Rapid quantitative assessment ofTheileria infection in ticks

A simplified method for methyl green pyronin staining is described for Theileria parva and T. annulata in whole salivary glands of Rhipicephalus appendiculatus and Hyalomma anatolicum subspecies respectively. The stain gives results comparable with Feulgen staining and can be used after the ticks have been in cold storage for 3 days. There is considerable variability in the rate and intensity of infection of these ticks with theilerial parasites and it is concluded that the method permits large samples (60 ticks per person per day) to be examined to overcome this variability when assessing infection quantitatively.     

An outbreak of listeriosis in cattle in Nigeria.

An outbreak of listeriosis in a herd of cattle associated with still birth, abortion, nervous signs and death is reported. Typical micro abscesses in the brain were not observed on histopathology but a marked purulent meningitis was seen and Listeria monocytogenes was isolated on culture.     

中国大陆高致病性禽流感发生风险定量评估

动物疫病风险评估是疫情防控的一个重要环节.本研究利用本实验室所建立的风险评估框架,对中国大陆2 369个县/市2006年1月至12月份高高致病性禽流感(HPAI)发生风险进行了定量评估,并利用疫情数据对评估结果进行了验证.结果显示在3月、4月、10月和11月高风险地区数量多、分布广,在华中、华北、西北和东北均有分布;1月、2月、5月、9月和12月HPAI高风险地区的数量相对较少,1月、2月和12月份主要分布在华南,5月和9月主要分布在华北和东北;6月、7月和8月HPAI高风险地区数量最少,而且分布集中,主要分布在青藏高原地区.通过对2006年疫情与评估结果的相关性分析发现,发生疫情的县/市当月的风险评估结果相对较高.本研究结果表明,HPAI定量风险评估方法对HPAI在大范围内发生风险进行定量评估具有可行性,该方法通过进一步优化可望应用于中国HPAI防控决策方面的研究.     

Treatment with toltrazuril in a natural outbreak of coccidiosis in calves

Treatment with toltrazuril (Baycox) in calves naturally infected with several enteropathogenic agents resulted in a reduction in the mean number of Eimeria oocysts shed. The mean faecal consistency for the treated calves also differed significantly from that of the untreated calves. There was virtually no difference in weight gain in the two groups.     

Major outbreak of suspected botulism in a dairy herd in the Republic of Ireland

This is the first report of a major outbreak of a paralytic disease in cattle on a farm in the Republic of Ireland. Thirty-six of 65 dairy cows were euthanased or died. A presumptive diagnosis of botulism was made on the basis of the clinical signs, the duration of the outbreak and the postmortem findings, and by ruling out other differential diagnoses.     

Survival of Listeria monocytogenes in wilted and additive-treated grass silage

Grass was field-dried to 3 different dry matter (DM) levels (200, 430 and 540 g/kg) and inoculated with 10(6)-10(7) cfu/g of a Listeria monocytogenes strain sharing a phagovar occasionally involved in foodborne outbreaks of listeriosis. Formic acid (3 ml/kg) or lactic acid bacteria (8 x 10(5)/g) with cellulolytic enzymes were applied only to forages with low and intermediate DM levels. Forages were ensiled in laboratory silos (1700 ml) and were stored at 25 degrees C for 30 or 90 days. After 90 days of storage, L. monocytogenes could not be detected in any silo, except one with the high dry matter grass without additive. After 30 days of storage, between 10(2) and 10(6) cfu L. monocytogenes/g silage were isolated from the untreated silages. Increasing the DM content from 200 to 540 g/kg did not reduce listeria counts possibly because of the lower production of fermentation acids (higher pH). In silages treated with additives, counts of L. monocytogenes were always lower than in silages without additive. In wet silages (DM 200 g/kg) both additives were effective, but in the wilted silages (DM 430 g/kg) only the bacterial additive reduced listeria counts below detection level. Listeria counts were highly correlated to silage pH (r = 0.92), the concentration of lactic acid (r = -0.80) and the pooled amount of undissociated acids (r = -0.83).     

A detailed assessment of the pattern of moxidectin tissue distribution after pour-on treatment in calves

The use of topical (pour-on) administration of endectocide drugs in cattle has reached world-wide acceptance. However, only limited information is available on the kinetic behaviour for topically administered moxidectin (MXD). To improve our understanding of the relationship between pharmacokinetics and efficacy for pour-on preparations, MXD concentration profiles were measured in tissues of endo- and ectoparasites location over 35 days postadministration. MXD distribution to the fluid content and mucosal tissue of the abomasum and different intestinal sections (duodenum, ileum, caecum and colon) was assessed. The comparative patterns of MXD distribution to skin and hypodermic tissue from different anatomical sites (backline, rib cage, thigh and face) were also investigated following the pour-on administration. Wide tissue distribution and long residence time characterized the kinetics of topically administered MXD. MXD was recovered between 1 and 35 days post-treatment in all the tissues investigated. The highest MXD availabilities were observed in the skin layers at the site of administration (backline) and in the fat tissue. The fluid contents of different intestinal sections showed MXD concentrations higher than those measured in their respective mucosal tissues, particularly at day 1 post-treatment. MXD concentrations in the skin (epidermis + dermis) were higher than those measured in the hypodermic tissue. Large differences in the availability of MXD in skin from different anatomical regions (backline > rib cage > thigh > face) were observed. The low plasma and the high skin availability indicate the formation of a skin depot of the drug, being released slowly to the plasma and reaching concentrations in systemic tissues (abomasal mucosa, lungs, etc.) similar to those measured after subcutaneous administration. These findings demonstrate that target parasites may be exposed to markedly different drug concentrations according to their location sites, which is particularly relevant for ectoparasites located in different anatomical regions. Knowledge of the tissue distribution of topically administered endectocides contributes to understand the differences observed in efficacy and/or persistence of activity and to optimize their use in cattle.     

Associations among Listeria monocytogenes genotypes and distinct clinical manifestations of listeriosis in cattle

OBJECTIVE: To determine whether specific strains of Listeria monocytogenes, as determined by genetic characteristics and virulence phenotypes, were associated with distinct clinical manifestations of listeriosis in cattle and thus may potentially have tissue specificity. ANIMALS: 32 cattle. PROCEDURE: DNA sequence data for the virulence genes actAand inlAwere used to infer the phylogeny of L. monocytogenes and to test for positive selection. Isolates were screened for the presence or absence of internalin genes and assigned an internalin profile. Plaquing assays were performed to determine the relative cytopathogenicity of each isolate. Categorical data analyses were performed to describe associations among L. monocytogenes genotypes, virulence phenotypes, and clinical manifestations of listeriosis. RESULTS: Results confirmed that L. monocytogenes represents 2 deeply separated evolutionary lineages. Genes actA and inlA contained amino acid sites under positive selection, and specific residues at some sites were associated with lineage and manifestation of listeriosis. Whereas lineage I was clonal and predominantly composed of isolates from cases of encephalitis, lineage II was more genetically diverse and equally represented by isolates from cases of encephalitis versus septicemia and fetal infection. Lineage I isolates also had greater cytopathogenicity in vitro, compared with lineage II isolates. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that L. monocytogenes virulence genes underwent positive selection that is consistent with the diversification of 2 evolutionary lineages: lineage I is clonal and associated with encephalitis, and lineage II is more genetically diverse and equally likely to cause both major forms of listeriosis in cattle.     

Use of tilmicosin in a severe outbreak of respiratory disease in weaned beef calves

Severe respiratory disease, associated with seroconversion to bovine respiratory syncitial virus (BRSV), caused the death of two cattle and necessitated antibiotic treatment of 70 calves (rectal temperature of 39.6°C or greater) from a group of 96 (73%) during an 8-day period. Tilmicosin injection resulted in a reduction in median rectal temperature from 40.3°C to 39.2°C and 39.0°C for the first and second days after treatment. The rectal temperature was 39.5°C or lower in 72% (48 of 67) and 96% (64 of 67) of cattle 1 and 2 days after tilmicosin treatment, respectively. Ten cattle were re-treated with tilmicosin 6 to 16 days after the first treatment. Our study demonstrated that bovine respiratory syncytial virus infection could cause severe respiratory disease in a beef herd that had no previous history of BRSV-related disease. Secondary bacterial invasion after BRSV infection was controlled effectively by tilmicosin treatment but repeat antibiotic treatments were occasionally necessary due to bacterial re-infection of the respiratory tract.     

使用Reveal试剂盒快速检测单增李斯特氏菌的研究

单核细胞增生李斯特氏菌(Listeria monocytogens,LM,简称为单增李斯特氏菌)是食品卫生上重要的病原菌。它广泛存在于自然界,可导致人和动物脑膜炎、流产、败血症等,病死率高达30%-70%,是目前人类最重要的食物源性病原菌之一。由于该菌生长温度范围较广,在