The consequences of infection of cattle with Akabane virus at the time of insemination

Sexual Transmission of Arboviruses: A Systematic Review

Arthropod-borne viruses (arboviruses) are primarily maintained in nature in transmission cycles between hematophagous arthropods and vertebrate hosts, but an increasing number of arboviruses have been isolated from or indirectly detected in the urogenital tract and sexual secretions of their vertebrate hosts, indicating that further investigation on the possibility of sexual transmission of these viruses is warranted. The most widely recognized sexually-transmitted arbovirus is Zika virus but other arboviruses, including Crimean-Congo hemorrhagic fever virus and dengue virus, might also be transmitted, albeit occasionally, by this route. This review summarizes our current understanding on the ability of arboviruses to be sexually transmitted. We discuss the sexual transmission of arboviruses between humans and between vertebrate animals, but not arthropod vectors. Every taxonomic group known to contain arboviruses (Asfarviridae, Bunyavirales, Flaviviridae, Orthomyxoviridae, Reoviridae, Rhabdoviridae and Togaviridae) is covered.

Schmallenberg virus: a systematic international literature review (2011-2019) from an Irish perspective

In Autumn 2011, nonspecific clinical signs of pyrexia, diarrhoea, and drop in milk yield were observed in dairy cattle near the German town of Schmallenberg at the Dutch/German border. Targeted veterinary diagnostic investigations for classical endemic and emerging viruses could not identify a causal agent. Blood samples were collected from animals with clinical signs and subjected to metagenomic analysis; a novel orthobunyavirus was identified and named Schmallenberg virus (SBV). In late 2011/early 2012, an epidemic of abortions and congenital malformations in calves, lambs and goat kids, characterised by arthrogryposis and hydranencephaly were reported in continental Europe. Subsequently, SBV RNA was confirmed in both aborted and congenitally malformed foetuses and also in Culicoides species biting midges. It soon became evident that SBV was an arthropod-borne teratogenic virus affecting domestic ruminants. SBV rapidly achieved a pan-European distribution with most countries confirming SBV infection within a year or two of the initial emergence. The first Irish case of SBV was confirmed in the south of the country in late 2012 in a bovine foetus.

Since SBV was first identified in 2011, a considerable body of scientific research has been conducted internationally describing this novel emerging virus. The aim of this systematic review is to provide a comprehensive synopsis of the most up-to-date scientific literature regarding the origin of SBV and the spread of the Schmallenberg epidemic, in addition to describing the species affected, clinical signs, pathogenesis, transmission, risk factors, impact, diagnostics, surveillance methods and control measures. This review also highlights current knowledge gaps in the scientific literature regarding SBV, most notably the requirement for further research to determine if, and to what extent, SBV circulation occurred in Europe and internationally during 2017 and 2018. Moreover, recommendations are also made regarding future arbovirus surveillance in Europe, specifically the establishment of a European-wide sentinel herd surveillance program, which incorporates bovine serology and Culicoides entomology and virology studies, at national and international level to monitor for the emergence and re-emergence of arboviruses such as SBV, bluetongue virus and other novel Culicoides-borne arboviruses.

Evidence of excretion of Schmallenberg virus in bull semen

Schmallenberg virus (SBV) is a novel orthobunyavirus, discovered in Germany in late 2011. It mainly infects cattle, sheep and goats and could lead to congenital infection, causing abortion and fetal abnormalities. SBV is transmitted by biting midges from the Culicoides genus and there is no evidence that natural infection occurs directly between ruminants. Here, we could detect SBV RNA in infected bull semen using qRT-PCR (three bulls out of seven tested positive; 29 positive semen batches out of 136). We also found that highly positive semen batches from SBV infected bulls can provoke an acute infection in IFNAR^-/- mice, suggesting the potential presence of infectious virus in the semen of SBV infected bulls.

First detection of Schmallenberg virus RNA in bovine semen, Germany, 2012

In analogy to the related Akabane virus, transmission of Schmallenberg virus (SBV) by contaminated semen has primarily been considered negligible. However, the potential economic consequences for stock-bull breeders prompted the investigation of reliable diagnostic methods for SBV-RNA detection in bovine semen. Twelve extraction methods were compared using a dilution series of SBV-spiked semen as well as serum and medium samples for control. The most promising methods were subsequently used with semen samples obtained in an intensive field study. In total, frozen semen from 95 SBV-seroconverted bulls collected in the field between May and November 2012 were tested for SBV-RNA with an optimised standard operating procedure. The highest diagnostic and analytical sensitivity for the extraction of SBV in semen was found for the Trizol(®) LS Reagent lysis with or without combined purification of the viral RNA with magnetic beads. A total of 29 of 766 semen batches from 11 of 95 SBV-infected bulls were PCR-positive (Cq-values 26-37). Intermittent virus excretion was observed in 2 of the bulls. SBV-RNA-positive semen was coincidentally detected with early SBV-antibodies in 4 bulls. In bulls that showed seroconversion together with consecutive positive semen batches, SBV-RNA was predominantly found in the seminal cell fraction, while in bulls with single positive results only, SBV-RNA was detected exclusively in the seminal plasma.

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.

Schmallenberg virus experimental infection of sheep

Since late 2011, a novel orthobunyavirus, named Schmallenberg virus (SBV), has been implicated in many cases of severely malformed bovine and ovine offspring in Europe. In adult cattle, SBV is known to cause a mild transient disease; clinical signs include short febrile episodes, decreased milk production and diarrhoea for a few days. However, the knowledge about clinical signs and pathogenesis in adult sheep is limited. In the present study, adult sheep of European domestic breeds were inoculated with SBV either as cell culture grown virus or as virus with no history of passage in cell cultures. Various experimental set-ups were used. Sampling included blood collection at different time points during the experimental period and selected organ material at autopsy. Data from this study showed, that the RNAemic period in sheep was as short as reported for cattle; viral genome was detectable for about 3-5 days by real-time RT-PCR. In total, 13 out of 30 inoculated sheep became RNAemic, with the highest viral load in animals inoculated with virus from low cell culture passaged or the animal passaged material. Contact animals remained negative throughout the study. One RNAemic sheep showed diarrhoea for several days, but fever was not recorded in any of the animals. Antibodies were first detectable 10-14 days post inoculation. Viral RNA was detectable in spleen and lymph nodes up to day 44 post inoculation. In conclusion, as described for cattle, SBV-infection in adult sheep predominantly results in subclinical infection, transient RNAemia and a specific antibody response. Maintenance of viral RNA in the lymphoreticular system is observed for an extended period.

Pathology of the corpus luteum of cows

The corpus luteum (CL) is a transient endocrine organ which can manifest a number of pathologic conditions such as cysts, inflammation, adhesions, dysfunction and neoplasia. Luteal and follicular cysts are the most commonly encountered abnormalities and need to be distinguished from cysts within a normal CL. Inflammatory lesions are also frequently encountered and can be caused by viral, bacterial, or iatrogenic causes. If inflammation is severe, adhesions and subfertility/infertility can result. Luteal dysfunction is a broad classification of another pathologic condition encountered in the cow. Generally this results in abnormal production of progesterone or abnormal luteal lifespan resulting in infertility. Neoplasms are relatively rare in the CL but include both primary and metastatic tumors. Understanding the pathologic conditions that occur within the CL will allow a more accurate clinical assessment of these very dynamic endocrine structures.

Experimental infection of pregnant cattle with bluetongue virus serotype 11 between postbreeding days 21 and 48

Four bluetongue virus (BTV)-seronegative heifers and 2 BTV-seropositive heifers were inoculated with the virulent strain UC-8 of BTV-11 between postbreeding days (PBD) 21 and 30. The heifers were observed for 10-18 days after inoculation for clinical signs, and pregnancy was monitored by ultrasound examination of the uterus and by plasma progesterone levels. Blood samples were collected daily after inoculation and processed for virus isolation and titration. Heifers were euthanized between PBD 31 and PBD 48, and tissues were collected for virologic and pathologic examination. All but 1 heifer inoculated on PBD 21 remained pregnant after BTV inoculation. A cystic corpus luteum was found in the ovary of the nonpregnant heifer, but BTV was not isolated from the reproductive tract of this heifer. Three of the inoculated heifers that remained pregnant showed mild multifocal areas of perivascular lymphocytic infiltration in the ovary. BTV was reisolated from spleen and prescapular and peribronchial lymph nodes 10 days after inoculation from 3 of the 4 BTV-seronegative heifers. BTV was also reisolated from the uterus of 1 of the heifers that remained pregnant, but microscopic lesions were not found in this organ.

Embryo transfer as a means of controlling the transmission of viral infections. VIII. Failure to detect foot-and-mouth disease viral infectivity associated with embryos collected from infected donor cattle

Foot-and-mouth disease (FMD) viral infectivity detectable in cell cultures or by animal inoculation was not found to be associated with any of 48 washed zona pellucida-intact (ZPI) embryos collected from 8 cattle during the acute stages of disease. Similarly, infectivity was not found to be associated with any of 42 washed ZPI embryos collected from 3 cattle 21 d after infection with FMD.

Ovarian lesions in heifers exposed to infectious bovine rhinotracheitis virus by non-genital routes on the day after breeding

Twelve heifers were exposed to either a Colorado infectious bovine rhinotracheitis (IBR) virus isolate or an Iowa IBR isolate obtained from a bovine respiratory disease outbreak. All inoculations were made on the day after the heifers had been in estrus and bred by an IBR virus-negative bull. Pairs of heifers were inoculated with each virus isolate intravenously, intramuscularly or exposed by aerosol. The heifers were killed 11-15 days after inoculation and their reproductive tracts and ovaries subjected to virological and pathological study. Virus was isolated from the ovaries of all 4 heifers inoculated intravenously and from 3 of the 4 heifers inoculated intramuscularly, but not from the ovaries of heifers exposed by aerosol. Virus isolations and lesions were, with only 1 exception, confined to the ovary containing the corpus luteum. In ovaries from which IBR virus was isolated, lesions in the corpus luteum ranged from focal necrosis and infiltration of mononuclear cells to diffuse hemorrhage and necrosis. Most of these ovaries also had necrotic follicles and a diffuse mononuclear cell accumulation in the stroma. Lesions were not found in ovaries from which IBR virus was not isolated. It was concluded that lesions are readily induced in the ovaries of post-estrus heifers as a result of hematogenous spread of IBR virus and suggest that the differences in lesion development observed with the 3 routes are related to whether or not a viremia occurred.