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Seediscussions,stats,andauthorprofilesforthispublicationat:https://www.researchgate.net/publication/7569039 EvaluationofEpizooticHaemorrhagicDisease VirusInfectioninSentinelCalvesfromtheSan JoaquinValleyofCalifornia ArticleinVeterinaryResearchCommunications·August2005 ImpactFactor:1.24·DOI:10.1007/s11259-005-1202-y·Source:PubMed CITATIONS READS 9 20 3authors,including: ImadeldinEAradaib BennieIrveOsburn UniversityofKhartoum UniversityofCalifornia,Davis 140PUBLICATIONS807CITATIONS 300PUBLICATIONS5,209CITATIONS SEEPROFILE Allin-textreferencesunderlinedinbluearelinkedtopublicationsonResearchGate, lettingyouaccessandreadthemimmediately. SEEPROFILE Availablefrom:ImadeldinEAradaib Retrievedon:24May2016 Veterinary Research Communications, 29 (2005) 447^451 # 2005 Springer. Printed in the Netherlands Short Communication Evaluation of Epizootic Haemorrhagic Disease Virus Infection in Sentinel Calves from the San Joaquin Valley of California I.E. Aradaib1, R.A. Mederos2 and B.I. Osburn2 1 Molecular Biology Laboratory (MBL), Department of Medicine, Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Khartoum, PO Box 32, Khartoum North, Sudan; 2Veterinary Teaching and Research Centre, Tulare and School of Veterinary Medicine, University of California, Davis, CA, USA *Correspondence: [email protected] Aradaib, I.E., Mederos, R.A. and Osburn, B.I., 2005. Evaluation of epizootic haemorrhagic disease virus infection in sentinel calves from the San Joaquin Valley of California. Veterinary Research Communications, 29(5), 447^451 Keywords: diagnostics, EHDV, epidemiology, RT-PCR Abbreviations: ds, double-stranded; EHDV, epizootic haemorrhagic disease virus; RT-PCR, reversetranscription polymerase chain reaction INTRODUCTION Epizootic haemorrhagic disease virus (EHDV), an arthropod-borne double-stranded (ds) RNA virus, is a member of the genus Orbivirus in the family Reoviridae (Borden et al., 1971). EHDV infects domestic, captive and free-ranging ruminants, of which the white-tailed deer (Odocoileus virginianus) is the most seriously a¡ected with the disease (Shope et al., 1960). EHDV serotypes 1 and 2 are recognized in the United States (Gorman, 1992). Because it is di¤cult to obtain more than one blood sample from the same wild animal under ¢eld conditions, routine surveillance of sentinel herds for virus infection and associated vector transmission of EHDV is the backbone of the epidemiological studies on EHDV in a particular geographical location. In the absence of clinical haemorrhagic disease, sentinel cattle herds provide the most e¡ective approach for monitoring animal health and obtaining EHDV isolates including recovery of new serotypes of EHDV from a particular location. The objectives of the present study were to determine the incidence of EHDV serotypes and their association with clinical haemorrhagic disease in sentinel cattle from the San Joaquin valley of California, and also to determine the interval after natural infection when EHDV could be detected in blood of infected calves, using conventional virus isolation and RT-PCR ampli¢cation technology. 447 448 MATERIALS AND METHODS A sentinel calf herd was maintained at the San Joaquin Valley of California. Eighteen calves of approximately 6^8 months of age were selected, ear-tagged, and housed as a group from March 1993 to February 1994. The animals were observed daily for signs of clinical haemorrhagic disease throughout the experimental period. The sentinel calves were fed a ration of concentrates and hay with free access to water. Processing of the blood samples for virus isolation (VI) was as described previously (Aradaib et al., 1995). The multiplex EHDV RT-PCR for simultaneous detection of EHDV serogroup and identi¢cation of EHDV-1 and EHDV-2 has been described previously (Aradaib et al., 1998). RESULTS AND DISCUSSION No signs of clinical haemorrhagic disease were observed in any of the sentinel calves. The incidence rate of EHDV in the sentinel calves as determined by virus isolation was found to be 3/18 (17%) (Table I). The incidence rate of EHDV infection as determined by RT-PCR was found to be 6/18 (34%) (Table II). EHDV infections were reported during late summer and early fall, which coincided with high activity of the insect vector, Culicoides imicola. The infection with EHDV-2 was found to be more prevalent than EHDV-1. TABLE I Results of virus isolation on BHK-21 cell line Months March April May June July August September October November December January February EHDV-1 EHDV-2 ^ ^ ^ ^ ^ ^ + ^ ^ ^ ^ ^ ^ ^ ^ ^ + ^ + ^ ^ ^ ^ ^ 449 TABLE II Results of serogroup^speci¢c EHDV and serotype^speci¢c EHDV-1 and EHDV-2 PCR-based detection assays Months March April May June July August September October November December January February EHDV serogroup EHDV-1 EHDV-2 ^ ^ ^ ^ + + ++ ++ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ + ^ ^ ^ ^ ^ ^ ^ ^ ^ + ^ + ++ ^ ^ ^ ^ Despite the extended nature of the study, only a few EHDV isolates were recovered. A lack of success in isolating EHDV from the blood samples of sentinel calves has been reported previously (Shope et al., 1960; Pearson et al., 1992; Aradaib et al., 1994, 1995). This could be attributed to viraemia being missed because of infrequent sampling. In experimentally infected calves, viraemia may be detected for 10^14 days post infection by conventional virus isolation, whereas PCR-based assay detected the viral nucleic acids for at least 28 days (Aradaib et al., 1994). In the present study, blood samples were collected from the sentinel calves on a monthly basis. More EHDV isolates could have been recovered if the animals had been bled at relatively shorter intervals. Even in the absence of clinical haemorrhagic disease, certi¢cation of animals free of EHDV infection by virus isolation or serology is necessary for import/export regulations (Pearson et al., 1992). Currently, only the rudiments of the epidemiology of the disease are known in domestic or wild ruminants. To advance beyond the current knowledge of the epidemiology of EHDV, we have evaluated EHDV infection in sentinel calves from the San Joaquin Valley, California. To our knowledge, this is the ¢rst time a sentinel cattle herd has been evaluated for EHDV infection in the United States. Infections of cattle with EHDV in local areas of endemicity are usually associated with indirect losses such as drop in milk production, loss of body weight and condition, and poor subsequent reproductive performance. (Mohammed et al., 1996). Nevertheless, a few reports have shown that the virus may also cause clinical haemorrhagic disease in North American cattle (Metcalf et al., 1991). 450 Application of these PCR-based detection assays for simultaneous serogroupspeci¢c detection and serotype-speci¢c identi¢cation of EHDV-1 and/ or EHDV-2 in blood samples from the sentinel calves provides a simple and rapid method for detection of EHDV infection, saves time and, above all, saved on cost. This is because the samples were tested once instead of individual testing against each individual serotype of EHDV serogroup. Since the EHDV PCR assays are extremely sensitive procedures, the point should be stressed that PCR-negative animals would more than ful¢l the present requirements for negative status for the purpose of export (Mohammed et al., 1996; Aradaib et al., 2003). It is worth mentioning that PCR-positive and culture-negative results, from the same clinical sample, are not uncommon. This is because virus isolation requires the presence of infectious virus, whereas PCR-positive results can be obtained from clinical samples containing incomplete virion or viral nucleic acid as well as intact infectious virus. The data presented in this communication indicate that EHDV-1 and EHDV-2 were being transmitted among sentinel calves in the San Joaquin valley of California as determined by virus isolation and RT-PCR technology. In addition, the infections were only transient and no clinical haemorrhagic disease was reported among the sentinel calves. Moreover, infected calves can amplify the virus and will provide infectious virus for insect transmission to more susceptible animals. The importance of virus isolationnegative calves, despite their PCR-positive status, in the epidemiology of the disease is yet to be investigated. REFERENCES Aradaib, I.E., Sawyer, M.M. and Osburn, B.I., 1994. Experimental epizootic hemorrhagic disease virus infection in calves: virologic and serologic studies. Journal of Veterinary Diagnostic Investigation, 6, 489^492. Aradaib, I.E., Akita, G.Y., Pearson, J.E. and Osburn, B.I., 1995. Comparison of polymerase chain reaction and virus isolation for detection of epizootic hemorrhagic disease virus in clinical samples from naturally infected deer. Journal of Veterinary Diagnostic Investigation, 7, 196^200 Aradaib, I.E., Ahmed, S., Ibrahim, K.E., Karrar, A.E., Cullor, J.S. and Osburn, B.I., 1998. A multiplex PCR for simultaneous detection and identi¢cation of United States serotypes of epizootic hemorrhagic disease virus. Sudan Journal of Veterinary Science and Animal Husbandry, 37, 1^12 Aradaib, I.E., Smith, W.E., Cullor, J.S. and Osburn, B.I., 2003. A multiplex PCR for Simultaneous detection and di¡erentiation of blue tongue and epizootic hemorrhagic disease viruses. Comparative Immunology, Microbiology and Infectious Diseases, 26, 77^87 Borden, E.C., Shope, R.E. and Murphy, F.A., 1971. Physicochemical and morphological relationships of some arthropod-borne viruses to bluetongue virus: a new taxonomic group: physicochemical and serological studies. Journal of General Virology, 3, 261^271 Gorman, B.M., 1992. An overview of the orbiviruses. In: T.E. Walton and B.I. Osburn (eds), Bluetongue, African Horse Sickness and Related Orbiviruses, (CRC Press, Boca Raton, FL), 335^347 Metcalf, H.E., Leduke, A.J. and Jochim, J.O., 1991. Epizootic hemorrhagic disease virus infection in cattle. In: T.E. Walton and B.I. Osburn (eds), Bluetongue, African Horse Sickness and Related Orbiviruses, (CRC Press, Boca Raton, FL), 222^237 Mohammed, M.E.H., Aradaib, I.E., Mukhtar, M.M, Oyijidi, A., Ghalib, H.W., Riemann, H.P. and Osburn, B.I., 1996. Application of molecular biological techniques for detection of epizootic hemorrhagic disease virus (EHDV-318) recovered from a sentinel calf in Central Sudan. Veterinary Microbiology, 52, 201^208 451 Pearson, J.E., Gustafson, G.A., Shafer, A.L. and Alstad, A.D., 1992. Diagnosis of bluetongue virus and epizootic hemorrhagic disease. In: T.E. Walton and B.I. Osburn (eds), Bluetongue, African Horse Sickness and Related Orbiviruses, (CRC Press, Boca Raton, FL), 533^546 Shope, R.E., MacNamara, L.G. and Mangold, R., 1960. A virus-induced epizootic hemorrhagic disease of the virginia white-tailed deer (Odocoileus virginianus). Journal of Experimental Medicine, 111, 155^170 (Accepted: 6 May 2004)