Seroprevalence of Chlamydia psittaci-specific antibodies in small stock in Namibia--epidemiological study with an enzyme-linked immunosorbent assay (ELISA)

An IgG (H+L)-ELISA was applied as a screening test for antibodies against Chlamydia (C.) psittaci in sera of goats and sheep in Namibia. In 576 (27.3%) of a total of 2,107 sera (299 = 25.2% of 1,185 caprine and 277 = 30.0% of 922 ovine sera) chlamydial antibodies could be detected. 86% of all farms tested revealed seropositive animals. Chlamydial infections were prevalent in all the geographical regions tested. The infection rates per State Veterinary District varied from 12.0% (Otjiwarongo) to 50.0% (Otavi) in goats and from 13.3% (Otjiwarongo) to 41.7% (Windhoek) in sheep. The regional distribution of chlamydial infections was not related to geographical or climatic factors. Sera from herds showing symptoms indicative for chlamydial infections showed significantly higher antibody rates (35% in goats and 39% in sheep) than sera from herds without health problems (18% in goats and 24% in sheep). Considering only sera from farms with clinical history of chlamydiosis, high seroprevalences were correlated to the symptoms abortion and keratoconjunctivitis. As in other countries, enzootic abortion seems to be the main manifestation of chlamydial infection in small ruminants in Namibia. C. psittaci might also play a considerable role in the etiology of infectious keratoconjunctivitis, whereas association with other clinical entities seems to be rare.     

Molecular evidence for chlamydial infections in the eyes of sheep

Ocular infections by chlamydiae are associated with ocular disease manifestations such as conjunctivitis and keratitis in humans and animals. Limited evidence exists that members of the order Chlamydiales can also cause ocular disease in sheep. In the current study, the prevalence of chlamydiae in the eyes of sheep was investigated by using PCR methods. Data obtained in sheep by broad-range 16S rRNA order Chlamydiales-specific PCR were compared to the prevalence of antibodies against chlamydiae detected by a competitive enzyme-linked immunosorbent assay (cELISA). Flocks tested included a clinically healthy flock and two flocks suffering from ocular disease and with histories of Ovine Enzootic Abortion (OEA). PCR detected DNA of Chlamydophila (Cp.) abortus and Cp. pecorum in the eyes of both healthy and sick animals but also identified Chlamydia (C.) suis and a variety of uncultured chlamydia-like organisms. Good correlation was found between the presence of Cp. abortus DNA in sheep conjunctival samples and seropositivity detected by cELISA. Despite these findings, no association was found between the presence of chlamydial DNA in the sheep conjunctival samples and the onset of clinical disease. These results suggest that the biodiversity of chlamydiae in the eyes of sheep is greater than that previously thought. Further investigations are needed to determine whether a causal relationship between infection by chlamydiae and ocular disease exists in these animals.     

Detection of Chlamydiaceae in ocular swabs from Australian pre‐export feedlot sheep

Infectious Ovine Keratoconjunctivitis (IOK) is a contagious ocular disease of sheep. A range of organisms have been observed as the aetiological agents of IOK. In this study, the presence of chlamydial pathogens (C. pecorum, C. abortus, C. psittaci) in conjunctival swabs was tested for. The swabs were collected from sheep with varying grades of IOK in an Australian pre‐export feedlot. The sheep had been rejected from a shipment because of the eye disease. The relative contribution of chlamydial pathogens to IOK and the rejection of animals was evaluated. In total, 149 conjunctival swabs were taken from rejected sheep (IOK Grades 1 to 6; n = 126) as well as those with healthy eyes (Grade 0; n = 23). Screening for chlamydial pathogens was done using species–specific qPCR assays. Chlamydial DNA was detected in 35.6% (53/149) of conjunctival samples. C. pecorum was the most predominant species with an overall prevalence of 28.9% (43/149). C. psittaci prevalence was 6.7% (10/149). Both organisms were detected in healthy as well as IOK‐affected eyes. All swabs tested negative for C. abortus. The results from this study demonstrate that Chlamydia spp can be readily detected in sheep presenting with IOK. The zoonotic C. abortus was not detected in any of the samples in this study, providing further evidence to the suggestion that this pathogen remains absent from Australia. Although the exact contribution of Chlamydia spp in the IOK pathogenesis is unclear, such studies are anticipated to be of benefit to Australian domestic and live export production systems.     

Chlamydia abortion in sheep: possibilities for serological diagnosis using a competitive ELISA and insight into the epidemiologic situation in Switzerland]

466 sheep sera out of 19 flocks in Switzerland were examined by a competitive enzyme linked immunosorbent assay (cELISA) for antibodies against Chlamydia psittaci "serotype 1" ("ovine enzootic abortion"). Since numerous positive reactors were found in flocks without abortion history, 30 fecal samples out of two of these flocks were examined by PCR for evidence of chlamydial DNA. One of these samples turned out to contain DNA of Chlamydia psittaci "serotype 1". These results suggest, that in Switzerland "serotype 1" of Chlamydia psittaci is widespread not only as cause of chlamydial abortion but also as latent intestinal infection in sheep. The resulting difficulties for serological diagnosis of chlamydial abortion and possible solutions based on the cELISA are discussed. The complement fixation test (CFT), still considered as standard method for serological examination for Chlamydiae, has additionally been applied.     

Detection of Chlamydia psittaci from various animal species by reverse passive haemagglutination

A reverse passive haemagglutination test (RPH) has previously been developed to detect the genus-specific antigen of Chlamydia. Clinical samples were obtained from various sites of different animal species. The RPH test detected chlamydial antigen from clinical cases of conjunctivitis in cats, abortion in sheep and psittacosis in birds. Although not as sensitive as cell culture isolation, this test has the advantages of rapidity and of detecting antigen from dead chlamydiae.     

Chlamydia psittaci infection and associated infertility in sheep.

Nineteen ewes were injected subcutaneously with the agent of enzootic ovine abortion, Chlamydia psittaci serovar 1, at 50 days gestation. Placental and fetal tissues were examined at 15 days postinfection and thereafter at ten day intervals. Placental infection was detected at 15 days postinfection. Only postinoculation sera collected from postinfected ewes contained antibodies reactive to C. psittaci. Five (26%) chlamydial infected ewes experienced inapparent fetal loss before day 105 of gestation. This finding is significant since C. psittaci infection in sheep is commonly associated with abortion and not infertility.     

Identification of Chlamydophila abortus and the development of lesions in placental tissues of experimentally infected sheep

Chlamydophila (C.) abortus is a major cause of infectious abortion in sheep in many countries. Twenty-one pregnant sheep were experimentally infected intranasally with C. abortus at 70 days of gestation (dg). Thereafter, a number of animals were killed at weekly intervals and a post-mortem examination was carried out. Evidence of chlamydial infection in the placenta was determined by isolation of the bacterium by tissue culture and detection of C. abortus DNA by real-time polymerase chain reaction (real-time PCR). In addition, histopathological changes in the placenta were assessed, as was the detection of chlamydial antigen by immunohistochemistry (IHC). Evidence of placental infection was observed as early as 2 weeks after inoculation, and while only relatively low numbers of bacteria were isolated by culture and/or detected by real-time PCR prior to 113-114dg, at 119-121dg, it was more numerous. This study, using the four criteria for assessment of infection, showed that while C. abortus gained access to the placenta as early as 85dg, characteristic histopathological changes were not apparent until 119/121dg. While the chronology of when the bacterium arrived in the placenta and subsequent lesion development is remarkable for its consistency this paper provides more reliable data on the former which in turn now allows study of the factors that permit its access to this tissue and govern its multiplication and the ensuing triggering of damage.     

Detection of the genome of Chlamydophila abortus in samples taken from the uteri of 304 sheep at an abattoir

A PCR was used to detect the genome of Chlamydophila abortus in samples of uterine tissue collected from 304 sheep by a sterile technique at an abattoir. The stage of pregnancy of the sheep was determined by measuring the dimensions of the embryo/fetus, and its morphology was recorded. Only samples from non-pregnant sheep and sheep up to 100 days of gestation were retained; the clinical history of the animals was unknown. The total prevalence of the chlamydial genome was 30.9 per cent, with a significantly higher prevalence in the pregnant animals (46.9 per cent). Higher detection rates were recorded during early gestation than during mid-gestation.     

Investigation of Chlamydiaceae in semen and cauda epididymidis and seroprevalence of Chlamydophila abortus in breeding bulls

Background

Reproductive disorders associated with chlamydial infection have been reported worldwide in cattle and there are indications of potential venereal transmission.

Methods

Semen samples from 21 dairy bulls and cauda epididymidis tissue samples from 43 beef bulls were analysed for chlamydial agent by real-time polymerase chain reaction (PCR) including an internal amplification control (mimic). Additionally, presence of antibodies against Chlamydophila (Cp.) abortus among the bulls was investigated with the commercial Pourquier^® ELISA Cp. abortus serum verification kit.

Results

No chlamydial agent was detected by PCR in either the semen samples or in the tissue samples. Additionally, no antibodies against Cp. abortus were detected.

Conclusions

The results suggest that Cp. abortus is very rare, or absent in Swedish bulls and thus the risk for venereal transmission of chlamydial infection through their semen is low. However, because Chlamydophila spp. infection rates seem to differ throughout the world, it is essential to clarify the relative importance of transmission of the infection through semen on cattle fertility.     

Serological response to pgp3 protein in animal and human chlamydial infections

Specific antibodies to plasmid-encoded protein pgp3 are known to be encountered in human Chlamydia (C.) trachomatis infections. In order to verify whether antibodies to this protein could be developed in animals infected with plasmid-carrying chlamydial strains, 454 animal sera were examined using a home-made pgp3 protein ELISA and Western blots (WB) of recombinant pgp3 protein from Chlamydophila (Cp.) psittaci. Likewise, 50 human sera were tested by ELISA and WB of recombinant pgp3 from C. trachomatis. The reactivity against pgp3 protein was compared to the reactivity against chlamydial elementary bodies (EBs) detected by microimmunofluorescence (MIF) test. The presence of pgp3-specific antibodies was demonstrated in most ducks and pigeons with Cp. psittaci infection detected by MIF, as well as in the majority of symptomatic cats and pigs infected with Cp. felis and C. suis, respectively, which reacted at high titres to Cp. felis and C. suis EBs by MIF. Moreover, most of the sera collected from patients with C. trachomatis culture-confirmed infection and seropositive to C. trachomatis by MIF, presented antibodies specific to C. trachomatis pgp3 recombinant protein. Therefore, pgp3 protein could be a useful marker of chlamydial infections in animals, as well as in humans.     

Precipitating antibodies in experimental visna and natural progressive pneumonia of sheep

Serological responses of Icelandic sheep experimentally infected with visna virus (vv) were contrasted with responses in American Targhee sheep naturally infected with progressive pneumonia virus (PPV). Precipitating antibodies assayed by immunodiffusion were compared with the neutralising and complementing fixing antibody response. In experimental infections with vv, complement fixing and neutralising antibodies appeared early after infection and rose to high levels in all sheep, while precipitating antibodies were detected only at minimal titre. In natural infections with PPV, immune responses were less consistent and precipitating antibodies were detected more frequently than complement fixing or neutralising antibodies against PPV. These results may suggest important biological differences between the lytic fibroblast-tropic virus strains used for experimental infection of Icelandic sheep and the nonlytic macrophage-tropic strains of PPV circulating in nature. Lytic strains evoke a brisk response against the viral glycoprotein with high titre neutralising antibody while nonlytic strains induce a less consistent response to the glycoprotein.     

实验感染山羊关节炎—脑炎病毒的绵羊抗体应答反应的研究

本实验用琼脂凝胶免疫扩散试验和免疫印迹试验对实验感染山羊关节炎—脑炎病毒（ＣＡＥＶ）的绵羊抗体应答反应进行了研究，用两种方法都可在接毒绵羊的血清中检测到ＣＡＥＶ的抗体。琼脂凝胶免疫扩散试验最早可于接毒后的第７周时检测到抗体，免疫印迹试验最早可于接毒后的第６周时检测到抗ＣＡＥＶ的ｇｐ１２５、ｇｐ４４、ｐ３５、ｐ２８和ｐ１４的抗体，这说明免疫印迹试验更为敏感一些。本实验的结果表明ＣＡＥＶ可在绵羊体内诱生明显的体液免疫应答反应，因此用ＣＡＥＶ通过绵羊体传代的方法可能会得到具有良好的抗原性的ＣＡＥＶ毒株，这对于人工培养ＣＡＥＶ强毒是非常重要的。此外，本实验还为ＣＡＥＶ通过绵羊体传代的研究提供了非常实用的检测手段     

A simple staining method for the identification of chlamydial elementary bodies in the fetal membranes of sheep affected by ovine enzootic abortion.

A dark-ground methylene blue (DGMB) staining method was used to demonstrate chlamydial elementary bodies in fetal membranes of sheep affected by Chlamydia psittaci. Before evaluation on material from clinically affected animals, the DGMB method was compared with modified Ziehl-Neelsen (MZN) and dark-ground Giemsa (DGG) staining methods for its ability to demonstrate chlamydial elementary bodies in hens' eggs which had been experimentally infected with C. psittaci. DGMB was more specific in its staining of chlamydial elementary bodies than DGG or MZN. The DGMB method was found to be a more reliable technique for the examination of fetal membranes from sheep affected with C. psittaci than DGG or MZN. Those samples diagnosed as positive using the DGMB showed a good correlation with those diagnosed as positive on macroscopic examination.     

Ovine enzootic abortion: experimental studies of immune responses

Eight pregnant and four non-pregnant ewes were exposed to experimental oral infection with the chlamydial agent of ovine enzootic abortion. Four non-pregnant ewes received a sham inoculum. Immune responses were investigated using a complement fixation test (CFT), a delayed-type hypersensitivity (DTH) skin test and a lymphocyte transformation assay (LTA). When these responses were correlated with clinical observations it was concluded that fetopathy occurred in those ewes which failed to mount or mounted only weak DTH responses. High antibody titres were not an indication of protective immunity; in pregnant animals there was evidence of an inverse correlation between DTH and humoral responses as detected by the CFT. In the LTAs, chlamydia specific blastogenesis was recorded in all infected sheep but there was little correlation with clinical findings.     

Aberrant chlamydial developmental forms in the gastrointestinal tract of pigs spontaneously and experimentally infected with Chlamydia suis

The phenomenon of persistence is well known from in vitro studies, where it is associated with the production of aberrant bodies, but its occurrence in vivo is less well documented. The objective of this study was to search for aberrant bodies in intestinal tissues from pigs, describe their ultrastructure, and investigate the suitability of immunohistochemical staining for chlamydial heat shock protein 60 (cHSP60) to detect such forms. Intestinal tissues derived from pigs naturally and experimentally infected with Chlamydia (C.) suis were examined by immunohistochemistry, transmission electron microscopy and immunogold electron microscopy. The chlamydial species involved in the natural infection were determined using an Array Tube Microarray to C. suis and Chlamydophila abortus. Ultrastructurally, aberrant bodies were detected in the gut of both naturally and experimentally infected pigs. Immunogold electron microscopy showed that the aberrant bodies were labeled less strongly than the normal forms by antibodies against LPS and cHSP60 respectively. It was concluded that aberrant bodies occur in vivo in pigs and that the gnotobiotic pig model might be suitable for the study of chlamydial persistence in vivo. The antibody against cHSP60 does not appear to be suitable to specifically detect such forms.     

Recombinant major outer membrane protein (MOMP) of Chlamydophila abortus, Chlamydophila pecorum, and Chlamydia suis as antigens to distinguish chlamydial species-specific antibodies in animal sera

Recombinant major outer membrane proteins (rMOMP) of Chlamydophila (Ch.) abortus, Ch. pecorum, and Chlamydia (C.) suis were used as antigens to distinguish chlamydial species-specific antibodies in (i) immune sera from six rabbits and three pigs raised against native purified elementary bodies, (ii) serum samples from 25 sows vaccinated with Ch. abortus, and (iii) 40 serum samples from four heifers experimentally infected with Ch. abortus. All post-exposition sera contained chlamydial antibodies as confirmed by strong ELISA seroreactivities against the chlamydial LPS. For the rMOMP ELISA mean IgG antibody levels were at least 5.8-fold higher with the particular rMOMP homologous to the chlamydial species used for immunisation or infection than with heterologous rMOMPs (P <0.001). Preferential rMOMP ELISA reactivities of sera were confirmed by Western blotting. The results suggest that the entire chlamydial rMOMP could provide a species-specific serodiagnostic antigen.     

2016—2018年广西玉林市和百色市主要家畜疫病定点监测

为了解广西地区口蹄疫(FMD)、猪瘟(CSF)、猪繁殖与呼吸综合征(PRRS)、猪伪狂犬病(PR)、布鲁氏菌病和小反刍兽疫(PPR)等重大动物疫病的免疫动态、疫情流行风险,按照国家动物疫病定点监测实施方案相关要求,2016—2018年运用ELISA和实时荧光定量PCR方法,对玉林市和百色市20个定点监测场点的猪、牛、羊开展病原学监测和抗体监测。病原监测结果显示:2016—2018年,未在牛羊群中检出FMD、PPR病原;2016年和2017年CSF病原检出率均为0.38%;3年内均有PRRS病原检出,检出率介于1.89%~6.32%。抗体检测结果显示:2016—2018年,猪O型FMD、CSF、PRRS和PR-gB抗体阳性率均在70%以上,A型FMD抗体阳性率逐年上升,NSP抗体和PR-gE抗体阳性率呈波动状变化;牛O型FMD抗体阳性率分别为94.78%、18.26%、71.11%,亚洲I型分别为76.52%、25.22%、27.78%,NSP抗体阳性率在22.61%~41.74%之间波动;仅2016年检出1份牛布鲁氏菌抗体阳性;3年间,羊O型、亚洲I型FMD和PPR免疫抗体阳性率都很低,未达到70%,且呈下降趋势,NSP抗体阳性率在0.95%~7.62%之间波动,未检出羊布鲁氏菌抗体。结果表明,广西玉林市和百色市的猪群O型FMD、CSF、PRRS、PR免疫效果较好,但牛羊群FMD和PPR免疫效果较差,猪群中仍有CSF、PRRS、PR等疫病流行,牛羊群中存在FMD流行的风险,但牛羊布鲁氏菌病得到有效控制。结果提示,应继续加强上述疫病的免疫和监测,针对免疫效果较差、病原流行率偏高的疫病,要重点做好防控和净化。     

Prevalence of Chlamydia psittaci in different cat populations in Britain

The prevalence of Chlamydia psittaci infection in household, feral and farm cats in Britain was investigated. Chlamydia were isolated from 30 per cent of conjunctival swabs collected from 753 household cats with conjunctivitis. The prevalence of active chlamydial infection was highest in cats in the age group five weeks to nine months. Males were more frequently infected than females. Cats with chlamydial conjunctivitis usually had antibody titres greater than 1024 as assessed by indirect immunofluorescence. Chlamydia appeared to be endemic in two out of three feral cat colonies on the basis of serological evidence and occasional isolations. Cats on 10 of 22 sheep farms (45 per cent) had serological evidence of chlamydial infection, and this was confirmed on two farms by isolation of the organism from conjunctival and, or, rectal swabs. This is the first survey of infection with Chlamydia psittaci in cat populations in Britain.     

Epizootiological survey of parainfluenza-3, reovirus-3, respiratory syncytial and infectious bovine rhinotracheitis viral antibodies in sheep and goat flocks in Quebec.

A serological survey was conducted in an attempt to detect antibodies against bovine respiratory viruses in sheep and goats from seven geographical areas of Quebec. Sera from 10% of the animals in 182 sheep flocks and 40 goat flocks were collected and specific antibodies against parainfluenza-3, reovirus type 3, respiratory syncytial and infectious bovine rhinotracheitis viruses were detected by hemagglutination-inhibition tests for the former viruses and complement fixation and seroneutralization assays for the latter viruses. Results showed prevalence rates of serological reaction to parainfluenza-3, reovirus type 3 and respiratory syncytial viruses of 28, 72 and 35% in sheep and 26, 64 and 36% in goats, respectively. No antibodies in infectious bovine rhinotracheitis virus were detected in sheep or goats tested. Prevalence rates varied according to the geographical area. No relationships were detected between age, sex, breed, size of flock and prevalence rates of different antibodies except that parainfluenza-3 antibodies were more common in large goat flocks and in sheep flocks with total confinement housing. A relationship between presence of clinical signs in the flocks and prevalence rates of antibodies was only demonstrated for parainfluenza-3 infection in goat flocks.     

Diagnosis of psoroptic sheep scab with an improved enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of specific antibodies against crude Psoroptes antigen. The diagnostic sensitivity was 93.7% in 191 sheep with clinical signs associated with mange. These animals originated from 29 flocks in which psoroptic mites were detected. All of 59 sheep infested with Psoroptes ovis were seropositive. Additionally, in 49% of 70 clinically unaffected sheep originating from P. ovis-infested flocks, specific antibodies could be detected, suggesting that asymptomatic infestations can be diagnosed by serology. The specificity of the ELISA was 96.5% as determined with 254 sheep originating from 44 flocks without clinical mange. Cross-reactivity in a low range was detected with selected sera of sheep with clinical chorioptic or forage mite infestations. Four sheep seroconverted 2 weeks after experimental P. ovis infestation, i.e. 2 weeks before clinical signs became obvious. After successful doramectin treatment of 14 sheep with naturally acquired P. ovis infestation, the ELISA values declined slowly but remained positive in seven cases beyond 17 weeks.