Angela M. Bosco-Lauth

Brucellosis is a significant public health challenge in Kenya, particularly in pastoralist communities where the disease is endemic. Reliable and accurate point-of-care diagnostics are essential for timely case identification and effective disease management. The Febrile Brucella Agglutination Test (FBAT) is commonly used for diagnosis of brucellosis in Kenya, but concerns have been noted about its diagnostic accuracy, prompting an independent evaluation. The aim of this study was to compare the diagnostic performance of five FBAT kits with a commercial Enzyme-Linked Immunosorbent Assay (ELISA) as the reference standard, and to build local laboratory capacity for in-house kit validation for the Kajiado County laboratory staff. A total of 200 serum samples (100 ELISA-confirmed positives and 100 negatives) were tested using the FBAT kits. Each kit was evaluated for its ability to detect antibodies to both B. abortus and B. melitensis antigens. Diagnostic performance indicators, including sensitivity, specificity, and Cohen’s Kappa, were calculated, and McNemar’s test was applied to assess concordance with the ELISA results. Overall, none of the FBAT kits proved to have acceptable sensitivity and specificity compared to ELISA. We conclude that FBAT kits are not sufficient for the diagnosis of brucellosis and that alternative diagnostics should be considered.

: Reports from endemic regions in Asia indicate that severe fever with thrombocytopenia syndrome virus (SFTSV), a canonically tick-borne virus, can be directly transmitted from infected humans and animals to naïve hosts. To understand this process, using a feline infection model, we observed that both intramuscular inoculation and oral inoculation resulted in adult cats developing viremia, with cats inoculated intramuscularly shedding virus orally. We also observed a potential organ tropism associated with the route of inoculation. Using an immunodeficient murine model, we further demonstrated that noncanonical routes of inoculation can result in lethal infections. However, we could not replicate the organ tropism seen in cats, possibly because of the immunodeficient nature of the mice. Like cats, mice shed SFSTV orally. These results indicate that SFTSV can exist in a vector-free cycle, highlighting a need for increased surveillance and precautions when handling potentially infected animals.

: West Nile virus (WNV), St. Louis encephalitis virus (SLEV), and Usutu virus (USUV) are zoonotic flaviviruses that cause neuroinvasive disease in humans and are maintained in overlapping avian-mosquito transmission cycles. West Nile virus and SLEV cocirculate in the United States, and WNV and USUV cocirculate in Europe. Cross-reactivity of immune responses against closely related flaviviruses is well documented. In birds, prior infection with WNV provides strong protection against SLEV genotype II and V infection, which may explain the decrease in SLEV circulation in the United States after WNV emergence in 1999. However, in 2015, a new SLEV genotype (III) emerged in the United States, suggesting that WNV immunity in birds may not provide cross-protection against this SLEV genotype. Here, we tested whether prior WNV infection protects birds against infection with SLEV genotype III, as well as USUV. First, we established a house sparrow (Passer domesticus) model of infection for SLEV genotype III. We then inoculated house sparrows with WNV and, 4 weeks later, challenged WNV-immune birds with SLEV genotype III or USUV. All birds were completely protected against secondary challenge, with no viremia detected. Low levels of cross-neutralizing antibodies against SLEV and USUV were found in the blood prior to secondary challenge. However, two naturally WNV-exposed house sparrows did develop SLEV genotype III and USUV viremia after inoculation. These results indicate that experimental WNV infection may protect birds against infection with SLEV genotype III and USUV; however, additional studies to investigate the role of avian immunity in flavivirus emergence are necessary.

Rabbit hemorrhagic disease virus 2 (RHDV2) emerged in the United States in 2018 and has spread in both domestic and wild rabbits nationwide. The virus has a high mortality rate and can spread rapidly once introduced in a rabbit population. Vaccination against RHDV2 provides the best protection against disease and should be considered by all rabbit owners. Here, we investigate the duration of immunity provided by vaccination with the Medgene Platform conditionally licensed commercial vaccine 6 months following the initial series. Rabbits received either the vaccination or a placebo and were challenged with RHDV2 6 months later. All vaccinated rabbits survived challenge whereas 18/19 non-vaccinated controls succumbed to infection within 10 or fewer days post-challenge. These results demonstrate lasting immunity following vaccination with the Medgene RHDV2 vaccine.

The magnitude and duration of vertebrate viremia are critical determinants of arbovirus transmission, geographic spread, and disease severity—yet, mechanisms determining arbovirus viremia levels are poorly defined. Previous studies have drawn associations between in vitro virion-glycosaminoglycan (GAG) interactions and in vivo clearance kinetics of virions from blood circulation. From these observations, it is commonly hypothesized that GAG-binding virions are rapidly removed from circulation due to ubiquitous expression of GAGs by vascular endothelial cells, thereby limiting viremia. Using an in vivo model for viremia, we compared the vascular clearance of low and enhanced GAG-binding viral variants of chikungunya, eastern- (EEEV), and Venezuelan- (VEEV) equine encephalitis viruses. We find GAG-binding virions are more quickly removed from circulation than their non-GAG-binding variant; however individual clearance kinetics vary between GAG-binding viruses, from swift (VEEV) to slow removal from circulation (EEEV). Remarkably, we find phagocytes are required for efficient vascular clearance of some enhanced GAG-binding virions. Moreover, transient depletion of vascular heparan sulfate impedes vascular clearance of only some GAG-binding viral variants and in a phagocyte-dependent manner, implying phagocytes can mediate vascular GAG-virion interactions. Finally, in direct contrast to mice, we find enhanced GAG-binding EEEV is resistant to vascular clearance in avian hosts, suggesting the existence of species-specificity in virion-GAG interactions. In summary, these data support a role for GAG-mediated clearance of some viral particles from the blood circulation, illuminate the potential of blood-contacting phagocytes as a site for GAG-virion binding, and suggest a role for species-specific GAG structures in arbovirus ecology.

Human-to-animal SARS-CoV-2 transmission was observed, including a veterinarian contracting COVID-19 through close contact with an infected cat, suggesting an atypical zoonotic transmission. This study investigated the prevalence of SARS-CoV-2 antibodies in cats during human outbreaks and elucidated the correlation between cat infections and human epidemics. A total of 1107 cat serum samples were collected and screened for SARS-CoV-2 antibodies using a modified indirect ELISA human SARS-CoV-2 antibody detection kit. The samples were confirmed using a cPass™ neutralization test. The SARS-CoV-2 seropositivity rate was 22.67% (199/878), mirroring the trend observed in concomitant human case numbers. The waves of the epidemic and the provinces did not significantly impact ELISA-positive cats. Notably, Chon Buri exhibited a strong positive correlation (r = 0.99, p = 0.009) between positive cat sera and reported human case numbers. Additionally, the cPass™ neutralization test revealed a 3.99% (35/878) seropositivity rate. There were significant differences in numbers and proportions of positive cat sera between epidemic waves. In Samut Sakhon, a positive correlation (r = 1, p = 0.042) was noted between the proportion of positive cat sera and human prevalence. The findings emphasize the need for ongoing surveillance to comprehend SARS-CoV-2 dynamics in both human and feline populations.

Rabbit hemorrhagic disease virus disease 2 (RHDV2) emerged in the United States in 2018 and has spread in both domestic and wild rabbits nationwide. The virus has a high mortality rate and can spread rapidly between infected individuals. Vaccination against RHDV2 provides the best protection against disease and should be considered by all rabbit owners. Here, we investigate the duration of immunity provided by vaccination with the Medgene Platform conditionally licensed commercial vaccine 6 months following the initial series. Rabbits received either the vaccination or a placebo and were challenged with RHDV2 6 months later. All vaccinated rabbits survived challenge whereas 18/19 non-vaccinated controls succumbed to infection within 10 or fewer days post-challenge. These results demonstrate lasting immunity following vaccination with the Medgene RHDV2 vaccine.

SARS-CoV-2 Infection of Elk and Mule Deer