Comparative studies with three different bovine blood sample BHV-1 ELISA tests: indirect ELISA and bG-blocking-ELISA

A total of 2754 bovine blood samples were examined for BHV1 antibodies in three different BHV-1 ELISA tests. The tests used were the CHEKIT Trachitest 2nd. Gen. "Best?tigungstest" Serum, the CHEKIT-BHV-1-gB-ELISA (Bommeli-Diagnostics/Intervet), and the BHV-1-gB Antibody Test Kit (IDEXX). A first testing identified 111 (4.0%) of the samples as positive and 2501 (90.8%) samples negative in all three tests. Onehundredand-fortytwo (5.2%) of the samples showed a not negative result in at least one of the two gB-ELISAs. The testing was repeated for 139 of the 142 samples and still 89 (3.2%) samples were found with discrepant results. The remaining 50 samples showed a negative reaction in the three ELISA tests. After Western blot analysis antibodies against glycoprotein B (gB) of BHV-1 were only detected in 11 of the 89 samples with a not negative reaction in at least one of the gB-ELISAs. Three of the 50 ELISA-negative samples showed a positive reaction in the Western blot. The high number of positive results in the gB-ELISAs which were negative in the Western blot assay leads to the conclusion that gB-ELISAs may have a lower specificity as the indirect ELISA. Introducing the gB-ELISA as the standard test for BHV1 serology in Bavaria would result to an increase of the number of BHV-1 positive farms by 8% (gB IDEXX) or 20% (gB Bommeli) 20%.     

A comparative study of serological tests for use in the bovine Herpesvirus 1 eradication programme in The Netherlands

We compared a gB-ELISA, a gE-ELISA and a Danish test system (consisting of a blocking and an indirect ELISA) for their specificity and sensitivity to detect antibodies against BHV1. The Danish test system showed the highest sensitivity and the gE-ELISA the lowest; the gB-ELISA showed an intermediate sensitivity. If the doubtful zone (25–50% blocking) of the gB-ELISA was considered as positive (gB-ELISA⁺), the sensitivity almost reached that of the Danish test system. The specificity of all tests appeared to be very high, 99.7, 96.7 100, 99.7% for the gB-ELISA, gB-ELISA⁺, gE-ELISA and the Danish test system, respectively. Seroconversion was detected in the gE-ELISA up to 3 weeks later than in the gB-ELISA and the Danish test system. It is concluded that the combination of a gB-ELISA (for screening) and the Danish test (for confirmation) system used in the BHV1 eradication programme in the Netherlands, provides for very high sensitivity (>99.0%) (Kramps et al., 1994) and a very high specificity (>99.9%).     

BHV-1 eradication program in Bavaria: a marker-independent strategy

In Bavaria a BHV-1 eradication program was initiated in 1986 and was changed to a compulsory program in 1998. The eradication success increased progressively from < 50% in 1986 to 87% of the farms in 2002. BHV 1-free farms are controlled by bulk milk serology twice a year along with blood serology in animals that are negative but from herds where positive field virus infected animals are present. All serological tests are performed with an indirect ELISA test, all positive results are confirmed by a gB ELISA. Currently about 100.000 virus infected cattle are in Bavarian herds, approximately 80% of these animals are in heavily infected herds (> 10 infected animals). These herds comprise about 5% of all Bavarian herds. The eradication of the virus in these heavily infected herds is the most diifficult, whereas the prevention of new infections appears controllable. In this review current problems in BHV1 eradication are named and possible improvements are discussed.     

The role of goats as reservoir hosts for bovine herpes virus 1 under field conditions

Bovine herpesvirus 1 (BoHV1) is the cause of economically significant viral infections in cattle. Respiratory symptoms associated with the infection are known as Infectious Bovine Rhinotracheitis (IBR). Sheep and goats are less sensitive to the infection although their role in inter-species viral transmission under field conditions is subject to controversy. The objective of this study was to investigate seroprevalence of BoHV1 infections in cattle, sheep, and goats raised together for at least a year. Blood serum samples were taken from 226 cattle, 1.053 sheep, and 277 goats from 17 small- to medium-scale farms. BoHV1-specific antibody presence and titers were determined using virus neutralization test. In total, 73 of the 226 cattle (32.3%) were seropositive. The infection was detected in 13 of the 17 farms. Infection rates ranged from 5.8 to 88.8%. Only one of the 1053 sheep (0.09%) was seropositive. However, 58 of the 277 (20.9%) goats were seropositive. Goat samples taken from 8 of the 17 farms were seropositive with infection rates ranging from 17 to 38.9%. Statistical analysis showed a significant correlation in infection rates between cattle and goats but not sheep. These results suggest that goats may be more sensitive to the BHV1 infection than sheep and the role of goats as possible reservoirs for BoHV1 in the control and eradication of BHV1 in cattle should be considered in future studies.

     

Risk factors for introduction of BHV1 into BHV1-free Dutch dairy farms: a case-control study

In May 1998, a compulsory eradication programme for BHV1 started in the Netherlands. In December 1999 approximately 24% of Dutch dairy farms were certified BHV1-free (Animal Health Service (AHS)). Ninety-three certified BHV1-free dairy farms participated in a cohort study that investigated the probability of introduction of infectious diseases. The probability of introduction of BHV1 was determined from March 1997 until April 1999. Ninety of these farms remained BHV1-free and could be used as control farms. From January 1997 until March 1998, BHV1 was introduced into 41 BHV1-free dairy farms in the Netherlands (case farms). Management data were collected for both cases and controls and were complete for 37 case farms and 82 control farms. For small data sets and for data in which both low and high frequencies were expected in the contingency tables, the asymptotic methods were unreliable. Our data set clearly resembled such a data set; the risk factors were rare events because the BHV1-free farms were closed farms on which few direct animal contacts occurred. Therefore, an exact stratified modelling approach was most suitable for the data. The study showed that dairy farms should prevent cattle from escaping or mingling with other cattle and that professional visitors should always wear protective farm clothing.     

Evaluating control strategies for outbreaks in BHV1-free areas using stochastic and spatial simulation

Several countries within the EU have successfully eradicated bovine herpesvirus type I (BHV1), while others are still making efforts to eradicate the virus. Reintroduction of the virus into BHV1-free areas can lead to major outbreaks - thereby causing severe economic losses. To give decision-makers more insight into the risk and economic consequences of BHV1 reintroduction and into the effectiveness of various control strategies, we developed the simulation model InterIBR. InterIBR is a dynamic model that takes into account risk and uncertainty and the geographic location of individual farms. Simulation of a BHV1-outbreak in the Netherlands starts with introduction of the virus on a predefined farm type, after which both within-farm and between-farm transmission are simulated. Monitoring and control measures are implemented to simulate detection of the infection and subsequent control. Economic consequences included in this study are related to losses due to infection and costs of control. In the simulated basic control strategy, dairy farms are monitored by monthly bulk-milk tests and miscellaneous farms are monitored by half-yearly serological tests. After detection, movement-control measures apply, animal contacts are traced and neighbour farms are put on surveillance. Given current assumptions on transmission dynamics, we conclude that a strategy with either rapid removal or vaccination of infected cattle does not reduce the number of infected farms compared to this basic strategy - but will cost more to control. Farm type with first introduction of BHV1 has a considerable impact on the expected number of secondarily infected farms and total costs. To limit the number of infected farms and total costs due to outbreaks, we suggest intensifying the monitoring program on farms with a high frequency of cattle trade, and monthly bulk-milk testing on dairy farms.     

Co‐infection with Bovine Herpesvirus 4 and Histophilus somni Significantly Extends the Service Period in Dairy Cattle with Purulent Vaginal Discharge

The aim of the study was to investigate the effect of Bovine Herpesvirus 4 (BoHV‐4) and Histophilus (H.) somni on fertility rate of cows in a Hungarian Holstein‐Friesian dairy herd with purulent vaginal discharge (PVD). Non‐pregnant cows (n = 188) with mature corpus luteum were treated with cloprostenol and 3 days later if they did not show oestrus, were examined by rectal palpation. Animals showing PVD (n = 60/31.9%/) and 14 controls with normal vaginal discharge (Score 0) were randomly selected and further examined by ultrasonography and blood samples were collected for detecting BoHV‐4 DNA and transcervical guarded swabs were collected from the uterus for bacteriological examination. Although the majority of the examined animals were infected with BoHV‐4 and H. somni including the control animals as well, in group of animals with PVD score 3, fewer animals became pregnant and the duration between the first treatment to pregnancy was significantly extended. Based on these clinical and comparative data, our results confirm that these two microorganisms together may impair important reproductive parameters which may cause large economic losses to dairy farms.     

Strains of bovine herpesvirus 1 that do not express an epitope on glycoprotein E in cell culture still induce antibodies that can be detected in a gE-blocking ELISA

Two bovine herpesvirus 1 (BHV1) field strains that do not express an epitope on glycoprotein E (gE) in cell culture were inoculated into calves to examine whether their sera became positive in a gE-blocking ELISA that detects antibodies against gE. This gE-blocking ELISA uses one monoclonal antibody that is directed against the above mentioned epitope. All calves, except one, infected with these gE-epitope negative BHV1 strains, became positive in this gE-blocking ELISA, about two weeks later than in another gE-ELISA and a gB-ELISA. However, cattle infected with BHVI strains that do express this particular gE-epitope showed a similar type of antibody responses. These findings demonstrate that BHV1 strains that do not express a particular gE-epitope in cell culture, still can induce antibodies that are detected in a blocking ELISA that measures antibodies against that epitope.     

Herd-level diagnosis for Salmonella enterica subsp. enterica serovar Dublin infection in bovine dairy herds

Herd-level sensitivities of bacteriological and serological methods were compared in 79 bovine dairy herds, recently infected with Salmonella enterica subsp. enterica serovar Dublin. All farms experienced clinical signs of salmonellosis for the first time and had no history of vaccination against salmonellosis. At the start of the study, infection with serovar Dublin was confirmed with at least one positive bacteriologic culture for serovar Dublin from a clinical case (gold standard for herd infection).Bacteriological culture was done on samples of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier clinical signs of salmonellosis. Blood samples of all animals and bulk-milk samples were tested using an ELISA.Herd-level sensitivity (HSe) of culture of dung-pits, drinking water, bulk-milk filters, and faeces of animals with current or earlier signs of salmonellosis was 45, 5, 7, and 38%, respectively. HSe for serology of all animals was 100%. If blood samples of all calves 4-6 months old were examined, at least one calf was seropositive on 91% of the infected farms. If serology was performed on samples of animals with current or earlier signs of salmonellosis, at least one animal was seropositive on 80% of the infected farms. HSe for bulk-milk samples was 54%. However, if clinical signs of salmonellosis were observed only in lactating animals, sensitivity of bulk-milk serology was 79%.Interesting combinations of methods were the combination of serology of bulk milk with either serology of animals with current or earlier signs of salmonellosis (HSe=91%), or serology of all calves of 4-6 months old (HSe=99%).     

Control of bovine viral diarrhea/mucosal disease in the district of Kamenz on a voluntary basis--ways, successes, limitations

In 69 dairy and beef herds in the district of Kamenz, Saxony, with a total number of 21,783 and 89.6% of the district's cattle, a voluntary BVDV eradication protocol was implemented from 2000 to 2007. The aim was to achieve eradication as comprehensive as possible and to prepare the herds for the mandatory eradication program. Essential preconditions for the accreditation of a herd as "free of BVD virus" were the antigen test of all cattle and their offspring for 12 months including completeness check and a negative serological random sampling of young cattle. Mean eradication period of infected herds lasted 45.6 months, herd size, and the number of newly purchased cattle were found to have a significant influence. In five infected farms calf losses significantly decreased after termination of the eradication. further examination of the 126 antigen test positive animals from 15 herds resulted in 87 persistently infected (PI) and 15 transiently infected (TI) individuals, 24 animals missed the second test. Furthermore, out of the 87 PI's 30 individuals (34%) had antibodies against BVDV. Eight farms vaccinated their whole herd, seven only the young stock before first breeding, and 54 herds did not vaccinate, respectively. Concluding from this study, the epidemiological particularities of the farms should be taken in account. Testing of all cattle in a minimum of time including, official monitoring of immediate culling of PI's, immediate epidemiological research, and serological monitoring of the eradication process is necessary.     

Evaluation of surveillance strategies for bovine brucellosis in Japan using a simulation model

Bovine brucellosis is caused by Brucella abortus and induces abortions in female cattle, with other cattle at risk of infection from the aborted fetus or contaminated placenta. In Japan, the number of cases has dramatically reduced due to national surveillance and eradication strategies. Bovine brucellosis is now believed to be eradicated in Japan. Here, we examine the surveillance strategies currently in place for early detection of infected cattle in the event of a future reintroduction of the disease. We compared current serological surveillance for the dairy population with bulk-milk surveillance and abortion surveillance, and used time to detection as the main criterion of surveillance efficacy. A stochastic individual-based model (IBM) was developed to simulate disease transmission within and between farms. Using outputs from the transmission model, a comparison of surveillance strategies was simulated. For evaluation of the robustness of the parameter values used in the transmission model, a sensitivity analysis was conducted. For the purpose of evaluating the direct costs of each surveillance strategy, the annual number of samples to be tested and the annual number of farms to be visited were estimated. Our results indicated that current serological surveillance with 60-month test intervals is not effective enough for rapid detection of a brucellosis outbreak. Bulk-milk surveillance appeared the most effective method based on the early detection of infected cows and a reduced number of samples required. The time to detection for abortion surveillance was greater than that of bulk-milk surveillance but varied widely depending on the reported ratio of abortions. Results from the surveillance model were consistent when alternative scenarios were applied to the transmission model. Although our model cannot exactly replicate an actual brucellosis outbreak, or the results of surveillance, our results may help decision-makers to choose the most effective surveillance strategy.     

The detection of bovine herpesvirus type 1 (BHV 1) using an intradermal test. I. Field studies

An intradermal test (delayed hypersensitivity test) for the diagnosis of BHV1 infection was evaluated in 791 cattle of 16 dairy farms. The skin reactions were compared with the results of serological examinations using a commercial BHV1 ELISA kit (Trachitest). As antigen concentrated, purified and inactivated BHV1 was used. The skin reaction (increase of the skin fold thickness) was used for the interpretation of test results. The best results were obtained with the control of the skin reaction on the third day after injection of the antigen. From 393 serologically BHV1 negative cattle with an age of more than 6 months 391 (99.5%) had a skin reaction up to 1.0 mm and 2 animals (0.5%) had a reaction of 1.3 and 1.9 mm, respectively. The mean increase of skin fold thickness was 0.2 mm. Out of 291 serologically BHV1 positive cattle with an age of more than 6 months 270 had antibodies from natural infection and, partially, from additional vaccination with inactivated BHV1 vaccine. 266 (98.5%) of these animals showed a skin reaction of more than 2.0 mm, in 3 animals (1.1%) a skin reaction up to 1.0 mm was observed and 1 animal (0.4%) had a reaction of 2.0 mm. The mean increase of the skin fold thickness was 6.3 mm. 21 animals had BHV1 antibodies only because of vaccination with inactivated BHV1 vaccine. Only 4 animals had a skin reaction of more than 2.0 mm. Among 107 animals with an age up to 6 months 30 were serologically BHV1 positive and 77 were BHV1 negative. In all animals the skin reaction was less than 1.0 mm, the mean was 0.2 mm.     

Feasibility of serological bulk milk testing as a method for BVD surveillance

A commercial ELISA detecting antibodies against bovine viral diarrhoea Virus (BVDV) was analysed for its applicability for bulk-milk screening. Detection limits were analysed using native and concentrated milk samples (milk treated with rennet and ammonium sulfate precipitated) from 10 cows whose sera showed different reactivity levels in the ELISA and from two cows which gave birth to persistently infected calves during the last year. Further this and a second commercial ELISA were used to screen 591 randomly selected bulk-milk samples. To clarify discrepancies thirty-nine herds were included in a follow-up study. A second bulk-milk sample and serum samples from 10 young cattle of 6 to 28 month of age per herd were analysed for antibodies against BVDV. The results of this second testing and the detection of viremic animals in 4 herds confirmed the results from initial bulk-milk testing with both tests. The analysed test is suitable for bulk-milk testing although its application is limited by vaccination.     

Factors associated with variation in Neospora caninum bulk-milk S/P ratios in initially bulk-milk negative testing Dutch dairy herds

We conducted a study on 81 initially bulk-milk ELISA negative dairy herds taken from a random sample of Dutch dairy herds to evaluate variation in bulk-milk S/P ratios and to study reasons for bulk-milk conversion. These herds were repeatedly (3-month intervals) tested between April 2004 and August 2005 and serostatus of all animals had previously been established as negative (N), low-positive (LP) or high-positive (HP). Of these herds, herd- and test-related factors associated with variation in sample over positive (S/P) ratios were analysed using a multivariable linear-mixed model with ‘herd’ as random effect. In addition, changes of animal serostatus in converting herds were described. S/P ratios were calculated as the optical density of the bulk-milk sample minus the optical density of the negative serum control divided by the difference in optical density between the positive and negative serum control.

Sixteen bulk-milk conversions in 12 dairy herds were seen with few indications of serological conversion in lactating cattle except for one herd in which recrudescence of infection appeared likely in nine cows. The effect of HP serostatus on bulk-milk S/P ratio was 2–3 times stronger compared with LP serostatus. In addition, bulk-milk S/P-ratio increased when the proportion of HP animals between 1 and 60 days in milk increased and decreased when the average milk-production level of the herd increased. Besides these herd-related factors, the use of different ELISA-testkits between test rounds had a significant effect on the S/P-ratio in bulk-milk samples.     

Insights into the dynamics of endemic Coxiella burnetii infection in cattle by application of phase-specific ELISAs in an infected dairy herd

Serological diagnosis of acute and chronic Q fever in humans relies on detection of antibodies to phase I (PhI) and II (PhII) antigens of Coxiella (C.) burnetii. Although phase-specific antigens are available, they are not yet used in ruminants as they are in humans. This study focuses on phase-specific serology as a tool for analysis of the dynamics of infection in cattle. As a prerequisite, sero-prevalence in Bavarian cattle (1) and sero-prevalences for age-groups (2) were determined by ELISA (CHEKIT Q-Fever; mix of PhI/PhII-antigen). Subsequently, phase-specific antigens were coated onto ELISA plates individually and tests were simultaneously applied in an endemically infected herd with about 90 dairy cows and 250 calves/heifers in April 2005, March 2006 and retrospectively in May and October 2004. From April 2005 onward, placentas were analysed for C. burnetii by PCR (3). (1) Sero- and herd prevalences based on 21,051 sera from 603 Bavarian dairy farms collected in 2003 were 14.8% ± 0.48% and 72.3% ± 3.6%, respectively. (2) Analysis of 3965 animals from 105 farms for which age was reported revealed a base level of sero-prevalence of less than 5% in 1-2 years old animals, it increased to 15% in 2-3 years old and reached a plateau (25-30%) in cows four years and older. (3) In May 2004 and April 2005 a peak of PhI(-)/PhII(+)-prevalence in primiparous cows (2.0-3.5 years) was observed; but not in October 2004 and March 2006. The PhI(-)/PhII(+)-pattern in primiparous cows changed to negative (one-third), PhI(+)/PhII(+) (1/3) or persisted (1/3). In contrast, sero-conversion was rare in multiparous cows (>3.5 years). If the PhI(-)/PhII(+) pattern was detected, it was due to an infection in preceding years. This pattern persisted (2/3) or changed to negative (1/3); a change to PhI(+)/PhII(+) did not occur. PhI(-)/PhII(+) in heifers (1-2 years) always changed to negative. Detection of PhII-antibodies was significantly associated with PCR-positive placentas. Remarkably, 45% of sera with the PhI(-)/PhII(+) pattern were negative for the CHEKIT Q-Fever ELISA, thus this test missed an important group of infected animals.     

Detection of foot-and-mouth disease virus infection in vaccinated cattle

The aim of this study was to evaluate the value of commercially available kits for the detection of foot-and-mouth disease (FMD) virus infection in vaccinated cattle. The cattle were vaccinated with a commercial aqueous FMD vaccine type A24 and subsequently challenged 28 days post vaccination with homologous FMD virus. Seven of eight animals were protected from clinical disease and all became carriers. They were bled sequentially for up to 130 days post infection and samples of sera were tested with three ELISA kits: CHEKIT FMD-3ABC, Ceditest FMDV-NS and SVANOIR FMDV 3ABC-Ab ELISA. The Ceditest kit appears to be relatively higher sensitive than the others. When examined with this ELISA, all cattle developed of FMDV nonstructural proteins (NSPs) antibodies and remained positive throughout the period of the experiment. The response of antibodies against 3ABC antigen delayed in two cattle challenged with FMDV A24 virus. One of the cattle reacted negatively in Svanoir ELISA kit and sera from two animals were found negative in CHEKIT ELISA. It can be concluded that all tested kits can be a promising tool for FMD control and eradication campaigns in situation where emergency vaccination was applied.     

Tick infestation and the prevalence of Borrelia burgdorferi and Babesia divergens in cattle in Bavaria

During the grazing period 2002 319 cattle from 31 farms located in 6 districts of southern Bavaria were examined for the presence of ticks in 4- to 5-week intervals, and 287 serum samples were tested for the presence of antibodies against Borrelia burgdorferi and Babesia divergens. Ticks were detected in all 31 farms with a mean prevalence of 69%. 3218 out of 3453 collected ticks were Ixodes ricinus; 139 nymphs, 19 larvae and 77 damaged adult specimens could only be determined to the Genus level (Ixodes).The seasonal pattern revealed the highest frequencies of ticks in May/June and September.The intensity of tick infestation of positive animals was generally low. 76.5% of parasitized cattle had 1-6 ticks per day of investigation. Individual cattle showed up to 250 ticks per day. The percentage of infested animals in each herd varied within the period between 0-100%. The examination of serum samples by immunofluorescence technique (IFAT) revealed positive anti-Borrelia antibody titers (> or = 1:64) for 45.6% of the animals. The within-farm seroprevalence of borreliosis ranged from 20 to 100% in 27 of the 31 farms. A significant correlation could be detected between the number of ticks/cattle and the anti-Borrelia burgdorferi IgG-titer. By contrast, there was no significant correlation between the age of the animals and anti-Borrelia serum titers. For comparative reasons, 64 IFAT-positive serum samples were tested by Western blot techniques for the presence of antibodies cross-reacting with Borrelia garinii antigen. These analyses revealed that 69% of the samples reacted positively, 28% were unclear and 3% were negative. Examinations of the 287 serum samples for the presence of anti-Babesia divergens antibodies revealed one positive animal with a titer of 1:16.     

A two year BTV-8 vaccination follow up: molecular diagnostics and assessment of humoral and cellular immune reactions

The compulsory vaccination campaign against Bluetongue virus serotype eight (BTV-8) in Germany was exercised in the state of Bavaria using three commercial monovalent inactivated vaccines given provisional marketing authorisation for emergency use. In eleven Bavarian farms representing a cross sectional area of the state the immune reactions of sheep and cattle were followed over a two year period (2008-2009) using cELISA, a serum neutralisation test (SNT) and interferon gamma (IFN-γ) ELISPOT. For molecular diagnostics of BTV genome presence two recommended real time quantitative RT-PCR protocols were applied. The recommended vaccination scheme led to low or even undetectable antibody titers (ELISA) in serum samples of both cattle and sheep. A fourfold increase of the vaccine dose in cattle, however, induced higher ELISA titers and virus neutralising antibodies. Accordingly, repeated vaccination in sheep caused an increase in ELISA-antibody titers. BTV-8 neutralising antibodies occurred in most animals only after multiple vaccinations in the second year of the campaign. The secretion of interferon gamma (IFN-γ) in ELISPOT after in vitro re-stimulation of PBMC of BTV-8 vaccinated animals with BTV was evaluated in the field for the first time. Sera of BTV-8 infected or vaccinated animals neutralising BTV-8 could also neutralise an Italian BTV serotype 1 cell culture adapted strain and PBMC of such animals secreted IFN-γ when stimulated with BTV-1.     

近期部分规模化猪场猪伪狂犬病野毒抗体监测情况调查

猪伪狂犬病仍然是我国猪群的重要威胁性传染病，通常造成母猪繁殖障碍以及仔猪的神经症状和高死亡率，同时伪狂犬病病毒也是猪呼吸系统疾病综合征的重要原发性病原。用gE-ELISA野毒鉴别诊断方法共检测了来自8个省、市46个猪场1940份血清样品，其中阳性样品657份，样品总阳性率33.87%，阳性猪场25个。在检测的各场中，阳性率最高猪场达到75.76%(125/165)。而部分进行了科学的疫苗免疫和实施了严格的生物安全措施的猪场始终保持猪伪狂犬病阴性(0/135)。利用基因缺失疫苗科学免疫配合伪狂犬抗体鉴别诊断技术是控制和净化伪狂犬病的重要手段。     

Animal production systems of small farms in the Kaski district of Nepal

The aim of this study was to describe animal production on small farms in the Kaski district of Nepal, with the goal of identifying areas where animal health and productivity could be improved. Eighty-five randomly selected farms from four different Village Development Committees were visited. Farmers were interviewed and premises and animals visually inspected on all farms. Feed samples were collected from a subset of farms. The most commonly kept species were water buffalo (used for milk and meat), cattle (used for milk and labor), and goats (used for meat). Average milk production levels were 4.7?kg/day for water buffalo and 1.9?kg/day for cattle. All animals were milked manually, no calves were weaned, and only one farm practiced artificial insemination. A majority of cattle and goats had access to pasture, and a majority of farms fed their working or producing animals concentrates; however, nutritional input was insufficient in terms of energy, protein, and micronutrient content to increase levels of production. Goat-raising was the most profitable endeavor, followed by water buffalo and cattle. We conclude that animals have the potential to contribute significantly to improved livelihoods of farmers in terms of both income generation and non-tangible benefits. However, we found that significant constraints on animal production exist, including insufficient nutritional levels and a lack of preventative care resulting in animal disease. Furthermore, cultural considerations reflecting attitudes toward cattle shape farming in ways that may limit production. Nevertheless, targeted interventions that improve animal health and productivity are possible without being cost prohibitive.