Neurological disease suspected to be caused by tick-borne encephalitis virus infection in 6 horses in Switzerland.

BACKGROUND: Reports on acute tick-borne encephalitis virus (TBEV) infections with signs of neurologic disease in horses are limited. OBJECTIVES: To describe the epidemiological, clinical, and laboratory findings of suspected acute TBEV infections in 6 horses. ANIMALS: Six horses originating from TBEV endemic regions of Switzerland were presented to equine hospitals with acute onset of neurologic disease between 2011 and 2019. METHODS: Retrospective case series. Horses with acute onset of signs of neurologic disease that were subjected to clinical and microbiological examinations to rule out infectious diseases affecting the central nervous system. RESULTS: All horses exhibited acute signs of neurologic disease including ataxia and proprioceptive deficits. Horses tested positive for TBEV using virus neutralization test and samples were further tested for TBEV-specific IgM. The presence of TBEV-specific IgM antibodies was confirmed in 5 horses (cases 1-5, Laboratory Unit [LU] values ranging from 30 to 56). One horse (case no. 6) with an LU value just below the test threshold (LU = 22.3) was also included under the hypothesis that the horse was transitioning from acute to chronic infection. All horses originated from areas where humans with confirmed tick-borne encephalitis reported to have been bitten by ticks. CONCLUSIONS AND CLINICAL IMPORTANCE: Acute TBEV infection should be a differential diagnosis in horses with signs of neurologic disease and originating from TBEV endemic areas. The establishment of harmonized diagnostic criteria would help to overcome the diagnostic challenges associated with TBEV and other Flavivirus infections in horses.

Non-discriminatory Exclusion Testing as a Tool for the Early Detection of Foot-and-Mouth Disease Incursions.

Endemic circulation of foot-and-mouth disease (FMD) in Africa and Asia poses a continuous risk to countries in Europe, North America, and Oceania which are free from the disease. Introductions of the disease into a free region have dramatic economic impacts, especially if they are not detected at an early stage and controlled rapidly. However, farmers and veterinarians have an obvious disincentive to report clinical signs that are consistent with FMD, due to the severe consequences of raising an official suspicion, such as farm-level quarantine. One way that the risk of late detection can be mitigated is offering non-discriminatory exclusion testing schemes for differential diagnostics, wherein veterinarians can submit samples without the involvement of the competent authority and without sanctions or costs for the farmer. This review considers the benefits and limitations of this approach to improve the early detection of FMD in free countries and gives an overview of the FMD testing schemes currently in use in selected countries in Europe and the Americas as well as in Australia.

Virological and pathological findings in Bluetongue virus serotype 8 infected sheep.

Twenty-seven sheep of the four most common Swiss breeds and the English breed Poll Dorset were experimentally infected with a northern European field strain of bluetongue virus serotype 8 (BTV-8). Animals of all breeds developed clinical signs, viremia and pathological lesions, demonstrating that BTV-8 is fully capable of replicating and inducing bluetongue disease (BT) in the investigated sheep. Necropsy performed between 10 and 16 days post-infectionem (d.p.i.) revealed BT-typical hemorrhages, effusions, edema, erosions and activation of lymphatic tissues. Hemorrhages on the base of the Arteria pulmonalis and the left Musculus papillaris subauricularis were frequently present. Histology confirmed the macroscopical findings. Using a score system, clinical manifestation and pathology were found to be significantly related. Furthermore, clinical signs and fever were shown to be indicative for the concurrent presence of high amounts of viral ribonucleic acid (RNA) in blood. Spleen, lung, lymph nodes and tonsils from all animals were analyzed regarding viral RNA loads and infectivity using real-time reverse transcriptase PCR (rRT-PCR) and virus isolation in cell culture, respectively. The highest amount of viral RNA was detected in spleen and lung and rRT-PCR revealed to be a more sensitive method for virus detection compared to virus isolation. A long-term follow-up was performed with three sheep showing that BTV-8 viral RNA in blood was present up to 133 d.p.i. and in certain tissues even on 151 d.p.i. No significant breed-related differences were observed concerning clinicopathological picture and viremia, and the Swiss sheep were as susceptible to BTV-8 infection as Poll Dorset sheep, demonstrating a remarkably high virulence of BTV-8 for indigenous sheep breeds.

Use of mapping and statistical modelling for the prediction of bluetongue occurrence in Switzerland based on vector biology.

Due to the spread of bluetongue (BT) in Europe in the last decade, a sentinel surveillance programme was initiated for Switzerland in 2003, consisting of serological sampling of sentinel cattle tested for BT virus antibodies, as well as entomological trapping of Culicoides midges from June until October. The aim of this study was to create a 'suitability map' of Switzerland, indicating areas of potential disease occurrence based on the biological parameters of Obsoletus Complex habitat. Data on Culicoides catches from insect traps together with various environmental parameters were recorded and analysed. A multiple regression analysis was performed to determine correlation between the environmental conditions and vector abundance. Meteorological data were collected from 50 geo-referenced weather stations across Switzerland and maps of temperature, precipitation and altitude were created. A range of values of temperature, precipitation and altitude influencing vector biology were obtained from the literature. The final combined map highlighted areas in Switzerland which are most suitable for vector presence, hence implying a higher probability of disease occurrence given the presence of susceptible animals. The results confirmed the need for an early warning system for the surveillance of BT disease and its vectors in Switzerland.

Canine distemper virus-induced depletion of uninfected lymphocytes is associated with apoptosis.

Canine distemper virus (CDV), a negative stranded RNA morbillivirus, causes a multisystemic disease in dogs, which is associated with a severe immune suppression. The aim of the study was to examine the influence of early CDV infection on leukocyte depletion, lymphopenia and virus-induced cell death in dogs infected with a virulent CDV strain. From 10 infected dogs, peripheral blood leukocytes were harvested periodically, phenotyped and analyzed for CDV antigen content and apoptosis using Annexin V-FITC and propidium iodide labeling. CDV infection induced a severe CD3+ T cell and CD21+ B cell depletion in all animals at 3 days post-infection (d.p.i.). For dogs with severe distemper, developing virus persistence in the lymphoid tissue and central nervous system, this lymphopenia lasted until the end of the experiment. Increased levels of lymphocyte apoptosis were found at 3 d.p.i., and monocyte apoptosis at 6 d.p.i. This was more prominent in the group of animals with severe distemper. At 3 d.p.i. no leukocyte infection was detectable indicating that the early lymphocyte depletion and apoptosis was not a direct consequence of virus infection. Taken together, our results demonstrate that CDV-induced lymphopenia is an early event and that the degree of lymphocyte depletion correlates with the severity of disease and virus persistence in the lymphoid tissue and central nervous system.

Concurrent infections with vector-borne pathogens associated with fatal hemolytic anemia in a cattle herd in Switzerland.

Bovine anaplasmosis is a vector-borne disease that results in substantial economic losses in other parts of the world but so far not in northern Europe. In August 2002, a fatal disease outbreak was reported in a large dairy herd in the Swiss canton of Grisons. Diseased animals experienced fever, anorexia, agalactia, and depression. Anemia, ectoparasite infestation, and, occasionally, hemoglobinuria were observed. To determine the roles of vector-borne pathogens and to characterize the disease, blood samples were collected from all 286 animals: 50% of the cows were anemic. Upon microscopic examination of red blood cells, Anaplasma marginale inclusion bodies were found in 47% of the cows. The infection was confirmed serologically and by molecular methods. Interestingly, we also found evidence of infections with Anaplasma phagocytophilum, large Babesia and Theileria spp., and Mycoplasma wenyonii. The last two species had not previously been described in Switzerland. Anemia was significantly associated with the presence of the infectious agents detected, with the exception of A. phagocytophilum. Remarkably, concurrent infections with up to five infectious vector-borne agents were detected in 90% of the ill animals tested by PCR. We concluded that A. marginale was the major cause of the hemolytic anemia, while coinfections with other agents exacerbated the disease. This was the first severe disease outbreak associated with concurrent infections with vector-borne pathogens in alpine Switzerland; it was presumably curtailed by culling of the entire herd. It remains to be seen whether similar disease outbreaks will have to be anticipated in northern Europe in the future.

[Import risk analysis in animal disease control]. / Importrisikoanalysen in der Tierseuchenbekämpfung.

At the Swiss Federal Veterinary Office risk analyses are conducted according to international standards. A risk analysis contains the elements risk management, risk assessment and risk communication. A risk assessment is based on risk profile, hazard identification and a pathway model. All available information is gathered, documented and assessed and the risk estimated. The question. "What is the probability that unprocessed wild boar meat imported to Switzerland from the federal state Mecklenburg Western Pommerania is contaminated with classical swine fever virus?" was answered by a release assessment. The hazard identification recognized classical swine fever virus and attenuated live virus vaccine used for oral immunization as hazards. The probability of contamination was estimated to be small. The question: "What is the likelihood to introduce Aujeszky's disease to Switzerland and infect the indigenous pig population with the disease, by means of importing pork and meat products?" was answered by assessing the release, exposure and resulting consequences. The risk of an infection of the indigenous pig population was estimated to be very small, as 80% of the imported products derive from countries or zones free from Aujeszky's disease. Furthermore the majority of the imported products are processed. The strict implementation of the regulations governing feeding of food wastes to pigs reduces the probability of exposure. In all assessments the risk management decides on a strategy to deal with the risk, taking into consideration the results and recommendations derived from the risk assessment as well as other relevant factors.

Early DNA vaccination of puppies against canine distemper in the presence of maternally derived immunity.

Canine distemper (CD) is a disease in carnivores caused by CD virus (CDV), a member of the morbillivirus genus. It still is a threat to the carnivore and ferret population. The currently used modified attenuated live vaccines have several drawbacks of which lack of appropriate protection from severe infection is the most outstanding one. In addition, puppies up to the age of 6-8 weeks cannot be immunized efficiently due to the presence of maternal antibodies. In this study, a DNA prime modified live vaccine boost strategy was investigated in puppies in order to determine if vaccinated neonatal dogs induce a neutralizing immune response which is supposed to protect animals from a CDV challenge. Furthermore, a single DNA vaccination of puppies, 14 days after birth and in the presence of high titers of CDV neutralizing maternal antibodies, induced a clear and significant priming effect observed as early as 3 days after the subsequent booster with a conventional CDV vaccine. It was shown that the priming effect develops faster and to higher titers in puppies preimmunized with DNA 14 days after birth than in those vaccinated 28 days after birth. Our results demonstrate that despite the presence of maternal antibodies puppies can be vaccinated using the CDV DNA vaccine, and that this vaccination has a clear priming effect leading to a solid immune response after a booster with a conventional CDV vaccine.

Canine distemper, a re-emerging morbillivirus with complex neuropathogenic mechanisms.

Paramyxoviruses are responsible for a wide variety of diseases both in humans and in animals. Common to many paramyxoviruses is the fact that they can cause neurological symptoms in their final host. Newly discovered paramyxoviruses, such as the Hendra and Nipah viruses, show the same pattern of pathogenesis as that of the paramyxoviruses already known. Canine distemper virus (CDV) is a well-studied member of the genus Morbillivirus. Study of the neuropathogenesis of CDV might give insight into disease mechanisms and suggest approaches for the prevention of other recently discovered paramyxovirus infections.