Tilapia Farming to Prevent Malaria
Strong Potential For Mosquito Control. But What About the Ecosystem?
Balancing the risk of ecological damage from introduced species with reduced pesticide use and the need for protein sources and disease control in developing countries.
In Kenya a recent study has shown that farming tilapia (Oreochromis niloticus L.), a cichlid species, may provide a secondary benefit by helping to control mosquitoes. This is an important consideration as drug resistant strains of malaria are becoming common, as are pesticide resistant insects. On the other hand, tilapia introductions in some areas have resulted in habitat damage and fish can’t be used to control mosquitoes that breed in puddles or muddy areas. A cautionary approach is warranted to preserve ecosystems while protecting and providing for humans.
The Malaria Problem
With the emergence of pesticide resistant insects and antibiotic resistant diseases, the use of biological controls is once again gaining favor. In the part of Kenya where a study of the effectiveness of tilapia as a mosquito control was carried out, there are over 2000 cases of pediatric malaria each year. Malaria is a highly important human health issue, not just in Kenya, with some countries returning to the use of DDT to control mosquitoes. And malaria is not the only mosquito borne disease. Dengue and yellow fevers and the equine encephalitis group are also transmitted by mosquitoes.
Study Results
Within a few months of initiating tilapia farming there was a 94% reduction in two types of Anopheles mosquito, the common malaria vector species in the pond where the tilapia was introduced. Culicine mosquitoes, vectors for dengue fever, yellow fever and equine encephalitis, were also reduced. This compared positively against an increase in mosquito numbers due to weather related factors in a control pond with no tilapia.
The Pros and Cons of Tilapia Farming
If this sounds too good to be true, in the larger sense it probably is. Like the old woman who swallowed a fly, introducing non-native species to control other non-native species often results in ecological damage.
Tilapia is already a common farm fish in Kenya so the introduction of the species has already occurred there but it would be wise not to start introducing tilapia everywhere to help with mosquito control. Tilapia introduced into Madagascar have eliminated some native species of fish. In other areas, habitat damage by tilapia has been significant. The idea of utilizing a food fish for vector control has great appeal, especially in countries where starvation and protein deprivation are common.
Perhaps the most sensible approach would be to determine which native species of food fish provide mosquito control and encourage the careful farming of those species in areas where mosquito vector diseases are a problem.
