Bats in China found to carry novel herpesviruses, hinting at cross-species transmission dangers

By Dr. Chinta SidharthanReviewed by Susha Cheriyedath, M.Sc.May 13 2024

In a recent study published in the journal Scientific Reports, a team of researchers from Wuhan, China, found that various insectivorous bat species in central China were natural hosts or reservoirs of β- and γ-herpesviruses, with viruses from the Herpesviridae family showing host range restrictions, and phylogenetic analyses indicating previous cross-species transmissions.

Study: Novel betaherpesviruses and gammaherpesviruses in bats from central China. Image Credit: Binturong-tonoscarpe / Shutterstock

Background

Zoonotic diseases have always posed a serious threat to human health and the economy, given that the human immune system and global medical technology are often unprepared to launch a defense against these viruses that have crossed over from other animal species. The coronavirus disease 2019 (COVID-19) pandemic is a prime example of zoonotic diseases' toll on human lives and the global economy.

Factors such as roosting in large groups and widespread distribution often result in bats acting as reservoirs for various pathogens. Genetic similarities between bats and other mammalian species, such as humans and livestock, have resulted in the outbreak of various zoonotic viruses, such as severe acute respiratory syndrome coronavirus (SARS-CoV), Ebola viruses, lyssaviruses, and henipaviruses.

Herpesviruses

Viruses belonging to the Herpesviridae family have linear, double-stranded deoxyribonucleic acid (DNA) with genome sizes ranging from 124 to 295 kilobase pairs (kbp). These viruses have been found in many fauna, including mollusks, fishes, amphibians, reptiles, birds, and mammals. The mammalian herpesviruses are divided into three subfamilies, namely α-, β-, and γ-herpesviruses, and a wide range of human herpesviruses such as human cytomegalovirus,   Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, and human herpesviruses 6A, 6B, and 7 are known to cause infections with severe morbidity.

The current study

In the present study, the researchers collected various species of insectivorous bats from caves in various regions around Wuhan City in Hubei Province and used molecular methods to determine the presence of herpesviruses in these bats. The epidemiological characteristics of the detected herpesviruses were examined using phylogenetic methods.

The bats were initially identified based on morphology, and subsequently, the cytochrome b gene was amplified using polymerase chain reaction (PCR) and sequenced from the DNA extracted from these bats to confirm the species identification. Genomic DNA obtained from liver and intestinal tissue was also used to perform a nested PCR amplification targeting the DNA polymerase gene dpol in herpesviruses. Additionally, the glycoprotein B gene was used for further characterization of herpesviruses.

Basic Local Alignment Search Tool or BLAST, which is provided by the National Center for Biotechnology Information, was used to obtain the published sequences of herpesviruses that were most similar to the ones sequenced in the current study. The published sequences and the ones generated in the study were then used to construct phylogenetic trees to understand the relationships between the newly detected and previously identified herpesviruses. The cytochrome b sequences generated for the bat species were also used to construct a host phylogenetic tree to determine patterns of correlation between herpesviruses and their hosts.

Major findings

The study found four strains of the genus Betaherpesvirus and 18 Gammaherpesvirus strains in 22 out of the 140 individual bats collected for this study. Of the bat species, Rhinolophus pusillus or the lesser horseshoe bat had a 26.3% prevalence of herpesviruses, while the microbat species Myotis davidii had an 8.4% prevalence. The most commonly detected strain of γ-herpesviruses was the RP701 strain, which also had the highest similarity with the ruminant γ-herpesvirus. One of the other Gammaherpesvirus strains, MD704, showed the highest similarity with the hedgehog γ-herpesvirus.

The distribution range of M. davidii extends from central to northern regions of China, while R. pusillus is found in the Indomalayan region. Other studies have also detected the RP701 γ-herpesvirus strain from bats found in the southern regions of China, indicating that the RP701 is widely distributed and shares a common ancestor with the herpesvirus found in ruminants.

Additionally, the four β-herpesviruses were all identified from M. davidii and showed between 79% and 83% similarity with known β-herpesviruses. These β-herpesviruses also belonged to the same clade as the β-herpesviruses identified from other bats from the Vespertilionidae family, the same family as M. davidii. These findings suggest that not only might these novel β-herpesviruses have other hosts than M. davidii, but that the close contact between individuals of different Vespertilionidae species in the roosts could have facilitated the cross-species transfer of these β-herpesviruses.

Conclusions

To summarize, the study identified four new β-herpesvirus strains and 18 new γ-herpesvirus strains from 22 bats collected from regions around Wuhan City. Two of the prevalent strains show similarities with herpesviruses found in ruminants and hedgehogs, indicating the potential for transfer to other mammalian species and possible zoonotic disease outbreaks.

These findings highlight the need for constant surveillance of large bat populations and monitoring of the viral reservoirs in these hosts to ensure preparedness for potential zoonotic disease outbreaks.