Rift Valley fever: current challenges and future prospects

Risk based serological survey of Rift Valley fever in Tunisia (2017-2018)

Rift Valley fever (RVF) has been reported in the sub-Saharan region of Africa, Egypt and Arabian Peninsula - Yemen and Saudi Arabia, over the past 20 years and is a threat to both the animal and human populations in Tunisia. Tunisia is considered as a high-risk country for the introduction of RVF due to the informal movements of diseased animals already reported in the neighboring countries. The objective of this study was to assess the status of RVF in small ruminants and camels in Tunisia. A risk-based serological survey was conducted to evaluate the presence of RVF based on spatial qualitative risk analysis (SQRA). Samples were collected from small ruminants (sheep and goats) (n = 1,114), and camels (n = 173) samples, belonging to 18 breeders in 14 governorates between November 2017 and January 2018. Samples were tested using an RVF specific multispecies competitive ELISA. Out of the 1,287 samples tested for the presence of RVF IgG antibodies by ELISA, only one positive sample 0.07% (1/1 287) was detected but not confirmed with the virus neutralization test (VNT) used for confirmation. So far, no RVF outbreaks have been reported in Tunisia and our study confirmed the absence of RVF in livestock up to January 2018. Further investigations are needed to confirm the RVF-free status of Tunisia today.

Chitosan and chitosan nanoparticles as adjuvant in local Rift Valley Fever inactivated vaccine

The present study aimed to improve the potency of inactivated Rift Valley Fever Virus (RVFV) vaccine using chitosan (CS) or chitosan nanoparticles (CNP) as adjuvants. Chitosan nanoparticles were prepared by ionic gelation method. Rift Valley Fever Virus (RVFV) inactivated antigen was loaded on CS and CNP to form two vaccine formulations, RVFV-chitosan nanoparticles based vaccine (RVFV-CNP) and RVFV chitosan based vaccine (RVFV-CS). Five groups of mice were used in this study, each group was injected with one of the following: phosphate buffer saline (group1 G1), RVFV-CNP (G2), (RVF-CS) (G3), RVFV-Alum based vaccine (RVFV-Alum) (G4) and adjuvant free RVFV inactivated antigen (RVFV-Ag) (G5). The immunization was performed twice with 2 weeks interval. The results showed that, RVFV-CNP vaccine enhanced strongly the phagocytic activity of peritoneal macrophage (PM), neutralization antibodies titer against RVFV and IgG values against RVFV nucleoprotein than other vaccine formulations did. In addition, the RVFV-CNP and RVF-CS vaccines upregulate the gene expression of IL-2, IFN-γ (which promote cell mediated immunity) and IL-4 (which promote humeral immunity), while RVFV-Alum vaccine upregulate the gene expression of IL-4 only. These findings indicated that CS and CNP were comparable to the alum as adjuvant in efficacy but superior to it in inducing cell-mediated immune response and might be a candidate adjuvant for inactivated RVFV vaccine.

Potential of Using Capripoxvirus Vectored Vaccines Against Arboviruses in Sheep, Goats, and Cattle

The genus capripoxvirus consists of sheeppox virus, goatpox virus, and lumpy skin disease virus, which affect sheep, goats, and cattle, respectively. Together capripoxviruses cause significant economic losses to the sheep, goat, and cattle industry where these diseases are present. These diseases have spread into previously free bordering regions most recently demonstrated with the spread of lumpy skin disease virus into the Middle East, some Eastern European countries, and Russia. This recent spread has highlighted the transboundary nature of these diseases. To control lumpy skin disease virus, live attenuated viral vaccines are used in endemic countries as well as in response to an outbreak. For sheeppox and goatpox, live attenuated viral vaccines are used in endemic countries; these diseases can also be contained through slaughter of infected animals to stamp out the disease. The thermostability, narrow host range, and ability of capripoxviruses to express a wide variety of antigens make capripoxviruses ideal vectors. The ability to immunize animals against multiple diseases simultaneously increases vaccination efficiency by decreasing the number of vaccinations required. Additionally, the use of capripoxvirus vectored vaccines allows the possibility of differentiating infected from vaccinated animals. Arboviruses such as bluetongue virus and Rift Valley fever viruses are also responsible for significant economic losses in endemic countries. In the case of Rift Valley fever virus, vaccination is not routinely practiced unless there is an outbreak making vaccination not as effective, therefore, incorporating Rift Valley fever vaccination into routine capripoxvirus vaccination would be highly beneficial. This review will discuss the potential of using capripoxvirus as a vector expressing protective arboviral antigens.

"We do not bury dead livestock like human beings": Community behaviors and risk of Rift Valley Fever virus infection in Baringo County, Kenya

Background

Rift Valley Fever (RVF), is a viral zoonotic disease transmitted by Aedes and Culex mosquitoes. In Kenya, its occurrence is associated with increased rains. In Baringo County, RVF was first reported in 2006–2007 resulting in 85 human cases and 5 human deaths, besides livestock losses and livelihood disruptions. This study sought to investigate the county’s current RVF risk status.

Methodology and principal findings

A cross-sectional study on the knowledge, attitudes and practices of RVF was conducted through a mixed methods approach utilizing a questionnaire survey (n = 560) and 26 focus group discussions (n = 231). Results indicate that study participants had little knowledge of RVF causes, its signs and symptoms and transmission mechanisms to humans and livestock. However, most of them indicated that a person could be infected with zoonotic diseases through consumption of meat (79.2%) and milk (73.7%) or contact with blood (40%) from sick animals. There was a statistically significant relationship between being male and milking sick animals, consumption of milk from sick animals, consuming raw or cooked blood, slaughtering sick livestock or dead animals for consumption (all at p≤0.001), and handling sick livestock with bare hands (p = 0.025) with more men than women engaging in the risky practices. Only a few respondents relied on trained personnel or local experts to inspect meat for safety of consumption every time they slaughtered an animal at home. Sick livestock were treated using conventional and herbal medicines often without consulting veterinary officers.

Conclusions

Communities in Baringo County engage in behaviour that may increase their risk to RVF infections during an outbreak. The authors recommend community education to improve their response during outbreaks.

The study focuses on the knowledge and socio-cultural practices around Rift Valley Fever (RVF) in Baringo County. It is intended to identify means through which communities in Baringo County could be exposed to RVF in the event of an outbreak. Specifically, it addresses knowledge of RVF transmission routes, practices in handling and consumption of meat, milk and blood; livestock disease management and disposal of dead animals/aborted foetuses. The study found that community members engaged in practices that would expose them to RVF in the event of an outbreak. These practices include milking and consuming milk from sick animals; consuming meat from slaughtered sick animals and those that die from disease; rarely having animals that were slaughtered at home inspected by a veterinary officer or a local animal expert before consumption; using uncertified techniques to test meat for safety of consumption; and treating sick livestock with both conventional and herbal treatments without the guidance of veterinary personnel. Further, RVF infections are likely to follow a gendered pattern based on the division of labor in livestock production. Based on their results, the study authors recommend community education to increase RVF awareness.