The microbial world is full of diversity with an astounding amount of organisms that are beneficial to humans, wildlife and the environment. However, as our customers know, there are also plenty of micro-organisms that are detrimental to employee health and production efficiency. In some cases, one of the ways to treat an infection in a system (whether it be industrial machinery or dental lines) is to use a germicide that will help to inhibit microbial growth. Recently, this same method has been employed by conservationists / scientists to help combat microbes that are unfortunately pushing some species close to extinction.

Case study 1: Bats

Millions of bats in North America have died due to a disease called white- nose syndrome which is caused by a fungus called Pseudogymnoascus destructans. Bats with the disease do not tend to survive winter hibernation as they use up their energy stores much faster than uninfected bats.¹

The sitution has become so bad that there has been a population decline of over 90%.² Due to the seriousness of the situation, scientists have turned to new methods to combat the disease. One of the reasons that this particular fungus has caused such devastation is that it persists in the environment and therefore, this is where the fightback needs to start.³

In Europe, the fungus exists but dies in Summer, with no natural way to repeat this process in North America, a different approach was taken. The treatment sites used for the experimental trial took place in four abandoned mines where the fungus was present.⁴ Chlorine dioxide gas was used to kill the fungus, although a little remained which gives the team involved (Virginia Tech university) reason to believe that other microbes will have survived also (therefore not eliminating other microbial communities which may have unknown consequences on the environment). The optimum amount of chlorine dioxide required was tweaked over time with very successful results (little brown bat overwinter survival rates increased to 76% from 14%). ⁵

Case study 2: Amphibians

Another endangered species, another fungus causing destruction. This time it's the Batrachochytrium dendrobatidis fungus. This fungus causes a disease called amphibian chytridiomycosis which has been wiping out amphibian populations in man made ponds in Spain.⁶

As well as an antifungal treatment to treat tadpoles, chemical disinfection was used in the ponds to help eradicate the fungus in the environment.⁷ This proved to be much more successful than previous attempts that only involved direct treatment to the animals themselves. If the pathogen stays within the environment then reinfection is likely so trying to eliminate the prevalence of the fungus within the ponds is a more effective strategy when tackling the spread of disease.⁸ The tadpoles were initially removed during the disinfection process and then returned to the ponds when considered safe to do so (this has since changed with amphibians remaining in ponds during disinfection)⁹. Chemical disinfection did eradicate infection at 4 out of 5 ponds that were treated and when monitored two years later, these ponds continued to be infection free.¹⁰

Case study 3: Coral

Our corals are under threat due to a variety of factors. Some of the danger comes from fungi and algae. Fungal pathogens are pushing some corals to the brink while algae is outcompeting and impeding growth of corals. In the case of algae, this is affecting the success of coral restoration projects. Coral restoration involves growing corals which can involve the collection of eggs and sperm.¹¹ Coral larvae may be positioned onto reefs to encourage settlement.¹² These corals are grown in nurseries before being planted into wild reef populations.¹³ Algae can overwhelm the recently settled coral and obstruct its light, which can threaten its ability to survive.¹⁴

When being restored, plugs are often used to mount the coral onto and to help anchor the coral (plugs can be seen in the photo above). These are often colonised by algae hindering the coral growth process. Due to this, research has recently taken place to investigate the efficacy of using biocidal, anti-adhesive and nano particle coatings to stop algal growth while not negatively impacting coral restoration.¹⁵ Since the algae stops the young coral from growing by coating the coral plug and overwhelming it, the treatments were applied directly to the coral plugs to assess if the algae would still cover the plugs. The study also looked at whether the treatments would stop the coral larvae from settling.¹⁶

The experiment was pretty conclusive with plugs that were not coated in the treatment, being heavily affected by algae. Two out of the three coatings (biocidal and anti-adhesive) were very effective at reducing algae growth.¹⁷ In addition to this, the algae larvae settled on the treated plugs (all types) and seemed unaffected by the coatings.¹⁸ The success of the different types of coatings in this experiment offers options for dealing with algal threats to young coral and future restoration projects.

Case study 4: Black footed ferrets and Prairie dogs

Prairie dogs are the main food source of the endangered black foot ferret. The black foot ferret is directly (by contracting the disease itself) and indirectly (due to the prarie dogs being affected by the disease) negatively impacted by Sylvatic plague. Sylvatic plague is a bacterial infection that is spread to mammals via fleas. The bacteria that causes the plague is called yersinia pestis (the bacteria that gave rise to the black death and plague in humans).¹⁹ The plague spreads very quickly and is almost always fatal to the ferrets and the prarie dogs.²⁰

An injectable vaccine is available for black footed ferrets but not for the prarie dogs so other tactics have been employed to help prevent the spread of the disease. One way this is being done is by deploying non injectable vaccine baits (peanut butter) to prarie dog communities (the efficacy of this method has been questioned).²¹ This has even been done via drone!²²

Due to the Sylvatic plague been spread by fleas, another method that has been used in the fight against the disease is to use insecticide. The insecticide is released into prarie dog burrows to help eliminate any fleas that may be carrying the infection.²³ In tandem, these interventions have helped keep the disease at bay but unfortunately, it has not been eliminated.²⁴ Tackling the plague is an expensive and time intensive process and has taken a mammoth effort so far.²⁵ However, like the fungus in the bat case study above, the bacteria seems to persist in the environment making it very difficult to completely eradicate.

It is becoming more apparent that there is an emerging threat of fungal diseases happening across the animal kingdom. Chemical disinfection of the environment in the case of current devastating fungal infections in reptiles, sea turtles, dolphins and birds is a much more tricky prospect than the cases cited above. The advantage that mine and pond dwelling wildlife have is that their habitats are much easier to locate and treat than the other animals mentioned above. They also live in communities whereas the habitats of other wildlife may be much more scattered and changeable.

However, the above cases illustrate how this new approach (where it can be applied) has been successful as a last resort in the case of near species collapse.

Of course, using chemicals comes with risks and relying solely on these methods in wildlife conservation and other areas (whether this be metal cutting fluid management or any other industry impacted by detrimental microbial growth ) will not always be the best approach. However, it's interesting to learn how methods such as chemical intervention are helping in environments where you'd least expect it.

References

1. Communications and Publishing. How does white-nose syndrome kill bats? | U.S. geological survey - USGS.GOV. USGS . January 5, 2015. Accessed June 15, 2023. https://www.usgs.gov/news/national-news-release/how-does-white-nose-syndrome-kill-bats.

2, 3, 6, 7. McGovan J. How disinfecting an old mineshaft saved a colony of Little Brown Bats. The Guardian. June 1, 2023. Accessed June 15, 2023. https://www.theguardian.com/environment/2023/jun/01/how-disinfecting-old-mineshaft-saved-colony-little-brown-bats-aoe.

4. Hoyt JR, Parise KL, DePue JE, et al. Reducing environmentally mediated transmission to moderate impacts of an emerging wildlife disease. Journal of Applied Ecology. 2023;60(5):923-933. doi:10.1111/1365-2664.14371

6. 7, 8, 9, 10. Bosch J, Sanchez-Tomé E, Fernández-Loras A, Oliver JA, Fisher MC, Garner TW. Successful elimination of a lethal wildlife infectious disease in nature. Biology Letters. 2015;11(11):20150874. doi:10.1098/rsbl.2015.0874

11, 13, 14. Fisheries N. Restoring coral reefs. NOAA. September 27, 2021. Accessed June 15, 2023. https://www.fisheries.noaa.gov/national/habitat-conservation/restoring-coral-reefs.

12, 15, 16, 17, 18. Roepke LK, Brefeld D, Soltmann U, Randall CJ, Negri AP, Kunzmann A. Antifouling coatings can reduce algal growth while preserving coral settlement. Scientific Reports. 2022;12(1). doi:10.1038/s41598-022-19997-6

19. 1,500-year-old plague victims shed light on disease origins. The Guardian. January 28, 2014. Accessed June 15, 2023. https://www.theguardian.com/science/2014/jan/28/plague-victims-shed-light-disease-origins.

20, 24, 25. An invisible enemy: The battle to save black-footed ferrets from the plague. The Guardian. September 7, 2020. Accessed June 15, 2023. https://www.theguardian.com/environment/2020/sep/07/an-invisible-enemy-the-battle-to-save-black-footed-ferrets-from-the-plague-aoe.

21. Matchett MR, Stanley TR, Mccollister MF, Eads DA, Boulerice JT, Biggins DE. Oral sylvatic plague vaccine does not adequately protect prairie dogs (cynomys spp.) for endangered black-footed ferret (mustela nigripes) conservation. Vector-Borne and Zoonotic Diseases. 2021;21(12):921-940. doi:10.1089/vbz.2021.0049

22, 23. Bly K. Newly patented technology helps save endangered black-footed ferrets. WWF. Accessed June 15, 2023. https://www.worldwildlife.org/stories/newly-patented-technology-helps-save-endangered-black-footed-ferrets#:~:text=Both%20black%2Dfooted%20ferrets%20and,infected%20with%20the%20plague%20bacterium.