A comparison of the cytobrush and uterine lavage techniques to evaluate endometrial cytology in clinically normal postpartum dairy cows

This study compares cytobrush and lavage techniques for the assessment of endometrial cytology (EC) in clinically normal postpartum dairy cows. The EC samples were collected from Holstein cows (n = 35) during visit 1 (V1) at 20 to 33 d in milk (DIM) and 2 wk later during visit 2 (V2) at 34 to 47 DIM by using both techniques. A minimum of 100 cells were counted to determine the percentage of cells that were neutrophils (%PMN). The mean %PMN was significantly different between the techniques at V1 (P = 0.001), but not at V2 (P = 0.474). Overall, the %PM N decreased with time postpartum (r2 = 0.36; P = 0.001), but not within V1 (P > 0.05) or V2 (P > 0.1). Uterine diameter was negatively correlated with fluid recovery by the lavage technique (r2 = 0.41; P = 0.002). The mean %PMN was not influenced by the volume of fluid recovered in successful attempts, but 17% (12/70) of attempts yielded no fluid. In conclusion, the cytobrush technique is a consistent and reliable method for obtaining endometrial samples for cystologic examination from postpartum dairy cows.     

Udder health in dairy cattle infected with Neospora caninum

Blood samples were collected from 3449 cows on 57 representative Ontario dairy herds during the summer of 1998 and analysed for antibody to Neospora caninum using an ELISA. Forty-eight herds (2742 cattle) contained at least one N. caninum-seropositive animal. Two composite milk samples were collected from all cattle: the first on the day of blood collection and the second 68 to 365 days later. All milk samples were submitted for bacteriological culture. Ontario Dairy Herd Improvement Corporation (DHI) data were available for 3162 cattle in the 57 herds at the time of bleeding. Furthermore, complete DHI data were available for 1658 cattle that were culled between 12 and 24 months following blood collection. Using a standardised ELISA sample-to-positive (S/P) cut-off of ≥0.45, the corrected seroprevalence was 8.2% overall and 10.1% within seropositive herds. At blood collection the odds of N. caninum-seropositive cows having a high linear score (≥4.0; equivalent to a somatic cell count ≥200,000 cells/ml) was 27% less than for seronegative animals. Similarly, at the time of culling, the odds of having a high linear score was 22% less in N. caninum-seropositive cattle. Overall, linear score was lower in N. caninum-seropositive cattle at culling. After controlling for herd, parity, days in milk, and the interval between collection of milk samples, the odds of N. caninum-seropositive cattle testing positive for an environmental pathogen (i.e. environmental Streptococcus species and coliforms) on the second milk sample was 56% less than for seronegative animals. The odds were 83% less at a higher ELISA S/P cut-off of ≥0.70. Finally, the odds of N. caninum-seropositive cattle developing a new infection with a major pathogen (environmental or contagious) were 60% less than seronegative cows using the higher ELISA S/P cut-off.     

Study of host-pathogen interactions to identify sustainable vaccine strategies to Marek's disease

Marek’s disease virus is a highly cell-associated, lymphotropic -herpesvirus that causes paralysis and neoplastic disease in chickens. The disease has been contained by vaccination with attenuated viruses and provides the first evidence for a malignant cancer being controlled by an antiviral vaccine. Marek’s disease pathogenesis is complex, involving cytolytic and latent infection of lymphoid cells and oncogenic transformation of CD4⁺ T cells in susceptible chickens. Innate and adaptive immune responses develop in response to infection, but infection of lymphocytes results in immunosuppressive effects. The remarkable ability of MDV to escape immune responses by interacting with, and down-regulating, some key aspects of the immune system will be discussed in the context of genetic resistance. Resistance conferred by vaccination and the implications of targeting replicative stages of the virus will also be examined.     

Infection rates in reactors to an absorbed ELISA used in a test and cull program for bovine Johne's disease

OBJECTIVE: To determine the proportion of cattle, whose sera gave positive reactions in a commercial enzyme linked immunosorbent assay (ELISA) for bovine Johne's disease, that were confirmed infected with Mycobacterium avium subsp paratuberculosis by histology and culture of tissues. PROCEDURE: Dairy cattle (n = 493) from the Echuca district of Victoria, whose sera were positive in the ELISA, were slaughtered at an abattoir where standard specimens were collected for histology and culture. Only if samples were histologically negative were further samples submitted for culture. RESULTS: The proportion of cattle in which infection was confirmed increased from 70.4% in 1996 to 89.4% in 2001 giving an overall confirmation rate of 79.9%. This was mainly because more reactors were confirmed by culture each year, the proportion increasing from 0% in 1997 to 27.5% in 2000 but decreasing to 16.7% in 2001. If all unconfirmed reactors were presumed to be uninfected, the minimum specificity of the ELISA was 99.62%. There were no significant differences between the age groups in the proportion confirmed infected. CONCLUSION: Confirmation rates and specificity of the ELISA were high when used in a typical JD-infected Victorian dairy cattle population. Imperfect sensitivity of histology and culture and the selection of reactors which favoured more false positives, means the estimates were probably conservative. Confirmation rates were not affected by age of ELISA reactor.     

鸡转移因子的制备及其应用研究 Ⅲ.对法氏囊病和马立克氏病的治疗试验

用鸡ＴＦ分别对人工感染发病的ＩＢＤ鸡和神经型ＭＤ自然发病鸡进行治疗。治疗结果显示鸡ＴＦ具有较好的治疗效果，尤其在重复感染时表现出巨大的优势，因而对ＩＢＤ污染严重的鸡场具有极好的使用价值。鸡ＴＦ对ＭＤ（神经型）有明显的抑制作用，但却不能最终治愈     

The immunologists' debt to the chicken

The immune system of the chicken is an invaluable model for studying basic immunology and has made seminal contributions to fundamental immunological principles. Graft versus host responses and the key role of lymphocytes in adaptive immunity were first described in work with chicken embryos and chickens. 2. Most notably, the bursa of Fabricius provided the first substantive evidence that there are two major lineages of lymphocytes. Bursa-derived lymphocytes, or B cells, make antibodies while thymus-derived, or T cells, are involved in cell-mediated immune responses. 3. Gene conversion, the mechanism used by the chicken to produce its antibody repertoire, was first described in the chicken and requires the unique environment of the bursa. Subsequently it has been shown that some mammals also use gene conversion. 4. The chicken's Major Histocompatibility Complex (MHC), the first non-mammalian MHC to be sequenced, is minimal, compact and some 20-fold smaller than that of mammals. Uniquely, the chicken MHC is strongly associated with resistance to infectious diseases. 5. The first attenuated vaccine was developed by Louis Pasteur against a chicken pathogen, fowl cholera, and the first vaccine against a natural occurring cancer agent, Marek's disease virus, was developed for the chicken. 6. Vaccination of chick embryos on the 18th d of incubation, another breakthrough using chickens, provides protection early after hatching. In ovo vaccination now is widely practised by the poultry industry. 7. Evidence that widespread and intensive vaccination can lead to increased virulence with some pathogens, such as Marek's disease virus and infectious bursal disease virus, was first described with chicken populations. It warns of the need to develop mo resustainable vaccination strategies in future and provides useful lessons for other species, including in the human population. 8. Recombinant DNA technologies now provide the opportunity for the rational design of new vaccines. Such vaccines could contain the protective immunogenic elements from several pathogens and immunomodulatory molecules to direct and enhance immune responses so providing improved protection. The important thing will be to design vaccines that are sustainable and do not drive pathogens to ever-increasing virulence.     

The prevalence of Cowdria ruminantium in free-living adult Amblyomma hebraeum collected at a communal grazing area and in 2 wildlife reserves in South Africa

In order to detect the prevalence of Cowdria ruminantium in the vector tick, Amblyomma hebraeum, free-living, unfed adult ticks were collected with the aid of pheromone/CO2 traps. Ticks were collected at the Rietgat communal grazing area, as well as in the southwestern Kruger National Park and in the Songimvelo Game Reserve, all located in heartwater-endemic areas of South Africa. The presence of C. ruminantium in these ticks was determined by polymerase chain reaction (PCR) analysis. Ticks from the Rietgat communal grazing area were assayed in 2 batches and 4.7% of the one and 11.3% of the other were positive for infection, while 5.7% of the ticks collected in the Kruger National Park and 25% in the Songimvelo Game Reserve were positive. These results support the contention that a vector-wildlife cycle of transmission of C. ruminantium, the cause of heartwater in domestic ruminants, can be maintained in the absence of the latter animals.     

Use of ionophores in lactating dairy cattle: a review

Ionophores are feed additives that alter rumen microbial populations through ion transfer across cell membranes. Although ionophores have been used widely in the beef industry for improved feed efficiency and control of coccidiosis, there has been limited use by the dairy industry. In Canada, the label warning prohibiting the use of monensin premix in lactating dairy cattle was removed in June 1996. Following this, in December 1997, a controlled release capsule containing monensin was approved for use in dairy cattle as an aid to prevent subclinical ketosis. Monensin may have several advantages for dairy cattle, including improved energy metabolism, increased milk production, and altered milk components. This literature review was primarily conducted in 1996 by using the Agricola and CAB search databases. Other relevant articles published since the search (up to 1998) have been added. This review will provide practitioners with relevant references in the published literature regarding ionophore use in dairy cattle. It should also give some guidance as to what effects might be anticipated with the use of ionophores in lactating dairy animals.     

用Dot-ELISA检测传染性法氏囊病病毒

用从抗传染性法氏囊病(IBD)高免卵黄液中提取IgG包被抗体和酶标记抗体,建立了检测IBD病毒的Dot-ELISA方法。经特异性检验,阻断实验及临床应用,证明此法具有良好的特异性、敏感性。病毒的检出率为100％,与组织病理学方法的符合率达100％,比免疫琼脂扩散法提高检出率40％,而且方法简便、节省材料、是IBD早期病原学诊断和流行病学调查的有效手段。