Failure to establish congenital bluetongue virus infection by infecting cows in early pregnancy

Roeder, PL; Taylor, W. P.; Roberts, Deborah; Wood, L.; Jeggo, MH; Gard, GP; Corteyn, Mandy; Graham, Simon P.

doi:10.1136/vr.128.13.301

Cited by 24 publications

(14 citation statements)

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“…10,1l More recent studies of this question have failed to produce viable animals with transplacentally acquired persistent BTV infections. 13,14,18,21,26 Our experimental and epidemiologic data are consistent with the concept that BTV infections may be prolonged but are of finite duration and not truly persistent. Even if the extended duration of hematologic BTV PCR positivity provides an explanation for the phenomenon of viral overwintering, the data indicate that this molecular viremia is not permanent and will disappear within about 5-6 months following infection.…”

Section: Discussionsupporting

confidence: 89%

Diagnostic Analysis of the Prolonged Bluetongue Virus RNA Presence Found in the Blood of Naturally Infected Cattle and Experimentally Infected Sheep

et al. 1994

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Bluetongue virus (BTV) RNA was detected by the polymerase chain reaction (PCR) in the blood of 24 naturally infected cattle as long as 160 days after the estimated date of infection. Blood samples from these animals and from 10 experimentally BTV-infected sheep, which also exhibited a prolonged hematologic BTV RNA presence, were concurrently evaluated for viral infectivity. Infectivity analyses were conducted using the sentinel sheep inoculation and embryonated chicken egg inoculation procedures. Blood specimens from the experimental sheep 50, 56, 71, and 89 days after BTV inoculation were uniformly negative for viral infectivity despite their uniformly positive status with PCR evaluation. Three collections of blood from the naturally infected cattle at least 100, 135, and 160 days after infection also revealed no recoverable viral infectivity but an initially high and progressively decreasing prevalence of BTV with the PCR technique. These retrospective epidemiologic and prospective experimental approaches were concordant in that both studies demonstrated consistent discrepancies between the viral infectivity and the PCR diagnostic data. The significance of these discrepancies is discussed with respect to Koch's postulates and with respect to the possibility that the biological vector of BTV (Culicoides variipennis) may recover BTV infectivity from PCR-positive but virus isolation-negative blood.

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Section: Discussionsupporting

confidence: 89%

Diagnostic Analysis of the Prolonged Bluetongue Virus RNA Presence Found in the Blood of Naturally Infected Cattle and Experimentally Infected Sheep

et al. 1994

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“…Because the next sampling was conducted 53 days later, it is impossible to determine when virus was cleared. In the other study, 23 the maximum length of detectable viremia for 20 pregnant cattle infected with US BTV serotype 11 was 38 days. No other information was provided.…”

Section: Discussionmentioning

confidence: 99%

“…19,23 In 1 of these studies, 19 viremia was measured at irregular intervals (30, 60, and 113 days postinoculation), but only 1 of the 18 animals that were inoculated with 1 of 3 BTV serotypes was still viremic at day 60. Because the next sampling was conducted 53 days later, it is impossible to determine when virus was cleared.…”

Section: Discussionmentioning

confidence: 99%

Maximal Predicted Duration of Viremia in Bluetongue Virus—Infected Cattle

2001

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Abstract. Central to the development of rational trade policies pertaining to bluetongue virus (BTV) infection is determination of the risk posed by ruminants previously exposed to the virus. Precise determination of the maximal duration of infectious viremia is essential to the development of an appropriate quarantine period prior to movement of animals from BTV-endemic to BTV-free regions. The objective of this study was to predict the duration of detectable viremia in BTV-infected cattle using a probabilistic modeling analysis of existing data. Data on the duration of detectable viremia in cattle were obtained from previously published studies. Data sets were created from a large field study of naturally infected cattle in Australia and from experimental infections of cattle with Australian and US serotypes of BTV. Probability distributions were fitted to the pooled empirical data, and the 3 probability distributions that provided the best fit to the data were the gamma, Weibull, and lognormal probability distributions. These asymmetric probability distributions are often well suited for decay processes, such as the time to termination of detectable viremia. The analyses indicated a Ͼ 99% probability of detectable BTV viremia ceasing after Յ 9 weeks of infection in adult cattle and after a slightly longer interval in BTV-infected, colostrum-deprived newborn calves.Bluetongue is an insect-transmitted, noncontagious viral disease of domestic and wild ruminants that is caused by bluetongue virus (BTV). 11,16,26 It is 1 of only 16 diseases included in List A by the Office International des Epizooties (OIE). Diseases included in OIE List A are defined as communicable diseases that have the potential for very serious and rapid spread, irrespective of national borders, that are of serious socioeconomic or public health consequence, and that are of major importance to the international trade of livestock and livestock products. 1 The major adverse economic impact of BTV infection in many regions of the world is its effect on international trade and movement of ruminant livestock and germplasm and not direct losses from bluetongue disease. 16,22,25 Central to the development of rational trade policies pertaining to BTV infection is determination of the risk posed by ruminants previously exposed to the virus. BTV infection of cattle is characterized by prolonged but not persistent viremia. 11 Virus is highly cell associated during viremia, and intimate association of BTV with erythrocytes is responsible for both prolonged viremia as well as infection of the hematophagous vector insects that transmit the virus. 4 Duration of viremia in BTV-infected cattle is related to the lifespan of the bovine erythrocyte, and precise determi-

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“…In contrast, earlier work with other field strains of BTV (not including BTV-2) did not show this property [19,20,27]. …”

Section: Discussionmentioning

confidence: 66%

“…More importantly, certain live attenuated BTV vaccine strains, passaged extensively in cell culture, were observed to be capable of transplacental transmission in both cattle and sheep [9,17,18] but early studies with wild-type (wt) BTV did not show this property (e.g. [19,20]). However, unexpectedly, following the introduction of the pathogenic BTV-8 into Northern Europe in 2006, it was observed that transplacental transmission of this virus strain occurred in both cattle and sheep [13,21-26].…”

Section: Introductionmentioning

confidence: 99%

Transplacental transmission of field and rescued strains of BTV-2 and BTV-8 in experimentally infected sheep

Rasmussen

Savini

Lorusso

et al. 2013

Vet Res

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Transplacental transmission of bluetongue virus has been shown previously for the North European strain of serotype 8 (BTV-8) and for tissue culture or chicken egg-adapted vaccine strains but not for field strains of other serotypes. In this study, pregnant ewes (6 per group) were inoculated with either field or rescued strains of BTV-2 and BTV-8 in order to determine the ability of these viruses to cross the placental barrier. The field BTV-2 and BTV-8 strains was passaged once in Culicoides KC cells and once in mammalian cells. All virus inoculated sheep became infected and seroconverted against the different BTV strains used in this study. BTV RNA was detectable in the blood of all but two ewes for over 28 days but infectious virus could only be detected in the blood for a much shorter period. Interestingly, transplacental transmission of BTV-2 (both field and rescued strains) was demonstrated at high efficiency (6 out of 13 lambs born to BTV-2 infected ewes) while only 1 lamb of 12 born to BTV-8 infected ewes showed evidence of in utero infection. In addition, evidence for horizontal transmission of BTV-2 between ewes was observed. As expected, the parental BTV-2 and BTV-8 viruses and the viruses rescued by reverse genetics showed very similar properties to each other. This study showed, for the first time, that transplacental transmission of BTV-2, which had been minimally passaged in cell culture, can occur; hence such transmission might be more frequent than previously thought.

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Failure to establish congenital bluetongue virus infection by infecting cows in early pregnancy

Cited by 24 publications

References 0 publications

Diagnostic Analysis of the Prolonged Bluetongue Virus RNA Presence Found in the Blood of Naturally Infected Cattle and Experimentally Infected Sheep

Diagnostic Analysis of the Prolonged Bluetongue Virus RNA Presence Found in the Blood of Naturally Infected Cattle and Experimentally Infected Sheep

Maximal Predicted Duration of Viremia in Bluetongue Virus—Infected Cattle

Transplacental transmission of field and rescued strains of BTV-2 and BTV-8 in experimentally infected sheep

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