Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

Viruses in New Zealand bats

Bats are important supernatural and cultural icons around the world. They are also known to harbour diseases capable of infecting humans. Rabies is probably the most widely known such disease, but bats may have also played host to SARS (a coronavirus), ebola virus and other viral hemorrhagic diseases.

The fearsome reputation of these creatures for transmission of disease may be due to facets of their biology, but as they also comprise nearly 20% of all mammal species, the chances are, some will be reservoirs of diseases that affect humans. Bats have also received a great deal of attention in recent times because researchers are interested in predicting where new animal reservoirs of disease may exist. It is hoped that such studies may predict, or even prevent, the emergence of future catastrophic pandemic diseases.

Studies of bat disease not only look to see what viruses may pose a risk to humans, but also to the bats themselves. Many bat species are threatened and have special conservation status, which is the case for New Zealand bats. New Zealand has only three terrestrial native mammals, and all three are bats. One species is recently extinct, but the other two species are widely distributed around New Zealand, albeit in small, concentrated populations; they are the long-tailed bat (Chalinolobus tuberculatus), and the lesser short-tailed bat (Mystacina tuberculata). A curious aspect about New Zealand bats is that prior to the arrival of humans and introduced mammals, they have been isolated from all other mammals for well over one million years, and in the case of the lesser short-tailed bat, for 30 million years. Are they susceptible to the same viral diseases carried by introduced mammals, or do they have their own unique viruses? And what are the risks posed by these viruses, both to human health and to the health of the bat populations in New Zealand?

Richard Hall at the Institute of Environmental Science and Research (ESR) and colleagues at Landcare Research and the Department of Conservation have started to answer these questions, applying specialist next-generation sequencing technologies (see article by Daniel White in this issue for details of this technique) to identify viruses in guano samples of the New Zealand lesser short-tailed bat, collected from Codfish Island.

Next-generation sequencing instruments are capable of sequencing all DNA (or RNA) present in a sample. For the last 30 years, scientists have used Sanger-sequencing (a processive biochemical method for sequencing small, individual pieces of known DNA), which requires some prior knowledge of the DNA being searched for. The new sequencing technologies are unbiased and allow researchers to discover new micro-organisms, and in particular, new viruses. A single experiment will provide millions of DNA sequences from one sample and each sequence can then be compared to genomic databases using a similarity search. In this way, it is possible to catalog most of the organisms present within a sample, even those which are quite novel.

Richard and his team have had some unexpected results. The team discovered not only a novel coronavirus, but also sequences that are related to polyomaviruses, papillomaviruses, hepeviruses and caliciviruses. While all of these families are known to contain viruses pathogenic to humans, the bat host or other animals, no conclusions can be drawn about the pathogenicity of the New Zealand bat viruses. However, this does show that New Zealand bats are likely to be infected with viruses, just as other mammalian species are. The types of viruses detected in our bats are similar to the profiles observed for exotic bats in other studies. This is quite surprising, given the long isolation that the lesser short-tailed bat has experienced. The results even challenge current theory on the evolution of coronaviruses, which were thought to be only 10,000 years old. This work raises the possibility that they may be much older. Or perhaps the bats have contracted these viruses since the arrival of introduced mammals in New Zealand.

A great deal more surveillance work needs to be conducted in New Zealand on our bat species and many questions remain unanswered. However, this work does illustrate that New Zealand bats can play host to similar viral species to those observed in bats overseas.

ScotophilusTuberculatus Ford

This work was funded by the core research fund from ESR and Landcare Research, provided by the Ministry for Business, Innovation and Employment.

Richard Hall (ESR)
Dan White