Invasives Blog

A highly invasive apple snail (Pomacea canaliculata) has been discovered in Kenya for the first time. This is what new research published today by CABI scientists and the Kenya Plant Health Inspectorate Service (KEPHIS) confirms.

The apple snail, which is generally considered to be one of the most invasive invertebrates of irrigation systems and waterways, now threatens Kenya’s rice production. It also raises two important questions: how much damage will it cause in Kenya and will it spread any further?

The research paper entitled ‘First report of the invasive apple snail, Pomacea canaliculata in Kenya’, was published in the CABI journal CABI Agriculture and Bioscience by scientists including lead author and Microbiology Research Leader at CABI, Dr Alan Buddie. Prior to this, in December 2020, an earlier version of the paper had also been posted to the re-launched CABI platform, agriRxiv, as a preprint.

The discovery was made following reports of an invasive snail causing damage to crops in the extensive Mwea irrigation scheme in Kenya. Snail and associated egg mass samples were collected and then sent to CABI’s laboratories in Egham, in the UK, for molecular identification. Confirmation that the snail was indeed Pomacea canaliculata came following DNA barcoding analyses using the cytochrome oxidase subunit I gene, supplemented by elongation factor 1-alpha sequencing. This was done to confirm that the snail was not a hybrid between P. canaliculata and P. maculata.

CABI discovered that the egg masses that were tested gave an identical barcode sequence to the adult snails of Pomacea canaliculata. This shows how beneficial molecular identification can be when combined with a reliable database such as that provided by the Barcoding of Life Data system.

Talking about the identification, Dr Buddie said, “Molecular tools provide an invaluable aid to species-level identifications within groups of organisms that look almost identical to non-specialists. In the present case, taxonomic experts in this group of invertebrates are rare. We demonstrated that, as long as we can obtain a small amount of DNA from a snail (or even a single egg), we can obtain the same level of identification if such experts have deposited authenticated sequences in public access sequence databases, or if we have access to those experts who can confirm the inferences made.”

To check and ensure a correct identification, Dr Buddie also contacted a recognized expert, who compared the sequences to his own database of authenticated barcode sequences. He confirmed the CABI identification was, indeed, correct.

A pest indigenous to the Americas, Pomacea canaliculata has been listed among ‘100 of the world’s worst invasive species’ and has already spread widely throughout South East Asia. Its introduction to this region was thought to have been intentional. It has since become a serious agricultural pest, causing substantial economic losses in wetland rice cultivation, and it also threatens biodiversity and native habitats.

Dr Ivan Rwomushana, Senior Scientist, Invasive Species Management, CABI, said, “We collected samples of the snail for barcoding. Following confirmation of the new species, we completed a delimiting survey to establish the extent of snail’s spread. Our findings show that other schemes are still unaffected, although seed and machinery brought from Mwea poses a risk for invasion. We will work with the relevant national agencies to develop a rapid response and containment strategy for this new invasive species.”

This threat makes quickly assessing and addressing the apple snail all the more important. In the Mwea region of Kenya, where over 70% of the country’s rice is grown, farmers are already talking about the damage it is causing to rice production.

It is now vital that a risk assessment is carried out on the snail including understanding the threat it poses in Africa, especially given the impact it has already had in Asia. This new threat to Kenyan agriculture and environment needs speedy implementation of an appropriate response.

Prof. Theophilus Mutui, Managing Director of KEPHIS, said, “Since its first point of detection in Mwea, apple snail has spread gradually to other areas. Strict quarantine measures should be instituted and implemented to curb not just the spread of the snail but entry into other rice producing risk areas in the country. To achieve this, areawide management should be exercised such as training and awareness creation, installation of physical barriers, mechanical control, and community-based snail management.”

Read the full paper here

For more information about the apple snail see the Apple snail portal

For more information about invasive species see Action on Invasives

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