Associations ofAscaris suum and Oesophagostomum spp. infections of sows with management factors in 83 Danish sow herds

Associations of the occurrence of Ascaris suum and Oesophagostomum spp. in sows with herd management factors were examined using logistic-binomial regression. The information used was from 11 to 78 sows sampled from each of 83 breeding herds (2961 sows in total) and examined for eggs per gram of faeces (EPG). A sow excreting at least 20 EPG was defined as ‘infected’. Management factors of the study herds were recorded using a questionnaire. A total of 263 sows from 50 herds (8.9% of sows) and 375 sows from 20 herds (12.7% of sows) were infected with A. suum and Oesophagostomum spp., respectively. For A. suum, sows from herds with more than 85 sows had significantly higher odds of being infected compared with those from 30 to 85 sows (P < 0.05). When bedding was provided for sows, the odds of A. suum infection was 5.4 compared with sows from herds in which bedding was not provided (P < 0.05). For Oesophagostomum spp., sows from herds with different specific pathogen free status had about one tenth the odds of being infected compared with those from conventional herds (P < 0.05). Sows that had been treated with anthelmintics had very low odds of being infected with Oesophagostomum spp. compared with those that were not treated (P < 0.05). The effects of these management factors in both final models did not differ when the definition of an ‘infected’ sow was changed. The present results suggest the importance of disposal of bedding material from pens in reducing the prevalence of A. suum in larger sow herds. Anthelmintic treatment is important in reducing the prevalence of Oesophagostomum spp. infection of sows.     

A longitudinal study of serological patterns of respiratory infections in nine infected Danish swine herds

Sixteen litters of seven pigs from each of nine Danish farrow-to-finish herds were followed to investigate the serological patterns caused by natural infection with Mycoplasma hyopneumoniae, Pasteurella multocida toxin and Actinobacillus pleuropneumoniae serotypes 2, 5–7, 12. In seven of the herds, pigs were followed as two separate cohorts started 4 weeks apart, and in two herds only one cohort was followed.

A total of 999 pigs were included in the study. The pigs were blood sampled at weaning and subsequently every fourth week until slaughter. All pigs were examined for antibodies against M. hyopneumoniae (enzyme-linked immunosorbent assay), P. multocida toxin (enzyme-linked immunosorbent assay) and A. pleuropneumoniae serotypes 2, 5–7, 12 (complement-fixation tests). The most-common pattern (28%) of seroconversion was that of pigs first seroconverting to A. pleuropneumoniae serotype 2, followed by seroconversion to M. hyopneumoniae. Each herd had a dominant serotype of A. pleuropneumoniae to which most pigs seroconverted. Seroconversion to the respiratory pathogens occurred mainly in the growing-to-finishing units (8–24 weeks). The risk of seroconversion to the P. multocida toxin was very low (<20%) and occurred late.

None, four and seven herds tested seropositive to PRRS and to swine influenza virus subtypes H3N2 and H1N1, respectively, when testing 10 pigs per herd (selected randomly among the study pigs) at the age of 20 weeks.     

Differential diagnosis of dog hookworms based on PCR-RFLP from the ITS region of their rDNA

Species of Ancylostoma infecting dogs and sometimes humans are sympatric in many parts of the world. The establishment of a specific molecular diagnostic tool is important, not only to refine information for epidemiological studies, but also to evaluate the efficacy of vaccine programmes and assist in the development of specific drug treatments. The ITS region from 20 specimens of A. braziliense, collected from three separate geographical areas of Brazil, and from 10 specimens of A. caninum, collected from the same area in Brazil were sequenced and analyzed. Alignment of sequences showed that this gene is highly conserved. The intraspecific polymorphism for both species was less then 1%, whereas the interspecific polymorphism was 6.2, 7.3 and 9.4% between A. ceylanicum and A. braziliense; A. caninum and A. ceylanicum and A. ceylanicum and A. braziliense, respectively. Among the three species it was 12.3%. This revealed the ITS region as highly conserved and consequently a good molecular marker for diagnostic studies. In this work, four restriction enzymes were used in a PCR-RFLP using the ITS region of rDNA, to establish a differential diagnosis which discriminates between three Ancylostoma species, A. braziliense, A. caninum and A. ceylanicum. The best pattern was given by the HinfI enzyme, which produced different fragment sizes for each of the three species. Furthermore, the diagnostic tool differentiates DNA extracted directly from faeces of Ancylostoma-infected dogs.     

Detection of intestinal parasites in pig slurry: A preliminary study from five farms in Spain

The aim of this study was to investigate the presence of intestinal parasites in pig slurries from several piggeries in Alicante (Spain). Pig slurries were collected in five highly-intensive pig farms (A–E), being sampled in each farm from the pits depending on the production cycle (gestating sows, farrowing sows, weaners, finishers). Samples were concentrated either through zinc sulphate flotation or by formalin–ethyl acetate sedimentation methods. Parasitological examination was performed by optical microscopy. Detection of Cryptosporidium sp. was performed using conventional acid-fast stain and by DNA extraction and PCR amplification. Cryptosporidium genus-specific primers (CPBDIAGF and CPBDIAGR) were used to amplify the Cryptosporidium SSU-rRNA variable region. Intestinal parasites were found in all farms studied. Several protozoa (Ballantidium coli, Entamoeba coli and Cryptosposidium sp.) and helminths (Ascaris suum, Trichuris suis, Fasciola hepatica, Strongylida and nematode larvae) were identified. Parasite viability studies are needed in order to assess the potential risk for animal and human health.     

宁乡猪FABPs、SLC13A5和NR1H4基因多态性及其与IMF含量的关联分析

旨在研究宁乡猪FABPs、SLC13A5和NR1H4基因的多态性及其与肌内脂肪（IMF）含量的关联性。本试验采用PCR-RFLP和Sanger测序的方法对172头宁乡阉公猪FABPs、SLC13A5和NR1H4基因的多态性进行检测,并探究多态性与宁乡猪IMF含量的关联性。结果表明,宁乡猪H-FABP-Hinf Ⅰ酶切位点存在多态性,其中Hh基因型个体的IMF含量最高,与HH、hh基因型个体的IMF含量差异极显著（P<0.01）;H-FABP-Hae Ⅲ酶切只检测到DD和Dd两种基因型,Dd基因型个体的IMF含量极显著高于DD基因型个体（P<0.01）;H-FABP基因的Hinf Ⅰ和Hae Ⅲ多态性位点共形成3种单倍型和5种单倍型组合,其中单倍型组合HD/hd个体具有最佳的IMF含量。H-FABP的Msp I酶切结果及A-FABP基因测序结果显示,宁乡猪不存在多态现象;SLC13A5基因多态性位点g.50705299T/C和NR1H4基因多态性位点g.83607915G/A处不同基因型间IMF含量的差异均不显著（P>0.05）。综上所述,H-FABP基因Hinf Ⅰ和Hae Ⅲ酶切位点多态性与宁乡猪IMF含量显著关联,其形成的单倍型组合HD/hd的IMF含量最高。以上结果可为宁乡猪IMF含量性状的早期分子选育提供参考。     

不同类型抗蒸腾剂对4种草本植物叶片水分利用效率的影响

为探究3种抗蒸腾剂叶片喷施对4种草本植物水分消耗和利用的影响规律,比较得出不同抗蒸腾剂的最佳使用浓度,为干旱荒漠区采煤迹地植被保育技术提供参考,本试验以蒙古冰草（Agropyron mongolicum Keng）、沙打旺（Astragalus adsurgens Pall.）、白花草木樨（Melilotus albus Medic.ex Desr.）、蜀葵（Althaea rosea （Linn.）Cavan.）4种草本植物为研究对象,每种草叶面分别喷施不同类型和浓度的抗蒸腾剂：旱地龙（Fulvic Acid,FA）浓度分别为1,2,3,4 g·L^-1;冠存（Guan Cun,GC）浓度分别为3,6,9,12 g·L^-1;高岭土（Kaolin,KL）浓度分别为20,40,60,80 g·L^-1,以喷施清水为对照,喷施3个月后测定其对4种草叶片蒸腾速率（Transpiration rate,Tr）、净光合速率（Net photosynthetic rate,Pn）、水分利用效率（Water use efficiency,WUE）和生物量的影响。结果表明：在试验浓度区间内,FA浓度越高,蒙古冰草、沙打旺、白花草木樨的Tr值越小、Pn值越小,WUE呈现先升高再降低的趋势;GC喷施浓度越高,蒙古冰草、沙打旺、白花草木樨叶片的Tr值越小、WUE值越大,Pn值较对照低但各浓度间未达到显著性差异;KL喷施浓度越高,蒙古冰草与蜀葵各浓度处理的Pn值越小、WUE值越小,Tr值较对照低但各浓度间未达到显著性差异。3种抗蒸腾剂对蒸腾速率的抑制程度均为GC和KL大于FA,对净光合速率的抑制程度均为KL和GC小于FA,对水分利用效率的提升程度均为KL和GC大于FA。综合3种抗蒸腾剂在植物叶面的喷施效果,GC和KL喷施效果较好,FA较差;蒙古冰草与沙打旺喷施12 g·L^-1的GC、白花草木樨与蜀葵喷施20 g·L^-1 KL的措施可用于干旱荒漠区采煤迹地的植被恢复。     

黑水虻幼虫粉对育肥猪盲肠食糜主要微生物数量和代谢产物的影响

旨在研究日粮中添加不同比例的黑水虻幼虫粉对育肥猪盲肠食糜主要微生物数量和代谢产物的影响。本试验选取72头130日龄、健康且初始体重相近（（76.0±0.56）kg）的杜×长×大三元杂交猪,随机分为3个处理组,每组8个重复,每个重复3头猪。对照组饲喂基础日粮,试验组分别饲喂含有4%（4%组）和8%（8%组）的黑水虻幼虫粉,通过调整日粮配方,3组日粮的蛋白含量和代谢能一致。于正式试验的第42天,每个重复选取1头体重接近平均体重的猪进行屠宰,取盲肠食糜用于相关指标的测定。结果表明：1）与对照组相比,日粮添加4%的黑水虻幼虫粉显著增加了盲肠食糜Bifidobacterium、Lactobacillus、Prevotella、Clostridium cluster IV和Roseburia的数量（P<0.05）,而降低了Escherichia coli的数量（P<0.05）;日粮添加8%的黑水虻幼虫粉显著增加了Prevotella和Bifidobacterium的数量（P<0.05）。2）与对照组相比,日粮添加4%和8%的黑水虻幼虫粉显著增加了盲肠食糜中乳酸、总短链脂肪酸和乙酸的浓度（P<0.05）,同时,日粮添加8%黑水虻幼虫粉还降低了戊酸的浓度（P<0.05）;对于氮代谢产物而言,与对照组相比,日粮添加4%的黑水虻幼虫粉显著降低了盲肠食糜中总生物胺、尸胺、腐胺、精胺、对甲酚和苯酚的浓度（P<0.05）,而日粮添加8%的黑水虻幼虫粉显著降低了尸胺和苯酚的浓度（P<0.05）。综上所述,本试验条件下,在日粮中添加4%的黑水虻幼虫粉可增加育肥猪盲肠食糜中部分有益微生物的数量和有益代谢物的浓度,降低潜在致病菌的数量和氮代谢化合物的浓度,表明一定比例的黑水虻幼虫粉可作为优质的蛋白质饲料原料应用于养猪生产中。     

Occurrence and species level diagnostics of Campylobacter spp., enteric Helicobacter spp. and Anaerobiospirillum spp. in healthy and diarrheic dogs and cats

In order to study the occurrence and co-infection of different species of Campylobacter, enteric Helicobacter and Anaerobiospirillum in dogs and cats and define a possible association between these microrganisms and gastrointestinal disorders, 190 dogs and 84 cats, either healthy or with diarrhea, were sampled between 2002 and 2003. Thirty-three C. upsaliensis, 17 C. jejuni, 2 C. helveticus, 1 C. lari isolates from dogs and 14 C. helveticus, 7 C. jejuni, 6 C. upsaliensis isolates from cats were identified using species-specific PCR and phenotypic tests. Whole cell protein profile analysis, phenotypic tests, PCR-RFLP of gyrB and a phylogenetic study of partial groEL and 16S rRNA sequences were used to identify 37 H. bilis, 22 H. canis and 14 H. cinaedi in dogs and 12 H. canis, 5 H. bilis and 2 H. cinaedi in cats. Whole cell protein profile analysis, phenotypic tests and species-specific PCR of 16S rRNA were used to identify 14 A. succiniciproducens, 12 A. thomasii isolates and one unidentified Anaerobiospirillum sp. isolate in dogs and 3 A. thomasii isolates in cats. Fifty-two animals (19%) were positive for the isolation of more than one genus. No significant statistical correlation was found between any isolates of Campylobacter, Helicobacter or Anaerobiospirillum spp. or the various co-infection rates, and the presence of diarrhea in either dogs or cats. Campylobacter isolates were also tested for antibiotic resistance using the agar dilution method.     

冰草组织培养再生体系建立及耐旱转基因研究

本研究以冰草属植物中的4个品种——蒙古冰草新品系(A.mongolicum Keng)、航道冰草(A.cristatum cv.Fairway)、诺丹冰草(A.desertorum cv.Nordan)和一个种间杂种冰草——蒙农杂种冰草(A.cristatum×A.desertorum cv.Hycrest-Mengnong)为材料,分别以幼穗为外植体建立了冰草组织培养再生体系。在此基础上,以调控脯氨酸生物合成最后一步的关键酶的突变体基因P5CS为目标基因,bar基因为筛选标记基因,用基因枪法轰击幼穗诱导的愈伤组织,获得转基因植株。利用PCR方法从拟南芥(Arabidopsis thaliana)基因组DNA中分离得到了CBF4及其启动子,并对CBF4启动子进行了序列分析和初步的功能分析。     

晋汾白猪ApoA5基因单倍型与体重和肉质性状的相关性分析

试验旨在探究晋汾白猪载脂蛋白A5（apolipoprotein A5,ApoA5）基因的单倍型与体重和肉质性状的相关性。选取180头晋汾白猪为研究群体,利用PCR技术检测ApoA5基因的单核苷酸多态性（single nucleotide polymorphism,SNP）,并采用Haploview软件分析这些SNP位点的连锁不平衡程度;筛选非完全连锁的SNP位点,构建不同的ApoA5基因单倍型,统计不同单倍型的基因频率,并通过SPSS软件分析不同ApoA5基因单倍型与晋汾白猪体重和肉质性状的相关性,鉴定优良性状的ApoA5基因单倍型。结果显示,晋汾白猪ApoA5基因共检测到21个SNPs位点,其中5个完全连锁单倍型块,分别包含5、2、3、4和2个SNPs位点;另外10个非完全连锁的标签SNP组合成不同的ApoA5基因单倍型,其中Hap 1的基因频率最高,达到46.7%,远高于其他单倍型;ApoA5基因单倍型与晋汾白猪的初生重、断奶重、6月龄体重、肌内脂肪含量、剪切力和滴水损失均具有明显的相关性,而与pH_{24 h}没有明显的相关性;ApoA5基因Hap 11晋汾白猪的初生重、断奶重、6月龄体重和肌内脂肪含量均最高,且剪切力最低,滴水损失也相对较低;Hap 6的初生重最低;Hap 2的断奶重和6月龄体重均最低;Hap 3的肌内脂肪含量最低,剪切力最高;Hap 10的滴水损失最高。晋汾白猪ApoA5基因Hap 11属于优良性状单倍型,是一个具有优良性状的分子标记,可以用于晋汾白猪的分子育种,提高选种效率。     

Correlation Analysis Between Haplotypes of ApoA5 Gene on Body Weight and Meat Quality in Jinfen White Pigs

This study was aimed to explore the correlation between the haplotypes of apolipoprotein A5 (ApoA5) gene and body weight,meat quality in Jinfen White pigs.180 Jinfen White pigs were selected,PCR was used to detect the single nucleotide polymorphism (SNP) of ApoA5 gene,and the linkage of these SNPs was analyzed by Haploview software.Non-fully linked SNPs were screened to form the haplotypes of ApoA5 gene,and the frequency of different haplotypes of ApoA5 gene were calculated.The correlation between the haplotypes of ApoA5 gene and body weight,meat quality was analyzed by SPSS software to identify the haplotypes of ApoA5 gene with excellent traits.The results showed that ApoA5 gene of Jinfen White pigs contained 21 SNPs and 5 completely linked regions which included 5,2,3,4 and 2 SNPs,respectively.Ten non-completely linked tag SNPs were selected to form the haplotypes of ApoA5 gene,Hap 1 had the highest gene frequency (46.7%).The haplotypes of ApoA5 gene had a significant correlation with the birth weight,weaning weight,6-month-old body weight,intramuscular fat content,shear force and drip loss,but no significant correlation with pH_{24 h} in Jinfen White pigs.Hap 11 of ApoA5 gene in Jinfen White pigs had the highest birth weight,weaning weight,6-month-old body weight and intramuscular fat content,the lowest shear force,and the lower drip loss.Hap 6 had the lowest birth weight.Hap 2 had the lowest weaning and 6-month-old weight.Hap 3 had the lowest intramuscular fat content and the highest shear force.Hap 10 had the highest drip loss.Hap 11 of ApoA5 gene in Jinfen White pigs had excellent traits,which could be used as a molecular marker to use in molecular breeding of Jinfen White pigs and improve the breeding efficiency.     

The influence of stocking rate on transmission of helminth parasites in pigs on permanent pasture during two consecutive summers

This study was made to elucidate the transmission of nematode infections in outdoor pigs at different stocking rates during two consecutive seasons. Five pigs (Group 1A) inoculated with low doses of Oesophagostomum dentatum, Ascaris suum, and Trichuris suis and five helminth-na?ve pigs (Group 1B) were turned out together in June 1996 on each of four pastures at stocking rates of 100, 240 (two pastures) and 576m(2) per pig, respectively. The pigs were slaughtered in early October, and pasture infectivity was subsequently measured using helminth-na?ve tracer pigs (Tracer). In 1997, 10 helminth-na?ve pigs were turned out on each pasture in May (Group 2) and again in August (Group 3), and allowed to graze for 12 weeks. The percentage of grass cover was reduced considerably at the high stocking rate in comparison to the other stocking rates. Transmission of all three helminths was observed on all pastures. In 1996, the O. dentatum faecal egg counts and worm burdens were significantly higher in pigs at the high stocking rate compared to pigs at the other stocking rates. O. dentatum did not survive the winter and pigs of Group 2 were inoculated with 3000 larvae each to reintroduce this parasite. Ascaris suum ELISA values and worm counts were highest at the high stocking rate in 1997 (Group 3). Transmission of T. suis was not significantly influenced by stocking rate. The results indicate that transmission of O. dentatum, and to some extent A. suum is influenced by stocking rate. However, both A. suum and T. suis eggs are still expected to constitute a high risk of infection on intensively used pastures where eggs may accumulate for years. The relationship between host density and helminth transmission seems more complex for grazing/rooting pigs than for grazing ruminants. This may be due to the differences in behaviour of the animals and the resulting differences in microclimate of the developing eggs/larvae.     

小麦族10种禾草叶片可消化性及矿物质含量的差异

利用扫描电镜及能量分散型荧光X射线新技术分析小麦族10种多年生禾草叶片的可消化性和矿物质含量.结果表明,供试草种叶片可消化性的高低顺次是:老芒麦>野大麦>航道冰草=加拿大披碱草>蒙农杂种冰草>诺丹冰草>肥披碱草≥新麦草=披碱草>蒙古冰草.叶片中7种矿物元素含量变幅为:Mg 0.21%～0.57%、Si 0.90%～3.31%、P 0.27%～0.3%、S 0.3%～0.0%、Cl 0.21%～0.52%、K1.44%～3.0%、Ca 0.42%～0.98%,草种间差异显著.     

Experimental infections with Hyostrongylus rubidus and the effects on performance of growing pigs

Pigs infected with Hyostrongylus rubidus at the rate of 550 larvae kg-1 body weight followed 15 days later with 220 larvae kg-1 body weight gained less weight (P less than 0.010) than uninfected control pigs. Feed efficiency (feed/gain) was 8% better (P greater than 0.10) in control than in infected pigs. Peak H. rubidus eggs per gram counts (EPG) occurred 22 days after each infection of pigs. H. rubidus EPG at necropsy were correlated with total number of adults recovered and with female/male ratio. High EPG were associated with H. rubidus populations composed of approximately equal numbers of males and females. Digestion trials consisted of pigs infected with 335 larvae kg-1 body weight compared to uninfected controls. Control pigs had higher (P less than 0.05) crude protein digestion coefficients, excreted less (P less than 0.05) N in feces and had a higher (P less than 0.05) N balance than infected pigs.     

Studies on vertical transmission of Trichinella spp. in experimentally infected ferrets (Mustela putorius furo), foxes (Vulpes vulpes), pigs, guinea pigs and mice

Vertical transmission of Trichinella spiralis was evaluated in ferrets (n = 21), foxes (n = 11), pigs (n = 12), guinea pigs (n = 16), and mice (n = 41). The placental barrier to be crossed by migratory Trichinella larvae varies structurally in different animal species. Ferrets and foxes have an endotheliochorial placenta structure, guinea pigs and mice a haemochorial, and pigs an epitheliochorial placenta. The non-encapsulating Trichinella pseudospiralis larvae have an extended muscle migration prior to entering a muscle cell. To evaluate if T. pseudospiralis was more likely to be transmitted to offspring, an additional group of foxes (n = 11) infected with T. pseudospiralis was included. Two different dose levels were used for ferrets, pigs, guinea pigs, and mice. In pigs and guinea pigs, infection was given at different times of the gestation period. Vertical transmission, measured as recovery of muscle larvae in the offspring, was demonstrated in both ferrets groups, in all four guinea pig groups, and in the high dose mouse group, but not in any fox or pig groups.     

劲直黄芪水浸提液化感作用研究

采用培养皿滤纸法,首次研究了分布于西藏自治区的劲直黄芪地上部分水浸液对4种受体植物燕麦、反枝苋、白三叶和荠菜种子萌发、幼苗根长、苗高和鲜重的化感效应以及对燕麦和白三叶丙二醛(MDA)含量、超氧化物歧化酶(SOD)、过氧化物酶(POD)活性的影响,旨在提示劲直黄芪的化感潜力,为劲直黄芪资源的进一步开发利用提供理论依据。结果表明,劲直黄芪水浸提液对燕麦种子萌发和幼苗生长均表现为抑制作用,且随着劲直黄芪水浸提液浓度的升高其抑制程度不断增强;对反枝苋、白三叶和荠菜种子萌发均表现为抑制作用,幼苗生长基本呈“低促高抑”的化感作用,且浓度达到100.0 mg/mL时,反枝苋种子不能萌发,被完全抑制了。不同浓度的劲直黄芪水浸提液影响燕麦和白三叶幼苗体内SOD、POD活性和MDA含量,当浓度为50.0 mg/mL时,SOD、POD活性和MDA含量明显增加;浓度升高到100.0 mg/mL时,MDA含量继续增加,而SOD和POD活性呈下降趋势。     

竞争效应对红色型豌豆蚜繁殖的影响

为明确种间竞争和种内竞争效应对红色型豌豆蚜生长和繁殖产生的影响,本研究以红色豌豆蚜克隆、绿色型豌豆蚜克隆及豌豆修尾蚜克隆作为试验材料,选用琼脂法,首先制备4种竞争试验区(1头区,2头区,种内竞争区和种间竞争区),观察各试验区蚜虫的种群动态,另准备3个(红色型、绿色型及豌豆修尾蚜)高密度种群处理,分别往里放入1头4龄红色克隆若虫,统计其3日总产蚜数。结果发现,种内竞争区和种间竞争区,二者的竞争效应都非常明显,竞争区混合种群的增殖率高于2头区,种间竞争区红色克隆胜利组单头红色克隆第10天新生蚜数高于其他处理。此外,高密度的绿色克隆和豌豆修尾蚜种群均能抑制红色克隆的繁殖。因此,红色型豌豆蚜能通过评估竞争种和同伴的相对密度来控制繁殖,无论是种间竞争还是种内竞争均能影响其繁殖,且种间竞争可能加速它的繁殖速率。     

Epidemiological studies on equine cestodes in central Spain: infection pattern and population dynamics

An epidemiological study on equine cestodosis was carried out in central Spain. A total of 372 digestive tracts from equids slaughtered in abattoirs located in central Spain were studied from November 2001 to May 2004. Anoplocephala perfoliata was detected in 24% of the animals and Anoplocephala magna in 18%. Individual tapeworm burden was from 1 to 491 tapeworms for A. perfoliata and from 1 to 64 tapeworms for A. magna. Low tapeworm burdens (less than 30 cestodes) predominated significantly (p < 0.01) in all seasons for both species.

Seasonal prevalence of infection by A. perfoliata was significantly higher (p < 0.01) in autumn (37.5%) and winter (32.3%) than in spring (9.2%) and summer (10.8%). Immature tapeworms were detected throughout summer (11%), autumn (23.4%) and winter (26.6%), signalling a summer to winter risk period for tapeworm infection in our conditions. Mature non-gravid tapeworms were collected in all seasons, with a decreasing pattern from summer (89%) to spring (6.7%). Conversely, gravid tapeworms showed an increasing pattern, from 0 in summer to a maximum (93.3%) in spring. Since prevalence of infection was significantly higher in winter than in spring, winter seems to be the season when more eggs would be available to be eaten by mites. A. perfoliata infection was detected in three different periods throughout the 3 year study: autumn 2001–winter 2002, summer 2002–spring 2003 and autumn 2003–spring 2004. This epidemiological pattern seems to describe the dependence of A. perfoliata to humidity in warm dry climate. In our conditions, A. perfoliata appears to follow a pattern of having only one generation per year, with a marked dependence on humidity. According to the results, autumn rainfall would influence the length, and late spring rainfall the appearance, of each annual generation.

A. magna showed a different pattern. Infection was detected throughout the whole study period. Seasonal prevalence was higher in autumn (25.5%) than in winter (14.9%), spring (12.1%) and summer (10.5%), but the differences were not statistically significant. Non-gravid A. magna tapeworms could be detected almost throughout the year but percentages were significantly higher (p < 0.01) in autumn (50.2%), indicating recent ingestion, than in the other seasons (30% in summer, 12.8% in winter and 0% in spring). However, data from spring were not enough to discard the season as a risk period for A. magna infection.     

Concurrent Ascaris suum and Oesophagostomum dentatum infections in pigs.

The aim of this study was to examine interactions between Ascaris suum and Oesophagostomum dentatum infections in pigs with regard to population dynamics of the worms such as recovery, location and length; and host reactions such as weight gain, pathological changes in the liver and immune response. Seventy-two helminth-na?ve pigs were allocated into four groups. Group A was inoculated twice weekly with 10000 O. dentatum larvae for 8 weeks and subsequently challenge-infected with 1000 A. suum eggs, while Group B was infected with only 1000 A. suum eggs; Group C was inoculated twice weekly with 500 A. suum eggs for 8 weeks and subsequently challenge-infected with 5000 O. dentatum larvae, whereas Group D was given only 5000 O. dentatum larvae. All trickle infections continued until slaughter. Twelve pigs from Group A and B were slaughtered 10 days post challenge infection (p.c.i.) and the remaining 12 pigs from the each of the four groups were slaughtered 28 days p.c.i.. No clinical signs of parasitism were observed. The total worm burdens and the distributions of the challenge infection species were not influenced by previous primary trickle-infections with the heterologous species. Until day 10 p.c.i. the ELISA response between A. suum antigen and sera from the O. dentatum trickle infected pigs (Group A) pigs were significantly higher compared to the uninfected Group B. This was correlated with a significantly higher number of white spots on the liver surface both on Day 10 and 28 p.c.i. in Group A compared to Group B. The mean length of the adult O. dentatum worms was significantly reduced in the A. suum trickle infected group compared to the control group. These results indicate low level of interaction between the two parasite species investigated.     

铁杆蒿枯落物对四种豆科牧草的化感作用

研究了黄土区优势植物铁杆蒿（Artemisia gmelinii）枯落物对红豆草（Onobrychis viciaefolia）、沙打旺（Astragalus adsurgens）、百脉根（Lotusc corniculatus）和紫花苜蓿（Medicago sativa）等四种常见豆科牧草种子萌发和幼苗生理特性的化感效应。结果表明：铁杆蒿对这几种豆科牧草的发芽率和发芽势总体上均呈现“低质量浓度促进,高质量浓度抑制”的效应;紫花苜蓿综合化感效应在不同处理中均受到抑制,随着铁杆蒿枯落物含量的增加,抑制作用增强;但红豆草、百脉根和沙打旺的综合化感效应表现出低促高抑的趋势;红豆草和沙打旺在30 g铁杆蒿枯落物浓度时促进效应最强,百脉根在60 g时促进效应最强。以上结果初步表明在有铁杆蒿分布的草地不适合种植以及补播紫花苜蓿,而适当密度的铁杆蒿分布有助于种植以及补播红豆草、百脉根和沙打旺。