Genetic and evolutionary characterization of RABVs from China using the phosphoprotein gene

Hsp90 Activity Is Necessary for the Maturation of Rabies Virus Polymerase

Mononegavirales is an order of viruses with a genome in the form of a non-segmented negative-strand RNA that encodes several proteins. The functional polymerase complex of these viruses is composed of two proteins: a large protein (L) and a phosphoprotein (P). The replication of viruses from this order depends on Hsp90 chaperone activity. Previous studies have demonstrated that Hsp90 inhibition results in the degradation of mononegaviruses L protein, with exception of the rabies virus, for which the degradation of P protein was observed. Here, we demonstrated that Hsp90 inhibition does not affect the expression of rabies L and P proteins, but it inhibits binding of the P protein and L protein into functional viral polymerase. Rabies and the vesicular stomatitis virus, but not the measles virus, L proteins can be expressed independently of the presence of a P protein and in the presence of an Hsp90 inhibitor. Our results suggest that the interaction of L proteins with P proteins and Hsp90 in the process of polymerase maturation may be a process specific to particular viruses.

Molecular Epidemiology of Rabies in Wild Canidae in Tunisia

Rabies is a viral zoonosis that is transmissible to humans via domestic and wild animals. There are two epidemiological cycles for rabies, the urban and the sylvatic cycles. In an attempt to study the epidemiological role of wild canidae in rabies transmission, the present study aimed to analyze the genetic characteristics of virus isolates and confirm prior suggestions that rabies is maintained through a dog reservoir in Tunisia. Virus strains isolated from wild canidae were subject to viral sequencing, and Bayesian phylogenetic analysis was performed using Beast2 software. Essentially, the virus strains isolated from wild canidae belonged to the Africa-1 clade, which clearly diverges from fox-related strains. Our study also demonstrated that genetic characteristics of the virus isolates were not as distinct as could be expected if a wild reservoir had already existed. On the contrary, the geographic landscape is responsible for the genetic diversity of the virus. The landscape itself could have also acted as a natural barrier to the spread of the virus.

Ledantevirus: a proposed new genus in the Rhabdoviridae has a strong ecological association with bats

The Le Dantec serogroup of rhabdoviruses comprises Le Dantec virus from a human with encephalitis and Keuriliba virus from rodents, each isolated in Senegal. The Kern Canyon serogroup comprises a loosely connected set of rhabdoviruses many of which have been isolated from bats, including Kern Canyon virus from California, Nkolbisson virus from Cameroon, Central African Republic, and Cote d'Ivoire, Kolente virus from Guinea, Mount Elgon bat and Fikirini viruses from Kenya, and Oita virus from Japan. Fukuoka virus isolated from mosquitoes, midges, and cattle in Japan, Barur virus from a rodent in India and Nishimuro virus from pigs in Japan have also been linked genetically or serologically to this group. Here, we analyze the genome sequences and phylogenetic relationships of this set of viruses. We show that they form three subgroups within a monophyletic group, which we propose should constitute the new genus Ledantevirus.

Rabies and rabies virus in wildlife in mainland China, 1990-2013

The number of wildlife rabies and wildlife-associated human and livestock rabies cases has increased in recent years, particularly in the southeast and northeast regions of mainland China. To better understand wildlife rabies and its role in human and livestock rabies, we reviewed what is known about wildlife rabies from the 1990s to 2013 in mainland China. In addition, the genetic diversity and phylogeny of available wildlife-originated rabies viruses (RABVs) were analyzed. Several wildlife species carry rabies including the bat, Chinese ferret badger, raccoon dog, rat, fox, and wolf. RABVs have been isolated or detected in the bat, Chinese ferret badger, raccoon dog, Apodemus, deer, and vole. Among them, the bat, Chinese ferret badger, and raccoon dog may play a role in the ecology of lyssaviruses in mainland China. All wildlife-originated RABVs were found to belong to genotype 1 RABV except for a bat-originated Irkut virus isolated in 2012. Several substitutions were found between the glycoprotein of wildlife-originated RABVs and vaccine strains. Whether these substitutions could affect the efficacy of currently used vaccines against infections caused by these wildlife-originated RABVs needs to be investigated further. Phylogenetic analysis showed that RABVs in the bat, Chinese ferret badger, and raccoon dog were distinct from local dog-originated RABVs, and almost all collected wildlife-originated isolates were associated with older China clades II to V, suggesting the possibility of wildlife reservoirs in mainland China through the ages.

Human rabies surveillance and control in China, 2005-2012

Background

Rabies reemerged in China during the 1990s with a gradual increase in the number and geographical dispersion of cases. As a consequence, a national surveillance program was introduced in 2005 to investigate the outbreak in terms of vaccination coverage, PEP treatment, and geographical and social composition.

Methods

The surveillance program was coordinated at the national level by the Chinese Center for Disease Control (CCDC) with data collected by regional health centres and provincial CCDCs, and from other official sources. Various statistical and multivariate analysis techniques were then used to evaluate the role and significance of implemented policies and strategies related to rabies prevention and control over this period.

Results

From 2005–2012, 19,221 cases were reported across 30 provinces, but these primarily occurred in rural areas of southern and eastern China, and were predominantly associated with farmers, students and preschool children. In particular, detailed analysis of fatalities reported from 2010 to 2011 shows they were associated with very low rates of post exposure treatment compared to the cases with standard PEP. Nevertheless, regulation of post-exposure prophylaxis quality, together with improved management and vaccination of domesticated animals, has improved prevention and control of rabies.

Conclusions

The various control policies implemented by the government has played a key role in reducing rabies incidences in China. However, level of PEP treatment varies according to sex, age, degree and site of exposure, as well as the source of infection. Regulation of PEP quality together with improved management and vaccination of domesticated animals have also helped to improve prevention and control of rabies.

Molecular phylodynamic analysis indicates lineage displacement occurred in Chinese rabies epidemics between 1949 to 2010

Rabies remains a serious problem in China with three epidemics since 1949 and the country in the midst of the third epidemic. Significantly, the control of each outbreak has been followed by a rapid reemergence of the disease. In 2005, the government implemented a rabies national surveillance program that included the collection and screening of almost 8,000 samples. In this work, we analyzed a Chinese dataset comprising 320 glycoprotein sequences covering 23 provinces and eight species, spanning the second and third epidemics. Specifically, we investigated whether the three epidemics are associated with a single reemerging lineage or a different lineage was responsible for each epidemic. Consistent with previous results, phylogenetic analysis identified six lineages, China I to VI. Analysis of the geographical composition of these lineages revealed they are consistent with human case data and reflect the gradual emergence of China I in the third epidemic. Initially, China I was restricted to south China and China II was dominant. However, as the epidemic began to spread into new areas, China I began to emerge, whereas China II remained confined to south China. By the latter part of the surveillance period, almost all isolates were China I and contributions from the remaining lineages were minimal. The prevalence of China II in the early stages of the third epidemic and its established presence in wildlife suggests that it too replaced a previously dominant lineage during the second epidemic. This lineage replacement may be a consequence of control programs that were dominated by dog culling efforts as the primary control method in the first two epidemics. This had the effect of reducing dominant strains to levels comparable with other localized background stains. Our results indicate the importance of effective control strategies for long term control of the disease.

Since 1949, there have been three rabies epidemics in China. The country is currently in the midst of a third epidemic. After the first two epidemics were brought under control, there was a rapid reemergence of the disease. In 2005, the government implemented a national surveillance program and as part of this work, samples were collected from humans and animals and screened for rabies. Positive samples were sequenced and combined with other publicly available sequences to form a dataset that spanned almost all epidemic regions in China. A phylogenetic tree was constructed the clustering of isolates according to geographic origin and lineage was investigated. We found that most isolates were grouped into two lineages China I and China II. However, the proportion of isolates in these lineages changed over time until almost all new isolates were placed in China I, indicating it has emerged as the dominant lineage. Furthermore, the significantly higher number of China II isolates compared to remaining lineages together with its established presence in wildlife suggests that it was dominant in the second epidemic, suggesting that lineage replacement also occurred during the previous epidemic.