Epidemiology and ecology of the sylvatic cycle of African Swine Fever Virus in Kenya.

African Swine Fever (ASF) is caused by a DNA virus (AFSV) maintained and transmitted by the Argasid ticks. The re-emergence of the disease in Africa coupled with its rapid spread globally is a threat to the pig industry, food security and livelihoods. The ecology and epidemiology of the ASFV sylvatic cycle, especially in the face of changing land use and land cover, further compounds the menace and impacts of this disease in Kenya. The study aimed to determine the occurrence and distribution of ASFV seroprevalence in warthog populations, the tick vectors and extent of tick infestation of warthog burrows, and the genotypes of ASFV in soft ticks in Kenya. Warthogs from different parts of Kenya were captured and venous blood was centrifuged to harvest sera. Warthog burrows were examined for their conditions and to extract ticks. Sera were analyzed for antibodies against ASFV using a commercial ELISA kit coated with p32 ASFV recombinant protein. Ticks were pooled, DNA extracted and the p72 gene of the ASFV was amplified by qPCR and conventional PCR. The overall seroprevalence of ASFV in warthogs was 87.5 %. A total of 228 warthog burrows were examined and 2154 argasid ticks were extracted from the burrows. Tick pools from Kigio Farm and Lewa Wildlife Conservancies were ASFV-positive by qPCR and conventional PCR. ASFV was further confirmed by the Twist Comprehensive Viral Research Panel (TCVRP), which also identified the argasid ticks as Ornithodoros porcinus. The ticks were infected with virus genotype IX, and their occurrence overlaps with regions of previous ASF outbreaks in domestic pigs. Further, Viruses that could be tick endosymbionts/commensals or due to bloodmeal were detected in ticks by TCVRP; Porcine type-C oncovirus; Pandoravirus neocaledonia; Choristoneura fumiferana granulovirus; Enterobacteria phage p7; Leporid herpesvirus 4 isolate; 5; Human Lymphotropic virus; Human herpesvirus 5. In conclusion, our results suggest that infected Ornithodoros spp. seems to have a rich virome, which has not been explored but could be exploited to inform ASF control in Kenya. Further, the ecology of Ornithodoros spp. and burrow-use dynamics are complex and more studies are needed to understand these dynamics, specifically in the spread of ASFV at the interface of wild and domestic pigs. Further, our results provide evidence of genotype IX ASFV sylvatic cycle which through O. porcinus tick transmission has resulted in high exposure of adult common warthogs. Finally, the co-circulation of ASFV genotype IX in the same location with past ASF outbreaks in domestic pigs and presently in ticks brings to focus the role of the interface and ticks on virus transmission to pigs and warthogs.

Hybrid capture-based next-generation sequencing of new and old world Orthohantavirus strains and wild-type Puumala isolates from humans and bank voles.

Orthohantaviruses, transmitted primarily by rodents, cause hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus pulmonary syndrome in the Americas. These viruses, with documented human-to-human transmission, exhibit a wide case-fatality rate, 0.5-40 %, depending on the virus species, and no vaccine or effective treatment for severe Orthohantavirus infections exists. In Europe, the Puumala virus (PUUV), carried by the bank vole Myodes glareolus, causes a milder form of HFRS. Despite the reliance on serology and PCR for diagnosis, the three genomic segments of Swedish wild-type PUUV have yet to be completely sequenced. We have developed a targeted hybrid-capture method aimed at comprehensive genomic sequencing of wild-type PUUV isolates and the identification of other Orthohantaviruses. Our custom-designed panel includes >11,200 probes covering the entire Orthohantavirus genus. Using this panel, we sequenced complete viral genomes from bank vole lung tissue, human plasma samples, and cell-cultured reference strains. Analysis revealed that Swedish PUUV isolates belong to the Northern Scandinavian lineage, with nucleotide diversity ranging from 2.8 % to 3.7 % among them. Notably, no significant genotypic differences were observed between the viral sequences from reservoirs and human cases except in the nonstructural protein. Despite the high endemicity of PUUV in Northern Sweden, these are the first complete Swedish wild-type PUUV genomes and substantially increase our understanding of PUUV evolution and epidemiology. The panel's sensitivity enables genomic sequencing of human samples with viral RNA levels reflecting the natural progression of infection and underscores our panel's diagnostic value, and could help to uncover novel Orthohantavirus transmission routes.

Hantavirus-specific IgA in saliva and viral antigen in the parotid gland in patients with hemorrhagic fever with renal syndrome.

The Hantavirus genus comprises rodent borne, zoonotic viruses of the Bunyaviridae family that cause hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus cardiopulmonary syndrome (HCPS) in the Americas. Rodent saliva contains infectious hantavirus and evidence suggests that hantavirus is also shed in human saliva, but person-to-person transmission is rare. In saliva, immunoglobulin (Ig) A is the predominant immunoglobulin class. Secretory IgA serves as an important first line of defence on epithelial surfaces and the binding of secretory IgA to pathogens can inhibit adherence of microorganisms to mucosal cells and neutralize viruses. This study investigated the presence and importance of salivary IgA in relation to viral antigen in the saliva by testing Puumala hantavirus (PUUV) specific IgA, and RNA in saliva in acutely ill patients with HFRS. In saliva samples, PUUV specific IgA was detected in 12 of 33 (36%) patients with HFRS and 20 (61%) were PUUV RNA positive. There was a statistically significant inverse association between the presence of salivary IgA antibodies and PUUV RNA in the saliva. PUUV-specific IgA in saliva was not found in a long-term follow-up, while PUUV IgA in serum was detected in three patients, 28-32 months after the initial study. Notably, both PUUV RNA and PUUV nucleocapsid antigen were detected in endothelial cells within the parotid gland of a deceased patient with HFRS.

Outbreak of Puumala virus infection, Sweden.

An unexpected and large outbreak of Puumala virus infection in Sweden resulted in 313 nephropathia epidemica patients/100,000 persons in Västerbotten County during 2007. An increase in the rodent population, milder weather, and less snow cover probably contributed to the outbreak.

Hantavirus RNA in saliva from patients with hemorrhagic fever with renal syndrome.

Hantaviruses cause 2 zoonotic diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome. Infection is usually initiated after inhalation of virus-contaminated rodent excreta. In addition to the zoonotic infection route, growing evidence suggests person-to-person transmission of Andes virus. For this reason, we studied whether saliva from HFRS patients contained hantavirus. During an outbreak in northern Sweden of nephropathia epidemica (NE), a milder form of hemorrhagic fever with renal syndrome, we collected saliva and plasma from 14 hospitalized NE patients with verified Puumala virus (PUUV) infection. PUUV RNA was detected in saliva from 10 patients (range 1,530-121,323 PUUV RNA copies/mL) by quantitative reverse transcription-PCR. The PUUV S-segment sequences from saliva and plasma of the same patients were identical. Our data show that hantavirus RNA could be detected in human saliva several days after onset of disease symptoms and raise the question whether interhuman transmission of hantavirus may occur through saliva.

Puumala hantavirus viremia diagnosed by real-time reverse transcriptase PCR using samples from patients with hemorrhagic fever and renal syndrome.

Puumala virus (PUUV) is the endemic hantavirus in northern Sweden and causes nephropathia epidemica (NE), a milder form of hemorrhagic fever with renal syndrome. There is a need for fast and reliable diagnostics to differentiate the disease from other infections. By aligning virus RNA sequences isolated from 11 different bank voles and one human patient, we designed a real-time reverse transcriptase (RT) PCR method for detection of PUUV RNA. The real-time RT-PCR assay showed linearity from 20 to 2 x 10(6) virus copies with a correlation coefficient above 0.98 to 0.99 for all experiments. The detection threshold for PUUV cDNA was two copies per reaction. A two-step qualitative RT-PCR to detect PUUV RNA showed 100% concordance with the real-time RT-PCR assay. PUUV RNA viremia was detected in 33 of 34 PUUV immunoglobulin M (IgM)-positive patients with typical clinical NE disease from the region of endemicity. One PUUV IgM-negative sample had PUUV RNA, and 4 days later, the patient was IgM positive. Of samples with indeterminate IgM, 43% were PUUV RNA positive. The kinetics of antibody titers and PUUV viremia were studied, and five of six NE patients displayed a decrease in PUUV viremia a few days after disease outbreak coupled with an increase in PUUV IgM and IgG. In one patient with continuously high PUUV RNA levels but low IgM and no IgG response, the infection was lethal. These findings demonstrated that real-time RT-PCR is a useful method for diagnosis of PUUV viremia and for detecting PUUV RNA at early time points, before the appearance of IgM antibodies.