Packaging of Rift Valley fever virus pseudoviruses and establishment of a neutralization assay method

Rift Valley fever (RVF) is an acute, febrile zoonotic disease that is caused by the RVF virus (RVFV). RVF is mainly prevalent on the Arabian Peninsula, the African continent, and several islands in the Indian Ocean near southeast Africa. RVFV has been classified by the World Organisation for Animal Health (OIE) as a category A pathogen. To avoid biological safety concerns associated with use of the pathogen in RVFV neutralization assays, the present study investigated and established an RVFV pseudovirus-based neutralization assay. This study used the human immunodeficiency virus (HIV) lentiviral packaging system and RVFV structural proteins to successfully construct RVFV pseudoviruses. Electron microscopy observation and western blotting indicated that the size, structure, and shape of the packaged pseudoviruses were notably similar to those of HIV lentiviral vectors. Infection inhibition assay results showed that an antibody against RVFV inhibited the infective ability of the RVFV pseudoviruses, and an antibody neutralization assay for RVFV detection was then established. This study has successfully established a neutralization assay based on RVFV pseudoviruses and demonstrated that this method can be used to effectively evaluate antibody neutralization.

Rift Valley fever among children and adolescents in Southwestern Saudi Arabia

Rift Valley fever [RVF] virus has expanded its geographical range, reaching Asia in 2000. This work investigated RVF seroprevalence among children born after the 2000-2001 outbreak in Saudi Arabia and compared it with the seroprevalence of adolescents born before the outbreak. In a seroepidemiological study in Southwestern Saudi Arabia [Jazan, Aseer, and Al-Qunfuda], a random sample of 389 children and adolescents was investigated. Data were collected regarding the subjects' sociodemographic status, housing conditions, and animal contact. Blood samples were collected and tested for RVF-specific IgG and IgM. None of the study samples were found to be seropositive for anti-RVF virus IgM. None of the study subjects aged 1-8 years [born after the outbreak] were positive for RVF-specific IgG. In contrast, 14 subjects [4.8%] aged 9-19 years [born before the outbreak] were positive for RVF-specific IgG. Among adolescents in our study, 4.9% were positive for anti-RVF IgG. This study showed that among adolescents, a history of contact with aborted animals [aOR = 13.361, 95% CI = 5.091-35.072] and transporting aborted animals [aOR = 18.861, 95% CI = 11.125-31.622] were significant risk factors. Despite the low virus activity recently reported among animals, neither clinically apparent RVF infections nor outbreaks among humans have been documented, indicating that the control measures taken by the Ministry of Agriculture and Ministry of Health are effective

rift valley fever: could re-emerge in Egypt again?

The Rift Valley fever [RVF] is a neglected, emerging, mosquito-borne disease with severe negative impact on human and animal health and economy. RVF is caused by RVF virus of the family of Bunyaviridae, genus Phlebovirus. RVF is an acute, febrile disease affecting humans and a wide range of animals. The virus is trans-mitted through the bites from mosquitoes and exposure to viremic blood, body fluids, or contact with tissues of infected animals or by inhaling natural virus aerosols, also possibly by consumption of infected unpasteurized milk. The RVF-virus replicate at the site introduction and in local lymphatic followed by viremia and spread to other organs as the liver and central nervous system, causing the hepatic necrosis and eosinophilia cytoplasmic degeneration. The main signs and symptoms are fever, headache, myalgia, arthralgia, photophobia, bradycardia, conjunctivitis and flushing face. Main complications include jaundice, hemorrhagic, meningoencephalitis and retinal lesions. Generally speaking, in the21[st] Century, the vector-borne infectious diseases, was accepted as the disaster issues with the considerable significant morbidity and mortality. These facts should be considered by the public health, veterinary and agricultural authorities

Rift valley fever in Saudi Arabia

A 40 year old Saudi man, a fire fighter by profession and resident in Najran, was diagnosed with Rift Valley fever on 28 April 2010. On 23 April, he presented with clinical signs of haemorrhagic fever to a health facility in Najran run by the Ministry of Health. He was hospitalized on the same day and his blood sample was sent to the Central Public Health Laboratory [Riyadh] and tested for various viral haemorrhagic fevers. The sample tested positive for Rift Valley Fever [RVF] on real time RT-PCR. Serological tests for Rift Valley fever virus IgM and IgG were negative. The patient recovered from his illness and was discharged from the hospital on 30 April 2010

An outbreak of rift valley fever in Sudan

During the period between 15 September 2007 till 15 January 2008, a total of 688 human cases of Rift Valley Fever [RVF] were reported from six states in the Sudan [White Nile, Gezira, Sinnar, Khartoum, River Nile and Kassala], including 222 deaths [CFR of 32.1%.]. Gezira State, which is known to have rich irrigation system and high mosquito density, reported more than 60% of cases. The outbreak was first reported from White Nile State, among semi-nomadic population then expanded to other states. In response to this outbreak, a joint team of Ministry of Health, Ministry of Animal Resources and Fisheries [MARF], WHO and FAO investigated the outbreak; appropriate preventive and control measures were instituted. Newly reported cases presented with ocular manifestation, a typical late-occurring feature of RVF infection. While active surveillance continues in all affected states, other than Gezira, no new cases have been reported since 5 January 2008

Domestic transmission of Rift Valley Fever virus in Diawara (Senegal) in 1998.

In 1998, circulation of the Rift Valley Fever (RVF) virus was revealed in Diawara by detection of IgM antibodies in sheep and isolation of the virus from mosquitoes caught outside a village. A seroprevalence study was carried out. Finger-prick blood samples, individual and collective details were obtained. One thousand five hundred twenty people (6 months - 83 years) were included. Overall prevalence in this group was approximately 5.2%. The prevalence in infants (6 months - 2 years) was 8.5%. Age, gender, contact with a pond, presence of sheep, and abortion among sheep, and individual or collective travel history were not statistically associated with prevalence. Prevalence increased significantly when the distance to a small ravine, located in the middle of the village, decreased. The results suggest a low, recent, not endemic circulation of the virus. Culex quinquefasciatus was captured near the ravine. This mosquito, similar to Culex pipiens, can play a similar role in human-to-human transmission of the RVF virus.

potential role of Rattus rattus in enzoonotic cycle of Rift Valley Fever in Egypt. 2 - Application of reverse transcriptase polymerase chain reaction [RT-PcR] in blood samples of Rattus rattus

A reverse transcriptase -polymerase chain reaction [RT-PCR] was applied to detect Rift Valley Fever Virus [RVF-V] in blood samples of Rattus rattus [R. rattus] collected from 3 different governorates of Egypt, Alexandria, Behira and Minia governorates [one hundred each]. Out of 300 blood samples 29 [9.67%] were positive for RVF-Virus by RT-PCR with higher percent in Behira governorate rural areas [16%], followed by Minia governorate rural areas [13.85%] while the lowest percent was in Alexandria governorate urban areas [0.00%]. The overall percent in rural areas were [13.5%] while it was only [2.0%] in urban areas. Our Study suggests that, this R.rattus play an important role in the maintenance cycle of RVF-V in rural areas of Egypt

Application of reverse transcriptase - polymerase chain reaction for detection of rift valley fever viral antigen from mosquito

A reverse transcriptase polymerase chain reaction [RT-PCR] was applied to detect rift valley fever virus [RVFV] in Culex pipiens mosquito pools collected from Alexandria and Behira governorates of Egypt [50 pools each]. All mosquito pools were subjected to double sandwich enzyme linked immunosorbent assay [ELISA] technique to detect RVF viral antigen. Out of all 100 mosquito pools, only 18 were positive by ELISA, 10 out of 50 pools were positive in Behira Governorate and 8 were positive in Alexandria Governorate. All positive samples [18], in addition to two negative samples [one was used as a negative control and the other was used as a positive control after the addition of 1.0 ml of 103 inactivated RVF virus] were subjected to RT-PCR. Out of these 18 positive samples by ELISA, only 7 were positive for RVF Virus by RT-PCR. These results gave the possibilities of the existence of other phleboviruses that cross react with RVF virus

Molecular epidemiology and emergence of Rift Valley fever

Rift Valley fever (RVF) is a mosquito-borne viral disease which manifested itself during recent epidemics and revealed its significant potential of emergence. Studies on molecular epidemiology undertaken to better understanding the factors leading to RVF emergence, have confirmed the mode of circulation of the virus and highlighted probable risks and obstacles for prevention and control. As for several other viral agents, molecular epidemiology is becoming a useful tool in the study of the emergence of RVF as a serious infectious disease.

Mutagenic effect of rift valley fever virus as measured by indication of chromosomal aberrations and formation of micronuclei in mice bone marrow cells

The mutagenic effect of Rift Valley fever [RVF] virus was tested in male mice bone marrow cells. Three virus titers were chosen [low [L], intermediate [IM] and high [H]]. These were 3, 300 and 3000 VP/dose, respectively. Mice were inoculated with each titer and samples were taken 24 and 48 hours later from bone marrow. An increase in chromosomal aberrations [structural and numerical] was observed in some treatments with RVF virus. The significant structural chromosomal aberrations are in the form of gape and centromeric attenuations, while the numerical aberration was endomitosis. All treatments showed a decrease in mitotic index [number of dividing nuclei per 300 cells], this decrease was highly significant. Although, the number of micronucleated PCE increased after inoculation with all treatments, the increase was below the significant level. Since there is no information available on the mutagenicity of RVF virus, more cytogenetic studies are suggested, the result of which could be compared with these results. This may throw some light on the mutagenic effect that could be produced by RVF virus

Antibodies to infectious bovine rhinotracheitis [IBR], rift valley fever [RVF] and bluetongue [BT] viruses in sheep sera

A total of 106 sheep sera were tested for the presence of neutralizing antibodies against IBR and RVF viruses and precipitating antibodies against BT virus. The results indicated that 13.2, 28.3 and 41.5% of the tested sera were seropositive to IBR, RVF and BT viruses, respectively