Zoo Mosquito Control

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Penguins Dead from Malaria

Photos by Guy Pitt

That unlikely headline was sadly true when a UK zoo lost some of their star performers, African and Gentoo penguins. Avian forms of malaria, unlike their human counterparts, are endemic in the UK in species such as blackbirds and starlings. They also differ in that, while human malaria parasites are passed from person to person by Anopheles mosquitoes that are relatively rare in Britain, the bird parasites can be transmitted by our most common type, the Culex mosquito. Therein lay the problem and the untimely deaths of the penguins, resulted in an animal friendly, biological control programme being established between Dr Colin Berry and the zoo to attempt to contain the mosquito problem.

The zoo has a wide range of exotic animals and several ponds supporting not only flamingos and other bird life but also less welcome inhabitants, the Culex mosquito larvae. From the late spring, the numbers of these mosquitoes would rise rapidly, providing ample insects to spread parasites amongst the birds and also create a nuisance for the human visitors. The situation clearly required a control programme but conventional, chemical pesticides were likely to prove harmful to the zoo’s animals. One of Dr Berry’s research interests is the mechanisms by which the bacterial pathogens Bacillus sphaericus and Bacillus thuringiensis, kill mosquitoes and so Mark Cleworth of Resource Chemicals was contacted for technical advice on the use of the larvicide ‘Vectobac 12AS’, a formulation of Bacillus thuringiensis produced by Valent Biosciences Corporation. This product contains a strain of the bacterium that produces at least six protein toxins that are highly specific for mosquito larvae. Working with the zoo's curator, a programme was developed whereby Vectobac 12AS was sprayed routinely onto all standing water and the zoo’s numerous biological water filtration plants. Since its introduction, this appears to have done the trick in controlling the problem insects without harming adjacent animals. The strategy has been so successful that it has aroused interest from other zoos throughout Europe. To date, mosquitoes have not developed resistance to the strains of Bacillus thuringiensis used in the field so the use of Vectobac may continue to afford protection to these (and other) important birds for years to come.

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Cardiff University

Updated February '08
by Dr. C Berry.

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Penguins Dead from Malaria
	Photos by Guy Pitt
That unlikely headline was sadly true when a UK zoo lost some of their star performers, African and Gentoo penguins. Avian forms of malaria, unlike their human counterparts, are endemic in the UK in species such as blackbirds and starlings. They also differ in that, while human malaria parasites are passed from person to person by Anopheles mosquitoes that are relatively rare in Britain, the bird parasites can be transmitted by our most common type, the Culex mosquito. Therein lay the problem and the untimely deaths of the penguins, resulted in an animal friendly, biological control programme being established between Dr Colin Berry and the zoo to attempt to contain the mosquito problem.