首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
A single Merino sheep, artificially infested with the sheep scab mite, Psoroptes ovis, and a similarly infested Dorper sheep were placed with 9 uninfested Merino or 9 uninfested Dorper sheep respectively during winter and the rate of spread of infestation on the uninfested sheep observed. The same procedure was repeated in summer. It took 14 and 8 weeks respectively in winter before all sheep in the 2 groups displayed lesions of sheep scab, whereas in summer it took 10 and 12 weeks before all sheep had lesions.  相似文献   

2.
Five Merino and five Dorper sheep were artificially infested with the sheep scab mite Psoroptes ovis and the effect of infestation on their haematology, serum protein levels and live mass recorded for a period of 14 weeks. The reaction of the Merino sheep to infestation was more severe than that of the Dorper sheep. Haematological values fluctuated within the normal range during the assessment period. The mean haemoglobin concentration of the Merino sheep declined until antiparastic treatment was administered 10 weeks after infestation, after which it gradually increased. The lymphocyte counts of both breeds of sheep declined from 2 weeks to 10 weeks post-infestation, but increased after treatment, while the highest eosinophil counts were recorded in the Merino sheep at the height of the acute disease 8-10 weeks post-infestation. Serum albumin values for both breeds and serum globulin values for the Merino sheep were higher than normal during the entire 14-week observation period. A decrease in serum albumin and an increase in serum globulin concentration occurred at the height of infestation in both breeds. The mean live mass of a second group of five infested Merino sheep decreased by 6.4 kg over a 16-week period compared to a gain of 4.56 kg for five infested Dorper sheep.  相似文献   

3.
The availability of large numbers of undamaged sheep scab mites, Psoroptes ovis, would be beneficial for discovery screening and development trials. There are several reported procedures for removing scab mites from sheep but they have limitations. To overcome this, a simple but versatile method employing the use of pumped saline was developed to remove all stages of the P. ovis mite from sheep. The method takes no more than 2 min to remove mites from the selected site with relative ease and is not affected by the condition of the fleece or lesion. The number of mites removed with the new method was 5-10 times more than detected by visual examination. These mites were undamaged and survived off-host for up to 16 days. The robust, portable equipment is easy to use under field conditions, making this method suitable for use as a diagnostic tool for early detection and monitoring of scab mites thus providing opportunities for development of novel alternative control strategies.  相似文献   

4.
Sheep scab mites, Psoroptes ovis, collected from a Merino donor sheep, were used to infest Merino and Dorper sheep, and Angora and Boer goats. Mites were placed on the sheep on 1 or 2 occasions and on 5 occasions on the goats. All the animals were examined at regular intervals for the presence of scab lesions and living mites. Both sheep breeds developed lesions, but those on the Merino sheep were always larger than those on the Dorper sheep at the same intervals after infestation. None of the goats developed lesions or showed signs of irritation, or harboured any mites.  相似文献   

5.
Pruritic behaviour and deranged fleece are often used as indicators of sheep louse infestation but the exact relationship between infestation and the observation of signs of pruritis was unclear. Two studies were conducted to examine this association. In the first, 24 castrate Merino sheep were randomly assigned to six pens in groups of four and the sheep in three pens infested with 10 lice each on the right mid-side. Louse numbers were counted, fleece derangement scored and pruritic behaviour assessed periodically on each sheep until 38 weeks after infestation. In the second study a single moderately infested sheep was paddocked for 15 weeks with 32 uninfested sheep and louse numbers and fleece derangement monitored for 41 weeks. In the pen studies, differences between infested and non-infested sheep in fleece derangement and pruritic behaviour first became significant (p<0.05) at 8 and 14 weeks, respectively and at louse densities of 0.06 and 0.27 per 10 cm wool part. Some sheep showed definite signs of deranged fleece as early as 5 weeks after initial infestation. In the paddock studies, it took 37 weeks until lice were detected on all sheep in the flock. The correlation between louse numbers and fleece derangement score first became significant (r=0.44 and p<0.05) at 9 weeks after introduction of the lousy sheep, reached a maximum of r=0.79 (p<0.001) at 22 weeks when 84% of sheep had lice detected and the mean louse density was 0.29 per part, and then declined to r=0.12 (n.s.) at 41 weeks when all sheep were infested and the mean louse density was 3.04 per part. It is concluded that fleece derangement is a powerful early indicator of the presence of lice and that sheep may exhibit signs of pruritis well before lice can be readily found by direct inspection. Fleece derangement may be useful as a basis for establishing economic thresholds for the application of long wool treatments in developing louse infestations but appears to be a poor indicator of louse numbers once the infestation is advanced.  相似文献   

6.
An investigation of sheep flocks in the main sheep raising areas of New South Wales showed that the itchmite Psorergates ovis was frequently associated with fleece derangement. In 26 of the 41 flocks examined, P. ovis was the only ectoparasite detected. P. ovis and the sheep body louse Damalinia ovis, were found in 5 flocks. No external parasites were found on sheep examined from the 10 remaining flocks. The type of fleece derangement most frequently recorded was rubbing which in some cases was combined with areas of chewed fleece. Among flocks, there were positive relations between the prevalence of fleece derangement and prevalence of itchmite or scurf and between itchmite count and mean scurf score. Within flocks, itchmite infested sheep or sheep with scurf had higher prevalences of fleece derangement than sheep on which no mites or no scurf were found. Itchmite infested sheep had a higher prevalence of scurf than those with no detectable mite infestation. There were no significant differences in itchmite populations or fleece derangement between untreated flocks and flocks treated with synthetic pyrethroids, organophosphates or arsenic and rotenone.  相似文献   

7.
OBJECTIVE: To investigate the roles of shade, fleece length and wool type in the protection of sheep from Hypericum perforatum poisoning. ANIMALS: Adult Merino ewes of superfine, fine and medium wool type. DESIGN: Seventy sheep were divided into seven equal groups. During late spring and summer a series of successive, replicate experiments was conducted, each using one group and lasting 5 days. The sheep carried 14 to 24 weeks wool growth. In each experiment the treatments tested were Hypericum +, sunlight + (n = 7); Hypericum +, sun - (n = 1); Hypericum -, sun + (n = 1); Hypericum -, sun - (n = 1). Next, 24 sheep in two equal groups were used in experiments of similar design to the above. Each group consisted of nine recently (1 to 3 weeks previously) shorn and three wool covered (25 to 26 weeks growth) sheep. The treatments tested were Hypericum +, sunlight +, fleece - (n = 9); Hypericum +, sun -, fleece + (n = 1); Hypericum -, sun +, fleece + (n = 1); Hypericum -, sun -, fleece + (n = 1). PROCEDURES: Finely milled Hypericum was administered by gavage to provide 3 mg hypericin / kg body weight. Sheep were sheltered from direct sunlight or were exposed for 5 h per day for 4 successive post-treatment days. Rectal temperatures were measured immediately before and at the end of each sunlight exposure session. Rectal temperature above 40 degrees C was considered indicative of hypericin poisoning. RESULTS: After Hypericum treatment hypericin poisoning was displayed by 26.5% of woolled sheep that were exposed to sunlight, but by none of those that were fully shaded. In similarly treated but recently shorn sheep 94% displayed hypericin poisoning when exposed to sunlight. In the wool covered group the percentages of poisoned animals based on wool type were: superfine 14%, fine 28.5%, medium 33.3%. In the recently shorn group the percentage for all three approached 100%. CONCLUSIONS: A majority of Merinos with at least 14 weeks wool growth will not be poisoned by a single oral dose of 3 mg hypericin /kg, but because hypericin persists in the blood circulation for several days this safe dose will be lowered by continuous daily ingestion. Sheep with access to substantial areas of shade could safely ingest much greater amounts of hypericin. Wool removal greatly increases the risk of poisoning. Superfine Merinos with a wool cover should be able to ingest more hypericin than comparable, medium wool types, without any increased risk of poisoning. The ability of ruminant livestock to safely ingest Hypericum is probably determined more by the amount of skin protection they have against incident sunlight than by differences in hypericin metabolism and excretion capacity.  相似文献   

8.
本研究旨在估计高山美利奴羊重要经济性状的遗传参数,为优化高山美利奴羊选育方案、建设品种完整结构、进行遗传评估及实施育种值选种提供理论技术支撑。采用甘肃省绵羊繁育技术推广站2003—2018年高山美利奴羊核心群数据资料,基于ASReml运用单性状个体动物模型和多性状个体动物模型估计高山美利奴羊体重、产羔数、产毛量、净毛量、净毛率、羊毛纤维直径、羊毛纤维直径变异系数、毛丛长度等重要经济性状的遗传参数。结果表明:高山美利奴羊产羔数为低等遗传力,其他所有性状均为中高等遗传力;大部分经济性状间呈正遗传相关,体重、产毛量、羊毛纤维直径与净毛率间呈负遗传相关,羊毛纤维直径变异系数与体重、产毛量、纤维直径呈负遗传相关。  相似文献   

9.
Transmission of sheep lice is thought to occur mainly by sheep to sheep contact although the possibility of other sources of infestation is often suggested. This study investigated the period of survival of Bovicola ovis after removal from sheep under varying conditions and assessed the likelihood of new infestations arising from contaminated facilities, wool caught on fences and shearers' footwear.In laboratory studies with lice held away from sheep at 4, 20, 25 and 36.5 degrees C, adults and nymphs survived longest at 25 degrees C (LT90 of 11.7 and 24.1 days for adults and large nymphs, respectively). Nymphs survived longer than adults and lice provided with raw wool survived longer than lice provided with wool that had been degreased. Nymphal lice survived for up to 29 days on unscoured wool at 36.5 degrees C, but the LT50 was less than 9 days in most experiments. In shearing sheds in winter and early spring lice survived for up to 14 and 16 days, respectively. These periods of survival are considerably longer than previously indicated for B. ovis. Most lice dropped out of wool staples attached to a fence within 1 h and only two of a total of 225 lice were still present after 24 h, suggesting that sheep are unlikely to become infested from wool caught on fences. Adult and nymphal lice readily transferred to shearers' moccasins and survived there for up to 10 days, indicating that transmission of lice on the footwear of shearers or other sheep handlers may be a cause of new infestations. Microwaving each moccasin for 5 min killed all lice and may provide a simple method of reducing the likelihood of transmission of B. ovis between properties.  相似文献   

10.
Merino sheep in Thornveld, Dorper sheep and Angora goats in inland Valley Bushveld, Angora goats and Boer goats in Valley Bushveld on the coastal plateau, and springbok, Antidorcas marsupialis, and black wildebeest, Connochaetes gnou, in Karroid Mountainveld, all in the Eastern Cape Province, were examined for the larvae of nasal bot flies. The sheep and goats were infested with the larvae of Oestrus ovis, and Dorper sheep and Boer goats harboured more larvae than Angora goats on the same farms. Most infestation was present from November to May in Merino sheep in Thornveld, from February to June in Dorper sheep in inland Valley Bushveld, and from May to September in Angora and Boer goats in Valley Bushveld on the coastal plateau. These patterns of seasonality appeared to be regulated by the severity of the summer temperatures at the various localities. The springbok were infested with the larvae of Rhinoestrus antidorcitis, most of which seemed to mature from June to August. All larval sages of Oestrus variolosus and Gedoelstia h?ssleri were present in the black wildebeest, and large numbers of 1st instar larvae of G. h?ssleri appeared to accumulate on the dura of the wildebeest from June to August.  相似文献   

11.
Knowledge of the presence or absence of lice in a flock of sheep enables wool growers to make informed decisions as to the need for insecticidal treatments. However, with inapparent infestations, traditional methods of detection are not sufficiently sensitive and, as a consequence, flocks may be left untreated. Conversely, the routine application of insecticide to sheep with no sign of infestation is an unnecessary cost. The sensitivity of 3 procedures for detecting lice was evaluated in 68 mobs of sheep from 50 farms. In 24 mobs of sheep known to be lightly infested, lice were detected in 17% by either parting the fleece of 10 sheep or by the lamp test in which 8 g samples of shorn wool from 30 randomly selected fleeces were placed under lamps for 10 min to repel the lice. Twenty of 23 mobs (87%) were found to be infested by the table locks test in which a 30 g sample of locks wool was dissolved in 10% sodium hydroxide and the filtered residue examined with x 40 magnification. A screening test, in which either fleeces on 5 sheep were examined by fleece parting or lice were repelled from 30 shorn fleeces for 5 minutes, detected about 60% of lightly infested mobs. When this was followed by the table locks test 91% of lightly infested mobs were detected. Conducting any one of the tests on more than one mob, and in large mobs testing more frequently, increases the sensitivity of detection of lice within the whole flock.  相似文献   

12.
SUMMARY An investigation of sheep flocks with unknown histories of fleece derangement, selected at random from the main sheep raising areas of New South Wales, showed that Psorergates ovis was present in 53 of the 177 flocks surveyed and In 162 of the 3495 sheep examined. Of the single causes of fleece derangement, the most prevalent was grass seed contamination (15.7%) followed by Infestation with sheep body lice, Bovicola ovis, (14.7%) and Infestation with Itch mite (7.8%). The prevalence of fleece derangement was significantly higher on sheep In which lice were the only ectoparasites found than on those In which Itch mites were the only ectoparasites present. The greatest prevalence of P ovis was In flocks In the Young, Yass, Mudgee and Tenterfield districts. In most affected flocks, more than one potential cause of fleece derangement was present. Itch mite Infestation was more prevalent in flocks that received no treatment for ectoparasites than in those that had been treated in the year preceding the survey. Our results did not support a commonly held belief among farmers that arsenical compounds control Infestations of Itch mites more effectively than other types of pesticides. There was no significant difference in prevalence of fleece derangement between flocks treated with different pesticide groups and those that received no treatment, but mean fleece derangement score was significantly lower in sheep treated with organophosphates than in untreated sheep. Infestations of lice were significantly more prevalent in sheep from flocks treated with synthetic pyrethroids than from those treated with organophosphates or those that received no treatment.  相似文献   

13.
The effects of both temperature and humidity on the survival of the mites Psoroptes ovis and Psoroptes cuniculi were considered in laboratory assays. When P. ovis and P. cuniculi were maintained at 95% humidity, maximum survival decreased linearly with increasing temperature, from approximately 15 days at 9 degrees C to 5 days at 30 degrees C. There was no significant difference between P. ovis and P. cuniculi in the effects of temperature on maximum survival. Adult male P. ovis and P. cuniculi had lower mean maximum survival than any of the other life cycle stages. There was a small but significant effect of humidity on survival for P. cuniculi; LT50 values were greater at 75-85% r.h. than at 55-65% r.h. The influence of off-host survival and the infestation of naive sheep from mites in the environment on the epidemiology of sheep scab are discussed.  相似文献   

14.
Skin biopsies from two Merino sheep heavily infested with Psorergates ovis were immersed in liquid nitrogen and cut into vertical frozen sections stained with lipophilic Sudan IV or Oil Red O and haematoxylin. A survey of the lateral distribution of mite sections showed a majority (ca 80%) were in or within 0.2 mm of the follicle mouth. A survey of vertical distribution showed no mite penetration deeper than inner stratum corneum where 57% of mite sections were seen; 30% were within outer stratum corneum or scurf; 13% were on the outer surface and less than 1% were detached. Lipid was the only material seen within stained mites at a location considered to be gut. This was supported by dosing sheep with quinacrine, taking biopsies at Day 6 and Day 14 and examining frozen sections under blue light. Fluorescent lipid was seen at a location considered to be mite gut. From these results it was recommended that acaricide treatments against P. ovis be lipophilic and administered transepidermally because less than 15% of mites were at a superficial location likely to be reached by topical application.  相似文献   

15.
为了解中国美利奴羊（新疆型）近年来遗传结构的变化趋势以及探讨毛用性状与繁殖性状的遗传关系,需要进一步研究这些性状的遗传力以及它们之间的关系。本研究收集额敏县聚鑫细毛羊养殖专业合作社1985-2018年中国美利奴羊（新疆型）共计9 428只羊毛生产记录和1987-2018共计5 887只年繁殖记录,运用BLUPF90软件结合Gibbs抽样方法,利用单性状模型对中国美利奴（新疆型）毛用性状（细度支数、等级、总评分、毛长、污毛重和鉴定时体重）和繁殖性状（配种次数、妊娠天数、胎产羔数和总产羔数）进行方差组分和遗传力估计,利用双性状模型分析毛用性状与繁殖性状之间的遗传相关与表型相关。结果显示,中国美利奴羊（新疆型）毛用性状细度支数、等级、总评分、毛长、污毛重、鉴定时体重的遗传力估计值分别为0.471±0.020、0.088±0.030、0.114±0.018、0.426±0.025、0.328±0.041、0.317±0.046;繁殖性状配种次数、妊娠天数、胎产羔数及总产羔数的遗传力估计值分别为0.056±0.009、0.022±0.010、0.120±0.018、0.163±0.016;毛用性状与胎产羔数、总产羔数之间的遗传相关范围为-0.031~0.286,鉴定时体重与胎产羔数（0.286）、总产羔数（0.204）遗传相关最高,细度支数与胎产羔数（-0.143）、总产羔数（-0.048）呈负的遗传相关;毛用性状与胎产羔数、总产羔数之间的表型相关范围为-0.210~0.216,毛长与总产羔数（0.216）表型相关最高,细度支数与胎产羔数（-0.137）、总产羔数（-0.210）呈显著负表型相关。本研究结果发现,毛用性状与繁殖性状之间存在一定的关系,这一结果可为今后制定中国美利奴羊育种规划提供数据基础,为选育优质高产、繁殖性能好的细毛羊提供理论依据,从而进一步提高细毛羊产业经济效益。  相似文献   

16.
The pattern of population growth of the ectoparasitic mite, Psoroptes ovis (Acari: Psoroptidae), on its ovine host is considered through the development of a Leslie matrix-based, simulation model. The model is parameterised using experimental data in conjunction with reanalysis of published data. The model shows that on sheep P. ovis populations grow at a rate of approximately 11% per day and the population doubles every 6.3 days. Additional rates of adult mortality, in excess of 50% per day, need to be imposed to prevent population growth. The predictions of the model are tested by comparison of the expected numbers of mites with the numbers recorded in lesions either on naturally infested sheep where the date of infestation can be estimated or on one artificially infested animal, where the initial number of mites and date of infestation are known precisely. In both cases the observed number of mites in lesions relate closely to the numbers expected from the simulations. The model simulations do not support the concept of a 'lag' phase as distinct from the 'growth' phase in the changing pattern of mite abundance on an infested sheep and suggests that the observed pattern of growth is a natural function of an exponential increase in numbers. The development of such models and their use in explaining the demographic processes which drive mite population dynamics are discussed.  相似文献   

17.
Goats and sheep were pastured together and held in close contact in yards twice a month for 21 months. The goats had a high prevalence of both the rabbit ear canker mite, Psoroptes cuniculi and the chorioptic mange mite, Chorioptes bovis. The sheep were not infested with P. cuniculi at the beginning of the study and viable C. bovis could not be detected. At no time during the study did P. cuniculi establish in the ears of sheep, despite a maximum prevalence of >95% P. cuniculi in goats. This may have been related to the viscous nature of sheep cerumen. Levels of cerumen in goats' ears increased with increasing prevalence of the mite in the flock. The prevalence of C. bovis in the sheep flock did not exceed 10%, despite a maximum prevalence of >90% infested goats. The difficulty of detecting light infestations of mites means that it was not clear whether the C. bovis infestation of sheep was derived from goats or was present when the study began. Whatever the source, close contact with goats with an active and extensive C. bovis infestation seems unlikely to seriously influence populations of the ectoparasite in sheep. Psoroptes cuniculi was found to he established in goats as young as five days and post-mortem examination of goats' ears was more successful at revealing P. cuniculi than was use of an otoscope during life.  相似文献   

18.
The eradication of lice from Merino sheep with wool up to 65 mm long was achieved by spraying insecticide onto the tip of wool over the sides and back. The insecticides used were cyhalothrin and diazinon in small volumes and at high concentration. When infested sheep were sprayed with 100 ml of cyhalothrin 1,500 ppm or diazinon 36,000 ppm, no live lice were seen 23 days after treatment. When treated sheep were challenged with live lice 100 days after treatment an infestation did not establish. Cyhalothrin at a lower concentration of 1,000 ppm gave excellent control but at 500 ppm only fair control was obtained. Diazinon at 24,000 ppm gave probable eradication and at 12,000 ppm excellent control. If a practical method of applying the insecticide to the tip of wool can be developed, then this technique should provide an effective means of eradicating lice in sheep with long wool. This would greatly assist the sheep industry in controlling and eradicating sheep lice.  相似文献   

19.
试验旨在分析6个绵羊群体骨形态蛋白受体1B（bone morphogenetic protein receptor-1B，BMPR-1B）基因多态性，为绵羊繁殖力的标记辅助选择和育种提供理论依据。采集新吉细毛羊、中国美利奴羊（无角型）、东北细毛羊、杜×寒杂交羊（F1）、杜×寒杂交羊（F3）、白头杜泊羊6个绵羊群体共381只个体的血样，通过PCR-RFLP技术检测BMPR-1B基因多态性，并用DNAStar软件预测蛋白质二级结构，利用Excel 2003软件计算基因频率、基因型频率、Hardy-Weinberg平衡，以及遗传多样性参数（杂合度（He）、纯合度（Ho）、有效等位基因数（Ne）和多态信息含量（PIC））。结果显示，新吉细毛羊、东北细毛羊、中国美利奴羊（无角型）、白头杜泊羊BMPR-1B基因均不存在多态性；杜×寒杂交羊（F1）、杜×寒杂交羊（F3）具有多态性，存在3种基因型：++、B+和BB。杜×寒杂交羊（F1）χ2值达到显著水平，处于Hardy-Weinberg不平衡状态；杜×寒杂交羊（F3）χ2值未达到显著水平，处于Hardy-Weinberg平衡状态。杜×寒杂交羊（F1）、杜×寒杂交羊（F3）的PIC分别为0.311和0.264，为中度多态。推测BMPR-1B基因不是新吉细毛羊、东北细毛羊、中国美利奴羊（无角型）、白头杜泊羊4个绵羊群体多胎性状的主效基因，但可作为杜×寒杂交羊（F1）、杜×寒杂交羊（F3）多胎性状的主效基因。  相似文献   

20.
Psoroptes ovis mites were removed from infected sheep and placed in positions where wool and mites normally accumulate during sheep scab outbreaks. The ambient temperature and humidity were monitored over a 3-week period and the survival and infectivity times were examined. The procedure was carried out during each of the seasons. The hatchability of mite eggs was also examined. It was found that little variation occurred between seasons, with mites regularly retaining viability and infectivity for 15 days during all seasons. Mites that survived for more than 16 days failed to infect sheep. Mite eggs retained hatchability for up to 7 days.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号