Ebola

Test code: S0059 - Ultrasensitive qualitative detection of Ebola virus by reverse transcription real time polymerase chain reaction

Viral hemorrhagic fever (VHF) is a clinical syndrome caused by a number of different viruses. These viruses include members of the Filoviridae family (Marburg virus [MBGV] and Ebola virus [EBOV]), Arenaviridae family (Lassa virus [LASV] and Junin, Machupo, Sabia, and Guanarito viruses), Bunyaviridae family (Crimean-Congo hemorrhagic fever virus [CCHFV], Rift Valley fever virus [RVFV], and Hanta viruses), and Flaviviridae family (yellow fever virus [YFV] and dengue virus [DENV]). The natural reservoirs of these viruses are arthropods, ticks, and rodents but the reservoir of filoviruses is not known.

Infections by these hemorrhagic viruses can result in a wide spectrum of clinical manifestations such as diarrhea, myalgia, cough, headache, pneumonia, encephalopathy, and hepatitis. Hemorrhage is the characteristic manifestation, although nonhemorrhagic infections are also common. The mortality rate of VHF infection is very high. Filoviruses, arenaviruses, and CCHFV are of particular relevance because they can be transmitted from human to human, thus causing epidemics with high mortality rates.

Among the VHF viruses, Ebola virus (EBOV) is of great concern as several outbreaks of this viral infection have been reported (Volchkov et al., 1997). This virus can cause severe hemorrhagic fevers in humans and nonhuman primates. Outbreaks such as the latest ones in the Democratic Republic of the Congo (MBGV) and Uganda (EBOV) are unpredictable and pose considerable public health concern to the affected as well as neighboring countries. In April 1996, laboratory testing of imported nonhuman primates (as mandated by quarantine regulations) identified 2 cynomolgus macaques (Macaca fascicularis) infected with Ebola (subtype Reston) virus in a US-registered quarantine facility (Rollin et al., 1999). The animals were part of a shipment of 100 nonhuman primates recently imported from the Philippines. Two additional infected animals, thought to be in the incubation phase, were also identified among the remaining 48 animals in the affected quarantine room.

The clinical syndrome of EBOV hemorrhagic fever is characterized by generalized fluid distribution problems, hypotension, coagulation disorders, variable degrees of hemorrhage, and widespread focal tissue destruction. Morphological studies on postmortem material indicate that mononuclear phagocytic cells are the primary targets for filovirus replication. There are two species of EBOV: the Zaire species shows the highest mortality in humans, whereas the Reston species may be apathogenic, based on very limited data.

In the absence of bleeding or organ manifestation, VHF is clinically difficult to diagnose, and the various etiologic agents of VHF can hardly be differentiated by clinical tests. The definitive diagnosis of a VHF relies mainly on laboratory testing and it is important to identify the causative viral agent to initiate the appropriate treatment and infection control procedures. Serological testing of EBOVs is not practical because patients usually die before developing antibodies, necessitating rapid virus detection. Detection of EBOVs using a molecular biology approach provides the best alternative for rapid diagnosis of EBOV.

Utilities:

• Confirm the disease causing agent
• Ensure that animal colonies are free of Ebola virus
• Early prevention of spread of the virus among a colony
• Minimize personnel exposure to the virus
• Safety monitoring of biological products and vaccines that derive from primates

References:
Leroy EM, Baize S, Lu CY, McCormick JB, Georges AJ, Georges-Courbot MC, Lansoud-Soukate J, Fisher-Hoch SP. (2000) Diagnosis of Ebola haemorrhagic fever by RT-PCR in an epidemic setting. J. Med. Virol. 2000 60:463-7.
Rollin, P.E., Williams, R.J., Bressler, D.S., Pearson, S., Cottingham, M., Pucak, G., Sanchez, A., Trappier, S.G., Peters, R.L., Greer, P.W., Zaki, S., Demarcus, T., Hendricks, K., Kelley, M., Simpson, D., Geisbert, T.W., Jahrling, P.B., Peters, C.J. and Ksiazek, T.G.(1999) Ebola (subtype Reston) virus among quarantined nonhuman primates recently imported from the Philippines to the United States. J. Infect. Dis.. 179 Suppl 1:S108-14.
Volchkov, V., Volchkova, V., Eckel, C., Klenk, H.D., Bouloy, M., LeGuenno, B. and Feldmann, H. (1997) Emergence of subtype Zaire Ebola virus in Gabon. Virology 232:139-44.

Specimen requirements: 1 ml whole blood in EDTA (purple top) or ACD (yellow top) tube, or 1 ml plasma or serum, shipped overnight at room temperature; or 1 ml frozen plasma or serum, shipped frozen.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative reverse transcription real time PCR

Normal range: Nondetected