Asian tiger mosquito (Aedes albopictus) // James Gathany, CDC

Besides its relevant role in the transmission of several diseases affecting humans, the Asian tiger mosquito may not be so involved in the transmission of avian malaria. This is the conclusion of a recent scientific review published in the journal Animals  where the impact of Aedes albopictus, the tiger mosquito, in the transmission of avian malaria pathogens has been assessed. This review, carried out by the Doñana Biological Station – CSIC, the University of Granada and the Lithuanian Nature Research Centre, highlights the expansion of the tiger mosquito’s distribution range to almost all continents and the potential alteration of the transmission dynamics of wildlife diseases. This work is part of the COST European Action WIMANET.

The Asian tiger mosquito is an invasive species with a wide current distribution range. In addition to being a nuisance due to its bites, this mosquito is a public health problem since it is a vector of several diseases affecting humans, such as dengue or Zika. Changes in its distribution area could facilitate the transmission of these diseases in the invaded areas, where most of the studies have been focused on diseases affecting humans. However, their role in the transmission of diseases such as avian malaria, affecting wild birds, is scarcely studied. The research team aimed at reviewing the information available to clear out the role of Asian tiger mosquitoes as vectors of these pathogens.

The reviewed studies, monitoring the presence of avian malaria pathogens in mosquitoes captured in the wild, showed a minimum infection rate, suggesting that, although the tiger mosquito is able to interact with these pathogens, its role as vector is limited. “We suggest that it may be due to its tendency to feed mainly on the blood of mammals, and not so much on birds,” explains Jesús Veiga, researcher at the Doñana Biological Station – CSIC and first author of the study. However, the number of studies exploring this possibility is small, and they have only been carried out in a few countries where this invasive mosquito is present.

This work also reviewed studies analyzing the development of avian malaria pathogens, genus Plasmodium, in the laboratory. A great variability was found depending on the species of pathogen involved. Species such as Plasmodium vaughani and Plasmodium circumflexum may not seem to be able to complete their development in the tiger mosquito. Others, such as Plasmodium gallinaceum seem to develop relatively well and even transmit effectively from one bird to another. Plasmodium gallinaceum significantly affects poultry and causes major economic losses due to the mortality of untreated birds, loss of meat quality, and reduction in egg production. Therefore, special attention should be given to the presence of tiger mosquitoes in these environments.

Por otro lado, en este trabajo también se revisaron los estudios que analizaron específicamente el desarrollo de los parásitos de la malaria aviar, del género Plasmodium, en el laboratorio, donde se encontró una gran variabilidad dependiendo de la especie de parásito que se tratase. Mientras que especies como Plasmodium vaughani y Plasmodium circumflexum no parecen ser capaces de desarrollarse en el mosquito tigre, otras como Plasmodium gallinaceum pueden completar su desarrollo e incluso transmitirse de manera efectiva de unas aves a otras. Plasmodium gallinaceum afecta de manera significativa a aves de corral y provoca graves pérdidas económicas debido a la mortalidad de aves no tratadas, la pérdida de calidad de su carne y la reducción en la producción de huevos. Por ello se debe poner especial atención a la presencia de mosquito tigre en estos entornos.

“However, the results obtained to date are limited to a few species and genetic lineages of avian Plasmodium, limiting the conclusions that we may reach for the role of this invasive mosquito in the circulation of avian malaria”, says Veiga. “This is especially relevant considering that there are more than 50 morphospecies and 1500 genetic lineages of avian Plasmodium.” Further studies considering other avian Plasmodium species and lineages are essential to forecast how the introduction of the tiger mosquito in new ecosystems may affect the epidemiology of avian malaria in nature.

This study was financed by the Spanish Ministry of Science and Innovation, the European Union, and other sources.