West Nile virus (WNV) is an important zoonotic flavivirus responsible for mild fever to severe, lethal neuroinvasive disease in humans, horses, birds, and other wildlife species. Since its discovery, WNV has caused multiple human and animal disease outbreaks in all continents, except Antarctica. Infections are associated with economic losses, mainly due to the cost of treatment of infected patients, control programmes, and loss of animals and animal products. The pathogenesis of WNV has been extensively investigated in natural hosts as well as in several animal models, including rodents, lagomorphs, birds, and reptiles. However, most of the proposed pathogenesis hypotheses remain contentious, and much remains to be elucidated. At the same time, the unavailability of specific antiviral treatment or effective and safe vaccines contribute to the perpetuation of the disease and regular occurrence of outbreaks in both endemic and non-endemic areas. Moreover, globalisation and climate change are also important drivers of the emergence and re-emergence of the virus and disease. Here, we give an update of the pathobiology, epidemiology, diagnostics, control, and “One Health” implications of WNV infection and disease.

Virulent strains of West Nile virus (WNV) are highly neuro-invasive and human infection is potentially lethal. However, no vaccine is currently available for human use. Here, we report the immunogenicity and protective efficacy of a vaccine derived from a chimeric virus, which was constructed using the structural proteins (prM and E) of the Kunjin strain of WNV (WNV_KUN) and the genome backbone of the insect-specific flavivirus Binjari virus (BinJV). This chimeric virus (BinJ/WNV_KUN-prME) exhibits an insect-specific phenotype and does not replicate in vertebrate cells. Importantly, it authentically presents the prM-E proteins of WNV_KUN, which is antigenically very similar to other WNV strains and lineages. Therefore BinJ/WNV_KUN-prME represents an excellent candidate to assess as a vaccine against virulent WNV strains, including the highly pathogenic WNV_NY99. When CD1 mice were immunized with purified BinJ/WNV_KUN-prME, they developed robust neutralizing antibody responses after a single unadjuvanted dose of 1 to 5 μg. We further demonstrated complete protection against viremia and mortality after lethal challenge with WNV_NY99, with no clinical or subclinical pathology observed in vaccinated animals. These data suggest that BinJ/WNV_KUN-prME represents a safe and effective WNV vaccine candidate that warrants further investigation for use in humans or in veterinary applications.

A survey was undertaken to characterize the honey production value chain and identify the challenges, limitations, and opportunities for beekeepers in Kayonza District, Eastern Rwanda, in light of the stagnation of the apiculture industry. The majority (86%, n = 100) of the beekeepers were adult males. Most of the respondents (71%) lacked primary level education. The majority of the hives were made from hollow tree logs (40%), tree barks (12%), banana leaves/bark (11%), cow dung (8%), mud (7%), grass (6%), tree leaves (6%), and the rest (20%) were improved beehives, particularly Langstroth hives. The hive pests encountered were hive beetles (25%), small black ants (19%), wax moths (12%), lizards (8%), termites (7%), birds (6%), mites (3%), and mice (2%). Fifty-five percent of the respondents hung their hives on trees to prevent pest invasion with 95% effectiveness, 25% frequently smoked their hives with 85% effectiveness, 16% cleared the bushes around apiaries with 55% effectiveness, and 4% used traditional plant insect repellents with 35% effectiveness. Forty-one percent of the respondents lacked adequate information on beekeeping, 25% had inadequate time to work on apiaries, 24% had inadequate technical knowledge and implements, and 10% needed additional labour for managing apiaries. Based on the results of this study, beekeeping in Kayonza is still largely traditional, characterized by the use of antiquated production methods and underutilization of available marketing channels. Perceptions in the district are that beekeeping is for the poor and illiterate. Challenges and limitations of beekeeping in Kayonza District include lack of education, gender bias, pests and diseases, absconding and swarming of bees, high costs, and lack of modern apicultural equipment. However, the potential for developing beekeeping enterprise (opportunities) is immense given the abundance of wild bee populations, possibility of women participation, abundance of honey collection centres (market), and availability of technical support from Government and development agencies. In conclusion, this study advocates the need for intervention measures to educate and promote production and marketing of quality honey, tackle pest and disease for beekeepers and boost Rwanda’s apiculture industry.

West Nile virus, Kunjin strain (WNV_KUN) is endemic in Northern Australia, but rarely causes clinical disease in humans and horses. Recently, WNV_KUN genomic material was detected in cutaneous lesions of farmed saltwater crocodiles (Crocodylus porosus), but live virus could not be isolated, begging the question of the pathogenesis of these lesions. Crocodile hatchlings were experimentally infected with either 10⁵ (n = 10) or 10⁴ (n = 11) TCID₅₀-doses of WNV_KUN and each group co-housed with six uninfected hatchlings in a mosquito-free facility. Seven hatchlings were mock-infected and housed separately. Each crocodile was rotationally examined and blood-sampled every third day over a 3-week period. Eleven animals, including three crocodiles developing typical skin lesions, were culled and sampled 21 days post-infection (dpi). The remaining hatchlings were blood-sampled fortnightly until experimental endpoint 87 dpi. All hatchlings remained free of overt clinical disease, apart from skin lesions, throughout the experiment. Viremia was detected by qRT-PCR in infected animals during 2–17 dpi and in-contact animals 11–21 dpi, indicating horizontal mosquito-independent transmission. Detection of viral genome in tank-water as well as oral and cloacal swabs, collected on multiple days, suggests that shedding into pen-water and subsequent mucosal infection is the most likely route. All inoculated animals and some in-contact animals developed virus-neutralizing antibodies detectable from 17 dpi. Virus-neutralizing antibody titers continued to increase in exposed animals until the experimental endpoint, suggestive of persisting viral antigen. However, no viral antigen was detected by immunohistochemistry in any tissue sample, including from skin and intestine. While this study confirmed that infection of saltwater crocodiles with WNV_KUN was associated with the formation of skin lesions, we were unable to elucidate the pathogenesis of these lesions or the nidus of viral persistence. Our results nevertheless suggest that prevention of WNV_KUN infection and induction of skin lesions in farmed crocodiles may require management of both mosquito-borne and water-borne viral transmission in addition to vaccination strategies.

In 2022, a genotype IV (GIV) strain of Japanese encephalitis virus (JEV) caused an unprecedented and widespread outbreak of disease in pigs and humans in Australia. As no veterinary vaccines against JEV are approved in Australia and all current approved human and veterinary vaccines are derived from genotype (G) III JEV strains, we used the recently described insect-specific Binjari virus (BinJV) chimeric flavivirus vaccine technology to produce a JEV GIV vaccine candidate. Herein we describe the production of a chimeric virus displaying the structural prM and E proteins of a JEV GIV isolate obtained from a stillborn piglet (JEV_NSW/22) in the genomic backbone of BinJV (BinJ/JEV_NSW/22-prME). BinJ/JEV_NSW/22-prME was shown to be antigenically indistinguishable from the JEV_NSW/22 parental virus by K_D analysis and a panel of JEV-reactive monoclonal antibodies in ELISA. BinJ/JEV_NSW/22-prME replicated efficiently in C6/36 cells, reaching titres of >10⁷ infectious units/mL - an important attribute for vaccine manufacture. As expected, BinJ/JEV_NSW/22-prME failed to replicate in a variety of vertebrate cells lines. When used to immunise mice, the vaccine induced a potent virus neutralising response against JEV_NSW/22 and to GII and GIII JEV strains. The BinJ/JEV_NSW/22-prME vaccine provided complete protection against lethal challenge with JEV_NSW/22, whilst also providing partial protection against viraemia and disease for the related Murray Valley encephalitis virus. Our results demonstrate that BinJ/JEV_NSW/22-prME is a promising vaccine candidate against JEV.

Ingestion of indigestible foreign bodies in cattle is a pathological condition of both economic and health importance. It is has mostly been reported in association with feed scarcity. The aim of this study was to investigate the occurrence and nature of indigestible foreign materials in abattoir fore-stomach specimens in Ngoma district, Rwanda. Each chamber was opened by incision, then given a thorough macroscopic examination by visual inspection and palpation for the presence of foreign materials. The results show that there is an overall occurrence of 17.4% foreign bodies in cattle. The highest occurrence (25.3%) was recorded in June (the driest month). Results further show that the majority of the foreign bodies were plastics (65.0%). More foreign bodies (29.5%) were found in older animals (5 years and above) than in younger and middle-aged animals (16.5 % and 6.0%, respectively). There was a higher prevalence of foreign bodies in female cattle (20.0%) than in males (15.7%). The presence of cassette tape, as observed in the study, has not been reported elsewhere. The high representation of plastics in animals (65.5%) in the light of a government plastic bag ban in supermarkets presents a major challenge to livestock production in Rwanda. What is disturbing is that it is not known if this problem is increasing or decreasing as there are no previous studies for comparison. However, the results will serve as a reference point for future studies to understand the true trend and true burden of plastic bags in livestock.