Seropositive Cows Research Articles

Occurrence of oxidative stress in dairy cows seropositives for Brucella abortus

Bovine brucellosis is an important zoonotic disease caused by the bacterium Brucella abortus that leads to economic losses due to animal discard and commercial restrictions. Since positive animals for brucellosis are culled, little is known about the pathogenesis of this disease. Therefore, the aims of this study were to evaluate possible changes in the activity of deaminase adenosine (ADA) and the oxidative stress in cows seropositives for brucellosis (Experiment I), and to evaluate the seroprevalence of B. abortus in dairy cows from the Western state of Santa Catarina, Southern Brazil (Experiment II). The Experiment I evaluated 20 pregnant cows: ten seropositives for B. abortus and ten seronegatives that were used as controls. The ADA activity and markers of oxidative stress (TBARS, catalase (CAT) and superoxide dismutase (SOD)) were evaluated in these animals. A reduction in the activity of ADA and catalase enzymes in seropositive animals was observed (p < 0.001). Conversely, there was an increase in TBARS levels and superoxide dismutase activity in cows infected by B. abortus (p < 0.001). The presence of oxidative stress and a reduction of ADA might be related to the modulation of the inflammatory response. The experiment II was performed due to a high number of herds with restrictions imposed by cases of brucellosis in the state of Santa Catarina in the last two years, and thus, the seroprevalence for B. abortus was evaluated in 1242 serum samples of cows of 69 herds. The serodiagnosis was performed using two tests: buffered acidified antigen and 2-mercaptoethanol. However, none of the serum samples were positive for B. abortus. Although we did not find seropositive animals for brucellosis in our study, the disease still requires continued surveillance, due to its economic impact, and to the oxidative stress caused by it, which may have contributed to cases of abortion in three seropositive cows (Experiment I) in the final third of the gestation.

Detection and characterization of Brucella spp. in bovine milk in small-scale urban and peri-urban farming in Tajikistan

Brucellosis is one of the most common zoonoses globally, and Central Asia remains a Brucella hotspot. The World Health Organization classifies brucellosis as a neglected zoonotic disease that is rarely in the spotlight for research and mainly affects poor, marginalized people. Urban and peri-urban farming is a common practice in many low-income countries, and it increases the incomes of families that are often restrained by limited economic resources. However, there is a concern that the growing number of people and livestock living close together in these areas will increase the transmission of zoonotic pathogens such as Brucella. This study investigates the presence of Brucella DNA in bovine milk in the urban and peri-urban area of Dushanbe, Tajikistan. Brucella DNA was detected in 10.3% of 564 cow milk samples by IS711-based real-time PCR. This finding is concerning because consumption of unpasteurized dairy products is common in the region. Furthermore, Brucella DNA was detected in the milk of all seropositive cows, but 8.3% of the seronegative cows also showed the presence of Brucella DNA. In addition, sequence analysis of the rpoB gene suggests that one cow was infected with B. abortus and another cow was most likely infected with B. melitensis. The discrepancies between the serology and real-time PCR results highlight the need to further investigate whether there is a need for implementing complementary diagnostic strategies to detect false serological negative individuals in Brucella surveillance, control, and eradication programmes. Furthermore, vaccination of cattle with S19 in addition to vaccination of small ruminants with Rev 1 might be needed in order to control Brucella infections in the livestock population but further research focusing on the isolation of Brucella is required to obtain a comprehensive understanding of the Brucella spp. circulating among the livestock in this region.

Can hierarchical modeling improve our understanding of bovine abortion due to Neospora caninum infection?

The purpose of this study was to use mixed logistic regression to evaluate the association between Neospora caninum serostatus and abortion, accounting for the effects of farms. The main objective was to explore the interpretation of this model and discuss the contribution of this analysis to our understanding of the disease’s epidemiology. A mixed-effects logistic model using farms as a random effect and the serostatus for N. caninum, age of cattle and farm location as fixed effects was performed. The data from 1256 cows over 15 months of age from 60 farms were used, and the abortion information was obtained from farm records. A significant association between N. caninum serostatus and abortion was found (p<0.0001). Seropositive cows had 6.63 times greater odds of having a history of previous abortion (95% CI: 4.35–13.37). There was remarkable variability across farms in the probability of a cow having a history of an abortion. Including the effects of the farms in the regression, it was possible to estimate an intraclass correlation coefficient (ICC) of 16%. That means that 16% of the variation in abortion occurrence that was not explained by the fixed effects was due to farms. In practical terms, this variation means that while there are farms with several seropositive cows and no/few abortion cases, the opposite is also true, with a high number of abortions in farms with low/medium seroprevalence. The remaining variability (84%) was not explained by the effect of N. caninum, age, region, and the effect of farms, i.e., it is due to unknown factors that are causing abortions. The results of this study reinforce the importance of N. caninum as a cause of abortions and demonstrate the significant heterogeneity in the probability of a cow having a history of an abortion that cannot be explained completely by N. caninum serostatus, age or location. Including the hierarchical structure of the population along with correct interpretation of the model estimates helps us understand the effect of the farms, i.e., the probability of a cow abortion conditional to the farms, which also contributes to our understanding of the epidemiology of abortions caused by neosporosis. The use of hierarchical models and reporting the ICC should be encouraged.

Epidemiological patterns of bovine besnoitiosis in an endemic beef cattle herd reared under extensive conditions

Bovine besnoitiosis is a parasitic disease caused by the protozoan Besnoitia besnoiti. Described many decades ago, recent epidemiological studies reveal its important spread within Europe in the last years. To date, many epidemiological aspects related to life cycle, routes of transmission, incidence rates and associated risk factors are lacking; hence, the establishment of appropriate disease control programmes poses an important challenge. Thus, the aim of the present study was to determine the epidemiological pattern of the disease in an endemic herd reared under extensive conditions (Spanish Pyrenees) by identifying main factors associated with infection and clinical disease dynamics. The study population consisted of 276 Brown Swiss and Pirenaica adult animals and 145 calves born and weaned at the farm during the study. Three sampling time frames were used: January 2010, September 2010 and February 2011, which allowed us to differentiate two periods designated as mountain and valley periods. The data related to animals (breed, sex and age) and herd management (animal grouping and time in housing) were recorded. The data collection methodology was mainly based on clinical examinations and defining the serological status against bovine besnoitiosis by the immunofluorescent antibody testing of blood samples. The total prevalence among adult animals was 38.34% (CI95%: 34.53–42.07), with 18.54% of seropositive animals showing clinical signs. In regard to the cumulative incidence, 34.57% of new infections were detected during the mountain period, in contrast to the 24.59% observed in the valley period. The incidence density was 0.058 and 0.061 new infections per animal-month for the mountain and valley periods, respectively. According to the seroepidemiological study, the seroconversion probability of B. besnoiti infection was directly associated with the number of seropositive cows with whom an animal had been stabled as well as the housing period duration, supporting horizontal transmission by close contact as one of the most important methods of disease spread. In addition, the risk of developing the clinical course increased with age, and the presence of clinical signs was related to higher antibody responses. Among calves (from 3.1 to 7.1 months old) sampled once at weaning, the total seroprevalence was 15.17% (CI95%: 9.36–21.04), and the chronic stage was observed in three animals, supporting the ability of B. besnoiti to infect and even cause disease in animals less than 6 months old. Finally, the risk of calf seroconversion was positively related to the serological status of the cows, suggesting postnatal transmission between dams and offspring by contact during the suckling period.

Molecular detection of Bluetongue Virus (BTV) and Bovine Leukemia Virus (BLV) in uterine biopsies of dairy cows with or without reproductive problems

Reproductive performance of dairy cows has a direct impact on herd productivity. Infectious agents, such as Bluetongue Virus (BTV) and Bovine Leukemia Virus (BLV), are associated with reproductive failure. However, it remains unknown if these viruses are present in the uterus and cause gestational loss. This study used molecular methods to assess if BTV and BLV can be detected in the uterus of serologically positive dairy cows with a record of abortions, stillbirths and repeat breeding (n=23) and without a record of reproductive problems (n =23). The cows came from three dairy herds of the state of Minas Gerais, Brazil. BTV was not detected in any of the uterine biopsies. Proviral DNA of BLV was detected in 54.5 % of the seropositive cows, but positivity for BLV in the uterus was not associated with the existence of reproductive problems. In conclusion, this study shows that BLV, but not BTV, is present in the uterus of seropositive cows, regardless of reproductive performance.

Estudio serológico de Neospora caninum en ganado de leche del altiplano Norte de Antioquia, Colombia

RESUMENObjetivos. Determinar la seroprevalencia de Neospora caninum en ganado lechero sin vacunar del altiplano Norte de Antioquia. Materiales y métodos. Se realizó un estudio transversal para determinar la prevalencia de neosporosis en bovinos de la principal zona lechera antioqueña. En Mayo-Junio del 2014 se recolectaron muestras de sangre de 1003 bovinos en 29 hatos ubicados en el municipio de San Pedro de los Milagros, en Antioquia. Los niveles de anticuerpos de N. caninum se midieron mediante un kit de inmunoensayo enzimático (ELISA) y los resultados se clasificaron como positivos o negativos. Resultados. Se observaron bovinos seropositivos en todos los hatos, con una prevalencia entre el 7 y 97%, y una media (±SE) del 37.1% (±4.2). La distribución de los animales seropositivos por grupos de &lt;1, 1-2, 2-3 y ≥3 años de edad fue del 25.5, 30.3, 46.1 y 39.1%, respectivamente. Conclusiones. Se detectó una alta tasa de seroprevalencia de N. caninum en la principal zona de ganado lechero de Antioquia. La gran variación entre hatos apunta a que existen factores de riesgo cuya identificación sería esencial a la hora de instaurar programas de control. En vista de que cualquier vaca seropositiva tiene un mayor riesgo de abortar que congéneres no infectados, los próximos estudios deberían abordar la epidemiología de abortos atribuible a neosporosis previo a establecer cualquier plan de control.

Frequency of Neospora caninum infections in beef cow–calf operations under extensive management

The aim of this study was to evaluate the frequencies of Neospora caninum horizontal and vertical transmissions in beef cow–calf operations under three different extensive management systems: group A: 0.75 head per hectare pasturing on natural grass; group B: 1.1 head per hectare on natural grass and improved cultured pastures; and group C: 2 head per hectare on natural grass, improved cultured pasture and whole corn silage. Serum samples from 72 multiparous cows assigned to each beef cow–calf operations were obtained every 3 months during 2 years. A group of 30 replacement heifers from each group were tested similarly since they were 10–21 months old. Twenty four, 20 and 34 calves from groups A, B and C respectively, were bled before colostrum intake and again 6 months later. The samples were analyzed by indirect fluorescence antibody test (IFAT) for detection of total IgG against N. caninum at a serological titre ≥200 for multiparous cows and replacement heifers, and a serological titre ≥25 for calves. Serum samples from seropositive cows were assessed by ELISA to evaluate the avidity of their specific antibodies. There were no differences in the proportion of seropositive cows from groups A, B and C at the beginning of the trial (p>0.05). Interestingly, the lowest serological titres in seropositive cows from all groups were observed during the first trimester (p<0.05). Although seropositive cows had medium to high avidity antibodies, suggesting chronic infection; seroconversion associated with low antibody avidity was found in 2, 3 and 3 seropositive cows from groups A, B and C. All replacement heifers remained seronegative. No abortions were recorded but 2, 1, and 2 calves from groups A, B and C were seropositive before colostrum intake, respectively. Seropositive calves born from cows having intermediate or high avidity remained with the same serostatus at 6 months of age. Even under varying extensive management conditions, both N. caninum horizontal and vertical transmission methods do occur in beef cow–calf operations.

Bovine Coronavirus (BoCV) Infection in Calves with Diarrhoea and Their Dams

Background: Bovine coronavirus (BoCV) is common with high seroprevalence in dairy cattle. It is reported in many countries. Also, BoCV causes diarrhea in dairy calves. The transmission of BoCV is the fecal-oral/aerosol-nasal routes. Feces from clinical cases or clinically normal dairy cattle are source of infection, also contamination of feed and water. The purpose of the current study was to investigate BoCV infection in diarrheic calves (age and sex) and their dams (age). For this reason, the serological and virological methods were used. Haematological parameters of the calves and their dams were compared using the statistical methods.Materials, Methods &amp; Results: In this study, following clinical examination of 3500 cattle and their calves from 25 number of dairy farms 184 calves with diarrhoea and their dams (183) (≥2 - ≤6 age) were sampled for BoCV presence by enzyme linked immunosorbent assay (ELISA). Additionally, all blood samples were examined by hematological methods. 172 (93.99%) cows and 172 (93.99%) calves were found antibodies (Ab) positive (+). The high levels of Ab for BoCV were detected as 36.05 % in dams 6 years and older ages. In the calves, Ab to BoCV were found at the highest level (25.26%) in the female calves ≥5 - ≤6 months ages. BoCV antigen (Ag) was detected in only faecal sample of a (0.54%) calf. When the haematological parameters were compared between BoCV Ab (+) and BoCV Ab negative (-) dams, only white blood cell (WBC) values were found statistically significant (P &lt; 0.05). When the haematological parameters were compared between BoCV Ab (+)/Ag (-) and BoCV Ab (-)/Ag (-) calves, WBC (P &lt; 0.05), lymphocyte (P &lt; 0.01) and granulocyte (P &lt; 0.01) values were found statistically important. When the haematological parameters were compared between BoCV Ab (+)/Ag (+) and BoCV Ab (-)/Ag (-) calves, both lymphocyte and granulocyte values were statistically important (P &lt; 0.01).Discussion: BoCV infection has found worldwide among cattle of all ages. The disease results in major economic losses in dairy herds that result from treatment costs and calf deaths. One hundred seventy two out of 183 mothers whose blood sampling was done were detected as seropositive. Many researchers found similar results in dairy cattle. It was detected the highest seropositivity in cattle more than six years old. One hundred seventy two blood samples out of 184 calves were detected seropositive. Also, the highest seropositivity was detected among of &gt; 5 and &lt; 6 months of age. BoCV Ag (+) presence was detected in only one faecal sample of one calf out of 184. Researchers were found same or higher BoCV Ag(+) rates in faeces of diarrheic calves. In the study lymphocyte counts of seropositive cows and in Ab(+)/Ag(+) calves determined decrease. However, the counts in seropositive calves were increased. Leukocytes levels were also high in seropositive calves. Haematocrit values were decreased in seropositive cows, calves and in Ab(+)/Ag(-) calves. BoCV infections were detected at low level in diarrheic calves. But, BoCV seropositive mature and diarrheic calves were found at high levels. Haematological application methods could be used to be supportive with the serological and virological methods. All farm managements should be maintained with strict hygiene practices. Milking bottle, calf pens or hutches need to be sanitized. The calves must be prevent contamination from faeces and urine of other calves. The protective vaccination must be applied all animals.

Sero-epidemiological analysis of vertical transmission relative risk of Borna disease virus infection in dairy herds.

Borna disease virus (BDV) is a virus that causes a neurological disease in domestic animals, including a variety of animal species in Japan. Few studies have examined the mode of transmission of this virus in cattle, and the exact mechanisms underlying the transmission of the virus need to be elucidated. This study aimed to examine the contribution of vertical transmission of the virus, which occurs when the virus is transmitted from the mother to offspring during gestation or birth. We used an epidemiological approach. The relative risk (RR) was calculated for cattle born to BDV sero-positive cows from farms with a higher within-herd prevalence of BDV (56.8%). We tested the sera of 1,122 dairy cattle from 24 dairy herds in Hokkaido Prefecture, Japan, for BDV infection using the ELISA and western blotting method. The overall level of BDV sero-prevalence was 22.1%. Seroprevalence was significantly higher in closed-breeding herds that do not have buying in cows (39.7%) than in farms that restock cattle by buying in cows (4.4%, P<0.01). The overall RR of BDV vertical transmission from infected mothers to their daughters was 1.86 (95% confidence interval (CI): 1.54–2.56). Our results show that vertical transmission contributes significantly to BDV transmission in the farms tested in this study.

Herd-level seroprevalence of Neospora caninum infection in dairy cattle in central and northeastern Poland.

A serosurvey was carried out to estimate the herd-level seroprevalence of Neospora caninum infection in cattle in central and northeastern Poland. Ninety seven dairy cattle herds from 2 provinces of Poland (Podlaskie, 47 herds and Łodzkie, 50 herds) were randomly enrolled in the study using two-stage cluster method. A simple random selection was applied within each herd to select a sample of adult cows (≥18 month-old). A total number of 734 cows were enrolled in the study. The animals were screened with a commercial competitive ELISA (Bio-X Diagnostics, Belgium). To calculate true herd-level seroprevalence test sensitivity and specificity were adjusted from an individual- to a herd-level using FreeCalc method. The true overall herd-level seroprevalence of N. caninum infection was 56.7% (95% CI: 47.5%, 65.9%). The true herd-level seroprevalence in Podlaskie was 63.3% (95% CI: 43.0%, 83.6%) and 50.5% (95% CI: 32.8%, 68.2%) in Łodzkie province and these figures did not differ significantly between the two provinces (chi2 test p = 0.238). One hundred forty three of 734 cows (19.5%) were seropositive which gave the true overall individual-level seroprevalence of 20.1% (95% CI: 17.4%, 23.2%). Percentage of seropositive cows in each herd varied from 6% to 80%. This study is the first epidemiological investigation of herd-level seroprevalence of N. caninum infection in Polish dairy cattle population. In conclusion, the result of the study confirmed previous data that N. caninum infection is widespread in the Polish cattle population and thus should be considered as a potential cause of spontaneous abortions.

Use of serology and real time PCR to control an outbreak of bovine brucellosis at a dairy cattle farm in the Nile Delta region, Egypt.

BackgroundBovine brucellosis remains one of the most prevalent zoonotic infections affecting dairy cattle in developing countries where the applied control programs often fail. We analyzed the epidemiologic pattern of bovine brucellosis in a dairy cattle herd that showed several cases of abortions after regular vaccination with RB51 (B. abortus vaccine). In 2013 thirty dairy cows, from a Holstein-Friesian dairy herd with a population of 600 cattle, aborted five months post vaccination by a regular RB51 vaccine. Blood samples were drawn from milking cows and growing heifers, as well as heifers and cows pregnant up to 6 months. These samples were collected in June 2013 (n = 257) and May 2014 (n = 263) and were tested by real time (rt)-PCR as well as serological tests, in particular Rose Bengal Test (RBT), Enzyme-Linked Immunosorbent Assays (ELISA) and Fluorescence Polarization Assay. Tissue specimens were also collected from an aborted fetus and cultured. Isolates were subjected to bacteriological typing tests at the genus and species levels.ResultsFive months post vaccination with RB51 vaccine, Brucella (B.) DNA was detected in blood samples of cows by rt-PCR. The serological tests also revealed the spread of Brucella field strains within the herd in 2013. Four Brucella isolates were recovered from specimens collected from the aborted fetus. These isolates were typed as follows: one B. abortus RB51 vaccine strain and three isolates of B. abortus field strain. The seropositive cows with positive rt-PCR might indicate an infection by the Brucella field strain; while the positive rt-PCR results from seronegative animals may either be due to circulating RB51 vaccine DNA in vaccinated animals or to circulating field strain in infected animals before seroconversion.ConclusionThe results herein suggest that PCR can be a good supplementary tool in an outbreak situation, if an assay is available that can differentiate vaccine and field strains with a high analytical sensitivity. We recommend using RBT and ELISA in parallel in outbreak situations, to identify as many infected animals as possible during the initial screenings. This test procedure should be repeated for at least three successive negative tests, with one month interval.

Reduction in daily milk yield associated with subclinical bovine herpesvirus 1 infection

The aim of this observational cohort study was to investigate the potential economic impact of subclinical bovine herpesvirus 1 (BoHV-1) infection in a commercial UK dairy herd in terms of...

Impact of spontaneous Neospora caninum infection on pregnancy loss and subsequent pregnancy in grazing lactating dairy cows

The impact of spontaneous Neospora caninum infection on pregnancy loss and subsequent pregnancy in grazing lactating dairy cows was evaluated. Data from 1273 females (878 multiparous and 395 first-calving cows) from six preselected dairy herds were analyzed. Cows were classified as seropositive (SP) (prevalence, 24%; range, 11%–33%) or seronegative (SN) by indirect immunofluorescence detection of antibodies against N caninum. Seropostive cows (prevalence, 40.0%) presented higher (P < 0.001) incidence of abortion compared with SN cows (prevalence, 4.1%). Neospora caninum DNA was detected by real-time polymerase chain reaction in 44.4% of intact aborted fetuses from SP cows, whereas none was found in those aborted from SN cows. The average daily milk production adjusted to 305 days was lower (P < 0.001) in SP (22.5 ± 0.3 L/day) than in SN cows (24.8 ± 0.2 L/day). Furthermore, SP cows presented greater occurrence of retained placenta (17.1% vs. 6.0%; P < 0.001) and acute postpartum metritis (9.8% vs. 2.4%; P < 0.001). Despite similar pregnancy rates after first postpartum artificial insemination (27.6% vs. 31.8%; P = 0.40), cumulative pregnancy rates during 300 days in milk (94.7% vs. 98.5%; P = 0.005) were greater in SN cows. A reduced (P = 0.0001) Cox proportional hazard of pregnancy rate at 300 days in milk and a longer interval from parturition or abortion to conception (median, 111 vs. 101 days) were observed in SP compared with SN cows. Spontaneous N caninum infection is a significant contributing factor of pregnancy loss and occurrence of uterine disease (i.e., retained placenta and metritis), negatively affecting subsequent pregnancy in grazing lactating dairy cows.

Vector-borne transmission of Besnoitia besnoiti by blood-sucking and secretophagous flies: epidemiological and clinicopathological implications.

BackgroundBovine besnoitiosis has been recently diagnosed in a three-parted herd of 796 Aubrac and Charolais beef cattle in Hungary. A large scale serological, histological and molecular survey was initiated in order to uncover important factors in the local epidemiology of the disease.FindingsBlood samples were collected (three times from the whole herd, and repeatedly from selected animals) for serological screening by ELISA. In addition, various organs from aborted fetuses and newborn calves, skin and colostrum samples of seropositive heifers/cows, and ticks collected from the cattle were histologically and/or molecularly analysed for the presence of Besnoitia besnoiti.All fetal and calf tissues, as well as colostrum and tick samples from cows were PCR negative. Based on ELISA results, only very few local cows seroconverted after mating with imported, infected bulls, and not necessarily as a consequence of this event. Among calves that were born to seropositive, imported cows and stayed with their mother until weaning at seven months of age, seroprevalence decreased significantly, but remained high. At the same time, 28 calves born from seropositive cows, but separated from their dams immediately after receiving colostrum, were successfully reared and remained uninfected.Following a second herd-level screening, all Aubrac cattle (except for heifer calves) and all seropositive Charolais cows and bulls were culled. Manifestation of the disease is currently sporadic. Among chronically affected heifers two types of skin lesions were noted, and histological evaluation indicated marked distension of sweat gland ducts with membrane-bound structures (resembling cystozoites) in their contents.ConclusionsTransmission through natural mating, as well as transplacental, colostral and tick-borne transmission of B. besnoiti was either unlikely or did not occur. However, the risk for spreading of the infection was high, when calves stayed with their mother during suckling, and if animals were kept in the same stable (although physically separated) during the main fly season. Herd replacement and generation exchange (i.e. early weaning and artificial feeding) appear to be the successful strategies for the local eradication of bovine besnoitiosis. Adding to the already known mechanical transmission of B. besnoiti by blood-sucking flies, results of the present study suggest that secretophagous flies should also be evaluated as potential vectors of this coccidium species.

Coxiella burnetii antibody dynamics in heifers born to vaccinated versus non-vaccinated dams in a chronically infected dairy herd.

This study was designed to compare Coxiella burnetii antibody dynamics in heifers born to vaccinated or non-vaccinated dams in a single high-producing dairy herd chronically infected with the bacterium. Antibody dynamics were examined from birth to the postpartum period in replacement heifers (n = 14) born to non-vaccinated dams (n = 7) or to dams that had been vaccinated on gestation days 171-177 (n = 7) and 192-198. Samples of blood, milk, faeces, vaginal fluid, colostrum and cotyledons (the latter two only at parturition) were obtained in the dams over the period from gestation days 171-177 to postpartum days 91-97. Blood samples were used to detect antibodies against C. burnetii and remaining samples for PCR identification of the bacterium. In their calves/heifers, blood samples for antibody determinations were collected from birth to postpartum at the time points 1-7 and 22-28 days and 3, 6 and 12 months of age; 90-96 and 210-216 days of gestation; and 22-28 days postpartum. All calves were born seronegative for C. burnetii. Irrespective of the shedding status of their mothers (7 were C. burnetii shedders), seroconversion occurred after colostrum intake in all calves born to seropositive cows (n = 9) and in two of three vaccinated seronegative dams. Thereafter antibody titres gradually declined and by 6 months of age all calves were seronegative. Seronegativity persisted until their first postpartum period. These findings indicate that cows vaccinated during advanced pregnancy transfer immunity to their calves via the colostrum. Maternal C. burnetii antibodies in calves persisted for three months in calves born both to seronegative vaccinated and seropositive dams.

Challenges for bovine viral diarrhoea virus antibody detection in bulk milk by antibody enzyme-linked immunosorbent assays due to changes in milk production levels.

BackgroundBovine viral diarrhoea (BVD) is considered eradicated from Denmark. Currently, very few (if any) Danish cattle herds could be infected with BVD virus (BVDV). The Danish antibody blocking enzyme-linked immunosorbent assay (ELISA) has been successfully used during the Danish BVD eradication program, initiated in 1994. During the last decade, the cattle herd size has increased while the prevalence of BVDV has decreased. In this study, we investigated how these changes could affect the performance of the Danish blocking ELISA and of the SVANOVIR®BVDV-Ab indirect ELISA. The latter has successfully been used to eradicate BVD in Sweden.Data (2003–2010) on changes in median herd size and milk production levels, occurrence of viremic animals and bulk milk surveillance were analysed. Additionally, the Danish blocking ELISA and the SVANOVIR ELISA were compared analyzing milk and serum samples. The prevalence of antibody positive milking cows that could be detected by each test was estimated, by diluting positive individual milk samples and making artificial milk pools.ResultsDuring the study period, the median herd size increased from 74 (2003) to 127 cows (2010), while the prevalence of BVDV infected herds decreased from 0.51 to 0.02 %. The daily milk yield contribution of a single seropositive cow to the entire daily bulk milk was reduced from 1.61 % in 2003 to 0.95 % in 2010 due to the increased herd size. It was observed that antibody levels in bulk milk decreased at national level. Moreover, we found that when testing bulk milk, the SVANOVIR®BVDV-Ab can detect a lower prevalence of seropositive lactating cows, compared to the Danish blocking ELISA (0.78 % vs. 50 %). Values in the SVANOVIR®BVDV-Ab better relate to low concentrations of antibody positive milk (R2 = 94-98 %), than values in the blocking ELISA (R2 = 23–75 %). For sera, the two ELISAs performed equally well.ConclusionsThe SVANOVIR ELISA is recommended for analysis of bulk milk samples in the current Danish situation, since infected dairy herds e.g. due to import of infected cattle can be detected shortly after BVDV introduction, when only few lactating cows have seroconverted. In sera, the two ELISAs can be used interchangeably.

Effect of Mycobacterium avium subsp. paratuberculosis infection status on culling and calving difficulty in dairy cattle

The present paper was designed to assess the effect of Mycobacterium avium subsp. paratuberculosis (MAP) infection status (antibody positive vs antibody negative, as measured by ELISA) on time to culling and calving difficulty in dairy cows. The study was carried out in 8 dairy farms in Galicia (north-west Spain). All of them were taking part in an ongoing paratuberculosis control program, as well as in a dairy herd improvement program. In order to estimate the relation between time to culling and MAP serological status of dairy cows, the present study followed the Andersen–Gill model for survival analysis. Similarly, in order to evaluate the influence on calving difficulty an ordinal logistic regression model was applied. The results indicated that seropositive cows were more likely to be culled due to death/urgent slaughter (hazard ratio=1.88), low productivity (hazard ratio=2.55), infertility (hazard ratio=4.64) and other causes (hazard ratio=1.67). Additionally, the probability of difficulties at calving time was 2.74 times higher for seropositive cows. The estimated effects could determine the economic benefits of a paratuberculosis control program.

Natural Besnoitia besnoiti infections in cattle: hematological alterations and changes in serum chemistry and enzyme activities

BackgroundThe emerging disease bovine besnoitiosis is caused by the apicomplexan parasite Besnoitia besnoiti. Clinical signs of acute besnoitiosis are pyrexia, anorexia and subcutaneous edema. In subacute and chronic besnoitiosis parasitic cysts arise in a variety of tissues and affected cattle display skin lesions and weight loss. In all stages of bovine besnoitiosis, lesions can be found in many organ systems and therefore presumably alter a variety of laboratory parameters. In this study, the impact of naturally acquired acute, subacute and chronic bovine besnoitiosis on hematologic parameters, serum chemistry, and enzyme activities was investigated. Laboratory parameters of two Simmental heifers and two Limousin cows were monitored during acute, subacute and chronic besnoitiosis and in another Simmental heifer during subclinical besnoitiosis. To determine aberrations of laboratory parameters, values were compared with reference ranges obtained from B. besnoiti negative Simmentals (224 samples of nine animals) and Limousins (41 animals). Further, laboratory parameters of B. besnoiti seropositive Limousin cows (54 animals; 32 of these showing clinical signs) and healthy B. besnoiti seronegative Limousin cows (41 animals) were compared.ResultsDuring acute and subacute besnoitiosis, a reduction of leukocyte and erythrocyte concentrations, hematocrit, serum albumin, urea, magnesium, and calcium concentrations were observed. Serum total protein, globulin, total bilirubin and creatinine concentrations were increased and aspartate transaminase (AST) and creatine kinase (CK) activities were elevated. In chronic besnoitiosis, erythrocyte parameters were statistically significantly lower, and total protein and globulin concentrations were significantly higher in B. besnoiti seropositive compared with B. besnoiti seronegative Limousin cows.ConclusionsIn this study, altered laboratory parameters during the course of naturally acquired acute, subacute and chronic bovine besnoitiosis are described for the first time. Only a few animals were examined in acute and subacute besnoitiosis, however the alterations of laboratory parameters during these stages reflected i) the acute inflammatory state (e.g. high levels of serum globulin fractions), ii) clinical findings such as disturbed condition (e.g. bilirubin concentrations), and iii) lesions such as muscle necroses described in the literature (e.g. AST or CK activities). Chronic besnoitiosis led to typical alterations of chronic inflammatory diseases like hyper-(gamma)-globulinemia or reduced erythrocyte concentrations.

Excretion of Coxiella burnetii in Cows with Secretion Disorder

Coxiella burnetii is the causative agent of a very important disease with zoonotic potential. Domestic ruminants are very important factor in transmission of this pathogen to humans. This pathogen can be found in feces, urine, lochia, placenta and milk of infected animals. Of all these routes, the excretion through milk lasts the longest, and can last over several lactations. In this paper, we examined the excretion dynamics of Coxiella burnetii through milk of seropositive cows and the levels of immunoglobulin G in milk and blood serum. Correlation between these parameters is also examined. Milk samples from infected cows were used for somatic cell count determination. The PCR method was used for determination of Coxiella burnetii genome. RID plates were used for determination of concentration of immunoglobulin. The excretion of the pathogen through milk differed between different stages of lactation: it was the lowest in the first stage (16.6%) and the highest in the second stage (80.0%). In the second stage the lowest concentration of immunoglobulin G was detected in milk serum (4.0 g). Somatic cell count was increased, some samples had very high values.

The Single Intradermal Cervical Comparative Test Interferes with Johne's Disease ELISA Diagnostics.

Enzyme-linked immunosorbent assays (ELISA) of milk and serum samples are a routinely used method of screening herds for Mycobacterium avium subspecies paratuberculosis (MAP). Infection with MAP causes granulomatous enteritis of ruminants known as Johne’s disease (JD). The sensitivity (Se) and specificity (Sp) of MAP ELISAs leads to difficulties in the identification of both infected and infectious animals. Interference with MAP ELISA Se and Sp has been reported in MAP seronegative cows following administration of purified protein derivative (PPD) as part of intradermal testing for bovine tuberculosis (bTB). The aim of this study is to examine the impact of the single intradermal cervical comparative test (SICCT) for bTB, on both serum and milk MAP ELISA tests, in a herd containing both seropositive and seronegative cows pre-SICCT. A secondary objective is to provide appropriate timing of JD ELISA tests in relation to the SICCT. A herd of 139 cows were serum and milk sampled pre- and post-SICCT administration. Prior to SICCT, 6% of the herd tested seropositive for MAP using milk ELISA, with 8% positive on serum. ID Screen Paratuberculosis Indirect Screening Test (ID Vet) was used to screen the herd. Within 14 days of PPD administration, a significant increase in the prevalence of seropositive cows was recorded. Identical prevalence’s were recorded with both test matrices (39%). ELISA values remained significantly higher until day 43 post-SICCT in milk (P = 0.850), and day 71 in serum (P = 0.602). If the “new” positives detected post-bTB testing are deemed false positives due to generation of cross-reacting antibodies by administration of PPD, milk would appear a more suitable sample for JD ELISA testing within 2 months of SICCT. In summary, sampling for JD utilizing milk ELISA should be avoided in the 43-day period following PPD administration, with serum ELISA sampling avoided for an additional 28 days.