ABSTRACT
BACKGROUND: Bluetongue (BT) is a vector-borne viral disease of ruminant and camelid species which is transmitted by Culicoides spp. The causative agent of BT is bluetongue virus (BTV) that belongs to genus Orbivirus of the family Reoviridae. The clinical disease is seen mainly in sheep but mostly sub-clinical infections of BT are seen in cattle, goats and camelids. The clinical reaction of camels to infection is usually not apparent. The disease is notifiable to the World Organization for Animal Health (OIE), causing great economic losses due to decreased trade and high mortality and morbidity rates associated with bluetongue outbreaks. The objective of this study was to investigate the seroprevalence of BTV in camels in Kassala State, Eastern Sudan and to identify the potential risk factors associated with the infection. A cross sectional study using a structured questionnaire survey was conducted during 2015-2016. A total of 210 serum samples were collected randomly from camels from 8 localities of Kassala State. The serum samples were screened for the presence of BTV specific immunoglobulin (IgG) antibodies using a competitive enzyme-linked immunosorbent assay (cELISA). RESULTS: Seropositivity to BTV IgG was detected in 165 of 210 camels' sera accounting for a prevalence of 78.6%. Potential risk factors to BTV infection were associated with sex (OR = 0.061, p-value = 0.001) and seasonal river as water source for drinking (OR = 32.257, p-value = 0.0108). CONCLUSIONS: Sex and seasonal river as water source for drinking were considered as potential risk factors for seropositivity to BTV in camels. The high prevalence of BTV in camels in Kassala State, Eastern Sudan, necessitates further epidemiological studies of BTV infection in camels and other ruminant species to better be able to control BT disease in this region.
ABSTRACT
Bluetongue (BT) is an infectious, noncontagious, vector-borne viral disease of wild and domestic ruminants. BTV is a member of the Orbivirus genus of the family Reoviridae. The present study aimed to investigate the seroprevalence of BTV in sheep and goats in Kassala State, Sudan. It also aimed to determine risk factors associated with BTV infection. The study was carried out by a structured questionnaire survey, and a total of 809 serum samples were collected from sheep (n = 459) and goats (n = 350) from 9 different localities in Kassala state. These samples were analyzed using a competitive enzyme-linked immunosorbent assay (cELISA) for the detection of BTV antibodies. The overall seroprevalence of BTV was 91.2% (738/809). In goats, the prevalence of BTV antibodies was comparatively higher (100%) than in sheep (84.5%). The prevalence differed between localities and was the highest in the center section of Kassala and Western Kassala (100%). Animals aged 6-11 months were highly infected (93.9%) compared to 1-year-old (85.5%). Caprine species was more likely to be infected (100%) than ovine (84.5%), and females were highly infected (92.8%) than males (85.5%). BTV infections were higher in the winter season (91.4%). Risk factors that showed significant associations with cELISA positivity included locality and sex (p ≤ 0.003) and species and age (p ≤ 0.000). Factors significantly associated with cELISA positivity in multivariate analysis were localities, species, age, and sex. BTV infection is prevalent in sheep and goat populations in Kassala state.
ABSTRACT
The diagnostic potential of RT-PCR for detection of bluetongue virus (BTV) ribonucleic acid (RNA) sequence in cell culture and tissue samples from infected ruminants from United States, Sudan, South Africa and Senegal, was evaluated. The non structural protein 1 (NS1) gene of North American BTV serotype 11 was targeted for PCR amplification. The United States BTV serotypes 2, 10, 11, 13 and 17 and the Sudanese BTV serotypes 1, 2, 4 and 16 and BTV serotype 4 from South Africa and BTV serotype 2 from Senegal were studied. RNAs from all BTV field isolates used in this study, propagated in cell cultures, were detected by the described RT-PCR-based assay. The first specific 790bp BTV PCR products were amplified using a pair of outer primers (BTV1 and BTV2). Specificity of the PCR products was confirmed by a nested amplification of a 520bp PCR product using a pair of internal (nested) primers (BTV3 and BTV4). The BTV PCR products were visualized on ethidium bromide-stained agarose gels. Amplification products were not detected when the RT-PCR-based assay was applied to RNAs from closely related orbiviruses including, epizootic hemorrhagic disease virus (EHDV) prototypes serotypes 1, 2, 4; RNA from Sudanese isolate of palyam orbiviruses serogroup and total nucleic acid extracts from uninfected Vero cells. Application of the nested BTV RT-PCR to clinical samples resulted in amplification of BTV RNA from blood and serum samples from goats experimentally infected with BTV4 and from naturally infected sheep, goats, cattle and deer. The results of this study indicated that this RT-PCR assay could be applied for rapid detection of BTV, in cell culture and clinical samples from susceptible ruminants during an outbreak of the disease, in the United States and African.
