Herd-level Prevalence Research Articles

Molecular detection of Cryptosporidium spp. infections in water buffaloes from northeast Thailand

The objectives of this study were to determine the individual and herd-level prevalence and genotype of Cryptosporidium and to identify putative risk factors associated with Cryptosporidium spp. infections in water buffaloes in northeast Thailand. Fecal samples from 600 water buffaloes of 287 farms in six provinces were collected and tested using DMSO-modified acid-fast staining and polymerase chain reaction. The overall prevalence of Cryptosporidium infections in buffaloes was 5.7 and 8.7% among individual animals and herds, respectively. The provinces with highest infected Cryptosporidium were located in the Sakon Nakhon Basin in the northern part of the region. In addition, higher herd prevalence was observed among farms with more than five buffaloes (30%) than those with five or less animals (16.2%). Thirty (88.2%) of the 34 Cryptosporidium-positive samples were Cryptosporidium parvum and four (11.8%) were Cryptosporidium ryanae.

Análise de detecção de cluster na caracterização espaço-temporal da tuberculose bovina no estado da Bahia

A tuberculose bovina (BTB) é uma enfermidade causada pela infecção pelo Mycobacterium bovis que acomete o homem e diversas espécies de mamíferos. A BTB tem grande importância por causar prejuízos econômicos nas regiões infectadas e por seu impacto na saúde pública. Foi realizado inquérito epidemiológico no Estado da Bahia, entre 2008 e 2010, com o objetivo de estimar a prevalência e conhecer a distribuição espaço temporal da enfermidade. O Estado foi estratificado em quatro regiões, cada uma com características epidemiológicas e demográficas homogêneas representativas de formas de produção pecuária. Um total de 18.810 cabeças com idade superior a 2 anos foi amostrado em 1350 propriedades. O teste cervical comparativo foi aplicado em cada animal selecionado, sendo considerados positivos os animais reagentes positivos ou duas vezes inconclusivos. Latitude e Longitude foram tomadas para cada propriedade amostrada com o auxilio do aparelho de Global Positioning System (GPS). O teste de Cuzick-and-Edwards e a análise de rastreio espacial (spatial scan statistic) foram utilizados para identificar qualquer agrupamento espacial de BTB. A prevalência de rebanho na Bahia, indicando a proporção de propriedades foco, foi de 1,6% (IC 95%: 1,0% - 2,69% por região). Nenhuma evidência significativa (P<0.05) de aglomeração espacial ou clustering foi detectada, possivelmente devido à baixa prevalência da doença. Estes resultados sugerem que a BTB tem baixa prevalência no estado da Bahia e que, nestas condições epidemiológicas, os focos encontrados não podem ser explicados por fatores espacialmente estruturados.

Prevalence of subclinical ketosis in mainly pasture-grazed dairy cows in New Zealand in early lactation

AIMS: The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in mainly pasture-grazed dairy cows in three dairy-farming regions of New Zealand 7–12, and 35–40 days post-calving. A second aim was to investigate herd- and cow-level factors associated with the prevalence of SCK.METHODS: A cross-sectional longitudinal prevalence survey was undertaken in 1,620 dairy cows from 57 herds. A random sample of cows without disease in the prior 30 days were enrolled at one farm visit within 5 days of calving, and blood samples were collected 7 and 28 days later (7–12 and 35–40 days post-calving) for measurement of beta-hydroxy butyrate (BHBA) concentrations using an electronic cow-side meter. SCK was defined as blood BHBA concentration ≥1.4 mmol/L.RESULTS: Mean cow-level prevalence of SCK varied with interval post-calving (16.8 and 3.2% at 7–12 days and 35–40 days post-calving, respectively) and age (13.0 and 13.1% of 2-year olds and ≥8-year olds, respectively, compared to 7.2% of 3–4-year-old cows). Mean herd-level prevalence of SCK was 14.3 (min 0, max 60.0)% and 2.6 (min 0, max 24.4)% at 7–12 days and 35–40 days post-calving, respectively, and was greater in Southland (13.3%) than Waikato and Canterbury herds (6.9 and 4.7%, respectively).CONCLUSIONS: This is the first population-based report of the prevalence of SCK in New Zealand dairy herds and demonstrates that age and interval post-calving are important risk factors determining prevalence; and that there is wide variation in prevalence between herds.CLINICAL RELEVANCE: Subclinical ketosis may be unrecognised but common in many New Zealand dairy cows in the first 2 weeks of lactation.

Comparison of modeled sampling strategies for estimation of dairy herd lameness prevalence and cow-level variables associated with lameness

Monitoring herd lameness prevalence has utility for dairy producers and veterinarians in their efforts to reduce lameness, for animal welfare assessment programs, and for researchers. Locomotion scoring is a method used to quantify lameness and calculate prevalence. Because of the time necessary to locomotion score each cow in large dairy herds, a sampling strategy to determine herd lameness prevalence that allows scoring of fewer cows would be useful. Such a sampling strategy must be validated for accuracy compared with the lameness prevalence when all cows in a herd are locomotion scored. The purpose of this study was to assess 3 previously suggested methods of estimating lameness prevalence by strategic sampling of dairy herds. Sampling strategies tested included (1) sampling a calculated number of cows in the middle third of the milking parlor exit order for each pen, (2) sampling a calculated number of cows weighted across pens and distributed evenly within each pen, and (3) sampling all cows in the high production, low production, and hospital pens. Lactating cows on 5 dairy farms in Washington and Oregon (n=4,422) were locomotion scored using a 5-point scale to determine herd-level lameness prevalence (percentage with locomotion score ≥3). Milking parlor exit order, order in headlocks at the feed bunk within each pen, and breed were recorded for each cow. The number of days in lactation, milk production, and parity were collected from farm computer records. Pen grouping strategy for each farm was obtained by interview with farm management. Sampling strategies were modeled using the locomotion score data set for each herd. Estimates of lameness prevalence obtained from the milking parlor exit order sample and the sample distributed across pens were within 5 percentage points of the whole herd prevalence. The third strategy estimated the lameness prevalence within 5 percentage points on 4 farms, but overestimated prevalence on 1 farm. Pen-level prevalence obtained by locomotion score of all cows in the pen was variable and not reliably predictive of herd-level prevalence. Cows of Holstein breed, parity >1, and exiting the milking parlor in the last 20% of the pen had greater odds of lameness compared with other breeds, parities, and milking parlor exit order groups in a multivariate analysis. This study indicates that the sampling strategies using the middle of milking parlor exit order and a calculated sample distributed across the herd may be used to obtain an estimate of herd lameness prevalence.

Herd-level prevalence of Map infection in dairy herds of southern Chile determined by culture of environmental fecal samples and bulk-tank milk qPCR

Paratuberculosis, an infectious disease of domestic and wild ruminants caused by Mycobacterium avium subsp. paratuberculosis (Map), is an economically important disease in dairy herds worldwide. In Chile the disease has been reported in domestic and wildlife animals. However, accurate and updated estimations of the herd-prevalence in cattle at national or regional level are not available. The objectives of this study were to determine the herd-level prevalence of dairy herds with Map infected animals of Southern Chile, based on two diagnostic tests: culture of environmental fecal samples and bulk-tank milk qPCR. Two composite environmental fecal samples and one bulk-tank milk sample were collected during September 2010 and September 2011 from 150 dairy farms in Southern Chile. Isolation of Map from environmental fecal samples was done by culture of decontaminated samples on a commercial Herrold's Egg Yolk Medium (HEYM) with and without mycobactin J. Suspicious colonies were confirmed to be Map by conventional IS900 PCR. Map detection in bulk-tank milk samples was done by real time IS900 PCR assay. PCR-confirmed Map was isolated from 58 (19.3%) of 300 environmental fecal samples. Holding pens and manure storage lagoons were the two more frequent sites found positive for Map, representing 35% and 33% of total positive samples, respectively. However, parlor exits and cow alleyways were the two sites with the highest proportion of positive samples (40% and 32%, respectively). Herd prevalence based on environmental fecal culture was 27% (true prevalence 44%) compared to 49% (true prevalence 87%) based on bulk-tank milk real time IS900 PC. In both cases herd prevalence was higher in large herds (>200 cows). These results confirm that Map infection is wide spread in dairy herds in Southern Chile with a rough herd-level prevalence of 28–100% depending on the herd size, and that IS900 PCR on bulk-tank milk samples is more sensitive than environmental fecal culture to detect Map-infected dairy herds.

Lentivírus em caprinos leiteiros do semiárido paraibano: prevalência de anticorpos, fatores de risco e detecção molecular

Os objetivos do presente trabalho foram determinar a prevalência de caprinos leiteiros soropositivos para a infecção por Lentivirus de pequenos ruminantes no semiárido do Estado da Paraíba, Nordeste do Brasil, identificar fatores de risco associados à prevalência de rebanhos positivos, e realizar a detecção molecular do agente. Foram utilizadas 1047 cabras leiteiras de 110 propriedades selecionadas aleatoriamente no Município de Monteiro, Estado da Paraíba, no período de março de 2009 a dezembro de 2011. Para o diagnóstico da infecção por Lentivirus, foi utilizado o teste de imunodifusão em gel de ágar (AGID). Um ano após foi realizada nova sorologia, e PCR em tempo real foi aplicada em amostras de sangue e leite de 48 cabras procedentes de quatro propriedades com animais soropositivos. As prevalências de propriedades positivas e de animais soropositivos na AGID foram 44,6% (IC 95% = 35,1% - 54,3%) e 8,1% (IC 95% = 5,6% - 16,8%), respectivamente. Realizar corte e desinfecção de umbigo (odds ratio = 2,44; p = 0,048) e condições de aglomeração de animais (odds ratio = 3,45; p = 0,048) foram associadas com a prevalência de propriedades positivas. Um ano após a realização do inquérito sorológico, foi verificada a permanência de animais infectados, detectados por PCR em tempo real a partir de amostras de sangue e leite. A PCR em tempo real das amostras de leucócitos circulantes apresentou boa performance, com sensibilidade de 100%, especificidade de 92,86%, concordância de 93,75% e indicador Kappa de 0,765. Sugere-se que seja realizado um trabalho de educação sanitária junto aos produtores sobre medidas de prevenção com o objetivo de reduzir a disseminação da infecção nos rebanhos.

Association between somatic cell count early in the first lactation and the longevity of Irish dairy cows

Reduced longevity of cows is an important component of mastitis costs, and increased somatic cell count (SCC) early in the first lactation has been reported to increase culling risk throughout the first lactation. Generally, cows must survive beyond the first lactation to break even on their rearing costs. The aim of this research was to assess the association between SCC of primiparous cows at 5 to 30 days in milk (SCC1), and survival over a 5-y period for cows in Irish dairy herds. The data set used for model development was based on 147,458 test day records from 7,537 cows in 812 herds. Cows were censored at their last recording if identified at a later date in other herds or if recorded at the last available test date for their herd, otherwise, date of disposal was taken to be at the last test date for each cow. Survival time was calculated as the number of days between the dates of first calving and the last recording, which was split into 50-d intervals. Data were analyzed in discrete time logistic survival models that accounted for clustering of 50-d intervals within cows, and cows within herds. Models were fitted in a Bayesian framework using Markov chain Monte Carlo simulations. Model fit was assessed by comparison of posterior predictions to the observed disposal risk for cows aggregated by parameters in the model. Model usefulness was assessed by cross validation in a separate data set, which contained 144,113 records from 7,353 cows in 808 herds, and posterior predictions were compared with the observed disposal risk for cows aggregated by parameters of biological importance. Disposal odds increased by a factor of 5% per unit increase in ln SCC1. Despite this, posterior predictive distributions revealed that the probability of reducing replacement costs by >€10 per heifer calved, through decreasing the herd level prevalence of cows with SCC1 ≥400,000cells/mL (from an initial prevalence of ≥20 to <10%) only exceeded 50% for less than 1 in 5 Irish herds. These results indicate that the effect of a reduction in the prevalence of cows with SCC1 ≥400,000cells/mL on replacement costs alone for most Irish dairy herds is small, and future research should investigate other potential losses, such as the effect of SCC1 on lifetime milk yield.

Association between somatic cell count early in the first lactation and the lifetime milk yield of cows in Irish dairy herds

Change in lifetime milk yield is an important component of the cost of diseases in dairy cows. Knowledge of the likelihood and scale of potential savings through disease prevention measures is important to evaluate how much expenditure on control measures is rational. The aim of this study was to assess the association between somatic cell count (SCC) at 5 to 30 d in milk during parity 1 (SCC1), and lifetime milk yield for cows in Irish dairy herds. The data set studied included records from 53,652 cows in 5,922 Irish herds. This was split into 2 samples of 2,500 and 3,422 herds at random. Linear models with lifetime milk yield and first-lactation milk yield as the outcomes and random effects to account for variation between herds were fitted to the data for the first sample of herds; data for the second sample were used for cross-validation. The models were developed in a Bayesian framework to include all uncertainty in posterior predictions and parameters were estimated from 10,000 Markov chain Monte Carlo simulations. The final model was a good fit to the data and appeared generalizable to other Irish herds. A unit increase in the natural logarithm of SCC1 was associated with a median decrease in lifetime milk yield of 864kg, and a median decrease in first-lactation milk yield of 105kg. To clarify the meaning of the results in context, microsimulation was used to model the trajectory of individual cows, and evaluate the expected outcomes for particular changes in the herd-level prevalence of cows with SCC1 ≥400,000cells/mL. Differences in mean lifetime milk yield associated with these changes were multiplied by an estimated gross margin for each cow to give the potential difference in milk revenue. Results were presented as probabilities of savings; for example, a 75% probability of savings of at least€97 or€115/heifer calved into the herd existed if the prevalence of cows with SCC1 ≥400,000cells/mL was reduced from ≥20 to <10 or <5%, respectively, and at least€71/heifer calved into the herd if the prevalence of cows with SCC1 ≥400,000cells/mL was reduced from ≥10 to <5%. The results indicate large differences in lifetime milk yield, depending on SCC early in the first lactation and the findings can be used to assess where specific interventions to control heifer mastitis prepartum are likely to be cost effective.

Prevalence of mastitis in dairy cows from smallholder farms in Zimbabwe

A cross-sectional study was conducted to determine the prevalence of sub-clinical and clinical mastitis and the associated factors in cows from selected smallholder dairy farms in Zimbabwe. Physical examinations were conducted on all lactating cows for evidence of signs of clinical mastitis. Composite milk samples were collected from all lactating cows for bacterial culture and somatic cell counting. Cows were categorised as clinical if they exhibited clinical features of mastitis, or sub-clinical if no apparent signs were present but they had a positive bacterial isolation and a somatic cell count of at least 300 x 103 cells/mL. Farm-level factors were obtained through a structured questionnaire. The association of mastitis and animal- and herd-level factors were analysed using logistic regression. A total of 584 animals from 73 farms were tested. Overall, 21.1%(123/584) had mastitis, 16.3%(95/584) had sub-clinical mastitis and 4.8% (28/584) had clinical mastitis. Herd-level prevalence was 49.3%. Coagulase-negative staphylococci (27.6%), Escherichia coli (25.2%), Staphylococcus aureus(16.3%), Klebsiella spp. (15.5%) and Streptococcus spp. (1.6%) were the most common isolates. In individual cows, pure dairy herds (OR = 6.3) and dairy crosses (OR = 3.1) were more likely to have mastitis compared to Mashona cows. Farms that used pre-milking teat dipping were associated with reduced mastitis prevalence. Further research is needed on the prevalence of mastitis and a comparison of data for both smallholder and commercial dairy farms in all regions of Zimbabwe should be undertaken.

Prevalence of Mycobacterium avium subsp. paratuberculosis in farmed red deer (Cervus elaphus) with grossly normal mesenteric lymph nodes

AIM: To estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) in farmed deer with no gross post-mortem evidence of Map infection slaughtered in New Zealand, and to assess predictors of infection. METHODS: Mesenteric lymph node (MLN) samples (n = 251) were collected from 60 lines of deer presented at two slaughterhouses in the North and two in the South Island of New Zealand between October 2008 and January 2009 and cultured for Map. Estimates of individual animal prevalence for each island were adjusted to account for the clustering of individual observations within herds. The national herd prevalence estimate was calculated as a weighted mean, with weights being the proportion of herds from which deer were slaughtered at North and South Island slaughterhouses among all herds slaughtering deer throughout New Zealand. Age, gender, and the presence of other carcasses with enlarged and/or granulomatous MLN in the same line (line status) were assessed as predictors of infection using multivariable logistic regression. RESULTS: A national cluster-adjusted individual animal prevalence of 45 (95% CI = 30–60)% was estimated, with North and South Island prevalences of 29 (95% CI = 16–45)% and 51 (95% CI = 36–66)%, respectively. Line status was a strong predictor of infection in young deer (OR 7.1, 95% CI = 2.4–21.5), but not in older deer. Herd-level prevalence was 44 (95% CI = 24–64)% in the North Island and 67 (95% CI = 49–85)% in the South Island. Weighted adjustment resulted in a national herd-level prevalence estimate of 59 (95% CI = 41–78)%. CONCLUSIONS: This study has provided a national baseline prevalence estimate for Map infection at the individual and herd-level, showing a contrast between the North and South Islands. More research to investigate the factors contributing to the difference in infection prevalence seen between the islands may help to identify suitable control measures for Map in deer herds.

Epidemiological Evaluation of Reproductive Infectious Agents in Sheep in the Brazilian Semiarid

The aim of this work was to identify sheep herds with history of reproductive failures (abortions and perinatal mortality) associated to presence of Chamydophila abortus, Brucella ovis and Leptospira spp. infections in the semiarid region of Northeastern Brazil. Blood samples were collected from 476 animals from 72 herds in 14 counties of the Sertão mesoregion, state of Paraíba. For the serological diagnosis of C. abortus, B. ovis and Leptospira spp. infections, complement fixation test (CFT), agar gel immunodiffusion test (AGID) and microscopic agglutination test (MAT) were used, respectively. Herd-level prevalence (herds with at least one seropositive animal) of C. abortus was 52.8%, followed by B. ovis (33.3%) and Leptospira spp. (27.7%); concerning seropositivity in animals there was also a higher frequency of C. abortus (19.7%), followed by B. ovis (12.1%) and Leptospira spp. (7.6%) (p < 0.05). Herds with history of abortion (31.9%; 23/72) and perinatal mortality (54.2%; 39/72) had at least one sheep seropositive to one of the infectious agentes. For abortions, herd-level prevalence of C. abortus was 60.8%, followed by B. ovis (43.4%) and Leptospira spp. (30.4%). For perinatal mortality, herd-level prevalence was 64.1% for C. abortus, 38.4% for B. ovis and 33.3% for Leptospira spp. It is suggested that these agents may be important causes of reproductive failures in the semiarid region, and, thus, it is recommended that herd owners should be informed on reasonable sanitary measures related to animal health, and advised to perform diagnosis in cases of abortion and perinatal mortality. Keywords: Reproduction diseases, small ruminants, epidemiology, control, Northeastern Brazil. Read more →

Prevalence and risk-mapping of bovine brucellosis in Maranhão State, Brazil

Between 2007 and 2009, a cross-sectional survey was carried out in Maranhão State, Brazil to estimate the seroprevalence of and risk factors for bovine brucellosis. In total, 749 herds and 6779 cows greater than two years of age were blood sampled. At the time of sampling a questionnaire to collect details on possible risk factors for bovine brucellosis was administered to the participating herd manager. A logistic regression model was developed to quantify the association between herd demographic and management characteristics and the herd-level brucellosis status. Spatial analyses were carried out to identify areas of the state where the presence of brucellosis was unaccounted-for by the explanatory variables in the logistic regression model.The estimated herd-level prevalence of brucellosis in Maranhão was 11.4% (95% CI 9.2–14) and the individual animal-level prevalence was 2.5% (95% CI 1.7–3.6). Herds with more than 54 cows older than two years of age, herds that used rented pasture to feed cattle, and the presence of wetlands on the home farm increased the risk of a herd being brucellosis positive. Infected farms were identified throughout the state, particularly in the central region and on the northwestern border. Spatial analyses of the Pearson residuals from the logistic regression model identified an area in the center of the state where brucellosis risk was not well explained by the predictors included in the final logistic regression model. Targeted investigations should be carried out in this area to determine more precisely the reasons for the unexplained disease excess. This process might uncover previously unrecognized risk factors for brucellosis in Maranhão.

Evidence of possible methicillin-resistant Staphylococcus aureus ST398 spread between pigs and other animals and people residing on the same farm

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged in a wide variety of animal species. However, little is known about the transmission routes of MRSA ST398 between different animal species, the barn environment and people residing on the same farm. In this study, two pig farms, two poultry-pig and two dairy-pig farms were investigated with respect to the presence of MRSA. On each farm, samples were collected from all animal species present, the barn environment, the farmer, household members and the herd veterinarians. Besides the MRSA prevalence, the obtained spa-, SCCmec-type and antimicrobial susceptibility profiles were also compared. Multilocus sequence typing (MLST) showed that MRSA ST398 was found in all animal species, in humans present on the farms and also in the pig barn environment. The presence of MRSA with the same spa-, SCCmec-type and antibiotic profile in the different animal species in direct or indirect contact with pigs suggests MRSA transfer. Furthermore, different pig age categories were investigated, with weaned piglets having the highest MRSA prevalence (86.3%). The herd-level prevalence was highly correlated (r=0.86, p=0.03) between sows and pre-weaned piglets. The results also indicate that companion animals, rats, mice and farmers could play an important role in the dissemination of MRSA, emphasizing the importance of internal biosecurity. However, external biosecurity is equally important because other spa-, SCCmec-types or antimicrobial resistances can be introduced through purchase of gilts. In this study we demonstrated that MRSA likely spreads between animal species, humans and the pig barn environment, which is why it is important to accurately implement control practices, in which not only pigs should be targeted, but also all other animal species present on farms.

Herd-level prevalence of Mycobacterium avium subsp. paratuberculosis infection in United States dairy herds in 2007

Testing of composite fecal (environmental) samples from high traffic areas in dairy herds has been shown to be a cost-effective and sensitive method for classification of herd status for Mycobacterium avium subsp. paratuberculosis (MAP). In the National Animal Health Monitoring System's (NAHMS) Dairy 2007 study, the apparent herd-level prevalence of MAP was 70.4% (369/524 had ≥1 culture-positive composite fecal samples out of 6 tested). Based on these data, the true herd-level prevalence (HP) of MAP infection was estimated using Bayesian methods adjusting for the herd sensitivity (HSe) and herd specificity (HSp) of the test method. The Bayesian prior for HSe of composite fecal cultures was based on data from the NAHMS Dairy 2002 study and the prior for HSp was based on expert opinion. The posterior median HP (base model) was 91.1% (95% probability interval, 81.6 to 99.3%) and estimates were most sensitive to the prior for HSe. The HP was higher than estimated from the NAHMS Dairy 1996 and 2002 studies but estimates are not directly comparable with those of prior NAHMS studies because of the different testing methods and criteria used for herd classification.

Herd characteristics and cow-level factors associated with Prototheca mastitis on dairy farms in Ontario, Canada

Prototheca spp. are algae that cause incurable acute or chronic mastitis in dairy cows. The aim of this case-control study was the identification of cow- and herd-level risk factors for this unusual mastitis pathogen. Aseptically collected composite milk samples from 2,428 milking cows in 23 case and 23 control herds were collected between January and May 2011. A questionnaire was administered to the producers, and cow-level production and demographic data were gathered. In 58 of 64 isolates, Prototheca spp. and Prototheca zopfii genotypes were differentiated using PCR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. All isolates were identified as Prototheca zopfii genotype 2. The mean within-herd prevalence for Prototheca spp. was 5.1% (range 0.0–12.5%). Case herds had a significantly lower herd-level prevalence of Staphylococcus aureus and a higher prevalence of yeasts than did control herds. The final logistic regression model for herd-level risk factors included use of intramammary injections of a non-intramammary drug [odds ratio (OR) = 136.8], the number of different injectable antibiotic products being used (OR = 2.82), the use of any dry cow teat sealant (external OR = 80.0; internal OR = 34.2), and having treated 3 or more displaced abomasums in the last 12 mo OR = 44.7). The final logistic regression model for cow-level risk factors included second or greater lactation (OR = 4.40) and the logarithm of the lactation-average somatic cell count (OR = 2.99). Unsanitary or repeated intramammary infusions, antibiotic treatment, and off-label use of injectable drugs in the udder might promote Prototheca udder infection.

Bovine viral diarrhoea virus seroprevalence and vaccination usage in dairy and beef herds in the Republic of Ireland.

BackgroundBovine viral diarrhoea (BVD) is an infectious disease of cattle with a worldwide distribution. Herd-level prevalence varies among European Union (EU) member states, and prevalence information facilitates decision-making and monitoring of progress in control and eradication programmes. The primary objective of the present study was to address significant knowledge gaps regarding herd BVD seroprevalence (based on pooled sera) and control on Irish farms, including vaccine usage.MethodsPreliminary validation of an indirect BVD antibody ELISA test (Svanova, Biotech AB, Uppsala, Sweden) using pooled sera was a novel and important aspect of the present study. Serum pools were constructed from serum samples of known seropositivity and pools were analysed using the same test in laboratory replicates. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. Results were used to guide selection of a proposed cut-off (PCO) PP. This indirect ELISA was applied to randomly constructed within-herd serum pools, in a cross-sectional study of a stratified random sample of 1,171 Irish dairy and beef cow herds in 2009, for which vaccination status was determined by telephone survey. The herd-level prevalence of BVD in Ireland (percentage positive herds) was estimated in non-vaccinating herds, where herds were classified positive when herd pool result exceeded PCO PP. Vaccinated herds were excluded because of the potential impact of vaccination on herd classification status. Comparison of herd-level classification was conducted in a subset of 111 non-vaccinating dairy herds using the same ELISA on bulk milk tank (BMT) samples. Associations between possible risk factors (herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.ResultsReceiver Operating Characteristics Analysis of replicate results in the preliminary validation study yielded an optimal cut-off PP (Proposed Cut-off percentage positivity - PCO PP) of 7.58%. This PCO PP gave a relative sensitivity (Se) and specificity (Sp) of 98.57% and 100% respectively, relative to the use of the ELISA on individual sera, and was chosen as the optimal cut-off since it resulted in maximization of the prevalence independent Youden’s Index.The herd-level BVD prevalence in non-vaccinating herds was 98.7% (95% CI - 98.3-99.5%) in the cross-sectional study with no significant difference between dairy and beef herds (98.3% vs 98.8%, respectively, p = 0.595).An agreement of 95.4% was found on Kappa analysis of herd serological classification when bulk milk and serum pool results were compared in non-vaccinating herds. 19.2 percent of farmers used BVDV vaccine; 81% of vaccinated herds were dairy. A significant association was found between seroprevalence (quartiles) and herd size (quartiles) (p < 0.01), though no association was found between herd size (quartiles) and herd-level classification based on PCO (p = 0.548).ConclusionsThe results from this study indicate that the true herd-level seroprevalence to Bovine Virus Diarrhoea (BVD) virus in Ireland is approaching 100%. The results of the present study will assist with national policy development, particularly with respect to the national BVD eradication programme which commenced recently.

Caracterização epidemiológica e fatores de risco associados à leptospirose em ovinos deslanados do semiárido brasileiro

Este trabalho teve como objetivo determinar a prevalência de rebanhos ovinos positivos (focos) e de animais soropositivos para leptospirose na região semiárida do Estado da Paraíba, bem como identificar fatores de risco. Foram colhidas amostras de sangue de 1.275 animais procedentes de 117 rebanhos em 19 municípios da mesorregião do Sertão, Estado da Paraíba. Para o diagnóstico sorológico da leptospirose foi utilizado o teste de soroaglutinação microscópica (SAM), com 24 sorovares de Leptospira spp. como antígenos. Um rebanho foi considerado positivo quando apresentou pelo menos um animal soropositivo. Das 117 propriedades utilizadas 33 (28,20%) apresentaram pelo menos um animal soropositivo, e dos 1.275 animais 69 (5,41%) foram soropositivos, com títulos variando de 100 a 3200. O sorovares reagentes foram Autumnalis (49,30%), Andamana (27,53%), Sentot (17,39%), Whitcomb (4,34%) e Australis (1,44%). Possuir mais de 48 animais no rebanho (odds ratio = 2,26; IC 95% = 1,33 -5,07; p = 0,021) e participação em exposições (odds ratio = 9,05; IC 95% = 0,96 - 85,71; p = 0,055) foram identificados como fatores de risco. Sugere-se a necessidade de estudos acerca do isolamento do agente, da caracterização de sua patogenicidade e do seu impacto econômico nos rebanhos ovinos da região, bem como recomenda-se maior controle sanitário nas aglomerações de animais.

Estimated Prevalence of Caprine Paratuberculosis in Boer Goat Herds in Missouri, USA

The objective of this study was to estimate true animal-level and herd-level prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) antibodies in Missouri Boer goat herds. Sera harvested from blood samples collected from goats ≥24 months of age in 25 Missouri Boer goat herds were tested for presence of MAP antibodies using a commercial ELISA kit. Herds were declared positive for MAP if one or more goats in the herd tested positive for MAP antibodies. True animal, within-herd, and between-herd prevalences were calculated using the Rogan-Gladen estimator and were 1.4% (95% CI = 0.1 to 3.6%), 3% (95% CI = 0 to 6%), and 54.7% (95% CI = 28.2 to 86.2%), respectively. Findings in this study confirmed that MAP infection is endemic in Missouri Boer goat herds.

Sub-clinical mastitis and associated risk factors on lactating cows in the Savannah Region of Nigeria

BackgroundSub-clinical mastitis limits milk production and represents an important barrier to profitable livestock economics worldwide. Milk production from cows in Nigeria is not at optimum levels in view of many factors including sub-clinical mastitis.ResultsThe overall herd-level prevalence rate for SCM was 85.33% (256/300 heads of cows) while the quarter-level prevalence rate of SCM was 43.25% (519/1,200 quarters). The prevalence of SCM was 50.67%, 43.67%, 39.67% and 39.13% for the left fore-quarter, right hind-quarter, left hind-quarter and right fore-quarter, respectively. The Rahaji breed had the highest prevalence of SCM with 65.91% (29/44), while the White Fulani breed had the least with 32.39% (57/176). A total of 32.33% (97/300) had only one mammary quarter affected, 30.33% (91/300) had two quarters affected, 16.00% (48/300) had three quarters affected while 6.67% (20/300) had all the four quarters affected. A total of 53.00% had SCM in multiple quarters (159/300). The risk of SCM decreased significantly among young lactating cows compared to older animals (OR = 0.283; P < 0.001; 95%CI = 0.155; 0.516). The Rahaji breed had significantly higher risk compared with the White Fulani breed (OR = 8.205; P = 0.013; 95% CI = 1.557; 43.226). Improved sanitation (washing hands before milking) will decrease the risk of SCM (OR = 0.173; P = 0.003; 95% CI = 0.054; 0.554).ConclusionSCM is prevalent among lactating cows in the Nigerian Savannah; and this is associated with both animal characteristics (age, breed and individual milk quarters) and milking practices (hand washing).Good knowledge of the environment and careful management of the identified risk factors with improved sanitation should assist farm managers and veterinarians in implementing preventative programmes to reduce the incidence of SCM.

Prevalence of paratuberculosis infection in dairy cattle in Northern Italy

Paratuberculosis is a chronic granulomatous infection caused by Mycobacterium avium subsp. paratuberculosis (MAP) that affects multiple ruminant species causing important economic losses. Therefore, control programmes at herd and regional levels have been established worldwide and prevalence estimates are needed for their implementation. Although different herd-level prevalence estimations for paratuberculosis have been reported in Europe, very few studies provided comparable and interpretable values, due to poor study designs and lack of knowledge about the accuracy of the diagnostic tests used. To overcome these problems we applied a latent class analysis to the results of two prevalence studies carried out in two neighbouring Northern Italian regions (Lombardy and Veneto) that account for over 50% of the Italian dairy cattle population. Serum samples from a randomly selected number of farms in the two regions were analyzed by different ELISA tests. The herd-level Apparent Prevalences ( AP) were 48% (190/391) for Lombardy and 65% (272/419) for Veneto. Median within-herd APs were 2.6% and 4.0% for Lombardy and Veneto, respectively. Posterior estimates for the herd-level True Prevalences ( TP) based on a Bayesian model were very similar between the two regions (70% for Lombardy and 71% for Veneto) and close to previous estimates of infected herds in Europe. The two 95% credibility intervals overlap each other, virtually showing only one distribution of the herd-level true prevalence for both regions. On the contrary, estimates of the within-herd TP distributions differed between the two regions (mean values: 6.7% for Lombardy and 14.3% for Veneto), possibly due to the different age distribution within the herds from the two regions.