Transboundary Animal Diseases in Mediterranean Ecosystem with Emerging Interest in Libya

SUMMARY The thesis investigate the seroprevalence of four transboundary viral diseases of emerging interest in Libya, namely Pest des Petits Ruminants (PPR), Bluetongue (BT), Epizootic Hemorrhagic Disease (EHDV) and Rift Valley Fever (RVF). The purpose was to update the epidemiological situation of the aforementioned diseases in Libya and to study the risk factors associated with each disease. The study was carried out through a field investigation with sampling collection in Libya and a laboratory investigation in Italy at the National Reference Centre for foreign diseases of animals (CESME) in the Istituto Zooprofilattico Sperimentale dell’ Abruzzo e del Molise in Teramo. During 2015-2016 a total of 857 serum samples were collected from domestic ruminants (166 cattle, 556 sheep and 135 goats) distributed in 96 farms belonging to eleven provinces in five branches: Green Mountain and Benghazi in East Libya; Tripoli in North Libya; West Mountain in West Libya; Sabha in South Libya. Two branches were not included in this study: Zawiyha branch in West Libya and Middle Area branch in North Libya. The samples were analyzed by competitive enzyme linked immunosorbentassay (c-ELISA) to detect antibody against PPRV, BTV, EHDV and RVFV. Serum neutralization test (SNT) was also performed to detect specific antibody against recognized serotypes of BTV and EHDV. The results showed 41% (95% CL = 37% to 45%) of PPRV seroprevalence for small ruminants, and an overall seroprevalence of 4% (95% CL = 2,8% to 5,4% ) and 48.43% (95% CL = 45.02% to 51.83%) for EHDV and BTV respectively. None of the serum samples collected resulted positive to RVF, however, Statistical analysis was carried out to assess the maximum expected number of infected animals and the maximum expected prevalence of RFV among ruminant population by province and the expected seroprevalence in the different provinces was calculated and mapped. SNT for EHD detected a sheep positive for EHDV-6 serotype in the Gharyan province. SNT for BT detected antibody against six different serotypes, namely BTV-1, BTV-2, BTV-3, BTV-4, BTV-9 and BTV26. Two out of 6 (BTV-3 and BTV-26) resulted novel serotypes for the Mediterranean region. Some risk factors (animal age, species and sex) were statistically analyzed to explore their association with the seroprevalence. The results showed that the seroprevalence of PPR was significantly higher in adult animals 41% (95% CL = 37% to 46%) than in the young 24% (95% CL = 17% to 32%). The results of EHDV seroprevalence showed that only the independent variables of age group and farm species were statistically significant. BTV seroprevalence was higher in goats 58.33% (95% CI= 49.92% to 66.74%). The highest seroprevalence for BTV was reported in Sabha province, Southern region (75.61%). The results showed that the seroprevalence of BTV was significantly higher in adult animals 55.2% (95% CL = 50.6% to 59.6%). In mixed flocks seroprevalence was 79.3% (95% CL = 64.57 to 94.05%) and 53.73% (95% CL = 48.48% to 58.87%) for cattle/goats (CG) and sheep/goats (SG) respectively. Co-infection was reported with various serotypes, in particular with BTV-3 and BTV-26 increasing the risk of emergence of reassortant viruses

Rift Valley fever virus: a serological survey in Libyan ruminants

A serological survey was carried out in Libya to investigate the circulation of Rift Valley fever virus (RVFV) among domestic ruminants. A total of 857 serum samples were collected from year 2015 to 2016 in eleven provinces of Libya belonging to five branches of the country. Samples were tested for RVFV antibodies using a competitive Enzyme-Linked Immunosorbent Assay (c-ELISA). Antibodies specific for RVFV were not detected in any of the 857 samples. However, a statistical analysis was carried out to assess the maximum expected number of infected animals and the maximum expected prevalence of RVFV among Libyan ruminants’ populations according to the sampled population. The overall maximum expected prevalence was estimated to be 1.8% for cattle and 0.4% for small ruminants. Results seem to exclude the circulation of RVFV, however, a surveillance plan should be implemented in areas at risk of RVFV introduction