Lassa virus in novel hosts: insights into the epidemiology of lassa virus infections in southern Nigeria

Identification of the diverse animal hosts responsible for spill-over events from animals to humans is crucial for comprehending the transmission patterns of emerging infectious diseases, which pose significant public health risks. To better characterize potential animal hosts of Lassa virus (LASV), we assessed domestic and non-domestic animals from 2021-2022 in four locations in southern Nigeria with reported cases of Lassa fever (LF). Birds, lizards, and domestic mammals (dogs, pigs, cattle and goats) were screened using RT-qPCR, and whole genome sequencing was performed for lineage identification on selected LASV positive samples. Animals were also screened for exposure to LASV by enzyme-linked immunosorbent assay (ELISA). Among these animals, lizards had the highest positivity rate by PCR. Genomic sequencing of samples in most infected animals showed sub-lineage 2 g of LASV. Seropositivity was highest among cattle and lowest in pigs. Though the specific impact these additional hosts may have in the broader virus-host context are still unknown - specifically relating to pathogen diversity, evolution, and transmission - the detection of LASV in non-rodent hosts living in proximity to confirmed human LF cases suggests their involvement during transmission as potential reservoirs. Additional epidemiological data comparing viral genomes from humans and animals, as well as those circulating within the environment will be critical in understanding LASV transmission dynamics and will ultimately guide the development of countermeasures for this zoonotic health threat.

Trypanosoma brucei-Induced apoptosis of leucocytes as a factor of trypanosusceptibility in infected goats

White blood cell apoptosis has been demonstrated and is suspected to contribute to the decrease in peripheral leukocyte count and the severity of the disease during acute T. brucei infection in rats. Thus, an investigation of blood and tissue leukocyte apoptosis during T. brucei infections in two natural hosts (Red Sokoto (RS) and West African dwarf (WAD) goats (12 per group)), with differing levels of trypanosusceptibility was conducted. Nine out of 12 animals in each breed group were infected intraperitoneally with 10⁴ parasites/mL and euthanized over time points. Blood and tissues were collected for detection and quantitation of apoptosis by three methods (DNA gel electrophoresis, light microscopy and transmission electron microscopy). T. brucei infected RS animals (trypanosusceptible) showed a significant increase in apoptosis of white blood cells (p=0.0092) and splenocytes (p=0.0239). The infected WAD animals (trypanotolerant) also showed a relatively lower but yet still significant (p=0.0022) increase in white blood cell apoptosis. Apart from the liver, significant increase (P<0.05) in tissue cell apoptosis was recorded in infected RS compared to non-infected controls. The mean white blood cell and splenocyte apoptosis was significantly higher (p=0.0072) in RS compared to WAD. In addition, the peak blood cell apoptosis tallied with peak parasitemia and anemia as well as with the lowest leukocyte count in RS animals. Our data support a relationship between peripheral and tissue white blood cell apoptosis and susceptibility to T. brucei infections. The molecular mechanisms mediating apoptosis of host cells during trypanosoma infections may reveal novel therapeutic or vaccine targets.