Explainer: Bats,diseases and role in ecosystem

Despite being associated with numerous diseases including COVID-19, bats play a crucial role in the ecosystem health, human health and agriculture. Bernard Agwanda, research scientist and curator, National Museums of Kenya explains more.

How many bat species are there globally?

We have about 1,200 species of bats in the World. Out of this about 10% are found in Kenya, so we’re talking about 110 species of bats. In Kenya, there are majorly three groups. One group principally, eating plants that is, fruits and leaves, and we generally call them fruit bats. And the other group eats invertebrates mainly insects. There is one other group: the False vampire that eats both insects and other bats, small rodents lizards and maybe frogs.

Bats have been associated with many diseases including, Ebola, Marburg, rabies, COVID-19, have you found any diseases specific to certain bats in the course of your research work?

It’s not sufficient to say this species of bats harbor this virus without being specific about the locality. You may find one population in this locality has the virus and the same species in another locality doesn’t have. I have a matrix of data showing which bat species harbors which virus in which locality, and when the virus was detected.

There are those that we have found with very unique viruses and we must make a distinction. We have found many viruses in bats that have not been reported to cause any diseases in human or other animals. That doesn’t mean they don’t cause diseases neither does it mean that they cause diseases. But there are viruses that we know cause diseases and we have found them in a particular bat in a particular location. I can provide a few example to illustrate evidences we have generated in Kenya.

From Striped Leaf-nosed bats technically called Macronycteris vittatus; (formerly called Hipposideros), we found a bat rabies new to science then, and named it Shimoni bat virus, after the cave and locality. A closer examination of the genes of the virus and the host bat showed prominent signature of coexistence, co-evolution between the bat and the virus and convinced us that the bat serves as reservoir host to the virus. This suggests that the virus and the bat coexist happily and have been doing so for millennia without apparent problem to human. As to whether it can infect human beings and cause fatal disease is another question requiring in-depth analyses. Since the bat and humans don’t ordinarily get in contact, probability of human infection is very low and so no cause for alarm but caution in touching bats live or dead without protection.

In another bat virus surveillance, we detected and extracted Lagos bat virus, in a dead Straw-coloured bat, I had picked from the ground under a tree in Maseno. Lagos bat virus also belongs to bat rabies virus group, previously reported in several countries in Africa including Lagos, Nigeria.  Though very rarely reported, but can infect human and cause death.  Unlike the Shimoni case, this virus can infect human directly (touching dead bat) or via cats or dogs that have feasted on the infected dead bat. This is not far-fetched. It had been isolated from a domestic cat in Zimbabwe in 1986, and twice from dogs in Ethiopia in 1989 and 1990. Our effort to screen people in western for this virus has shown no signs. Caution is called for in interacting with bats sick or dead. Safe disposal by burying or burning is highly recommended.

I give you another one that causes diseases in children, rotavirus. This is a virus that can infect and cause mild disease in humans mainly diarrhea in children. It is very rare in adults and so in immunosuppressed individuals. We found a form of rotavirus in a Giant mastiff bat in Suswa.

We were able to detect Marburg virus from a bat called Egyptian fruit bat in Mt. Elgon. Marburg virus has had several outbreaks across the continent but the most prominent ones have been in Uganda and that’s the closest neighbor to Kenya. Also in DRC, and Angola and Zimbabwe. There were also reported fatal cases in Kenya previously. Whereas human cases in Uganda and DRC had been aptly traced to bats, no evidence had been provided on bats. We detected this deadly virus from a single bat in a very big colony in the cave. We believe the virus happily live among bats and only take human disturbance and direct interaction with bats to cause spillover to human.

How do bats transmit diseases to human beings?

Rabies viruses are typically transmitted by getting contact with saliva (via a bite) of infected bat, dog or cat. The spin in Africa and indeed caution to medical personnel attending to patients, is that dogs may transmit either classical dog rabies or as a vector transmit bat rabies to human. The Ethiopian case serves this caution. The challenge here is that current biologics vaccines against rabies are only for classical dog rabies. They don’t offer any protection against bat rabies. Hunters of bushmeat and especially using dogs to harass wildlife especially the vulnerable groups. they transmit through biting.

Some bat-borne viruses such as the corona, paramyxo and Ebola groups can be transmitted via urine or faeces (droppings). They can also transmit through their urine because some viruses go all the way to the kidneys and kidneys is where the urine is produced as a byproduct. One can be infected through the feaces. And also when you eat bats, you can interact with the blood or fluid on the bat and if the blood or fluid is infected, you can get the virus being transmitted from the bat to you.

Human beings and bats rarely interact because bats come out at night so how does the transmission take place?

That’s why the bats have got so many viruses yet only very few is transmitted to us. The Ebola case in West Africa that took place in 2014 and went for several years is thought to have occurred when some people extracted bats from their hide out in the day and butchered it. So, bush meat harvesting of bats or butchering bats or handling them particularly when they look sick is one way of getting the virus out from safety of the bats to calamity in humans.

The first cases of people who suffered from Marburg virus in Uganda, were of mine workers who visited the bat cave. They either touched the bats or the bat fluids; the saliva, the urine or the poop or a combination of all that.

Interacting with the bats directly is the cause whether you are butchering to eat or sampling them or you are unknowingly touching where they are. That’s how the transmission occurs, now it’s called spillover event, that can spontaneously blow out of control and cause epidemic or even pandemic.

Are there any benefits associated with bats being in our ecosystem?

Firstly, any organism in nature is important just because it’s an organism. Every organism has a role in the ecosystem even if it causes death in human beings. Every organism contributes to ecosystem health (environmental health), which serves us hugely, generation after generation.

Secondly, bats pollinate many plant species, and so maintain essential genetic diversity among plants depending on them for pollen transfer. In fact some plants such as Baobab (parent tree from which Mabuyu fruits come) depends on bat pollination, since their flowers only open at night when bees and birds are asleep.

Many fruit bats are practically environment engineers that seed cleared forest patches in landscape through seed dispersal. This is a critical ecosystem function enabling many plant species to avoid incest and associated lethal genetic bottle necks. More importantly they broadcast seeds in cleared forest patches and so contribute to re-afforestation.

Both plant pollination and seed dispersal are critical to ecosystem health and prerequisite to ecosystem goods and services human enjoy.

The other one is managing insect pest for us so that we don’t have to spray the field with chemicals pesticides. They eat a lot of pests at night that if they didn’t eat, our crops will be heavily infested that we have to spray using chemicals that we buy expensively or we’ll have to incur a lot of crop losses. They are already controlling pest for us naturally without as paying much attention to them.

They also consume vectors like mosquitoes that would bite and transmit many diseases. Malaria is just one of them, but there are so many diseases or pathogens that mosquitoes and other vectors would transmit to us with our livestock. These include Rift Valley fever, Yellow fever, Zika virus, Dengue fever and Chikungunya among others. Some of these diseases don’t cause lots of death but the sickness they cause among the population make people sick. They can’t go to work and therefore there is economic loss.

So they help us from human health, ecosystem health to agriculture to just general environmental maintenance. Those are the benefits; the other benefit is that some people eat bats. You may not believe it, but they do and I know people talk about West Africa where you can find it in the market but in Kenya some people eat bats as a source of protein.

What can be done to ensure that bats and human beings co-exist peacefully, to maintain the status quo?

There are things that can be done at individual, community and government levels. Individually, we just have to appreciate nature for what they are. To try to imagine that this one is dangerous and we have to exterminate it, may have a ripple effect whose impact can be unpredictably disastrous. Each species has a role hence we need to avoid exterminating them. And each species has its natural enemy to control its rage over the other.

Secondly, we need to have decorum when we interact with the wildlife. I know we watch movies of how particularly, whites get very close and cozy with animals even kissing them, for wildlife, you can’t do that. You are giving these pathogens happily living in the wildlife a bridge- an epidemiological bridge- to get to you which they would have never gotten. And because you’re a new land, they can start growing uncontrollably in numbers that they would not do in their natural host, and cause fatal damage (diseases) to your organs and systems. It would jump to your loved ones next to you or caring for you and affect them too and so spread to become pandemic.

This should happen with pets as well, pets you don’t understand, you don’t interact with them anyhow like dogs and cats unless you are sure they’re well taken care of medically. And even so there is still a chance you can be infected like in the Ethiopian case. By the way we isolated a rabies virus from a zebra being raised in a conservancy alongside a dog in Kenya!

Also, where an animal is enforcing its interaction with you, it’s good to consult an expert, for instance a bat can be in your house and it seems it doesn’t want to fly out, just around you or maybe it has dropped down or is struggling to fly. It’s not good to panic, but call an expert and if you can’t call anybody use some protective gear to get it out of your way without squeezing it and put it far away from the house. This is because some of this virus can make them sick and mad and by the time you notice, the behavior is the moment it can actually drop the bombshell not because it wants but because it’s also sick and confused.

Communities must avoid disturbing bats like going to the caves and lighting fire or bulbs that would force bats out. Disturbing and disrupting bats from their natural roosts is the best way to cause a human pandemic and crop disease pandemic.

At Government level, there are so many laws protecting wildlife but there are far less guidelines on how we can protect them so we can live with them happily and that has set a centre stage of conflict all the time. We can protect the bats when you see them, but we are destroying their food, their roosts and poisoning them through herbicide and pesticides. So in other words, we are also destroying them. Therefore, guidelines on how to protect the bats, their habitat or any other wildlife is the best way to go.

The government should have certain policies and guidelines on how to appreciate nature and give incentives to people who do their best to protect nature. Unless this is done, it will be difficult for the government to protect wildlife outside protected areas.