Increased Virulence of Culicoides Midge Cell-Derived Bluetongue Virus in IFNAR Mice.

Bluetongue (BT) is a Culicoides midge-borne hemorrhagic disease affecting cervids and ruminant livestock species, resulting in significant economic losses from animal production and trade restrictions. Experimental animal infections using the α/ß interferon receptor knockout IFNAR mouse model and susceptible target species are critical for understanding viral pathogenesis, virulence, and evaluating vaccines. However, conducting experimental vector-borne transmission studies with the vector itself are logistically difficult and experimentally problematic. Therefore, experimental infections are induced by hypodermic injection with virus typically derived from baby hamster kidney (BHK) cells. Unfortunately, for many U.S. BTV serotypes, it is difficult to replicate the severity of the disease seen in natural, midge-transmitted infections by injecting BHK-derived virus into target host animals. Using the IFNAR BTV murine model, we compared the virulence of traditional BHK cell-derived BTV-17 with C. sonorensis midge (W8) cell-derived BTV-17 to determine whether using cells of the transmission vector would provide an in vitro virulence aspect of vector-transmitted virus. At both low and high doses, mice inoculated with W8-BTV-17 had an earlier onset of viremia, earlier onset and peak of clinical signs, and significantly higher mortality compared to mice inoculated with BHK-BTV-17. Our results suggest using a Culicoides W8 cell-derived inoculum may provide an in vitro vector-enhanced infection to more closely represent disease levels seen in natural midge-transmitted infections while avoiding the logistical and experimental complexity of working with live midges.

Evidence of Active Orbivirus Transmission in 2016 in Kansas and Nebraska.

Retrospective serological and case diagnostic data of endemic bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) provide evidence of viral transmission among livestock and wildlife from 2016 in Kansas and Nebraska. Serological testing of mature cattle in nine distinct regional zones of Kansas revealed 76% to 100% had detectable antibodies to BTV and/or EHDV. Specimens tested in the Kansas Veterinary Diagnostic Laboratory (55 submissions) were 51% test positive for antibodies to BTV and/or EHDV. Specimens tested in the Nebraska Veterinary Diagnostic Center (283 submissions) were 25% test positive for antibodies to BTV and/or EHDV. Low disease incidence in white-tailed deer and other susceptible wild ungulates was observed during 2016. However, there were no confirmed reports of disease in livestock in either state. The reasons for emergence of significant clinical disease in livestock and wildlife populations remain undefined.

Recent Advances in the Diagnosis of Classical Swine Fever and Future Perspectives.

Classical swine fever (CSF) is a highly contagious viral disease of pigs, including wild boar. It is regarded as one of the major problems in the pig industry as it is still endemic in many regions of the world and has the potential to cause devastating epidemics, particularly in countries free of the disease. Rapid and reliable diagnosis is of utmost importance in the control of CSF. Since clinical presentations of CSF are highly variable and may be confused with other viral diseases in pigs, laboratory diagnosis is indispensable for an unambiguous diagnosis. On an international level, well-established diagnostic tests of CSF such as virus isolation, fluorescent antibody test (FAT), antigen capture antibody enzyme-linked immunosorbent assay (ELISA), reverse-transcription polymerase chain reaction (RT-PCR), virus neutralization test (VNT), and antibody ELISA have been described in detail in the OIE Terrestrial Manual. However, improved CSF diagnostic methods or alternatives based on modern technologies have been developed in recent years. This review thus presents recent advances in the diagnosis of CSF and future perspectives.

Mosquito host choices on livestock amplifiers of Rift Valley fever virus in Kenya.

BACKGROUND: Animal hosts may vary in their attraction and acceptability as components of the host location process for assessing preference, and biting rates of vectors and risk of exposure to pathogens. However, these parameters remain poorly understood for mosquito vectors of the Rift Valley fever (RVF), an arboviral disease, and for a community of mosquitoes. METHODS: Using three known livestock amplifiers of RVF virus including sheep, goat and cattle as bait in enclosure traps, we investigated the host-feeding patterns for a community of mosquitoes in Naivasha, an endemic area of Rift Valley fever (RVF), in a longitudinal study for six months (June-November 2015). We estimated the incidence rate ratios (IRR) where mosquitoes chose cow over the other livestock hosts by comparing their attraction (total number collected) and engorgement rate (proportion freshly blood-fed) on these hosts. RESULTS: Overall, significant differences were observed in host preference parameters for attraction (F2,15 = 4.1314, P = 0.037) and engorgement (F2,15 = 6.24, P = 0.01) with cow consistently attracting about 3-fold as many mosquitoes as those engorged on sheep (attraction: IRR = 2.9, 95 % CI 1.24-7.96; engorgement: IRR = 3.2, 95 % CI = 1.38-7.38) or goat (attraction: IRR = 2.7, 95 % CI 1.18-7.16; engorgement: IRR = 3.28, 95 % CI 1.47-7.53). However, there was no difference between the attraction elicited by sheep and goat (IRR = 1.08; 95 % CI 0.35-3.33 or engorgement rate (IRR = 0.96, 95 % CI 0.36-2.57). CONCLUSION: Despite the overall attractive pattern to feed preferentially on cows, the engorgement rate was clearly independent of the number attracted for certain mosquito species, notably among the flood water Aedes spp., largely incriminated previously as primary vectors of RVF. Our findings suggest that insecticide treated cattle (ITC) can be exploited in enclosure traps as contact bait in the monitoring and control of disease-causing mosquitoes in RVF endemic areas.

Vaccines for emerging and re-emerging viral diseases of companion animals.

It is likely that new viral diseases may continue to emerge in companion animals. It is more likely that genetic or antigenic virus variants or geographically translocated viruses may emerge or re-emerge in companion animals, however. This latter possibility represents the greater risk. Because this represents an ongoing threat, research and development should continue to maximize broad efficacy and effectiveness in addition to safety. To achieve these goals, the research and development effort should evaluate newer available technologies that may also reduce any barriers to use and availability.

A review of the effectiveness of vaccine potency control testing.

The use of potency control testing is a valuable tool for testing the actual relative strength of manufactured assembly lots of vaccine. Biological-based manufacturing methods are inherently variable and potency testing is a tool to ensure lot-to-lot consistency of commercial vaccines. A strong historical link to clinical efficacy has been established where correlation to efficacy and adequate test validation have been achieved. The link to immunogenicity and efficacy has traditionally been strongest with attenuated vaccines and toxoids. Control potency test failure does predict that a serial or batch of vaccine would most likely provide insufficient immunogenicity in typical field applications. Because of the complexity of pathogenic processes and associated immune responses, potency tests may not always directly predict the effectiveness of a vaccine. Thus, vaccines that pass control potency testing may not always provide adequate efficacy. This is particularly true of adjuvanted, inactivated vaccines. In the development of vaccine formulations and control tests for vaccines, the nature of the desired protective immune responses to the targeted pathogen (when known) should be considered. These considerations could provide better alternatives in the assays chosen as correlates of immunity and may more accurately predict efficacy and assure batch-to-batch consistency. Also, the effects of the dose and duration of antigen exposure as well as the nature of antigen presentation and generation of extrinsic cytokines could be characterised and correlated to vaccine potency as additional indicators of vaccine efficacy.