Contribution to the Schmallenberg virus biology in ruminants

On the autumn 2011, the Friedrich Loeffler Institute (Germany) isolate the genetic material of a hitherto unknown virus which is associated with an unexplained syndrome of fever, drop of milk and diarrhea reported in the dairy farms from the Netherlands and Northwest Germany. The newcomer was named Schmallenberg virus based on the geographical origin of the first positive samples. It belongs to the Orthobunyavirus genus. For the first time in Western Europe, an arbovirus of this group circulates among ruminants. Such an emergence is, by many ways, similar to the type 8 Bluetongue virus emergence in 2006 and is one indication that the global infectious diseases dynamic is changing in Europe. Thus, understanding and documenting the Schmallenberg virus emergence, in that context, is of great importance. The present thesis is part of this approach and aim to contribute to the knowledge and the understanding of the virus biology and the associated disease. It is comprised of three studies that investigate the problematic at three different levels. The first study is a description of the lesions found in the bovine fetus after the transplacental passage of the virus. This study is a confirmation that the lesions are limited to the neurologic and myo-arthro-skeletal systems. The two characteristic lesions associated with the in-utero infection are the micromyelia and the arthrogryposis. The study strongly suggests that the key element of the pathogeny of these lesions is the virus-induced destruction of the spinal cord motoneurons. The second study follows the seroprevalence of the virus in the wild deer populations in Wallonia from 2012 to 2017. The study substantiates the hypothesis of a hypo-endemic installation of the virus with cyclic pulsations. This particular endemic state has been described for close viruses. It is characterized by several years of low-level circulation followed by one year of higher circulation. Moreover, according to this study, deer are not the main reservoir of the virus. The populations of wild ruminants do participate to the circulation of the virus. Nevertheless, they have a minor impact on the global dynamic of the Schmallenberg virus circulation. The third study focuses on one of the main effectors of the interferon response, the Mx1 protein. The aim is to describe the effect of the latter on the viral cycle. By comparing, in vitro, Mx1 proteins from different mammals (bovine, canine, equine, porcine Mx proteins), the study shows an antiviral effect for the four tested proteins. However, the canine Mx1 is significantly less active. The second main result is the observation of a not previously described dose-dependent effect of the Mx antiviral effect. Those three studies, because they explore the Schmallenberg virus biology from different angles, provide a broad overview of the questions raised by the Schmallenberg virus emergence.A l’automne 2011, le Friedrich Loeffler Institute (Allemagne) identifie le matériel génétique d’un virus jusqu’alors inconnu et l’associe à un syndrome de fièvre avec chute de lactation, combiné à de la diarrhée, observé dans les troupeaux de vaches laitières situés aux Pays-Bas et dans la partie nord-ouest de l’Allemagne. Baptisé virus de Schmallenberg, en référence à l’origine géographique des prélèvements qui ont servi à la découverte, ce nouveau virus appartient au genre Orthobunyavirus. C’est la première fois qu’un arbovirus de ce genre, circulant dans les populations de ruminants, est identifié en Europe. Cette émergence qui, par bien des aspects, fait écho à l’émergence du sérotype 8 du virus de la fière catarrhale ovine en 2006, est l’une des preuves que la dynamique générale des maladies infectieuses en Europe de l’ouest est en pleine mutation. Il est donc particulièrement important d’étudier et de comprendre cette émergence. Cette thèse s’inscrit dans cette optique et cherche à contribuer aux connaissances accumulées sur ce virus et sur la maladie qu’il induit. Elle regroupe trois études qui envisagent la problématique posée par le virus de Schmallenberg à trois niveaux. La première étude s’attache à décrire les lésions provoquées chez les fœtus bovins par le passage transplacentaire du virus. Elle confirme que les lésions se limitent aux systèmes neurologique et myo-arthro-squelettique. Les deux lésions caractéristiques de cette infection in utero sont une micromyélie associée à de l’arthrogrypose. L’étude suggère fortement que l’élément central de la pathogénie de ces lésions est la destruction des neurones moteurs de la moelle épinière. La seconde étude suit la séroprévalence du virus de Schmallenberg dans les populations de cervidés sauvages de Wallonie de 2012 à 2017. Cette étude corrobore l’hypothèse d’une installation dans un état d’hypo-endémie traversée de pulsations cycliques. Cet état a été observé pour les virus proches dans les autres parties du monde. Cet état se traduit par des saisons de circulation intense du virus après plusieurs années de circulation à très bas niveau. Par ailleurs, cette étude suggère que les cervidés sauvages participent à la circulation du virus mais n’en sont pas le réservoir principal. La troisième étude s’intéresse à l’impact d’un des principaux effecteurs de la réponse interféron, la protéine Mx1, sur le cycle du virus. En comparant, in vitro, l’impact de protéines Mx issues de différents mammifères (origines bovine, canine, équine, porcine), elle démontre un effet antiviral de toutes les protéines testées avec, cependant, un effet moins marqué de la protéine Mx1 d’origine canine. En outre, cette étude met en évidence un effet dose dépendant dans l’action de la protéine Mx1 qui n’avait, jusqu’ici, pas été observé. Ces trois études éclairent la question du virus de Schmallenberg sous différents angles qui, parce qu’ils sont complémentaires, permettent une vue assez large des problématiques que pose l’émergence de ce virus

Prevalence of Angiostrongylus vasorum in southern Belgium, a coprological and serological survey.

BACKGROUND: Canine angiostrongylosis, a gastropod-borne helminthic infection, is increasingly being described in North America and is now reported in many European countries. In dogs, Angiostrongylus vasorum may cause a wide spectrum of clinical signs. Respiratory distress such as coughing and dyspnoea are the most frequently described manifestations. The aim of the present study was to gain additional information on the distribution, prevalence and risk factors associated with A. vasorum infection in dog from southern Belgium through the combined used of a commercially available in-clinic assay for detection of circulating antigen (Angio Detect, IDEXX, Westbrook, USA) and coprology in two different canine populations: dogs with clinical signs compatible with angiostrongylosis and asymptomatic dogs or dogs presented for unrelated conditions (control). RESULTS: A total of 979 dogs were enrolled in the study from November 2014 until February 2016. Seven hundred fifty-seven dogs were included in the control group, whereas 222 dogs had clinical signs compatible with angiostrongylosis. Forty-six dogs out of 979 (4.7 %) had A. vasorum circulating antigen. There was a highly significant difference between the two populations (3.6 % (27/747) and 8.6 % (19/222) in control and symptomatic dogs, respectively) (P = 0.00379). First stage larvae (L1) of A. vasorum were found in seven out of 24 serologically positive control dogs and in six out of 17 serologically positive symptomatic dogs. Interestingly, L1 of Crenosoma vulpis were detected by Baermann technique in one control and nine symptomatic dogs, respectively. Out of 17 Angio Detect (IDEXX, Westbrook, USA) positive dogs with negative (14) or not performed Baermann test (three), one dog was positive in both in-house ELISAs (Ag and Ab) and one dog was positive for Ag. Statistical analysis was unable to detect any risk factors associated with the direct and/or indirect detection of A. vasorum. CONCLUSIONS: This seroepidemiological study demonstrated for the first time a high seroprevalence in Southern Belgium for A. vasorum. The Angio Detect was found to be suitable in this context as the collection, preservation and examination of stools were difficult. Nevertheless, discrepancies were observed between the different available tests. Additional research is clearly needed. Also, coproscopy remains a very useful tool in dogs infected for less than nine weeks and for the identification of other canine lung nematodes such as C. vulpis. This study also demonstrates that asymptomatic dogs may shed A. vasorum L1 in their faeces and therefore contribute to the maintenance of A. vasorum life-cycle

An obstructive upper respiratory emergency in a pregnant Belgian blue heifer

peer reviewedIn this case report, the surgical intervention and aftercare are described of an upper airway obstruction in a two-and-a-half year old, seven-months pregnant Belgian blue heifer. The animal had been referred to the Clinic for Ruminants (University of Liège) for complaints of stridor and dyspnea and suffered from necrotic laryngitis, complicated by the formation of an obstructive granuloma. Emergency tracheotomy was performed to save the life of the cow and its calf. Through the use of a self-retaining cannula, the modified tracheotomy site could be kept patent until the calf was born and the pathology resolved two months after admission. Healing of the larynx was checked and documented by use of nasal and retro-tracheal endoscopy

Antimicrobial susceptibility profile of several bacteria species identified in the peritoneal exudate of cows affected by parietal fibrinous peritonitis after caesarean section

peer reviewe

Antimicrobial Susceptibility Profile of Several Bacteria Species Identified in the Peritoneal Exudate of Cows Affected by Parietal Fibrinous Peritonitis after Caesarean Section

peer reviewedAbstract: The aim of this study was to identify the species and antimicrobial susceptibility of bacteria involved in parietal fibrinous peritonitis (PFP).We studied 156 peritoneal fluid samples from cows presenting PFP after caesarean section. Bacteria were cultured in selective media and their antimicrobial susceptibility was tested by disk diffusion assay. Bacteria were isolated in the majority (129/156; 83%) of samples. The majority (82/129; 63%) of positive samples contained one dominant species, while two or more species were cultured in 47/129 (36%) samples. Trueperella pyogenes (T. Pyogenes) (107 strains) was the most identified species, followed by Escherichia coli (E. coli) (38 strains), Proteus mirabilis (P. mirabilis) (6 strains), and Clostridium perfringens (C. perfringens) (6 strains). Several other species were sporadically identified. Antimicrobial susceptibility was tested in 59/185 strains, predominantly E. coli (38 strains) and P. mirabilis (6 strains). Antibiotic resistance, including resistance to molecules of critical importance, was commonly observed; strains were classified as weakly drug resistant (22/59; 37%), multidrug resistant (24/59; 41%), extensively drug resistant (12/59; 20%), or pan-drug resistant (1/59; 2%). In conclusion, extensive antibiotic resistance in the isolated germs might contribute to treatment failure. Ideally, antimicrobial therapy of PFP should be based upon bacterial culture and susceptibility testing

Blood Inflammatory, Hydro-Electrolytes and Acid-Base Changes in Belgian Blue Cows Developing Parietal Fibrinous Peritonitis or Generalised Peritonitis after Caesarean Section

peer reviewedThis study aimed to describe the inflammation, hydro-electrolyte and acid-base imbalances caused by generalised peritonitis (GP) and parietal fibrinous peritonitis (PFP) after caesarean section. After clinical examination, blood was sampled from 11 cows with PFP, 30 with GP and 14 healthy cows. Serum and plasma refractometry and glutaraldehyde tests were used to evaluate the inflammation level, while hydro-electrolytes and acid-base parameters were assessed using an EPOC® device. In addition to clinical signs of dehydration (>10%), blood analysis showed a high fibrinogen concentration (PFP: 8.64 ± 8.82 g/L; GP: 7.83 ± 2.45 g/L) and fast glutaraldehyde coagulation (<3 min) indicative of severe inflammation in both diseases compared to the control group (p < 0.05). Moreover, a severe decrease in electrolytes concentration (Na+: 126.93 ± 5.79 mmol/L; K+: 3.7 ± 1.3 mmol/L; Ca++: 0.89 ± 0.12 mmol/L; Cl−: 82.38 ± 6.45 mmol/L) and a significant increase in bicarbonate (30.87 ± 8.16 mmol/L), base excess (5.71 ± 7.42 mmol/l), L-lactate (8.1 ± 4.85 mmol/L) and creatinine (3.53 ± 2.30 mg/dL) were observed in cows with GP compared to the control group (p < 0.05). In contrast, few major perturbations were noticed in PFP, where only K+ (3.64 ± 0.25 mmol/L) and Ca++ (1.06 ± 0.09 mmol/L) were significantly modified (p < 0.05). In conclusion, a high dehydration and severe inflammation are induced by PFP and GP. Nevertheless, GP causes more electrolytes and acid-base disturbances than PFP