Evaluation of farm-level parameters derived from animal movements for use in risk-based surveillance programmes of cattle in Switzerland

BACKGROUND: This study focused on the descriptive analysis of cattle movements and farm-level parameters derived from cattle movements, which are considered to be generically suitable for risk-based surveillance systems in Switzerland for diseases where animal movements constitute an important risk pathway. METHODS: A framework was developed to select farms for surveillance based on a risk score summarizing 5 parameters. The proposed framework was validated using data from the bovine viral diarrhoea (BVD) surveillance programme in 2013. RESULTS: A cumulative score was calculated per farm, including the following parameters; the maximum monthly ingoing contact chain (in 2012), the average number of animals per incoming movement, use of mixed alpine pastures and the number of weeks in 2012 a farm had movements registered. The final score for the farm depended on the distribution of the parameters. Different cut offs; 50, 90, 95 and 99%, were explored. The final scores ranged between 0 and 5. Validation of the scores against results from the BVD surveillance programme 2013 gave promising results for setting the cut off for each of the five selected farm level criteria at the 50th percentile. Restricting testing to farms with a score ≥ 2 would have resulted in the same number of detected BVD positive farms as testing all farms, i.e., the outcome of the 2013 surveillance programme could have been reached with a smaller survey. CONCLUSIONS: The seasonality and time dependency of the activity of single farms in the networks requires a careful assessment of the actual time period included to determine farm level criteria. However, selecting farms in the sample for risk-based surveillance can be optimized with the proposed scoring system. The system was validated using data from the BVD eradication program. The proposed method is a promising framework for the selection of farms according to the risk of infection based on animal movements.

Investigating the potential of reported cattle mortality data in Switzerland for syndromic surveillance

Systems for the identification and registration of cattle have gradually been receiving attention for use in syndromic surveillance, a relatively recent approach for the early detection of infectious disease outbreaks. Real or near real-time monitoring of deaths or stillbirths reported to these systems offer an opportunity to detect temporal or spatial clusters of increased mortality that could be caused by an infectious disease epidemic. In Switzerland, such data are recorded in the "Tierverkehrsdatenbank" (TVD). To investigate the potential of the Swiss TVD for syndromic surveillance, 3 years of data (2009-2011) were assessed in terms of data quality, including timeliness of reporting and completeness of geographic data. Two time-series consisting of reported on-farm deaths and stillbirths were retrospectively analysed to define and quantify the temporal patterns that result from non-health related factors. Geographic data were almost always present in the TVD data; often at different spatial scales. On-farm deaths were reported to the database by farmers in a timely fashion; stillbirths were less timely. Timeliness and geographic coverage are two important features of disease surveillance systems, highlighting the suitability of the TVD for use in a syndromic surveillance system. Both time series exhibited different temporal patterns that were associated with non-health related factors. To avoid false positive signals, these patterns need to be removed from the data or accounted for in some way before applying aberration detection algorithms in real-time. Evaluating mortality data reported to systems for the identification and registration of cattle is of value for comparing national data systems and as a first step towards a European-wide early detection system for emerging and re-emerging cattle diseases.

Risk Factors for Whole Carcass Condemnations in the Swiss Slaughter Cattle Population

We used meat-inspection data collected over a period of three years in Switzerland to evaluate slaughterhouse-level, farm-level and animal-level factors that may be associated with whole carcass condemnation (WCC) in cattle after slaughter. The objective of this study was to identify WCC risk factors so they can be communicated to, and managed by, the slaughter industry and veterinary services. During meat inspection, there were three main important predictors of the risk of WCC; the slaughtered animal's sex, age, and the size of the slaughterhouse it was processed in. WCC for injuries and significant weight loss (visible welfare indicators) were almost exclusive to smaller slaughterhouses. Cattle exhibiting clinical syndromes that were not externally visible (e.g. pneumonia lesions) and that are associated with fattening of cattle, end up in larger slaughterhouses. For this reason, it is important for animal health surveillance to collect data from both types of slaughterhouses. Other important risk factors for WCC were on-farm mortality rate and the number of cattle on the farm of origin. This study highlights the fact that the many risk factors for WCC are as complex as the production system itself, with risk factors interacting with one another in ways which are sometimes difficult to interpret biologically. Risk-based surveillance aimed at farms with reoccurring health problems (e.g. a history of above average condemnation rates) may be more appropriate than the selection, of higher-risk animals arriving at slaughter. In Switzerland, the introduction of a benchmarking system that would provide feedback to the farmer with information on condemnation reasons, and his/her performance compared to the national/regional average could be a first step towards improving herd-management and financial returns for producers.

Delivery of the p67 sporozoite antigen of Theileria parva by using recombinant Salmonella dublin: secretion of the product enhances specific antibody responses in cattle

The p67 sporozoite antigen of Theileria parva has been fused to the C-terminal secretion signal of Escherichia coli hemolysin and expressed in secreted form by attenuated Salmonella dublin aroA strain SL5631. The recombinant p67 antigen was detected in the supernatant of transformed bacterial cultures. Immunization trials in cattle revealed that SL5631 secreting the antigen provoked a 10-fold-higher antibody response to p67 than recombinant SL5631 expressing but not secreting p67. Immunized calves were challenged with a 80% lethal dose of T. parva sporozoites and monitored for the development of infection. Two of three calves immunized intramuscularly with the p67-secreting SL5631 strain were found to be protected, whereas only one of three animals immunized with the nonsecreting p67-expressing SL5631 strain was protected. This is the first demonstration that complete eukaryotic antigens fused to the C-terminal portion of E. coli hemolysin can be exported from attenuated Salmonella strains and that such exported antigens can protect cattle against subsequent parasite challenge.

Interferon-gamma and interleukin-4 mRNA expression by peripheral blood mononuclear cells from pregnant and non-pregnant cattle seropositive for bovine viral diarrhea virus

The acceptance of the fetal allograft by pregnant women and mice seems to be associated with a shift from a Th 1 dominated to a Th 2 dominated immune response to certain infectious agents. The goal of this study was to examine cytokine expression in peripheral blood mononuclear cells (PBMCs) from cattle immune to bovine viral diarrhea virus (BVDV) to determine whether pregnancy also has an influence on the type of immune response in this species. Forty-six heifers and cows between 14 months and 13 years of age were included in this study. Twenty-four were seropositive and 22 seronegative for BVDV. Eleven of the seropositive animals and 11 of the seronegative animals were in the eighth month of gestation, the remaining animals were virgin heifers. PBMC from these animals were analyzed for Interferon (IFN)-gamma and Interleukin (IL)-4 mRNA expression by real-time RT-PCR after stimulation with a non-cytopathic strain of BVDV. Additionally, an ELISA was performed to measure IFN-gamma in the supernatants of stimulated cell cultures. In BVDV seropositive animals, IFN-gamma mRNA levels were significantly higher than in BVDV seronegative animals and there was a significant positive correlation between the changes in IFN-gamma and IL-4 mRNA expression. There was, however, no significant difference in IFN-gamma and IL-4 mRNA levels between pregnant and non-pregnant animals. These results are inconsistent with BVDV inducing a Th1 or Th2 biased immune response. Furthermore, a shift in the cytokine pattern during bovine pregnancy was not evident.

Clinicopathological Phenotype of Autosomal Recessive Cholesterol Deficiency in Holstein Cattle.

BACKGROUND Cholesterol deficiency (CD), a newly identified autosomal recessive genetic defect in Holstein cattle, is associated with clinical signs of diarrhea, failure to thrive, and hypocholesterolemia. HYPOTHESIS/OBJECTIVES The objective is to describe the clinicopathological phenotype of affected Holstein cattle homozygous for the causative apolipoprotein B gene (APOB) mutation. ANIMALS Six Holstein cattle, 5 calves with a clinical history of chronic diarrhea, and 1 heifer with erosions in the buccal cavity and neurologic symptoms were admitted to the Clinic for Ruminants. METHODS This case review included a full clinical examination, a complete blood count, blood chemistry, and measurements of cholesterol and triglycerides. The animals were euthanized and necropsied. A PCR-based direct gene test was applied to determine the APOB genotype. RESULTS All 6 animals were inbred, could be traced back to the sire Maughlin Storm, and were confirmed homozygous for the APOB mutation. The clinical phenotype included poor development, underweight, and intermittent diarrhea in the calves, and neurologic signs in the heifer included hypermetria and pacing. Hypocholesterolemia and low triglycerides concentrations were present in all animals. The pathological phenotype of all animals was steatorrhea with enterocytes of the small intestine containing intracytoplasmic lipid vacuoles. The peripheral nervous system of the heifer displayed degenerative changes. CONCLUSIONS AND CLINICAL IMPORTANCE Suspicion of CD in Holstein cattle is based on the presence of chronic diarrhea with no evidence of primary infections. Confirmation of the associated APOB gene mutation is needed. Additionally, the heifer demonstrated primarily signs of neurologic disease providing an unexpected phenotype of CD.

Lethal chondrodysplasia in a family of Holstein cattle is associated with a de novo splice site variant of COL2A1

Background Lethal chondrodysplasia (bulldog syndrome) is a well-known congenital syndrome in cattle and occurs sporadically in many breeds. In 2015, it was noticed that about 12 % of the offspring of the phenotypically normal Danish Holstein sire VH Cadiz Captivo showed chondrodysplasia resembling previously reported bulldog calves. Pedigree analysis of affected calves did not display obvious inbreeding to a common ancestor, suggesting the causative allele was not a rare recessive. The normal phenotype of the sire suggested a dominant inheritance with incomplete penetrance or a mosaic mutation. Results Three malformed calves were examined by necropsy, histopathology, radiology, and computed tomography scanning. These calves were morphologically similar and displayed severe disproportionate dwarfism and reduced body weight. The syndrome was characterized by shortening and compression of the body due to reduced length of the spine and the long bones of the limbs. The vicerocranium had severe dysplasia and palatoschisis. The bones had small irregular diaphyses and enlarged epiphyses consisting only of chondroid tissue. The sire and a total of four affected half-sib offspring and their dams were genotyped with the BovineHD SNP array to map the defect in the genome. Significant genetic linkage was obtained for several regions of the bovine genome including chromosome 5 where whole genome sequencing of an affected calf revealed a COL2A1 point mutation (g.32473300 G > A). This private sequence variant was predicted to affect splicing as it altered the conserved splice donor sequence GT at the 5’-end of COL2A1 intron 36, which was changed to AT. All five available cases carried the mutant allele in heterozygous state and all five dams were homozygous wild type. The sire VH Cadiz Captivo was shown to be a gonadal and somatic mosaic as assessed by the presence of the mutant allele at levels of about 5 % in peripheral blood and 15 % in semen. Conclusions The phenotypic and genetic findings are comparable to a previously reported COL2A1 missense mutation underlying lethal chondrodysplasia in the offspring of a mosaic French Holstein sire (Igale Masc). The identified independent spontaneous splice site variant in COL2A1 most likely caused chondrodysplasia and must have occurred during the early foetal development of the sire. This study provides a first example of a dominant COL2A1 splice site variant as candidate causal mutation of a severe lethal chondrodysplasia phenotype. Germline mosaicism is a relatively frequent mechanism in the origin of genetic disorders and explains the prevalence of a certain fraction of affected offspring. Paternal dominant de novo mutations are a risk in cattle breeding, especially because the ratio of defective offspring may be very high and be associated with significant animal welfare problems.

A new predilection site of Mycoplasma bovis: Postsurgical seromas in beef cattle

Mycoplasma bovis is a highly contagious bacterium, which predominantly causes chronic pneumonia, otitis and arthritis in calves and mastitis in adult cattle. In humans, Mycoplasma species have been associated with post-surgical infections. The present study aimed to identify the bacteria associated with three outbreaks of infected seromas after caesarian section in Belgian Blue beef cattle. A total of 10 cases occurred in three herds which were in close proximity of each other and shared the same veterinary practice. M. bovis could be cultured from seroma fluid in five of the six referred animals, mostly in pure culture and was isolated from multiple chronic sites of infection (arthritis and mastitis) as well. DNA fingerprinting of the isolates targeting two insertion sequence elements suggested spread of M. bovis from chronic sites of infection (udder and joints) to the postsurgical seromas. Identical genetic profiles were demonstrated in two animals from two separate farms, suggesting spread between farms. Mortality rate in the referred animals positive for M. bovis in a seroma was 80% (4/5), despite intensive treatment. A massive increase in antimicrobial use was observed in every affected farm. These observations demonstrate involvement of mycoplasmas in outbreaks of postsurgical seromas in cattle.