Bluetongue in small ruminants: An opinionated review, with a brief appraisal of the 2014 outbreak of the disease in Greece and the south-east Europe

Kyriakis, Constantinos S.; Billinis, C.; Papadopoulos, E.; Vasileiou, N.G.C.; Athanasiou, Labrini V.; Fthenakis, G.C.

doi:10.1016/j.vetmic.2015.08.004

Cited by 28 publications

(35 citation statements)

References 69 publications

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“…This variability in the severity of BTV infection has been attributed to numerous host factors, such as the breed, health and age of the ruminant (Caporale et al., ; Maclachlan, Drew, Darpel, & Worwa, ). It has been previously reported that in field settings, environmental factors, such as exposure to sunlight, elevated temperatures, stress and bacterial or viral co‐infections can exacerbate BT clinical signs in sheep (Kyriakis et al., ). Therefore, the clinical presentation of infection with the BTV‐8 strains in the field is likely to be more severe than what we have reported in this study where animals were housed within the high‐sanitary and controlled‐husbandry conditions of the containment facilities.…”

Section: Discussionmentioning

confidence: 99%

Evidence of reduced viremia, pathogenicity and vector competence in a re‐emerging European strain of bluetongue virus serotype 8 in sheep

Flannery

Sanz-Bernardo

Ashby

et al. 2019

Transbound Emerg Dis

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Summary The outbreak of bluetongue virus (BTV) serotype 8 (BTV‐8) during 2006–2009 in Europe was the most costly epidemic of the virus in recorded history. In 2015, a BTV‐8 strain re‐emerged in France which has continued to circulate since then. To examine anecdotal reports of reduced pathogenicity and transmission efficiency, we investigated the infection kinetics of a 2007 UK BTV‐8 strain alongside the re‐emerging BTV‐8 strain isolated from France in 2017. Two groups of eight BTV‐naïve British mule sheep were inoculated with 5.75 log 10 TCID 50 /ml of either BTV‐8 strain. BTV RNA was detected by 2 dpi in both groups with peak viraemia occurring between 5–9 dpi. A significantly greater amount of BTV RNA was detected in sheep infected with the 2007 strain (6.0–8.8 log 10 genome copies/ml) than the re‐emerging BTV‐8 strain (2.9–7.9 log 10 genome copies/ml). All infected sheep developed BTV‐specific antibodies by 9 dpi. BTV was isolated from 2 dpi to 12 dpi for 2007 BTV‐8‐inoculated sheep and from 5 to 10 dpi for sheep inoculated with the remerging BTV‐8. In Culicoides sonorensis feeding on the sheep over the period 7–12 dpi, vector competence was significantly higher for the 2007 strain than the re‐emerging strain. Both the proportion of animals showing moderate (as opposed to mild or no) clinical disease (6/8 vs. 1/8) and the overall clinical scores (median 5.25 vs. 3) were significantly higher in sheep infected with the 2007 strain, compared to those infected with the re‐emerging strain. However, one sheep infected with the re‐emerging strain was euthanized at 16 dpi having developed severe lameness. This highlights the potential of the re‐emerging BTV‐8 to still cause illness in naïve ruminants with concurrent costs to the livestock industry.

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Section: Discussionmentioning

confidence: 99%

Evidence of reduced viremia, pathogenicity and vector competence in a re‐emerging European strain of bluetongue virus serotype 8 in sheep

Flannery

Sanz-Bernardo

Ashby

et al. 2019

Transbound Emerg Dis

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“…During the epizootic wave of a novel BTV‐4 reassortant in the Balkan region, the highest morbidity and case fatality rates were reported in sheep (8.5% and 37.0%), followed by goats (1.5% and 24.5%) and cattle (2.5% and 6.5%) (Kyriakis et al., ). However, reports of morbidity and case fatality rates in domestic ruminants were contradictory, particularly the morbidity rate in cattle (Katsoulos et al., ; Kyriakis et al., , ProMED‐mail, ). In the 10 ruminants experimentally infected with BTV‐4, clinical signs were mild in sheep and goats and no obvious clinical signs were observed in cattle, except for a transient increase in body temperature.…”

Section: Discussionmentioning

confidence: 99%

“…Sequence comparison of the 10 segments of BTV‐4 isolates from Greece, Bulgaria, Hungary and Corsica revealed reassortment events between segments of various homotypic and heterotypic BTV serotypes. These serotypes included BTV‐24, BTV‐4, BTV‐2 and BTV‐1 strains from North African and Western Mediterranean countries, respectively (Hornyák et al., ; Kyriakis et al., , ProMED‐mail, ; Sailleau et al., ). This novel BTV‐4 strain encountered a largely BTV‐naïve ruminant population in 2014, and a rapid spread throughout the Balkan region was observed.…”

Section: Introductionmentioning

confidence: 99%

“…The highest morbidity and case fatality rates in domestic ruminants by species were reported in sheep (8.5% and 37.0%), followed by goats (1.5% and 24.5%) and cattle (2.5% and 6.5%). However, morbidity and case fatality rates varied considerably between countries (Kyriakis et al., ). In contrast to the initial reports of an exceptionally high morbidity rate in cattle in Romania (ProMED‐mail, ), a comprehensive field study in Greece in 2014 did not confirm these rates, and no clinical signs of BT were reported (Katsoulos et al., ).…”

Section: Introductionmentioning

confidence: 99%

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Experimental infection of sheep, goats and cattle with a bluetongue virus serotype 4 field strain from Bulgaria, 2014

Schulz

Sailleau

Bréard

et al. 2017

Transbound Emerg Dis

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In 2014, a new bluetongue virus serotype 4 (BTV-4) strain was detected in southern Greece and spread rapidly throughout the Balkan Peninsula and adjacent countries. Within half a year, more than 7,068 outbreaks were reported in ruminants, particularly in sheep. However, the reported morbidity and case fatality rates in ruminants varied. The pathogenesis of a Bulgarian BTV-4 strain isolated from sheep during the BTV-4 epizootic was studied in different species. Therefore, four sheep, three goats and three cattle were experimentally infected with the isolate BTV-4/BUL2014/15 and monitored for clinical signs up to several weeks. Serum and whole-blood samples were collected at regular intervals and subjected to serological and virological analyses. In this context, BTV-4-specific real-time RT-PCR assays were developed. The infection kinetics were similar to those known for other traditional BTV serotypes, and only mild BT-like clinical signs were observed in goats and sheep. In cattle, no obvious clinical signs were observed, except a transient increase in body temperature. The study results contrast with the severe clinical signs reported in sheep experimentally infected with an African BTV-4 strain and with the reports of BT-like clinical signs in a considerable proportion of different ruminant species infected with BTV-4 in the Balkan region and Italy. The discrepancies between the results of these animal trials and observations of BTV-4 infection in the field may be explained by the influence of various factors on the manifestation of BT disease, such as animal breed, fitness and virus strain, as described previously.

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“…southeastern Europe for the first time in 2014 (serotype 4); see Kyriakis et al [7] for a review of European outbreaks of BTV up to 2014 by country and serotype. Recently, BTV serotype 8 has re-emerged in France [8].…”

Section: Introductionmentioning

confidence: 99%

The impact of temperature changes on vector-borne disease transmission: Culicoides midges and bluetongue virus

Brand

Keeling

2017

J. R. Soc. Interface.

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It is a long recognized fact that climatic variations, especially temperature, affect the life history of biting insects. This is particularly important when considering vector-borne diseases, especially in temperate regions where climatic fluctuations are large. In general, it has been found that most biological processes occur at a faster rate at higher temperatures, although not all processes change in the same manner. This differential response to temperature, often considered as a trade-off between onward transmission and vector life expectancy, leads to the total transmission potential of an infected vector being maximized at intermediate temperatures. Here we go beyond the concept of a static optimal temperature, and mathematically model how realistic temperature variation impacts transmission dynamics. We use bluetongue virus (BTV), under UK temperatures and transmitted by Culicoides midges, as a well-studied example where temperature fluctuations play a major role. We first consider an optimal temperature profile that maximizes transmission, and show that this is characterized by a warm day to maximize biting followed by cooler weather to maximize vector life expectancy. This understanding can then be related to recorded representative temperature patterns for England, the UK region which has experienced BTV cases, allowing us to infer historical transmissibility of BTV, as well as using forecasts of climate change to predict future transmissibility. Our results show that when BTV first invaded northern Europe in 2006 the cumulative transmission intensity was higher than any point in the last 50 years, although with climate change such high risks are the expected norm by 2050. Such predictions would indicate that regular BTV epizootics should be expected in the UK in the future.

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Bluetongue in small ruminants: An opinionated review, with a brief appraisal of the 2014 outbreak of the disease in Greece and the south-east Europe

Cited by 28 publications

References 69 publications

Evidence of reduced viremia, pathogenicity and vector competence in a re‐emerging European strain of bluetongue virus serotype 8 in sheep

Evidence of reduced viremia, pathogenicity and vector competence in a re‐emerging European strain of bluetongue virus serotype 8 in sheep

Experimental infection of sheep, goats and cattle with a bluetongue virus serotype 4 field strain from Bulgaria, 2014

The impact of temperature changes on vector-borne disease transmission: Culicoides midges and bluetongue virus

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