National Reference Laboratory for Rift Valley fever virus
Institute for Novel and Emerging Infectious Diseases
Martin H. Groschup, Martin Eiden
Rift Valley fever virus (RVFV), a bunyavirus of the genus phlebovirus that only occurs in a single serotype, has only been detected in Africa and on the Arabian Peninsula to date. The virus is transmitted either directly by mosquito bites (mostly Aedes and Culex spp.), or indirectly through contact with infectious material and an infection causes peracute or acute zoonotic diseases. Certain climatic conditions increase the breeding of the vector, resulting in a higher infection rate with the Rift Valley fever virus. Typical clinical signs are a hemorrhagic fever and a massive liver damage. Sheep, goats and cattle are especially affected by the disease with a high mortality rate in newborns and high abortion rates in pregnant animals. Older, nonpregnant animals are also susceptible to an infection, but more resistant to clinical disease. Breeds or strains from non-endemic areas or breeds that are exotic to Africa seem to have a higher susceptibility to an infection with RVFV. The abortion rate in camels is as high as in cattle, but most infections are clinically inapparent.
Humans can be infected by contact to virus-contaminated material or by mosquito bites. In countries or areas with a relatively small population of animal hosts there is a high probability of a human infection by the vectors. In such areas, the occurrence of RVFV may first be detected in humans. Infections with RVFV have already caused severe disease in laboratory workers with hepatitis, meningitis und fever. A vaccination of laboratory staff is therefore highly recommended.
At the national reference laboratory for Rift Valley fever virus, several diagnostic methods have been established so that any suspect samples can be anaysed. These methods include a real-time RT-PCR for the nucleic acid detection. Therefore, the two published protocols for the detection of the M segment (Drosten et al., 2002) or the S segment (Bird et al., 2007) were established and validated against some available control sera. In parallel, different commercially available ELISA tests were purchased. These tests can be used for the detection of IgM or IgG antibodies or for the detection of antigen in sera of suspect animals. The establishment and validation of these tests will be done in due time. Aiming at a profound quality control of these methods, cooperations with different institutes in Africa (Tanzania, Senegal, South Africa, Ethiopia) have been initiated which will of course also include scientific cooperations.
In 2009 no diagnostic material has been analysed at the national reference laboratory.