Paratuberculosis on small ruminant dairy farms in Ontario,Canada: A survey of management practices

A cross-sectional study was undertaken (October 2010 to August 2011) to determine the risk factors for dairy goat herds and dairy sheep flocks testing positive for paratuberculosis (PTB) in Ontario, Canada. A questionnaire was administered to 50 producers during a farm visit in which concurrently, 20 randomly selected, lactating animals over the age of 2 years underwent sampling for paratuberculosis testing. Only 1 of 50 farms (2.0%) was closed to animal movement, whereas 96.6% of dairy goat farms and 94.1% of sheep farms purchased livestock from other producers. Only 10.3% of dairy goat, and no dairy sheep farms used artificial insemination. Manure was spread on grazing pastures by 65.5% and 70.6% of dairy goat and dairy sheep farms, respectively. Because of the high true-prevalence of paratuberculosis infection detected, no risk factor analysis could be performed. This study demonstrates that biosecurity practices conducive to transmission of PTB are highly prevalent in Ontario small ruminant dairy farms.     

Herd-level risk factors associated with Leptospira Hardjo seroprevalence in Beef/Suckler herds in the Republic of Ireland

Background

The aim of the present study was to investigate risk factors for herd seropositivity to Leptospira Hardjo in Irish suckler herds. Herds were considered eligible for the study if they were unvaccinated and contained ≥ 9 breeding animals of beef breed which were ≥ 12 months of age. The country was divided into six regions using county boundaries. Herd and individual animal prevalence data were available from the results of a concurrent seroprevalence study. Herds were classified as either "Free from Infection" or "Infected" based on a minimum expected 40% within-herd prevalence.Questionnaires were posted to 320 farmers chosen randomly from 6 regions, encompassing 25 counties, of the Republic of Ireland. The questionnaire was designed to obtain information about vaccination; reproductive disease; breeding herd details; the presence of recognized risk factors from previous studies; and husbandry on each farm. Data collected from 128 eligible herds were subjected to statistical analysis.

Results

Following the use of Pearson''s Chi-Square Test, those variables associated with a herd being "infected" with a significance level of P < 0.2 were considered as candidates for multivariable logistic regression modelling. Breeding herd size was found to be a statistically significant risk factor after multivariable logistic regression. The odds of a herd being positive for leptospiral infection were 5.47 times higher (P = 0.032) in herds with 14 to 23 breeding animals compared with herds with ≤ 13 breeding animals, adjusting for Region, and 7.08 times higher (P = 0.033) in herds with 32.6 to 142 breeding animals.

Conclusions

Breeding herd size was identified as a significant risk factor for leptospiral infection in Irish suckler herds, which was similar to findings of previous studies of leptospirosis in dairy herds.     

Risk factors for culling and deaths in eight dairy herds

Objectives To identify risk factors for culling of dairy cows from eight New South Wales dairy herds.
Design A longitudinal population study of dairy cow culling in eight non-seasonally calving dairy herds in the Camden district of New South Wales. Cox's proportional hazards model was used to evaluate various risk factors for culling for a specific reason (sales, deaths, reproductive failure, disorders of the udder and low milk production).
Results Age at first calving was not a significant risk factor for culling. Milk production in the first lactation greater than the population mean did not influence length of productive life overall, but was associated with a greater hazard of removal for disorders of the udder. Risk of culling for reproductive failure differed significantly between farms, and was not related to events in the previous lactation such as calving-to-first service interval or calving-to-conception interval. Shorter calving intervals were associated with increased risk of removal for low milk production and disorders of the udder.
Conclusion Longitudinal surveys to accurately identify reasons for removal from a wide range of herds, identification of herds with low culling rates (especially for reproductive failure and udder disorders), and the identification of practices associated with these culling rates would be worthwhile to the Australian dairy industry.     

Effect of replacement rate,crossbreeding and sexed semen on the efficiency of beef production from dairy herds in Finland

Abstract

In Finland, during the past 10 years, the number of dairy cows has declined considerably leading to decreased domestic beef production which is partly compensated by increased suckler beef production. However, production of meat originating from dairy herds has been shown to be economically more profitable and to produce less greenhouse gas emissions per unit of product than beef production from suckler cow systems. Therefore, when safeguarding beef self-sufficiency, the intensification of beef production from dairy herds is a more promising option to consider. In this study, the possibility of different options for increasing dairy beef production was assessed by using a deterministic simulation. Increasing the use of crossbreeding in dairy herds, especially when combined with the use of Y-sorted semen, appeared to be the most efficient strategy for increasing dairy beef production. The decrease in the replacement rate increased beef production through the potential for enhancing crossbreeding.     

A novel method to identify herds with an increased probability of disease introduction due to animal trade

In the design of surveillance, there is often a desire to target high risk herds. Such risk-based approaches result in better allocation of resources and improve the performance of surveillance activities. For many contagious animal diseases, movement of live animals is a main route of transmission, and because of this, herds that purchase many live animals or have a large contact network due to trade can be seen as a high risk stratum of the population. This paper presents a new method to assess herd disease risk in animal movement networks. It is an improvement to current network measures that takes direction, temporal order, and also movement size and probability of disease into account. In the study, the method was used to calculate a probability of disease ratio (PDR) of herds in simulated datasets, and of real herds based on animal movement data from dairy herds included in a bulk milk survey for Coxiella burnetii. Known differences in probability of disease are easily incorporated in the calculations and the PDR was calculated while accounting for regional differences in probability of disease, and also by applying equal probability of disease throughout the population. Each herd's increased probability of disease due to purchase of animals was compared to both the average herd and herds within the same risk stratum. The results show that the PDR is able to capture the different circumstances related to disease prevalence and animal trade contact patterns. Comparison of results based on inclusion or exclusion of differences in risk also highlights how ignoring such differences can influence the ability to correctly identify high risk herds. The method shows a potential to be useful for risk-based surveillance, in the classification of herds in control programmes or to represent influential contacts in risk factor studies.     

Prevalence and geographic distribution of bovine viral diarrhoea (BVD) infection in Finland 1993-1997

Bulk milk samples from every herd supplying milk to dairies in Finland were examined for the presence of antibodies to BVD virus (BVDV) annually during 1993-1997. The highest prevalence, 0.99% in 1994, declined to 0.37% in 1996; however, this favourable trend appeared to discontinue in 1997, where the prevalence remained at 0.41%. In 1993, sera of all individual animals from bulk milk antibody-positive herds were examined for the presence of these antibodies. Since 1994, only sera of animals from herds with a bulk milk absorbance reading greater than 0.250 in the EIA test were examined individually. Three geographic foci of BVDV antibody-positive dairy herds were resolved in 1994, one in the north-western, another in the eastern and a diffuse third in the southern part of Finland. A distinct limiting of the spread was apparent in 1997. Beef cattle were also studied during 1993-1997; in 1993 breeding units, in 1994 mainly beef suckler herds and in 1995-1997 serum samples of beef animals at slaughter were examined for the presence of antibodies to BVDV. The prevalence of seropositive herds in 1993 and 1994 was 30.2% and 3.2%, respectively, while the prevalence among slaughter animals ranged 0.8-1.6%. Seronegative animals in herds with > 50% of seropositive animals were examined for the presence of BVD-virus. A total of 40 dairy herds and two beef herds with viraemic (persistently infected, PI) animals was encountered during 1993-1997. A comprehensive control programme and a more specific, cooperatively funded eradication programme for dairy cattle were launched in 1994. These programmes most probably contributed to the decline in prevalence during 1994-1996.     

Evidence for transmission of bovine leukemia virus by rectal palpation in a commercial dairy herd

The risk of Bovine Leukemia Virus (BLV) transmission by rectal examination was determined over 22 months in a commercial dairy herd. All 167 BLV seronegative cattle, of breeding age or greater, were divided randomly into two groups and identified by neck-chain color. In the treatment group, routine rectal palpation occurred after a BLV infected animal and without a change of sleeve, while in the other group, palpation occurred in a similar manner with the exception that sleeves were changed between animals. When BLV seronegative cattle in either group were palpated after BLV infected cattle, the event and identification of the cattle involved were recorded. Serologic testing was performed eight times during the 22 month study to determine the number of animals that became infected following a palpation (an event). Thirty-one animals seroconverted during the study; 24 in the treatment (no sleeve change) group and seven in the sleeve change group. Sixteen of the animals in the treatment group that seroconverted had been palpated prior to their seroconversion. A hazard ratio (relative risk) for BLV seroconversion was determined between the two groups. Cows palpated with no sleeve change had a 2.8-fold increase in risk (confidence interval 1.1–6.8) of BLV infection. The increased risk of BLV infection associated with rectal palpation may have been affected by the presence of some highly infectious cows in the herd. This study confirms that rectal palpation without a change of sleeve may be a significant risk factor in some herds, and if efforts are made to decrease the spread of BLV in a herd, the potential for rectal sleeve transmission must be considered.     

Factors affecting calf mortality in Iranian Holstein dairy herds

The objective of this study was to document mortality reasons and risk factors for mortality in dairy calves in the northeast of Iran. This was a prospective cohort study of calves born on ten commercial dairy herds from 21 March 2009 to 20 March 2010. A total of 4097 live calves were followed for 90 days after birth. For each calf details of sex, parity of the dam, type of parturition and season of birth were recorded. The interval (in days) from the date of birth to the date of death and the reason for death was recorded for those calves that died before 90 days of age. A Cox proportional hazards model, including a frailty term to account for unmeasured herd-level effects was developed to quantify the effect of factors associated with time to death. Two hundred and sixty-six (6.5%, 95% CI: 5.8-7.3%) of the 4097 live-born calves died or were euthanised before 90 days of age. The most important reasons for death were digestive tract disorders (58% of all deaths, 95% CI: 52-64%) followed by respiratory diseases (13% of all deaths, 95% CI: 9-17%). Calves exposed to dystocia at birth had 2.09 (95% CI: 1.49-2.92) times the daily hazard of death compared with calves born from a normal calving. The daily hazard of death for calves born in the summer was 1.93 (95% CI: 1.41-2.64) times greater than the hazard for those calves born in the autumn. Inclusion of the herd-level frailty term had a significant effect on hazard estimates indicating that the study herds were heterogeneous in the distribution of unmeasured herd-level factors influencing calf survival. Our results show that diarrhoea is the most important cause of calf mortality in dairy herds in this area of Iran and that environmental and management factors affect calf mortality rate.     

Antelopes in The Pleistocene of Southern Africa

The study area of 2 786 ha contained over 200 springbok. The data were gathered during 78 separate day visits over four years. The most important social groups were (1) nursery herds of females and young; (2) harem herds similar to (1) but containing one adult male; (3) bachelor herds of males; and (4) solitary males. Other groupings, e.g. mixed adults of both sexes, were very uncommon. About twice as many adult females were to be found in harem herds as in nursery herds. The mean size of female herds (1 and 2 above) was between seven and nine animals (range 2-40) and of bachelor herds about five animals (range 2-14). Rutting and lambing tended to be seasonal. The lambing peak appeared to be about mid-September, though lambs were seen in every month September-April. It is suggested that lambing is correlated with the onset of Spring rains. Courtship activity seemed to be most intense during February-April. The adult sex ratio was about 85 males : 100 females.     

Salmonella Dublin infection in dairy cattle: risk factors for becoming a carrier

Long-term Salmonella Dublin carrier animals harbor the pathogen in lymph nodes and internal organs and can periodically shed bacteria through feces or milk, and contribute to transmission of the pathogen within infected herds. Thus, it is of great interest to reduce the number of new carrier animals in cattle herds. An observational field study was performed to evaluate factors affecting the risk that dairy cattle become carrier animals after infection with Salmonella Dublin. Based on repeated sampling, cattle in 12 Danish dairy herds were categorized according to course of infection, as either carriers (n = 157) or transiently infected (n = 87). The infection date for each animal was estimated from fecal excretion and antibody responses. The relationship between the course of infection (carrier versus transiently infected) and risk factors were analyzed using a random effect multilevel, multivariable logistic regression model. The animals with the highest risk of becoming carriers were heifers infected between the age of 1 year and 1st calving, and cows infected around the time of calving. The risk was higher in the first two quarters of the year (late Winter to Spring), and when the prevalence of potential shedders in the herd was low. The risk also varied between herds. The herds with the highest risk of carrier development were herds with clinical disease outbreaks during the study period. These findings are useful for future control strategies against Salmonella Dublin, because they show the importance of optimized calving management and management of heifers, and because they show that even when the herd prevalence is low, carriers are still being produced. The results raise new questions about the development of the carrier state in cattle after infection with low doses of Salmonella Dublin.     

Vertical and horizontal transmission of Neospora caninum in dairy herds in Québec

Neospora caninum is an important cause of abortion in dairy cattle. The objective of this observational study was to estimate the rate of vertical transmission of N. caninum in dairy herds in Québec and to investigate horizontal transmission in the same herds. The genealogy of cows from 23 dairy herds were examined. Prevalence of seropositive animals in herds studied varied from 4.3% to 61.8% (average, 21.9%). The overall rate of vertical transmission was estimated to be 44.4%, varying from 0% to 85.7%. Seven cases of horizontal transmission were identified in 6 of the 23 herds studied. Estimated vertical transmission rate varied from herd to herd, but appeared to be higher in herds with a high prevalence of seropositive animals. Although horizontal transmission was identified in 6 herds, it does not appear to be the major route of infection for N. caninum.     

Seroprevalence and association with abortion of leptospirosis in cattle in Ontario.

Sera were collected using a systematic random sampling from 348 cattle herds in Ontario, in proportion to the cattle population in different areas. One cow in five from 296 dairy herds and one in three from 52 beef herds were sampled. The sera were analyzed for prevalence of antibodies to Leptospira interrogans serovar grippotyphosa, hardjo, icterohaemorhagiae and pomona using the microscopic agglutination test. Herd seroprevalence (one or more animals with titer greater than or equal to 80) in beef and dairy herds combined was grippotyphosa 2%, hardjo 13.8%, icterohaemorrhagiae 10.1% and pomona 25.8%; 39% of all herds showed evidence of leptospiral infection with one or more serovars; 44.2% of 52 beef herds had serological evidence of infection with serovar hardjo compared to 8.4% of 296 dairy herds (P less than 0.0001). Seroprevalence of other serovars was not significantly different between beef and dairy herds. The proportion of beef animals seropositive for hardjo and for pomona increased with age, particularly for hardjo; 26.5% of beef animals aged nine years or over were seropositive for hardjo. Dairy animals showed a significant rise of hardjo but not pomona titers with age. The seroprevalence of pomona infection was significantly higher in dairy cattle in eastern Ontario than in other regions. Thirty-four (6.1%) of 553 aborted bovine fetuses had leptospires detected by immunofluorescence techniques. Sixty-five percent of these fetuses were from submissions made between November and January. Leptospires were identified as serovar hardjo by specific immunofluorescence. There appeared, however, to be a paradoxical serological response in that eight aborting cows had antibody titers to pomona rather than hardjo.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neospora caninum seroprevalence in dairy and beef cattle from the northwest region of Spain, Galicia

Herd and individual animal seroprevalence for Neospora caninum (N. caninum) in dairy, beef and mixed cattle were obtained in all populations within the Galician Farmer Sanitary Defence Associations (ADSG) in 2004. All animals ≥1 year of age were examined serologically by indirect ELISA. 1147 dairy herds (37,090 animals), 1464 beef herds (20,206 animals) and 141 mixed herds (2292 animals) were surveyed. True herd seroprevalence was estimated to be 80.6% (87.7% dairy, 76.7% beef and 78.4% mixed herds), true animal seroprevalence was estimated to be 23.2% (21.9% dairy, 25.1% beef and 24.9% animal to mixed herds), and within-herd seroprevalence was estimated to be 25.4% (23.6% dairy, 28.3% beef and 28.6% to mixed herds). Seropositivity was significantly associated with herd type (higher in dairies), herd size (increased when herd size increases), animal type (higher in beef) and age (lineal increase with the age). Results obtained in this study will be used for the development of a N. caninum control programme in the ADSG in Galicia.     

Prevalence and distribution of paratuberculosis (Johne's disease) in cattle herds in Ireland

A simple random survey was conducted in Ireland during 2005 to estimate the ELISA-prevalence of paratuberculosis, commonly called Johne's disease (JD), in the cattle population. Serum samples were collected from all 20,322 females/breeding bulls over 12 months-of-age in 639 herds. All samples were tested using a commercially available absorbed ELISA. The overall prevalence of infected herds, based on the presence of at least one ELISA-positive animal, was 21.4% (95% CI 18.4%-24.9%). Herd prevalence levels amongst dairy herds (mean 31.5%; 95% CI: 24.6%, 39.3%) was higher than among beef herds (mean 17.9%; 95% CI: 14.6%-21.8%). However, the animal level prevalence was similar. The true prevalence among all animals tested, was calculated to be 2.86% (95%CI: 2.76, 2.97) and for animals >= 2 yrs, it was 3.30% (95%CI: 3.17, 3.43). For animals in beef herds, true prevalence was 3.09% (95%CI: 2.93, 3.24), and for those in dairy herds, 2.74% (95%CI: 2.59, 2.90). The majority of herds had only one ELISA-positive infected animal. Only 6.4% (95% CI 4.7%-8.7%) of all herds had more than one ELISA-positive infected animal; 13.3% (CI 8.7%-19.7%) of dairy herds ranging from two to eight ELISA-positive infected animals; and, 3.9% beef herds (CI 2.4%-6.2%) ranging from two to five ELISA-positive infected animals. The true prevalence of herds infected and shedding Mycobacterium avium subspecies paratuberculosis is estimated to be 9.5% for all herd types; 20.6% for dairy herds; and 7.6% for beef herds. If ELISA positive animals <2-years-of-age are excluded, the true herd prevalene reduces to: 9.3% for all herd types; 19.6% for dairy herds; and 6.3% for beef herds based on a test specificity (Sp) of 99.8% and test sensitivity (Se) (i.e., ability to detect culture-positive, infected animals shedding at any level) of 27.8-28.9%.     

Bovine spongiform encephalopathy: epidemiological features 1985 to 1990.

Following the identification of bovine spongiform encephalopathy (BSE) in the British cattle population in 1986 epidemiological studies were launched. This paper provides an updated account of the epidemiological features of BSE from 1985, when the first cases, based on clinical histories, occurred, until 1990. The number of cases up to December 1989 represents an annual incidence of 3.9 confirmed cases per 1000 adult animals in Great Britain. Many more dairy herds were affected than beef suckler herds, a difference attributable to the difference in feeding practices between the two herd types. The geographical variation in incidence previously described has persisted with the highest incidence in the south and east of England. Other features of the epidemiology, including the low within-herd incidence, remained unaltered from the earlier findings. The results support the previously suggested hypothesis that the outbreak of BSE was due to the sudden exposure of the cattle population to a scrapie-like agent in 1981/82. There was no evidence of direct transmission between cattle during the period considered.     

A longitudinal study of Neospora caninum infection on three dairy farms in Brazil

Neospora caninum is an apicomplexan protozoan parasite that is one of the most important infectious causes of abortion in both dairy and beef cattle in many countries. The objectives of this longitudinal study were to determine the prevalence, rates of vertical and horizontal transmission of N. caninum and hazard for culling of N. caninum-seropositive animals in three Brazilian dairy herds. Blood samples from all animals were collected nine times at each of the three farms over a two-year period. Serum was tested for antibodies against N. caninum using the indirect fluorescent antibody test with a cutoff value of 1:100. The percentage of N. caninum-positive samples at each sampling time ranged at Farm I from 3.32% to 11.71%, at Farm II from 3.90% to 22.06% and at Farm III from 3.90% to 22.06%. The number of positive serological reactions varied in relation to the number of repeated samples taken from individual animals at each farm. In all herds, there was a high degree (P<0.05) of association between the N. caninum serological status of dams and daughters. The seropositive conversion rate was estimated as 0.37%, 3.00% and 6.94% per 100 cow-years at Farms I, II and III, respectively. The seronegative conversion rate was estimated as 31.58% and 11.11% per 100 cow-years at Farms I and III, respectively. In all herds, there was no difference (P>0.05) in the culling rate between the cattle that were seropositive cattle and seronegative for N. caninum infection. The results from this study confirm the importance of vertical transmission in the epidemiology of N. caninum. Although a few positive seroconversions indicated horizontal transmission, it does not appear to be the major route of infection for N. caninum.     

Should they stay,or should they go? Relative future risk of bovine tuberculosis for interferon-gamma test-positive cattle left on farms

Bovine tuberculosis (bTB), caused by Mycobacterium bovis, is a serious infectious disease that remains an ongoing concern for cattle farming worldwide. Tuberculin skin-tests are often used to identify infected animals (reactors) during test-and-cull programs, however, due to relatively poor sensitivity, additional tests can be implemented in parallel. For example, in Northern Ireland interferon-gamma (IFN-g) testing is used in high-risk herds. However, skin-test negative animals which are positive to the IFN-g test are not required by law to be slaughtered – therefore the final choice for these animals’ fate is left with the owner. During this study we investigated whether these animals represented a greater risk of becoming a skin reactor, relative to IFN-g test negative animals from the same herds. Our study population included 1107 IFN-g positive animals from 239 herds. A Cox-proportional hazard model indicated that animals which tested IFN-g positive were 2.31 times (95% CI: 1.92-2.79; P < 0.001) more likely to become a reactor compared with IFN-g negative animals. Animals from dairy herds, and from herds in the south-east, were of higher risk than animals from beef herds and other regions, respectively. Our findings suggest that IFN-g positive animals represent a higher risk of failing a skin-test in the future, indicating the value of IFN-g testing for identifying early-stage infected animals. These IFN-g positive animals are not under any disease restriction, and may move freely (trade), which may put recipient herds at increased risk. Our findings provide important evidence for stakeholders engaged in bTB eradication programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-015-0242-8) contains supplementary material, which is available to authorized users.     

我国马可波罗盘羊种群数量和年龄结构

根据野外实地考察,绘制帕米尔高原马可波罗盘羊的分布图。我国马可波罗盘羊主要分布在塔什库尔干自然保护区和萨雷阔勒岭。采用截线取样法对马可波罗盘羊种群数量进行研究,截至2001年,盘羊种群数量为1 650～2 150只;近年我国马可波罗盘羊种群数量超过3 000只。对37群949只盘羊的数据进行分析,盘羊的性比为♂：♀=1：3,群体大小平均为26.4只,最大雌性群为156只。由于山体庞大、地势开阔、冬季无人,在帕米尔高原,盘羊经常结成大群。40～50只以上的大群占所有观察个体数的50.3%,大群除了混合群外,还有雄性群和雌性群。在确定年龄的基础上,对177只雄性盘羊的年龄分布进行分析,成体雄性盘羊占所有识别年龄雄性盘羊的61.0%,8龄及以上年龄级的动物,占雄性个体的20.9%。     

Comparison of the Prevalence and Incidence of Infection with Bovine Virus Diarrhoea Virus (BVDV) in Denmark and Michigan and Association with Possible Risk Factors

Based on 2 previous surveys on the occurrence of infection with bovine virus diarrhoea virus (BVDV) in Danish and Michigan dairy herds, the prevalence and incidence of the infection were compared. The presence of certain possible risk factors for the occurrence of infection in the 2 areas were summarized and it was investigated if any of these risk factors had significant effect on the presence of animals persistently infected (PI) with BVDV in the dairy herds. Information on the cattle population density in the 2 areas was obtained from statistical yearbooks. Further information for the individual farms on age distribution, housing of animals, herd size, pasturing and purchasing policy was gathered. The prevalence of PI animals was more than 10 times higher in Denmark as compared to Michigan. In herds without PI animals, the annual incidence of seroconversion as calculated from the age specific prevalence of antibody carriers varied in most age groups between 20–25% in Denmark and between 5–10% in Michigan. All investigated risk factors except for herd size were in favour of a lower prevalence of infection in Michigan. The use of having animals on pasture and at the same time having purchased more than 40 animals within recent 31/2–4 years were significantly associated with presence of PI animals in the dairy herds (p = 0.01) when tested by the Mantel-Haenszel χ². Using mul-tivariable logistic regression, the occurrence of PI animals was found to be significantly related to the study area (Michigan and Denmark) as well as to herd size and purchase intensity.