合肥市奶牛隐孢子虫病流行病学调查

为查明合肥市某奶牛场奶牛隐孢子虫感染情况,采用饱和白糖溶液漂浮法对该场381头奶牛的粪样进行检查,在52头奶牛的粪样中查到了隐孢子虫卵囊,其感染率为13.62%(52/381)。经鉴定,所获虫体为鼠隐孢子虫Crtptosporidium.muris。     

奶牛隐孢子虫病流行病学调查及初生犊牛感染试验

应用饱和糖溶液漂浮法和改良抗酸染色法调查郑州、商丘和洛阳3个地区的5个奶牛场、2个专业村的582份粪样，查出阳性样品64份，隐孢子虫总阳性率11％（64／582），发现两种不同形态的卵囊，根据其形态结构等特点鉴定为小球隐孢子虫（C．parvum）和安氏隐孢子虫（C．andersoni）。其中2个场奶牛感染安氏隐孢子虫，有1个场的奶牛感染小球隐孢子虫，且感染强度较小。犊牛感染率较育成牛、成年牛高。并进行小球隐孢子虫分离株对初生犊牛的致病性试验，其结果为潜隐期7天，排卵囊高峰出现在感染后第16天，高峰期5天。剖检后消化道黏膜经抗酸染色鉴定，仅在回肠中段发现卵囊。     

河南省奶牛安氏隐孢子虫感染的流行病学调查

为了解河南省奶牛安氏隐孢子虫病流行情况,采用饱和蔗糖溶液漂浮法和改良抗酸染色法对河南省12个规模化奶牛场和7个奶牛养殖小区共计2 268份粪便样本进行检查,发现109份为阳性粪便样本,感染率为4.8%。卵囊呈长椭圆形,平均大小为7.8μm×6.4μm,卵囊指数为1.22;12个养殖场中10个为阳性场,7个养殖小区中4个为阳性小区,不同地区奶牛安氏隐孢子虫感染率统计学差异显著(P0.05);不同年龄段奶牛安氏隐孢子虫感染率统计学差异极显著(P0.01);不同养殖方式奶牛隐孢子虫感染率统计学差异不显著(P0.05)。结果表明:奶牛隐孢子虫感染流行范围较广,存在一定人兽共患风险。     

新孢子虫病与奶牛生产性能关系的研究

1984年Bjerkas等在患脑膜炎和肌炎的幼犬体内发现了一种外被包囊的原虫,形态与龚地弓形虫（Toxoplasma gondii）相似.Dubey等对诊断为弓形虫病的23只患犬的器官标本进行了重新诊断,也发现了这种与T gondii相似但形态结构不同的原虫,并命名为犬新孢子虫（Neospora caninum）.Dubey等从美国墨西哥州一个持续发生流产牛场的胎牛脑组织中分离到类似T gondii的组织包囊,这种组织包囊与抗N caninum的抗体发生反应,而不于T gondii抗体发生发应,认为其为牛流产的病原.Mc Alister在犬粪便里检出N caninum卵囊,证实犬是N caninum的终末宿主.迄今为止,研究报道最多的是奶牛新孢子虫病,它广泛发生于世界各地.     

黄牛隐孢子虫病流行病学调查

隐孢子虫病是一种世界性的人兽共患原虫病.病人和病畜主要表现为腹泻,免疫正常的个体多可自愈,但免疫缺陷和幼年的个体则可致持久而严重的腹泻.我国已有不少省市发现该病,继1998年李培英等首次在安徽省发现黄牛隐孢子虫后.对本省蒙城县黄牛隐孢子虫流行病学特点作进一步调查,以期为黄牛生产提供必要的资料.     

吉林省白山地区牛新孢子虫病流行病学调查

为了解吉林省白山地区牛新孢子虫病的流行情况,本研究应用间接ELISA方法对采自吉林省白山地区5个县区193份牛血清样品进行了检测,并对不同地区、不同养殖方式、不同品种及不同年龄段牛新孢子虫病感染情况进行了比较分析。结果显示,检测样本的总体阳性率为35.8%(69/193);经统计学分析,不同地区、不同养殖方式及不同年龄段牛新孢子虫感染率差异显著(P0.05);而不同品种牛新孢子虫感染率差异不显著(P0.05)。调查表明,吉林省白山地区是牛新孢子虫病的流行区域,此次调查为该地区牛新孢子虫病的防控提供了科学的理论依据。     

奶牛新孢子虫病诊断方法研究进展

新孢子虫病是导致奶牛流产的主要原因之一，给奶牛业造成很大的经济损失。各国学者对新孢子虫病的诊断方法进行了大量的研究工作。本文对奶牛新孢子虫病的临床诊断、病原学诊断、血清学诊断及分子生物学诊断方法的研究进展进行了综述。     

安徽省黄牛隐孢子虫病流行病学调查

为查明安徽省黄牛隐孢子虫感染情况 ,取该省 6个县 (市 )进行了黄牛隐孢子虫感染情况的调研 ,在 42头黄牛的粪样中查到了隐孢子虫卵囊 ,其感染率为 1 5 2 7% (42 /2 75)。经鉴定 ,所获虫体为鼠隐孢子虫 (Cryptosporidiummuris)和小隐孢子虫 (Gryptosporidiumparvum)。黄牛隐孢子虫感染存在年龄和地区性差异 ,但与性别无关。     

河南省奶牛犬新孢子虫病流行病学调查

奶牛犬新孢子虫病是由孢子虫纲、真球虫目、新孢子虫属的犬新孢子虫引起的多种动物共患的一种原虫病,本病奶牛、肉牛均能感染,但对奶牛的危害严重,主要引起孕畜流产或死胎以及新生儿运动神经障碍等[1].目前有许多国家和地区报道有该病发生,我国一些省份和地区陆续有报道该病的发生和流行病学调查[2-8],为了解河南省奶牛犬新孢子虫病的感染情况,我们于2009年8～10月间对河南省5个地区27家奶牛场的468头奶牛进行了犬新孢子虫抗体检测,证实本省以上5个地区均有该病感染.     

牛新孢子虫病和弓形虫病的流行病学调查

为了调查我国牛新孢子虫和弓形虫的感染情况，应用新孢子虫酶联免疫吸附试验（ELISA）和弓形虫间接血凝试验（IAT）分别检测了来自国内10个省（市、自治区）的262份乳牛、10份肉牛和40份水牛血清。结果显示，乳牛新孢子虫的抗体阳性率为17．2％，弓形虫的抗体阳性率为2．3％，没有检测到既有新抱子虫抗体又有弓形虫抗体的乳牛血清。各牛场所检乳牛血清的新孢子虫抗体阳性率在0～34．4％之间。在水牛和肉牛血清中未检测到新孢子虫抗体和弓形虫抗体。流产乳牛血清的新孢子虫抗体阳性率为20．2％，未流产乳牛为16．1％，其中血清抗体阳性乳牛主要在妊娠中晚期流产。各个年龄段乳牛血清的抗体阳性率差异不显著（P〉0．05）。不同妊娠胎次的乳牛血清抗体阳性率差异不显著（P〉0．05）。确认新孢子虫病在国内大部分牛场存在。     

Udder health in dairy cattle infected with Neospora caninum

Blood samples were collected from 3449 cows on 57 representative Ontario dairy herds during the summer of 1998 and analysed for antibody to Neospora caninum using an ELISA. Forty-eight herds (2742 cattle) contained at least one N. caninum-seropositive animal. Two composite milk samples were collected from all cattle: the first on the day of blood collection and the second 68 to 365 days later. All milk samples were submitted for bacteriological culture. Ontario Dairy Herd Improvement Corporation (DHI) data were available for 3162 cattle in the 57 herds at the time of bleeding. Furthermore, complete DHI data were available for 1658 cattle that were culled between 12 and 24 months following blood collection. Using a standardised ELISA sample-to-positive (S/P) cut-off of ≥0.45, the corrected seroprevalence was 8.2% overall and 10.1% within seropositive herds. At blood collection the odds of N. caninum-seropositive cows having a high linear score (≥4.0; equivalent to a somatic cell count ≥200,000 cells/ml) was 27% less than for seronegative animals. Similarly, at the time of culling, the odds of having a high linear score was 22% less in N. caninum-seropositive cattle. Overall, linear score was lower in N. caninum-seropositive cattle at culling. After controlling for herd, parity, days in milk, and the interval between collection of milk samples, the odds of N. caninum-seropositive cattle testing positive for an environmental pathogen (i.e. environmental Streptococcus species and coliforms) on the second milk sample was 56% less than for seronegative animals. The odds were 83% less at a higher ELISA S/P cut-off of ≥0.70. Finally, the odds of N. caninum-seropositive cattle developing a new infection with a major pathogen (environmental or contagious) were 60% less than seronegative cows using the higher ELISA S/P cut-off.     

乳牛流产胎儿中新孢子虫的鉴定

在血清学调查的基础上，进行了流产胎牛体内新孢子虫的鉴定。取新孢子虫血清抗体阳性乳牛的流产胎牛的脑、心、肺、脾、肝等组织进行病理学检查，经HE染色观察到脑组织中存在类似于新孢子虫包囊样结构，经免疫组织化学染色排除刚地弓形虫包囊的存在，确认该包囊为新孢子虫包囊。同时提取流产胎牛脑组织DNA，应用新孢子虫特异性引物Np6／Np21进行PCR扩增，扩增出的特异性目的争带的序列与新孢子虫标准株Nc-1的gene5序列的一致性为98％。首次证实我国大陆流产胎牛脑组织中存在新孢子虫。     

Financial analysis of various strategies for the control of Neospora caninum in dairy cattle in Switzerland

The present study was conducted to estimate the direct losses due to Neospora caninum in Swiss dairy cattle and to assess the costs and benefits of different potential control strategies. A Monte Carlo simulation spreadsheet module was developed to estimate the direct costs caused by N. caninum, with and without control strategies, and to estimate the costs of these control strategies in a financial analysis. The control strategies considered were “testing and culling of seropositive female cattle”, “discontinued breeding with offspring from seropositive cows”, “chemotherapeutical treatment of female offspring” and “vaccination of all female cattle”. Each parameter in the module that was considered to be uncertain, was described using probability distributions. The simulations were run with 20,000 iterations over a time period of 25 years.

The median annual losses due to N. caninum in the Swiss dairy cow population were estimated to be € 9.7 million. All control strategies that required yearly serological testing of all cattle in the population produced high costs and thus were not financially profitable. Among the other control strategies, two showed benefit–cost ratios (BCR) >1 and positive net present values (NPV): “Discontinued breeding with offspring from seropositive cows” (BCR = 1.29, NPV = € 25 million) and “chemotherapeutical treatment of all female offspring” (BCR = 2.95, NPV = € 59 million). In economic terms, the best control strategy currently available would therefore be “discontinued breeding with offspring from seropositive cows”.     

Associations between pregnancy outcome and serological response to Neospora caninum among a group of dairy heifers

AIM: To monitor pregnancy in a group of rising 2-year-old dairy heifers on a farm on which abortion due to Neospora caninum was known to occur in previous years.

METHODS: A prospective cohort study group of 164 rising 2-year-old heifers was pregnancy-tested and blood-sampled at 4–5-week intervals throughout gestation. Sera were tested for antibodies to N. caninum at 3–4-month intervals, using an enzyme-linked immunosorbent assay (ELISA). When loss of pregnancy was detected, an N. caninum indirect fluorescent antibody test (IFAT) was conducted retrospectively on stored sera collected the month before abortion, the month abortion was detected, and for the following 2 months, from heifers that aborted. All fetal and placental material detected following abortion was subjected to gross post-mortem and histopathological examination.

RESULTS: Eleven of 18 (61%) heifers that were seropositive and 4/146 (3%) heifers that were seronegative to N. caninum by ELISA, aborted. The relative risk for abortion among ELISApositive heifers was 23.6. Abortion occurred predominantly between Days 120 and 152 gestation among the ELISA-positive heifers and throughout gestation among the ELISA-negative heifers. IFAT titres rose around the time of abortion in most of the heifers that were previously seropositive by ELISA, but dropped rapidly again in post-abortion samples. IFAT titres among 4/6 ELISA-positive heifers that did not abort increased, but later in gestation than the time other heifers aborted. IFAT titres remained negative in heifers that aborted that were ELISAnegative.

CONCLUSIONS: Heifers that were seropositive to N. caninum by ELISA had a much greater risk of abortion than seronegative heifers. Most seropositive heifers showed evidence of a reactivation of infection during pregnancy. High (≥1:2,000) N. caninum IFAT titres also occurred in non-aborting heifers.

CLINICAL RELEVANCE: Culling of replacement heifers seropositive to N. caninum may be a cost-effective strategy for minimising risk of abortion. Pregnancy testing heifers before 5 months gestation may overestimate the number that calve in N. caninum-infected herds, but would assist in documenting the occurrence of abortion. Reliance on a high (>1:2,000) IFAT titre to rule-in N. caninum as a cause of abortion is likely to produce false-positive results.     

Seroprevalence of Neospora caninum infection following an abortion outbreak in a dairy cattle herd

OBJECTIVE: To investigate the seroprevalence of Neospora caninum infection in a commercial dairy cattle herd, 15 months after detection of an abortion outbreak. PROCEDURE: Sera from the whole herd (n = 266) were examined for N caninum antibodies by indirect fluorescent antibody test (IFAT) and immunoblot analysis. Herd records were reviewed to collate serological results with abortion history, proximity to calving, and pedigree data. RESULTS: The seroprevalence of N caninum infection was 24% (63/266) for IFAT titre > or = 160, 29% (78/266) for immunoblot positive (+ve), and 31% (82/266) for IFAT > or = 160 and/or immunoblot +ve; 94% (59/63) of animals with IFAT > or = 160 were immunoblot +ve. The association between seropositivity (IFAT > or = 160 and/or immunoblot +ve) and history of abortion was highly significant (P < 0.001); the seroprevalence was 86% (18/21) in aborting cows, compared with 30% (50/164) in non-aborting animals. The abortion rate for seropositive cows was 26% (18/68) compared with 3% (3/117) for seronegative animals. IFAT titres of infected cows were higher within 2 months of calving than at other times (P < 0.001). The association between seropositivity in dams and daughters was highly significant (P = 0.009). CONCLUSIONS: The abortions were associated with N caninum infection and there was evidence of reactivation of latent infection close to calving and congenital transmission of infection. Immunodominant antigens identified by immunoblots may prove useful for improved diagnostic tests.     

Factors associated with Neospora caninum serostatus in cattle of 20 specialised Costa Rican dairy herds

Twenty-five specialised Costa Rican dairy farms (located in the Poás area) were used to determine neosporosis seroprevalence and the association of seropositivity with environmental and management factors. The farms involved were selected intentionally and all of them use VAMPP 5.1 (Veterinary Automated Management and Production Control Programme) as management-information system. Holstein–Friesian, Jersey and crosses between them were the most-frequent breeds in these herds. The number of females per farm varied from 41 to 296. Our cross-sectional study had two phases. In the first phase, we determined the presence or absence of seropositivity at herd level. For the second phase, all females in 20 seropositive farms were bled. Serum samples were tested for antibodies to Neospora caninum using an indirect enzyme-linked immunosorbent assay (ELISA). A questionnaire with factors mentioned in the literature was administered to the farmers. Logistic regression (LR with herd as random effect) was used to assess the relationships of the serostatus at the individual level with characteristics of the cows and environmental factors. In the first phase all herds had >20% seropositive females; therefore, all herds were eligible for the second phase. In the second phase, the overall prevalence was 39.7% (1191/3002), and within-herd prevalences were between 25.0 and 70.5%. Age 3–6 years, parity ≤2 of the dam of the cow, Jersey breed and lack of purposive sampling to diagnose abortive infectious disease were associated with positive serostatus; other management and environmental factors did not show significant associations. The lack of association between management and environmental factors with serostatus might be because all farms were exposed to a considerable number of potential factors. That all herds of this study were seropositive for neosporosis and the within-herd prevalence was considerable raises questions about how far the infection is spread in other dairy areas of Costa Rica.     

Nationwide seroprevalence of Neospora caninum among dairy cattle in Japan

Serum samples from 2420 clinically healthy dairy cattle, randomly selected from stored sera in 18 districts of Japan, were tested for the presence of Neospora caninum antibodies using an indirect fluorescent antibody test (titer > or =1:200). Nationwide seroprevalence is estimated at 5.7% (139/2420). Seropositive cattle were detected in all surveyed districts despite the evidence of confirmed case reports of bovine neosporosis, showing that N. caninum is widely distributed throughout Japan. Age-specific seroprevalence did not increase with cattle age, suggesting that Neospora infection is likely to be transmitted vertically rather than horizontally in Japan. Considering that N. caninum seropositive cows are thought to be more likely to abort, substantial fetal losses may be induced by N. caninum infection in Japan. Devising strategies are needed to reduce the economic impact on the Japanese dairy industry. This is the first study to investigate the nationwide seroprevalence of N. caninum in cattle in Asia.     

Simulating the impact of four control strategies on the population dynamics of Neospora caninum infection in Swiss dairy cattle

A dynamic deterministic simulation model was developed to assess the impact of different putative control strategies on the seroprevalence of Neospora caninum in female Swiss dairy cattle. The model structure comprised compartments of “susceptible” and “infected” animals (SI-model) and the cattle population was divided into 12 age classes. A reference model (Model 1) was developed to simulate the current (status quo) situation (present seroprevalence in Switzerland 12%), taking into account available demographic and seroprevalence data of Switzerland. Model 1 was modified to represent four putative control strategies: testing and culling of seropositive animals (Model 2), discontinued breeding with offspring from seropositive cows (Model 3), chemotherapeutic treatment of calves from seropositive cows (Model 4), and vaccination of susceptible and infected animals (Model 5). Models 2–4 considered different sub-scenarios with regard to the frequency of diagnostic testing. Multivariable Monte Carlo sensitivity analysis was used to assess the impact of uncertainty in input parameters.

A policy of annual testing and culling of all seropositive cattle in the population reduced the seroprevalence effectively and rapidly from 12% to <1% in the first year of simulation. The control strategies with discontinued breeding with offspring from all seropositive cows, chemotherapy of calves and vaccination of all cattle reduced the prevalence more slowly than culling but were still very effective (reduction of prevalence below 2% within 11, 23 and 3 years of simulation, respectively). However, sensitivity analyses revealed that the effectiveness of these strategies depended strongly on the quality of the input parameters used, such as the horizontal and vertical transmission factors, the sensitivity of the diagnostic test and the efficacy of medication and vaccination. Finally, all models confirmed that it was not possible to completely eradicate N. caninum as long as the horizontal transmission process was not interrupted.