我国犬埃立克体病研究现状

犬埃立克体病是由严格细胞内寄生的埃立克体所致的疾病。目前,我国已经发现的犬埃立克体病原有犬埃立克体(Ehrlichia)和扁平埃立克体(E.platy)两种。我国已发现的犬埃立克体病均为E.canis和E.platy的混合感染。临床症状包括发热、体重严重减轻、流鼻血和腹泻带血等;白细胞和血小板计数同时下降是我国犬埃立克体病的特点;严重的病犬常因广泛性出血或继发感染而死亡。犬埃立克体病的病原学诊断主要依靠镜检、血清学试验和PCR等。犬血清埃立克体抗体的调查结果表明,我国犬埃立克体病的流行与蜱活动密切相关。四环素类抗生素是治疗犬埃立克体病的有效药物。     

犬在埃立克体病研究中的作用

随着新病原及病原新的致病性不断被发现 ,埃立克体及埃立克体病已经成为预防医学和兽医学研究热点。在已经发现的 1 1种埃立克体病原中 ,有 5种可以直接感染犬 ,引起不同的犬埃立克体病 ;另外 2种为早先分别从人单核细胞埃立克体病和粒细胞埃立克体病患者中分离的病原 ,在流行区的犬体内也可以分离到。资料表明犬对许多埃立克体都极为敏感 ,犬在埃立克体及埃立克体病研究上占有重要地位。鉴于这是我国近年才发现的新病原 ,许多兽医及研究工作者不认识它 ,文章就相关埃立克体对犬的感染和所致疾病以及在流行病学上的意义进行了综述。     

我国犬埃立克体病病原分离与鉴定Ⅲ.病原的电镜观察

对埃立克体感染犬的单核细胞和血小板进行了透射电镜观察，结果表明，单核细胞的细胞质和血小板中均存在埃立克体包涵体，其中单核细胞的包涵体内病原多达８个，血小板的包涵体内至少有３个病原。这一结果从形态学角度进一步证实了引起了广州市郊栽养犬基地流行犬埃立克体病的病原为２处，即感染单核细胞的犬埃立克体（Ｅｈｒｌｉｃｈｉａ ｃａｎｉｓ）和感染血小板的扁平埃立克体（Ｅ．ｐｌａｔｙｓ）。     

应用PCR检测犬埃立克体病的研究

用已确证为扁平埃立克体（Ehrlichia platys)和犬埃立克体（E.canis）混合感染的犬全血对6只格犬进行人工感染，通过对其临床症状，血流学变化，血涂片包涵体观察，并将其PCR结果与后来确诊为犬埃立克体病的18只病犬血的PCR结果比较，表明PCR方法能够对早期犬埃立克体病做出准确诊断。     

广州地区犬血清埃立克体抗体季节消长规律

为了解犬埃立克体全年消长情况，从而掌握犬埃立克体病在广州地区流行规律，以便更有效地预防和控制犬埃立克体病。以查菲埃立克体28kD重组为抗原，采用免疫印迹法，逐月检测犬血清埃立克体抗体水平。结果表明，1－3月抗体呈缓慢上升趋势，4月后急剧上升，并维持高水平至10月，之后急剧下降。其抗体消长情况与先前我们调查的犬埃立克体病的发病和流行规律相一致，与该地区蜱活动时间基本一致。     

比格犬埃立克体病实验模型的建立

为犬埃立克体病的病理学、临床学、病原学的深入研究，我们用Beagle(比格犬）复制犬埃立克体病以建立犬埃立克体病实验模型。比格犬静脉接种E.platy和E.canis后，利用PCR和电镜技术确证感染成功。进一步的观察发现，接种后比格犬与最最感的德国牧羊犬自然感染埃立克体病的临床症关放病理学变化基本吻合。结果说明通过静脉接种病原成功建立了比格犬埃立克体病实验模型。     

犬埃立克体病诊断与防治研究进展

犬埃立克体病是由严格细胞内(白细胞或血小板)寄生的埃立克体(Ehrlichia,属立克次体科)所致的疾病。该病是以热带和亚热带为主的全球性分布的疾病,由于犬埃立克体主要对犬的白细胞和脾脏等造成损伤,病犬表现为免疫力低下、极度消瘦,犬埃立克体病也被称为犬的艾滋病。近年来我国有多起关于犬发生犬埃立克体病的报道。论文就该病进行系统的论述,希望能够对该病的诊断和防治带来帮助。     

1例犬埃立克体病的诊治

犬埃立克体是一种重要的人兽共患传染性病原体,可引起犬科动物的犬单核细胞埃立克体病。为确诊1例临床上以发热、精神沉郁、黏膜苍白为主要特征的宠物犬病例,进行了血常规、血液生化检查、实时荧光定量PCR检测、犬埃立克体抗体检查,最终确诊该病例为犬埃立克体感染,使用盐酸多西环素治疗后患犬恢复良好。     

比格犬埃立克体病实验模型研究Ⅲ病原观察

为了观察犬埃立克体病病犬血细胞中病原的感染情况,对6只人工感染埃立克体的比格犬血细胞进行了光镜和透射电镜观察.结果发现,单核细胞的细胞质和血小板中均存在埃立克体包涵体,其中单核细胞的包涵体内病原多达8个,血小板的包涵体内也发现数个病原.这一结果进一步证实我们成功地建立了比格犬埃立克体病实验模型,也为临床上诊断犬埃立克体病提供了形态学依据.     

我国犬埃立克体病病原的分离与鉴定——Ⅰ.病原16SrRNA基因序列测定与分析

用实验动物接种法,分离保存我国某养犬基地犬埃立克体病病原。以此病原对易感犬接毒,接毒犬发病后采集急性期全血提取基因组,对病原 １６ Ｓｒ Ｒ Ｎ Ａ 基因进行扩增、克隆测序。结果,病原被保存在病犬血细胞内,并能成功地使健康犬感染发病;检测到的 ２ 种致犬埃立克体病病原 １６ Ｓ ｒ Ｒ Ｎ Ａ 基因序列与国外已发现的相应病原基因序列有一定差异,显示其为不同菌株,分别命名为埃立克体 Ｇｚｈ ９８１ 株和 Ｇｚｈ９８２ 株。进一步分析表明,导致我国某养犬基地犬埃立克体病的病原为扁平埃立克体和犬埃立克体。     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

Evaluation of biohydrogenation rate of canola vs. soya bean seeds as unsaturated fatty acids sources for ruminants in situ

An experiment was conducted to study disappearance of C14 to C18 fatty acids, lag times and biohydrogenation (BH) rates of C18 fatty acids of ground soya bean and canola seeds in situ. Three ruminally fistulated Dallagh sheep were used to determine ruminal BH of unsaturated fatty acids (UFAs). Differences in the disappearance of fatty acids through the bags and lag times were observed between the oilseeds. We saw that the longer the incubation time of the oilseeds in the rumen, the lower the content of C18:2 and C18:3. Significantly higher lag times for both C18:2 and C18:3 were observed in ground canola compared to ground soya bean. BH rates of C18:2 and C18:3 fatty acids in soya bean were three times higher than those of canola. These results suggest that the fatty acid profile of fat source can affect the BH of UFAs by rumen micro‐organisms. So that UFAs of canola had higher ability to escape from ruminal BH. It seems that fatty acid profile of ruminant products is more affected by canola seed compared to soya bean seed.     

Serum biochemical values and mineral element contents of tissues in yaks

Serum biochemical values and the wet weight to dry weight ratios of tissues were determined in yaks in Shandan county of Gansu province. The liver, kidney, heart and muscle contents of seven elements in yaks were also analysed. Most serum biochemical values were similar to those of cattle, camels and sheep, but the calcium concentration was considerably above the normal range for other ruminants. The liver contained the highest concentrations of copper, manganese and cobalt and the kidney of selenium, iron and calcium.Abbreviations Alb albumin - ALT alanine aminotransferase - AST aspartate aminotransferase - BUN blood urea nitrogen - Chol cholesterol - Glob globulin - -GT -glutamyl transpeptidase - IP inorganic phosphorus - TP total protein     

Avian brood parasitism — a growing research area in behavioral ecology (part Ⅱ)

正We are pleased to publish the second special issue on avian brood parasitism and to be responsible guest editors for the two special issues of Chinese Birds (Vol. 3, No. 4, 2012 and Vol. 4, No. 1, 2013), entitled "Avian Brood Parasitism - A Growing Research Area in Behavioral Ecology". The first issue was published in December 2012. The goal of the two special issues is to publish accumulated knowledge and some of the recent developments in     

Internal Parasites and Haematological Values in Cattle Slaughtered in Buea Subdivision of Cameroon

Tropical Animal Health and Production -