Rabies Cases in the West of China Have Two Distinct Origins

Genetic characteristics and geographic distribution of rabies virus in China

China is one of the largest countries with endemic rabies. In this study, we examined the full-length genome sequences of 87 rabies virus (RABV) strains identified in China from 1931 to 2019. Chinese RABV isolates were divided into two major clades, GI and GII. Clade GI consisted of viruses from the Asian clade, which was further divided into three subclades: Asian1, Asian2, and Asian3. Clade GII consisted of viruses from the Cosmopolitan, Arctic-related, and Indian clades. A phylogeographic network showed that the variation of rabies virus was more closely associated with geographic location than with the host species. Recombination appears to be one of the factors driving the emergence of new viral strains.

A Descriptive Analysis of Human Rabies in Mainland China, 2005-2020

Epidemiological characteristics of human rabies in mainland China, 2005-2020 were analyzed to evaluate the effect of rabies control in China in recent years. A total of 24,319 human rabies cases were recorded in 2097 counties in 321 cities of 31 provinces in mainland China. Only 202 cases, located in 143 counties, were recorded in 2020, compared with 3305 cases in 992 counties in 2007; however, rabies was still relatively severe in Hunan Province even in 2020. Peak periods occurred in July-November; August was often the month with the most cases. Guizhou, Hunan, Guangdong, and Guangxi Provinces, in the central and southern regions, accounted for 50.0% of the cases in 2005-2020. Cases occurred almost exclusively in rural areas with 96.7% versus 3.3% in urban areas. A paradoxical relative expansion from southern, eastern, and central towards southwestern, northwestern, northern, and northeastern regions was observed along with the overall reduction of cases. Some regions witnessed complete elimination. The male-to-female ratio was 2.33:1; 66.8% of all cases were reported in the 0-10 (13.8%) and 41-70 (53.0%) age groups. Farmers (68.3%), followed by students (12.2), and diaspora children (6.5%) were most frequently involved. Our results provide objective information for the improvement of rabies prevention and control efforts. This will aid policymakers in China and elsewhere achieve the "Zero human deaths from dog-mediated rabies by 2030" global goal.

Knowledge, attitudes and practices regarding to rabies and its prevention and control among bite victims by suspected rabid animals in China

Rabies is a major public health problem and the incidence of suspected rabid animal bites remains high in China. This study aimed to assess the knowledge, attitudes, and practices (KAP) about rabies of bite victims in Wuhan, China. A cross-sectional study was conducted among 1015 bite victims visiting rabies prevention clinics. We performed a face-to-face interview to investigate the rabies KAP of these victims using a self-designed questionnaire. Factors associated with the KAP were evaluated using logistic regression models. Only 56.85% of respondents knew that rabies is infectious. More than 20% of respondents thought that it is not necessary to vaccinate dogs and cats against rabies usually. About 70% of participants stated that they never need to be reminded to vaccinate when they were bitten. Lower education level (odds ratio [OR] = 3.77, 95% confidence interval [CI]: 2.65-5.38 for secondary school or less and OR = 1.74, 95% CI: 1.28-2.38 for high school or vocational school, p-trend<0.0001) was independently associated with poor knowledge of rabies. Respondents who had experienced two or more times of animal bites (OR = 0.62, 95% CI: 0.39-0.97) were inclined to have appropriate attitudes about rabies prevention and control. Older respondents were more likely to show proper behaviors towards rabies prevention and control (OR = 0.44, 95% CI: 0.33-0.58 for age group 31-60 and OR = 0.34, 95% CI: 0.21-0.54 for age group >60, p-trend <0.0001). The level of rabies KAP among bite victims in China was suboptimal. It is necessary to conduct interventions focusing on improving public awareness of rabies and ameliorating behaviors of rabies post-exposure prophylaxis.

Molecular evolutionary analysis reveals Arctic-like rabies viruses evolved and dispersed independently in North and South Asia

Background

Arctic-like (AL) lineages of rabies viruses (RABVs) remains endemic in some Arctic and Asia countries. However, their evolutionary dynamics are largely unappreciated.

Objectives

We attempted to estimate the evolutionary history, geographic origin and spread of the Arctic-related RABVs.

Methods

Full length or partial sequences of the N and G genes were used to infer the evolutionary aspects of AL RABVs by Bayesian evolutionary analysis.

Results

The most recent common ancestor (tMRCA) of the current Arctic and AL RABVs emerged in the 1830s and evolved independently after diversification. Population demographic analysis indicated that the viruses experienced gradual growth followed by a sudden decrease in its population size from the mid-1980s to approximately 2000. Genetic flow patterns among the regions reveal a high geographic correlation in AL RABVs transmission. Discrete phylogeography suggests that the geographic origin of the AL RABVs was in east Russia in approximately the 1830s. The ancestral AL RABV then diversified and immigrated to the countries in Northeast Asia, while the viruses in South Asia were dispersed to the neighboring regions from India. The N and G genes of RABVs in both clades sustained high levels of purifying selection, and the positive selection sites were mainly found on the C-terminus of the G gene.

Conclusions

The current AL RABVs circulating in South and North Asia evolved and dispersed independently.

Neglected challenges in the control of animal rabies in China

Complex rabies transmission dynamics, including in dogs, wildlife livestock, and human-acquired rabies, can be observed in China. A temporary decrease in human rabies deaths with a simultaneous increase in animal rabies transmission is a typical example of "sectoral management separation" but not of the recommended "one-health" concept. In contrast to reliance on mass dog vaccination, reliance on postexposure prophylaxis to reduce human rabies burden is costly and ineffective in the prevention of rabies transmission from dogs to humans and other susceptible animal species. To answer the WHO call for the "elimination of dog-mediated human rabies by 2030," China faces the challenge of a lack of a strong political commitment and a workable plan and must act now before the rabies transmission dynamics become increasingly complicated by spreading to other species, such as ferret badgers in the Southeast and raccoon dogs and foxes in the North.

Animal Rabies Surveillance, China, 2004-2018

Rabies is a severe zoonotic disease in China, but the circulation and distribution of rabies virus (RABV) within animal reservoirs is not well understood. We report the results of 15 years of surveillance of the first Chinese Rabies Surveillance Plan in animal populations, in which animal brain tissues collected during 2004–2018 were tested for RABV and phylogenetic and spatial–temporal evolutionary analyses performed using obtained RABV sequences. The results have provided the most comprehensive dataset to date on the infected animal species, geographic distribution, transmission sources, and genetic diversity of RABVs in China. In particular, the transboundary transmission of emerging RABV subclades between China and neighboring countries was confirmed. The study highlights the importance of continuous animal rabies surveillance in monitoring the transmission dynamics, and provides updated information for improving current control and prevention strategies at the source.

Human rabies in China: evidence-based suggestions for improved case detection and data gathering

Background

China still suffers heavily from rabies, although reported human cases continue to decrease year over year. There are far fewer laboratory-confirmed human cases than clinically diagnosed cases, which is a big problem that needs to be addressed. In this report, we summarize analyses of all specimens from human cases tested in our laboratory over the past 15 years, in order to promote laboratory diagnosis of rabies.

Methods

From 2005 to 2019, a total of 271 samples from 164 suspected rabies cases were collected from local hospitals by the local Centers for Disease Control and Prevention (CDCs) in China. Saliva, cerebrospinal fluid (CSF), serum (blood) and urine were collected for ante-mortem diagnosis, and brain tissue, neck skin tissue and cornea were collected for post-mortem diagnosis. All of the specimens were tested by reverse transcription-polymerase chain reaction (RT-PCR), and brain tissues were also tested using fluorescent antibody test (FAT). The number of positive test results obtained using different fluids or tissues, and at different stages of the disease, were compared using a chi-square test and a more effective sampling program is recommended.

Results

As the national reference laboratory for rabies surveillance in China, our laboratory has tested 271 samples from 164 suspected rabies cases collected by local CDCs since 2005. We found that saliva gave the highest number of positive test results (32%), compared with CSF and other fluids. We also found that serum or blood specimens collected in the last 3 days of life can test positive by RT-PCR.

Conclusions

Serum or blood samples collected in the last 3 days of a patient’s life can be used to measure viral RNA, which means that serum samples, as well as saliva and CSF, can be used to detect viral RNA for anti-mortem diagnosis of rabies. Because of our findings, we have modified our “National Surveillance Project for Human Rabies”, by adding the collection and testing of serum samples from the end of the survival period. This will improve our national surveillance and laboratory diagnosis of human rabies.

Fox rabies outbreaks in the republic of Buryatia: Connections with neighbouring areas of Russia, Mongolia and China

The Republic of Buryatia (RB) is located southeast of Lake Baikal and shares a long border with Mongolia. This region of Russia was rabies-free from 1982 to 2010. The first outbreak of fox rabies in RB was identified in 2011, about 30 km from the Russian-Mongolian border. We assessed the possible pathways to further spread the 'steppe' phylogenetic lineage of the rabies virus near the northeastern limits of its known distribution. All rabies cases were located 30-210 km north of the Russia-Mongolia border, with a distance of up to 320 km from each other. Rabies has spread to the north across steppe landscapes and river valleys, with foxes being the main natural hosts of the infection. All RABV isolates from RB belong to the 'steppe' phylogenetic lineage, and three major phylogenic groups could be separated. Group 1 contains sequences from RB, Mongolia, China (Inner Mongolia), and bordering regions of Russia. Group 2 is formed by isolates from other regions of Eastern Siberia, which have no borders with RB and foreign countries. Group 3 contains samples from Western Siberia with endemic fox rabies since the 1950s. The most probable cause of fox rabies epizooty in the RB was multiple drift of the RABV across the Russian-Mongolian border. Our data show that after 2010, fox rabies affected new areas in Central Asia and extended to the north and northeast. Affected areas are similar to the Mongolian-type steppes in their zoogeographical aspect. Closely related genetic lineages of RABV are circulating in RB, Mongolia and the nearest areas of China. International cooperation is necessary to prevent the spread of rabies in the bordering territories of these countries.

Echinococcosis transmission on the Tibetan Plateau

Since the mid-1990s detailed studies and field investigations on the Tibetan Plateau have revealed human echinococcosis to be an under-reported major public health problem, particularly in the dominant pastoral communities in the eastern and central regions. Human prevalence surveys showed that cystic echinococcosis (CE, caused by Echinococcus granulosus) and alveolar echinococcosis (AE, caused by Echinococcus multilocularis) are co-endemic with higher burdens of each disease than other endemic world regions. Epidemiological investigations identified some major risk factors for human CE and AE including dog ownership, husbandry practices and landscape features. Dogs appear to be the major zoonotic reservoir for both E. granulosus and E. multilocularis, but the latter is also transmitted in complex wildlife cycles. Small mammal assemblages especially of vole and pika species thrive on the Plateau and contribute to patterns of E. multilocularis transmission which are influenced by landscape characteristics and anthropogenic factors. Tibetan foxes are a principal definitive host for both E. multilocularis and E. shiquicus. In 2006 a national echinococcosis control programme was initiated in Tibetan communities in northwest Sichuan Province and rolled out to all of western China by 2010, and included improved surveillance (and treatment access) of human disease and regular deworming of dogs with annual copro-testing. Control of echinococcosis in Tibetan pastoral communities poses a difficult challenge for delivery and sustainability.

The reemergence of human rabies and emergence of an Indian subcontinent lineage in Tibet, China

Coordinated surveillance, vaccination and public information efforts have brought the Chinese rabies epizootic under control, but significant numbers of fatalities are still reported annually with some cases occurring in previously rabies free regions. Tibet has remained virtually rabies free for 16 years, but since 2015 one human rabies case has been reported each year. To better understand the origins of these cases, we sequenced three human samples and an additional sample isolated from a dog in 2012. Three genomes were sequenced from brain samples: human case 1 (reported in 2015), human case 3 (2017), and the 2012 dog case. For human case 2 (2016), the rabies N gene was sequenced from a limited saliva sample. Phylogenetic analysis shows that Case 1 (CXZ1501H) and the dog case (CXZ1201D) belong to China IV lineage (equivalent to Arctic-like-2 in global rabies), suggesting an association with a wildlife spillover event. However, Case 2 (CXZ1601H) is placed within the dominant lineage China I, and was most similar with recent strains from neighboring Yunnan province, indicating the current epizootic has finally reached Tibet. Most surprisingly however, was the finding that Case 3 (CXZ1704H) is distinct from other Chinese isolates. This isolate is placed in the Indian Subcontinent clade, similar to recent Nepal strains, indicating that cross-border transmission is a new source for rabies infections. Thus, the complex mixture of the rabies epizootic in Tibet represents a major new challenge for Tibet and national rabies control.

Inner Mongolia: A Potential Portal for the Spread of Rabies to Western China

In recent years, the number of human rabies cases in China has decreased annually. However, some western provinces with no human cases for more than 10 years have begun to report rabies cases, and all of the rabies lineages that circulated in western China were found in Inner Mongolia as well. In this study, we generated a phylogenetic tree with all the Inner Mongolia rabies strains available in GenBank and our laboratory, as well as strains from western China and representative viruses from neighboring countries, based on the N gene sequence. Furthermore, the possible relationships underlying the spread of the virus within Inner Mongolia and neighboring regions were analyzed. Three of six rabies lineages of China (China I-VI) were shown to exist in Inner Mongolia, and a spatial cluster analysis supported that the China I lineage, the dominant cluster of China, likely spread to Ningxia from Inner Mongolia. Wild raccoon dog rabies (China IV/Arctic-like-2) may have spread to Inner Mongolia from Russia and likely continued to spread to Qinghai and Tibet. The red fox lineage (China III/Cosmopolitan), which likely spread from Russia and Mongolia, has been shown to circulate in Inner Mongolia and was a serious threat to Xinjiang, which is adjacent to Inner Mongolia. Thus, Inner Mongolia likely became a location where national and international rabies viruses collected and developed into a potential portal for the spread of rabies to western China. To effectively control the spread of rabies in China, both prevention and control of dog and wild animal rabies in Inner Mongolia should be a top priority.

Rabies Outbreaks and Vaccination in Domestic Camels and Cattle in Northwest China

In contrast to many countries where rabies has been well controlled in humans and livestock, even in wildlife, rabies is still endemic in almost regions of China. In Northwest China, rabies transmitted by stray dogs and wild foxes has caused heavy economic losses to local herdsmen, as well as causing numbers of human cases. In this study, as part of an investigation of ways to prevent rabies epidemics in livestock, we report an analysis of domestic cattle and camel rabies cases in Ningxia Hui (NHAR) and Inner Mongolia Autonomous Region (IMAR) and the immune efficacy of canine inactivated rabies vaccines in these animals. We found that rabies viruses from these animals are closely related to dog-hosted China I and fox-associated China III lineages, respectively, indicating that the infections originated from two different sources (dogs and wild foxes). As well as the previously reported Arctic and Arctic-related China IV lineage in IMAR, at least three separate phylogenetic groups of rabies virus consistently exist and spread throughout Northwest China. Since there is no licensed oral vaccine for wild foxes and no inactivated vaccine for large livestock, local canine inactivated vaccine products were used for emergency immunization of beef and milk cattle and bactrian (two-humped) camels in local farms. Compared with a single injection with one (low-efficacy) or three doses (high-cost), a single injection of a double dose of canine vaccine provided low-price and convenience for local veterinarians while inducing levels of virus neutralizing antibodies indicative of protection against rabies for at least 1 year in the cattle and camels. However, licensed vaccines for wildlife and large domestic animals are still needed in China.

Rabies virus continues to cross carnivorous species and to infect humans and livestock in China. Rabies vaccination of the principal reservoir animals is even now being neglected in most regions of China, resulting in continuous expansion of rabies epidemics. Since there is no oral vaccine for stray dogs and wild animals and no inactivated vaccine for large domestic animals, rabies is not currently controlled in this country. We report rabies outbreaks caused by bites of dogs and wild foxes and the long-term effects on protection against rabies using canine inactivated vaccines in domestic camels and cattle. Our results indicate that at least three separate phylogenetic groups of rabies virus consistently exist and spread throughout Northwest China. Local canine vaccine products can be used to induce levels of virus neutralizing antibodies indicative of protection against rabies in cattle and camels; however, licensed oral and inactivated vaccines for reservoir carnivores and large domestic animals are urgently needed for elimination of rabies in China.