Establishing Galleria mellonella as an invertebrate model for the emerging multi-host pathogen Helcococcus ovis

Helcococcus ovis (H. ovis) can cause disease in a broad range of animal hosts, including humans, and has been described as an emerging bacterial pathogen in bovine metritis, mastitis, and endocarditis. In this study, we developed an infection model that showed H. ovis can proliferate in the hemolymph and induce dose-dependent mortality in the invertebrate model organism Galleria mellonella (G. mellonella). We applied the model and identified H. ovis isolates with attenuated virulence originating from the uterus of a healthy post-partum dairy cow (KG38) and hypervirulent isolates (KG37, KG106) originating from the uterus of cows with metritis. Medium virulence isolates were also isolated (KG36, KG104) from the uterus of cows with metritis. A major advantage of this model is that a clear differentiation in induced mortality between H. ovis isolates was detected in just 48 h, resulting in an effective infection model able to identify virulence differences between H. ovis isolates with a short turnaround time. Histopathology showed G. mellonella employs hemocyte-mediated immune responses to H. ovis infection, which are analogous to the innate immune response in cows. In summary, G. mellonella can be used as an invertebrate infection model for the emerging multi-host pathogen Helcococcus ovis.

A Tale of Two Flaviviruses: A Seroepidemiological Study of Dengue Virus and West Nile Virus Transmission in the Ouest and Sud-Est Departments of Haiti

Though plans to eliminate malaria from the island of Hispaniola have recently received much attention, arbovirus surveillance continues to be largely neglected in Haiti. To support surveillance efforts and encourage vector-control strategies, a cross-sectional study of dengue virus (DENV) and West Nile virus (WNV) transmission was conducted using standard seroepidemiological methods. Blood samples (N = 673) were collected from 278 males and 395 females from three locations in the Ouest and Sud-Est Departments of Haiti. Serum was separated and tested for the presence of anti-DENV and anti-WNV immunoglobulin G (IgG) antibodies using an indirect enzyme-linked immunosorbent assay (ELISA). Anti-DENV IgG antibodies were detected in 72.1% (95% confidence interval [CI] = 68.7, 75.5) of the sample population; with no significant differences in seroprevalence by study location, participant gender, or age group (P > 0.1, in all tests). Anti-WNV IgG antibodies were detected in only 1% (95% CI = 0.3, 1.8) of the sample population, all which originated from participants located in Gressier. The high prevalence of anti-DENV IgG antibodies among all age groups, including those in the youngest age group (2-5 years of age), suggests hyperendemic transmission of DENV in the Ouest and Sud-Est Departments of Haiti. In contrast, the relative absence of anti-WNV IgG antibodies, even among older population members, further supports the notion that WNV transmission in this population is largely absent. These findings highlight the large burden of disease from DENV and the need for enhanced arbovirus surveillance and implementation of vector control strategies throughout Haiti.