Snail Dissections

Snail Dissections: Hi I have a teacher that wants to do a snail dissection with 13 year old students.  I thought we were not allowed to do them due to the number of parasites that snails can carry.  Is this the case?  As we have not purchased laboratory breed snails.

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Publication Date: 19 July 2016
Asked By: jedho1
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Snail Dissections

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Jurisdictional legislation and policies: It is essential to consult your school or school sector to determine the policies and procedures they require you to follow regarding dissection. When considering dissections in schools, it is important to take into account the ethical and safety concerns involved.


For the safety of staff and students, it is essential that all materials used for dissections are free from disease and sourced from a supplier of food for human consumption or from a biological supplier. We advise against dissecting road kill or dead animals brought in from the family farm!  


Therefore when conducting dissection activities schools should consider using dead whole animals e.g. fish, crustaceans and molluscs that are suitable for human consumption and therefore disease free, which can be purchased readily from food outlets. Alternatively, consider using prepared specimens, which can be purchased from biological supply companies. Small vertebrate and invertebrate animals can also be purchased through authorised biological companies. See our list of School science suppliers for details of appropriate suppliers.


Land snails: The likelihood of common garden snails being infected with parasite larvae is very low and the risk of infection comes from eating the raw snails which could be infected with parasite larvae.  However, it is still advisable to exercise caution when handling terrestrial gastropods (land snails) and is essential that after any contact with snails, hands are thoroughly washed.


Science ASSIST recommends that snails required for snail dissections, are sourced from either a food outlet, e.g. a snail farm that supplies restaurants, or a biological supplier.


Additional Information:


Snails:


Snails can harbour parasites1,2. There have been a number of reports where land snails have been eaten and have infected humans with their parasites and caused serious diseases.  For example:


  • Angiostrongylus cantonensis: It is estimated that 5% of common garden snails in and around Sydney, NSW; contain larvae of the parasite Angiostrongylus cantonensis, commonly known as the rat lungworm. It is more widespread in Brisbane and occurs on the coast from far north Queensland down to Jervis Bay, NSW. The snails and slugs (molluscs) are infected when they come into contact with larvae in the rat’s faeces. These larvae go through developmental stages in the mollusc, and the cycle is completed when slugs and snails are eaten by rats.  It becomes a health problem when the slugs and snails are accidently eaten by dogs, wildlife species and humans3,4,5.

  • Brachylaima cribbi: Introduced European land snails are common in southern Australia, and their parasites can infect people who accidentally eat them. The parasitic fluke worm Brachylaima cribbi is a small trematode flatworm, up to 6mm long that lives as a parasite in the intestines of mammals, birds, and reptiles. It uses land snails as intermediate hosts. The snails become hosts for the worm when they eat their eggs in animal faeces. These then hatch in their gut to produce 'sporocyst' larvae known as cercariae which pass into the environment through the snail's slime trail and infect other snails. When mammals, birds and reptiles eat the snails, juvenile larvae are released, going on to develop into mature adult worms in the small intestine.  People cannot be infected by the eggs of the worm, only by ingesting the juvenile worms from the snail6,7.

Therefore raw snails should not be eaten and care should be taken with food preparation to ensure that all vegetables are thoroughly washed prior to consumption to remove any snails, so that they are not accidentally eaten.


Land snails in Australia:


Land snails are molluscs – a type of invertebrate (without a backbone). They belong to the class Gastropoda which possess a well-developed head with mouth, tentacles and eyes. They have a soft body containing reproductive and digestive organs and a large foot with a creeping sole. Most land snails have a developed a pulmonary cavity or lung. They also have a shell that houses and protects the snail’s soft body parts.


Most of the native snails are restricted to areas with native vegetation.


Garden Snails are found throughout south eastern Australia. They were introduced to Australia from Europe over 120 years ago, and are now established in urban areas, most commonly found in managed gardens and disturbed areas rather than native bushland.


Snails eat a variety of foods, and so can be called omnivores. Some snails feed on plant material; others are carnivorous eating small invertebrates such as insects and other snails and slugs.


Snails are hermaphrodites (which means, they can fertilise each other).


The following websites have some interesting information regarding the identification, distribution and habitat of land snails in Australia:


Garden Snails, Minibeast Wildlife https://www.minibeastwildlife.com.au/resources/garden-snails/


Snail dissections:


The following websites have detailed information regarding terrestrial snail dissections, a YouTube video and basic snail anatomy


Snail Dissection. University of Florida. United States Department of Agriculture http://idtools.org/id/mollusc/dissection_snail.php  


Terrestrial Snail Dissection — Coe — You Tube https://www.youtube.com/watch?v=3YUpON4-c6M 


Land Snail- Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Land_snail


Use of animals in schools:


School Animal Ethics Committee (SAEC) approval is required when certain animals are used in schools for scientific purposes, teaching activities or classroom observation. The animal research decision guide can be found on the NHMRC Australian Code for the Care and use of animals for scientific purposes


Ethical concerns:


It is a decision for either the school or school sector to make the ethical decision regarding whether they will permit the dissection of animals. In most jurisdictions there are requirements for reporting to an animal ethics committee and sometimes permission is required before arranging to conduct a dissection.  You may however conduct dissection activities using invertebrates (animals without backbones) such as snails without the prior approval of an ethics committee.


It is recommended that schools consider the educational objectives for the activity and explore the ethical considerations with students. Students should not be forced to participate in a dissection and alternative activities such as videos and virtual dissections can be used for these students instead, as well as to supplement the actual activity.


Science ASSIST has developed an information sheet with links to biological safety and jurisdictional SAECs, see AIS: Links — Biological sciences safety


In addition we have answered related questions which cover various safety aspects of dissections see:


Piglet Dissection:


Preparation of Equipment for Dissections:


fainting during dissections


Lung Dissection


Dissecting cane toads in WA


Dissection materials


References


1 Snails, Slugs, and Semi-slugs: A Parasitic Disease in Paradise', CDC Public Health Matters Blog website, https://blogs.cdc.gov/publichealthmatters/2009/04/snails-slugs-and-semi-slugs-a-parasitic-disease-in-paradise/ (April 2009)


2 Parasites - Angiostrongyliasis (also known as Angiostrongylus Infection), CDC website, https://www.cdc.gov/parasites/angiostrongylus/index.html (November 2010)


3 Malik, Richard and Spielman, Derek. 2016. 'Kids, put down the snails, they could carry rat lungworm', The Conversation website.  https://theconversation.com/kids-put-down-the-snails-they-could-carry-rat-lungworm-50183 (March 2016)


4 Salleh, Anna. 2003. ‘Man's brain infected by eating slugs’, Health and medical news, ABCwebsite, http://www.abc.net.au/science/news/health/HealthRepublish_969551.htm  October 2013)


5 ‘Land snail’, Wikipedia website, https://en.wikipedia.org/wiki/Land_snail (Accessed July 2016)


6 Horstman, Mark. 2002. 'Snails can give you worms'. ABC Science website. http://www.abc.net.au/science/articles/2002/10/18/704700.htm (October 2002)


7 Butcher, Andrew R. 2016. Children, snails and worms: the Brachylaima cribbi story. Microbiology Australia March 2016: 30-33, http://microbiology.publish.csiro.au/?act=view_file&file_id=MA16012.pdf

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