The extent of parasite-associated necrosis in the placenta and foetal tissues of cattle following Neospora caninum infection in early and late gestation correlates with foetal death

The protozoan parasite Neospora caninum is the most frequently diagnosed abortifacient in the UK and a leading cause of abortion worldwide but the mechanisms leading to abortion are not fully understood. The distribution of parasites and the histopathological changes in the placenta and foetus were compared in 12 cows following experimental infection of cattle with N. caninum in early (n=6) and late (n=6) gestation, by PCR, immunohistology, light microscopy and transmission electron microscopy. Twelve uninfected pregnant cattle were used as controls. Infection in early gestation led to foetal death. In the placentae of cattle immediately following foetal death, N. caninum DNA was detected and there was evidence of widespread parasite dissemination. This was associated with extensive focal epithelial necrosis, serum leakage and moderate maternal interstitial mononuclear cell infiltration. In the foetuses, parasites were evident in all tissues examined and were associated with necrosis. In the placenta of cattle infected in late gestation, N. caninum DNA was detected sporadically but parasites were not evident immunohistologically. Small foci of necrosis were seen associated with mild interstitial mononuclear cell infiltration. Detection of N. caninum DNA in the foetuses was sporadic and parasites were demonstrated immunohistologically in brain and spinal cord only, with an associated mononuclear cell infiltration. This data is consistent with uncontrolled parasite spread in an immunologically immature foetus and could, via multiparenchymal necrosis of foetal tissues or the widespread necrosis and inflammation observed in the placenta, be the cause of Neospora-associated abortions.     

Treatment of low-grade non-Hodgkin's lymphoma with continuous infusion of low-dose recombinant interleukin-2 in combination with the B-cell-specific monoclonal antibody CLB-CD19

Seven patients with low-grade non-Hodgkin's lymphoma were treated with a combination of a murine monoclonal antibody directed against the B-cell-specific antigen CD19 (CLB-CD10), given twice weekly, and continuous infusion of low-dose recombinant interleukin-2 (rIL-2). We demonstrated stable serum CLB-CD19 levels throughout the 12 weeks of treatment, and homing of the antibody into the tumour sites. A variable degree of antigenic modulation was noted. Prolonged treatment resulted in a sustained increase in the number of natural killer cells in the circulation with enhanced cytotoxic capacity, including antibody-dependent cellular cytotoxicity. During the first weeks of treatment, T cell activation occurred in the majority of patients. Toxicity was related to the rIL-2 treatment and consisted of transient constitutional symptoms and a flu-like syndrome without organ dysfunction. A partial remission occurred in one patient, and in another patient who was primarily leukaemic a greater than 50% reduction of circulating B cells was noted. An antitumour effect occurred early during treatment and could not be related to rIL-2-induced modulation of natural killer cell or T lymphocyte activation.     

Onchocerca ochengi: Mimic, model or modulator of O. volvulus?

The cattle parasite, Onchocerca ochengi, is widely distributed in West Africa. Significantly, Simulium darnnosum, the vector o f the important human parasite, O. volvulus, the cause o f river blindness, also appears to be the vector of O. ochengi. For epidemiological reasons it is therefore vital to be able to distinguish the infective larvae o f these filoriae. Here, Sandy Trees also describes other features of the cattle parasite that make it of significance to investigations of human filariases.     

Optimizing Seed Water Content:Relevance to Storage Stability and Molecular Mobility

This research was conducted to determine the optimum moisture content (MC) that gave maximum longevity to seeds. Three species were used to represent seeds with different dry matter reserves, which gives them different sorption properties: maize (Zea mays L.), elm (Ulmus pumila L.) and safflower (Carthamus tinctorius L.). The seeds of elm, safflower, and maize embryos with MC ranging from 0.00– 0.15 g H2O/g dry weight (DW) were stored at 35 °C for different periods of time. The results showed that the optim...     

Evolution of acaricide resistance: phenotypic and genotypic changes in field populations of Rhipicephalus (Boophilus) microplus in response to pyrethroid selection pressure

There have been few, if any, studies of arthropod field populations quantifying the kinetics of evolution of phenotypic and genotypic resistance to chemicals in response to the presence or absence of selection pressure. A prospective intervention study was undertaken over 2 years in Mexico to measure changes in resistance phenotype and genotype in the presence or absence of pyrethroid selection pressure on field populations of Rhipicephalus (Boophilus) microplus ticks on 11 farms with varying degrees of pyrethroid resistance. The resistance phenotype was evaluated by bioassay in a larval packet test expressed as the resistance factor (RF) derived from probit analysis of dose mortality regressions, and resistance genotype by an allele-specific PCR (AS-PCR) to determine the frequency of a sodium channel mutation (F1550I) associated with pyrethroid resistance. To validate the AS-PCR, a Pyrosequencing? method was developed to detect the F1550I mutation. There was good concordance with the genotypes identified by both Pyrosequencing? and AS-PCR (Kappa: 0.85). On five farms cypermethrin (CY) was exclusively used at intervals and on six farms amitraz was used. On two of the five CY-treated farms, the experiment was prematurely terminated due to unacceptably high levels of tick resistance. For all five farms, after 8–24 months of continued selection pressure with CY, the RF had increased 2–125-fold. The frequency of the resistance allele increased on all five farms from a starting range of 5–46% to a range of 66–95% after 8–24 months. On six farms treated with amitraz neither the RF nor the frequency of the resistance allele changed. A clear correlation between the phenotype and genotype was found in three of four treated farms confirming that the F1550I mutation is a major cause of synthetic pyrethroid resistance in Mexico. These results show that the pyrethroid resistance trait is stable (> 2 years) and that resistance is acquired much faster than it is lost. Hence, alternation of pyrethroid acaricide with other chemicals is likely to lead to the stepwise acquisition of synthetic pyrethroid resistance but not additional prolongation of its efficacious lifespan.     

美洲黑杨与大青杨杂种无性系耐寒性的初步研究

以美洲黑杨与大青杨杂种无性系1年生扦插苗为材料,测定其低温胁迫中多个生理指标的变化。结果表明,6个杂种无性系SOD、POD和APX活性在低温胁迫中均表现出先上升后下降的趋势,而电解质渗漏率、活性氧含量、CAT和GR活性保持逐渐升高的趋势。无性系间差异显著,其中DU146和DU147电解质渗漏率和活性氧含量最低,而5种抗氧化酶活性均最高,表明其具有较强的耐寒性;而DU135和DU150电解质渗漏率和活性氧含量最高,而5种抗氧化酶活性均最低,表明其耐寒性差。     

Epidemiology of a Salmonella enterica subsp. enterica Serovar Typhimurium Strain Associated with a Songbird Outbreak

Salmonella enterica subsp. enterica serovar Typhimurium is responsible for the majority of salmonellosis cases worldwide. This Salmonella serovar is also responsible for die-offs in songbird populations. In 2009, there was an S. Typhimurium epizootic reported in pine siskins in the eastern United States. At the time, there was also a human outbreak with this serovar that was associated with contaminated peanuts. As peanuts are also used in wild-bird food, it was hypothesized that the pine siskin epizootic was related to this human outbreak. A comparison of songbird and human S. Typhimurium pulsed-field gel electrophoresis (PFGE) patterns revealed that the epizootic was attributed not to the peanut-associated strain but, rather, to a songbird strain first characterized from an American goldfinch in 1998. This same S. Typhimurium strain (PFGE type A3) was also identified in the PulseNet USA database, accounting for 137 of 77,941 total S. Typhimurium PFGE entries. A second molecular typing method, multiple-locus variable-number tandem-repeat analysis (MLVA), confirmed that the same strain was responsible for the pine siskin epizootic in the eastern United States but was distinct from a genetically related strain isolated from pine siskins in Minnesota. The pine siskin A3 strain was first encountered in May 2008 in an American goldfinch and later in a northern cardinal at the start of the pine siskin epizootic. MLVA also confirmed the clonal nature of S. Typhimurium in songbirds and established that the pine siskin epizootic strain was unique to the finch family. For 2009, the distribution of PFGE type A3 in passerines and humans mirrored the highest population density of pine siskins for the East Coast.     

Immunisation with a Multivalent,Subunit Vaccine Reduces Patent Infection in a Natural Bovine Model of Onchocerciasis during Intense Field Exposure

Human onchocerciasis, caused by the filarial nematode Onchocerca volvulus, is controlled almost exclusively by the drug ivermectin, which prevents pathology by targeting the microfilariae. However, this reliance on a single control tool has led to interest in vaccination as a potentially complementary strategy. Here, we describe the results of a trial in West Africa to evaluate a multivalent, subunit vaccine for onchocerciasis in the naturally evolved host-parasite relationship of Onchocerca ochengi in cattle. Naïve calves, reared in fly-proof accommodation, were immunised with eight recombinant antigens of O. ochengi, administered separately with either Freund''s adjuvant or alum. The selected antigens were orthologues of O. volvulus recombinant proteins that had previously been shown to confer protection against filarial larvae in rodent models and, in some cases, were recognised by serum antibodies from putatively immune humans. The vaccine was highly immunogenic, eliciting a mixed IgG isotype response. Four weeks after the final immunisation, vaccinated and adjuvant-treated control calves were exposed to natural parasite transmission by the blackfly vectors in an area of Cameroon hyperendemic for O. ochengi. After 22 months, all the control animals had patent infections (i.e., microfilaridermia), compared with only 58% of vaccinated cattle (P = 0.015). This study indicates that vaccination to prevent patent infection may be an achievable goal in onchocerciasis, reducing both the pathology and transmissibility of the infection. The cattle model has also demonstrated its utility for preclinical vaccine discovery, although much research will be required to achieve the requisite target product profile of a clinical candidate.