Ludovic Martinelle

Field veterinary survey on clinical and economic impact of Schmallenberg virus in Belgium.

We implemented a questionnaire-based methodology targeting veterinary field practitioners to evaluate clinical and economic impact of Schmallenberg virus in Belgium. First suspicious cases were detected as soon as July 2011. The mean cost for individual symptomatic treatment was 65 or 107 Euros, in case of fatal outcome or apparent recovery, respectively.

Preliminary survey on the impact of Schmallenberg virus on sheep flocks in south of Belgium.

Between late February and May 2012, a preliminary anonym survey was conducted among sheep farmers in south of Belgium in order to contribute to future estimations of the economic losses caused by Schmallenberg virus (SBV). Based on clinical signs consistent with SBV infection, this survey involved 13 meat sheep flocks considered as positive flocks with subsequent SBV detection by RT-qPCR [SBV-positive flocks (PF); total of 961 animals], and 13 meat sheep flocks considered as negative flocks (NF; total of 331 animals). These preliminary results indicated several significant characteristics that were more present in PF than in NF. These include an increased rate of abortions (6.7% in PF versus 3.2% in NF), of lambs born at term but presenting malformations (10.1% in PF versus 2.0% in NF) and of dystocia (10.1% in PF versus 3.4% in NF). Lamb mortality during the first week of life was reported more frequently in PF (8 of 13 PF, 61.5%) than in NF (1 of 13 NF, 7.7%). In PF, the observed prolificacy rate was 2-fold lower (93%) than expected (186%). The implementation of a survey at larger scale, including a high number of breeders, is necessary to allow a more detailed analysis of the SBV impact in the sheep sector.

Original Findings Associated with Two Cases of Bovine Papular Stomatitis

ABSTRACT Bovine papular stomatitis virus was isolated from two calves in an animal house with biosafety level 3 confinement. The hypotheses on the origin of the infection, the interesting features of the partial amino acid sequences of the major envelope viral protein, and the importance of diagnostic tools available for animal diseases that are not listed by the World Organization for Animal Health (OIE) are discussed.

Clinical Pattern Characterization of Cattle Naturally Infected by BTV-8

Forty-one cattle from seven Belgian farms and two French farms confirmed as infected with bluetongue virus serotype 8 (BTV-8) were monitored from the onset of clinical signs to describe the disease pattern and estimate the duration of blood RT-qPCR and competitiveELISA positivity under field conditions. On each visit, blood samples were taken, and a standardized clinical form was filled in for each animal. A clinical score was calculated for every week until the end of clinical signs. A classification and regression tree (CART) analysis was conducted to determine the most important clinical signs every week for the first 7 weeks. The highest scores were recorded within 2 weeks of clinical onset. The first recorded clinical signs were quite obviously visible (lethargy, conjunctivitis, lesions of nasal mucosa, nasal discharge). Skin lesions, a drop in milk production and weight loss appeared later in the course of the disease. A biphasic pattern regarding nasal lesions was noticed: the first peak concerned mainly congestive and ulcerative lesions, whereas the second peak mainly concerned crusty lesions. The median time estimated by survival analysis to obtain negative RT-qPCR results from the onset of clinical signs was 195 days (range 166-213 days) in the 23 cattle included in the analysis. Serological results remained strongly positive until the end of the study. These results should ensure more accurate detection of an emerging infectious disease and are of prime importance in improving the modelling of BTV-8 persistence in Europe.

Two alternative inocula to reproduce bluetongue virus serotype 8 disease in calves

The aim of this study was to investigate the consequences in calves of two forms of inocula alternative to the use of wild type infectious blood. Two groups of five calves were infected with low cell-passaged virus and infectious blood issued from one animal passage of the same strain. A longitudinal study was implemented and characterised by clinical standardised observations, haematology, BTV RNA detection and viral isolation from blood, detection of serogroup and neutralising antibodies, cytokine expression and post-mortem examination 46 days post-infection (PI). Both tested inocula were able to reproduce clinical expression of the disease, in the bloodstream viral genome was detected until the end of the experiment while virus isolation was possible between days 7 and 31 PI. Humoral immune response developed earlier in calves infected with low cell-passaged virus, while in both groups a massive antibody production was confirmed by the immune balance between IL-4 and IFN-γ expression. Both tested inocula are presented as valid alternative to the use of wild type infectious blood in the study of the pathogenesis of BTV-8 or the efficacy of current and future vaccines.

Dose-dependent effect of experimental Schmallenberg virus infection in sheep.

Schmallenberg virus (SBV) is an orthobunyavirus affecting European domestic ruminants. In this study, the dose-dependent effect of experimental infection of sheep with SBV was evaluated. Four groups of three ewes were each inoculated subcutaneously with 1 mL of successive 10-fold dilutions of an SBV infectious serum. The ewes were monitored for 10 days, but no clinical signs were observed. The number of productively infected animals within each group, as evidenced by viraemia, seroconversion and viral RNA in the organs, depended on the inoculated dose, indicating that a critical dose has to be administered to obtain a homogeneous response in infected animals under experimental conditions. In the productively infected animals, no statistical differences between the different inoculation doses were found in the duration or quantity of viral RNA circulating in blood, nor in the amount of viral RNA present in virus positive lymphoid organs.

Experimental Infection of Sheep at 45 and 60 Days of Gestation with Schmallenberg Virus Readily Led to Placental Colonization without Causing Congenital Malformations.

Background Main impact of Schmallenberg virus (SBV) on livestock consists in reproductive disorders, with teratogenic effects, abortions and stillbirths. SBV pathogenesis and viral placental crossing remain currently poorly understood. Therefore, we implemented an experimental infection of ewes, inoculated with SBV at 45 or 60 days of gestation (dg). Methodology “Mourerous” breed ewes were randomly separated in three groups: eight and nine ewes were subcutaneously inoculated with 1 ml of SBV infectious serum at 45 and 60 dg, respectively (G45 and G60). Six other ewes were inoculated subcutaneously with sterile phosphate buffer saline as control group. All SBV inoculated ewes showed RNAemia consistent with previously published studies, they seroconverted and no clinical sign was reported. Lambs were born at term via caesarian-section, and right after birth they were blood sampled and clinically examined. Then both lambs and ewes were euthanatized and necropsied. Principal Findings/Significance No lambs showed any malformation suggestive of SBV infection and none of them had RNAemia or anti-SBV antibodies prior to colostrum uptake. Positive SBV RNA detection in organs was rare in both G45 and G60 lambs (2/11 and 1/10, respectively). Nevertheless most of the lambs in G45 (9/11) and G60 (9/10) had at least one extraembryonic structure SBV positive by RTqPCR. The number of positive extraembryonic structures was significantly higher in G60 lambs. Time of inoculation (45 or 60 dg) had no impact on the placental colonization success rate but affected the frequency of detecting the virus in the offspring extraembryonic structures by the time of lambing. SBV readily colonized the placenta when ewes were infected at 45 or 60 dg but infection of the fetuses was limited and did not lead to congenital malformations.

Experimental co-infections of calves with Bluetongue virus serotypes 1 and 8

The contemporary circulation of multiple bluetongue virus (BTV) serotypes or strains within the same territory can imply the co-infection of the ruminant and/or the vector populations. As a consequence, the clinical and pathological outcomes of co-infections as well as the biological properties of the viral progeny could be influenced and exhibit relevant variation. In this study, two independent co-infection experiments were carried out in calves using European strains of BTV serotypes 1 and 8 (BTV-1 and BTV-8, respectively), with the objective of studying the clinical and virological outcomes in comparison with BTV-1 and BTV-8 single infections. Synchronous co-infections using the same titre for the two viral strains were performed and the clinical signs were quantified using a standardized clinical form. Serotype-specific real-time RT-PCRs and viral isolation were used to monitor the course of viraemia. Neutralizing antibody titres were measured during the experiments, and necropsy with viral detection in the affected organs was performed. In the co-infected calves, a high BTV-8 viraemia was detected, while BTV-1 viraemia was irregular and sporadic. During BTV-1 single infection the development of viraemia and high titres of anti-BTV-1 neutralizing antibodies proved that the inoculum was infectious and the detection protocols were efficient. Several hypotheses could explain the predominant detection of BTV-8 in the co-infected calves, such as the occurrence of a privileged BTV-8 segment 2 reassortment, as recently described during in vitro BTV-1/BTV-8 co-infections; interference between the two viral strains; or a higher BTV-8 tropism for the bovine species.

Pulmonary artery haemorrhage in newborn calves following bluetongue virus serotype 8 experimental infections of pregnant heifers.

The emergence of bluetongue disease (BT) among livestock in Europe in 2006 raised many questions including the occurrence and epidemiological significance of foetal infections in cattle. To clarify these aspects, vaccinated and unvaccinated pregnant heifers were sequentially infected twice in an isolation facility (biosafety level 3) with a northern European outbreak strain of Bluetongue virus serotype 8 (BTV-8). The study was terminated 2 months after calving with necropsy of the dams and their offspring. The cattle were monitored throughout the study by clinical scoring and for the presence of circulating neutralising antibodies, and after calving for the presence of infectious virus and viral RNA in blood and milk. Four calves, one born from a vaccinated dam and three from non-vaccinated ones, that were infected at 120 days of gestation had obvious haemorrhage of the pulmonary artery at necropsy. Although haemorrhage of the pulmonary artery is highly characteristic of BT, viral RNA was not detected in any of these calves. Furthermore, although none of the calves born from heifers infected prior to mid-gestation had teratogenic BTV typical brain lesions, some had lesions at birth suggestive of in utero BTV infection. Despite the lack of viral RNA detection, the presence of haemorrhage of the pulmonary artery deserves to be reported as a new observation in the context of the multiple investigations having as main subject the BTV placental crossing in cattle.

Demodicosis in two Holstein young calves

Demodicosis in cattle is caused by a microscopic mite, Demodex bovis. The parasites live sometimes in large numbers in the hair follicles and associated skin glands. The disease is well described and quite common in tropical zones, but rare and most likely underestimated in temperate regions, especially in Europe (Fisher, 1973; Matthes, 1994). Demodectic mange in cattle is known to be usually a chronic and benign disease. Lesions consist in papules and small nodules filled with a creamy-colored caseous material possibly associated with hair loss mainly observed in the periocular region, on the neck, and on the shoulders. Itching is usually absent. Under certain circumstances, such as stress, nutritional deficiencies, concurrent diseases and hot and humid weather the condition can extend to most parts of the body and lead to a loss of body condition.