with a single strain of Malassezia pachydermatis on a pig farm

Twenty-nine isolates of Malassezia pachydermatis were recovered from a single farm of 100 pigs in Croatia. In contrast, 290 farm pigs from other locations (northern parts of Croatia and Slovenia) yielded only two non-lipid dependent isolates of M. pachydermatis using the same swabbing procedure. Ten of the 29 isolates from a single farm had their identity confirmed by karyotyping, and were typed by restriction fragment length polymorphism (RFLP) analysis. All but one of these isolates sub-typed were indistinguishable, one isolate produced a slightly different RFLP profile. Control isolates recovered from dog skin gave RFLP profiles that were easily distinguished from those produced by the pig isolates. These results suggest that a single strain of M. pachydermatis had colonised this pig herd.     

1株可形成生物膜鸡白痢沙门菌的分离鉴定

鸡白痢沙门菌在世界范围内引起养殖业的严重经济损失,虽然其病原体血清型一致,但不同菌株的生物学特性存在很大差异.沙门菌可形成生物膜,而处于生物膜状态的细菌可增强对外界的抵抗力,造成持续感染和重复感染 [1].因此,有必要在鸡白痢沙门菌分离鉴定的同时进行生物膜形成能力研究.我们从1例疑似鸡白痢的病鸡中分离出1株鸡白痢沙门菌,测定其生物膜形成能力,为进一步了解鸡白痢沙门菌生物膜的作用奠定了基础.     

Inhibition of virus replication in the tonsils of pigs previously vaccinated with a Chinese strain vaccine and challenged oronasally with a virulent strain of classical swine fever virus

After an oronasal (O.N.) infection with classical swine fever (C.S.F.) virus, virus multiplication can be detected in the tonsils from Day 2 post infection (p.i.) till death. The course of viral replication during the first 10 days after O.N. challenge exposure of pigs, previously vaccinated with a Chinese strain vaccine in the presence or absence of maternal antibodies, was studied using direct immunofluorescence techniques on cryostat sections and virus isolations. When piglets were challenged O.N. in the presence of maternal antibodies, virus replication in the tonsils still occurred. The multiplication period and the localization of the virus, however, were directly correlated to the maternal antibody levels. The maternal antibody level also seems responsible for the efficacy of the vaccination to prevent challenge virus replication in the tonsils: vaccination in the presence of low maternal antibody titers completely inhibited virus replication; vaccination in the presence of high maternal antibody titers only reduced the multiplication period of the O.N.-administered virulent virus. In both cases, animals were challenged 1 week post vaccination. Vaccination of seronegative animals resulted in an almost complete inhibition of the virus replication in the tonsils during a full fattening period: cryostat sections revealed a limited virus replication in three out of 20 animals. In one of these animals, virus replication was probably so negligible that virus isolation remained negative.     

Protection by oral administration of brucella abortus strain 19 against an oral challenge exposure with a pathogenic strain of Brucella

Twenty heifers were vaccinated orally with Brucella abortus strain 19. These heifers and 21 control heifers were challenge exposed in midgestation with strain 2308 by the oral route. Ten of 19 pregnant control heifers aborted and 14 were culture positive. Two additional heifers were seropositive at slaughter. Strain 2308 was recovered from 4 vaccinates at slaughter; none of the vaccinates aborted. Titers after oral vaccination persisted for less than 82 days.     

Monitoring chronic infection with a field strain of Aleutian mink disease virus

Aleutian mink disease virus (AMDV) readily spread within farmed mink and causes chronic infections with significant impacts for welfare and economy. In the present study a currently circulating Danish AMDV strain was used to induce chronic experimental infection of farmed mink.PCR was used to detect viral DNA in full blood, organs, faeces and oro-nasal swabs weekly for the first 8 weeks and then biweekly for another 16 weeks after AMDV challenge inoculation of wild type mink. The mink (n = 29) was infected and seroconverted 2–3 weeks after AMDV inoculation and AMDV antibodies persisted during the maximum experimental period of 24 weeks. Viraemia and faecal excretion of viral DNA was detected in the mink (n = 29) at various and intermittent time intervals. Excretion of viral DNA in oro-nasal swabs was detected for 1–8 weeks in 21 mink. This highlights the risk of transmitting AMDV between infected farms.PCR was successfully used to detect viral DNA in organs 8, 16 and 24 weeks after AMDV inoculation with only minor differences between these weeks which is of diagnostic interest.This AMDV challenge model was also used to mimic natural infection of susceptible sapphire mink. Four of 6 sapphire mink were infected indirectly via the AMDV inoculated wild type mink whereas the other 2 sapphire mink remained uninfected.     

Clinical disease in kittens inoculated with a pathogenic strain of Bartonella henselae

OBJECTIVE: To evaluate disease in kittens inoculated with Bartonella henselae strain LSU16. ANIMALS: Eighteen 12-week-old specific-pathogen-free kittens. PROCEDURE: Kittens were inoculated with B henselae strain LSU16 or saline (0.9% NaCl) solution. Blood samples were collected from kittens on alternate weeks, and bacteremia, clinical signs, and antibody concentrations were monitored for 6 months after inoculation. RESULTS: Kittens developed raised, erythematous areas at the site of inoculation within 72 hours. Swelling peaked at 14 days and resolved by 28 days after inoculation. Fever had a biphasic pattern, with an episode of 1- to 3-days' duration beginning 6 to 7 days after inoculation followed by an episode of 3- to 8-days' duration beginning 11 to 13 days after inoculation. Kittens were bacteremic by day 14 with peak bacteremia at days 14 to 28. Strong antibody responses to B henselae were detected. Clinical disease resolved before bacteremia became undetectable, but signs of disease correlated with the highest degree of bacteremia. Regional lymphadenopathy also was evident. CONCLUSION AND CLINICAL RELEVANCE: Clinical disease in kittens was similar to that in adult cats infected with B henselae strain LSU16, except that lethargy and anorexia were less severe in kittens, and a biphasic pattern of fever was detected in kittens. Clinical disease after inoculation with B henselae may be strain-dependent. To limit transmission of Bartonella organisms, appropriate flea prevention should be instituted. IMPACT FOR HUMAN MEDICINE: Kittens that are febrile, anorectic, lethargic, and that have lymphadenopathy should be tested for Bartonella organisms, and contact with immunocompromised owners should be discouraged.     

Babesia argentina: Immunization of cattle with a killed antigen against infection with a heterologous strain

Cattle were immunized againts infection with a heterogologous strain of Babesia argentina by the subcuntaneous inoculation of killed antigen mixed with Freund's complete adjuvant. The most effective antigen, infectted erythrocyte antigen (IEA), which confered protection comparable with that conferred by the presence of subclinical infection, was prepared by the disruption of parasitized erythrocytes in a French pressure cell. In contrast, antigen prepared from the plasma of infected animals was weakly immunogenic. The inoculation of IEA by the intravenous route without adjuvant did not confer protection but demonstrated the presence of a “kallikrein activating” substances(s) in the contents of the parasitized erythrocytes.     

Experimental infection of pigs with a thymidine kinase negative strain of pseudorabies virus

Sixteen 20 day old pigs, devoid of neutralizing antibody to pseudorabies virus (PRV), were divided into two groups of eight, and the animals of each group were housed in a separate unit. In each group 6 pigs were inoculated intranasally with the thymidine kinase (TK⁻) mutant (Group 1) or the field strain of PRV (Group 2), each pig receiving an inoculum of 4 ml. The remaining 2 pigs in each group served as uninoculated controls. The only clinical sign observed in the pigs of Group 1 was a transient febrile reaction, in the case of six pigs inoculated with the TK⁻ mutant of PRV, whereas no signs of disease were seen in the uninoculated controls. The virus was isolated from the 6 infected pigs of the group only on post infection day (PID) 2, whereas it was never isolated from the controls. By contrast, the pigs of Group 2, had a severe clinical response and one, among those that were inoculated with the field strain of the PRV, died on PID 9. Virus was consistently isolated from all pigs of Group 2, inoculated and control. On PID 30 all pigs, i.e. the 8 of Group 1 and 7 of the Group 2 which survived to the infection, were subjected to dexamethasone (DMS) treatment. After DMS treatment virus was never isolated from the nasal swabbings obtained from the pigs of Group 1, whereas it was consistently isolated from pigs of Group 2. After 30 d from the start of DMS treatment the pigs were killed and several tissues were collected from each pig for virus detection, by isolation in tissue culture and by PCR analysis. At necropsy no lesions were found in pigs of Group 1, whereas acute pneumonia and gliosis in the trigeminal ganglia were observed in pigs of Group 2. Virus was never isolated from any of the tissues taken from pigs of both, Group 1 and Group 2, nevertheless sequences of PRV were detected by PCR analysis in the trigeminal ganglia of the pigs of both Groups.