Schmallenberg Virus: Viral Detection, Morphological Identification and a Spatial Distribution Modeling of its Vectors
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Date
2020-06
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Abstract
Schmallenberg virus (SBV) is a novel Orthobunyavirus that causes drop milk production,
diarrhea, fever, congenital malformation and abortion to the affected animal. First it spread
rapidly throughout the European continent and then to other parts of the world. In Ethiopia, there
was no previous study conducted on the detection of SBV in Culicoides and ensemble modeling
of SBV vectors in Ethiopia. Thus, this study aimed to conduct entomological survey, SBV
detection and ensemble modeling of the vectors. An entomological survey was conducted during
the study from October, 2019 to May, 2020 in Adama, Bishoftu, Holeta, Jimma, and Sebeta. The
result showed that from the total of 6356 adult Culicoides midges collected, C. imicola (32%), C.
kings (30%), C. deltus (4%), C.milnei (13%), and not identified (20%) were recorded. Detection
of SBV from a total of 29 pools of Culicoides midges containing 70-160 Culicoides/pool was
performed using real-time RT-PCR. The results revealed that, none of the Culicoides midges
were positive for SBV genome. Ensemble model were developed using predictor variables land
cover data, livestock, mean annual maximum temperature, mean annual minimum temperature,
precipitation, solar radiation, water vapour and wind. The overall contributions of the variables to
the model were mean annual minimum temperature (49.5%) highest and land cover (3.9%)
lowest. Of 30 individual models developed, 27 had ROC > 0.90 and 24 had TSS and Kappa >
0.80. The ensemble model of the 30 models showed most parts of Ethiopia are suitable for C.
imicola. The suitability differs across zones. High probability of suitability occurs in Borena,
Bale, East Hararge, East Shewa, North Shewa, West Shewa, Hadiya, North Wollo, Southern
Tigray, and Eastern Tigray while low suitable areas were occurs in Benchimaji, Shaka, Kafa,
Gambela, Zone 1 and 2 and Afar Regional State. Thus, our results suggested that more work is
needed on viral detection of SBV, modeling of the spatial and temporal situations of both vector
and the disease.
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Keywords
Culicoides, Ensemble modeling, Occurrence, Schmallenberg Virus, Viral detection