The tiger mosquito in the transmission of avian malaria

The tiger mosquito, native to Asia, is an invasive species with a wide distribution today. In addition to its annoying bites, this dipteran represents a public health problem since it is a vector of pathogens that cause diseases in humans, such as dengue or Zika. The change in its distribution area enables the transmission of these diseases in the invaded areas, where most studies have focused on those diseases that affect people. However, its role in the transmission of diseases such as avian malaria, which affects wild birds, is poorly studied.

Scientists decided to review the available information in order to clarify the role of the tiger mosquito as a vector of these parasites.

This review of study results is the work of a scientific team from the Doñana Biological Station (EBD, dependent on the Spanish National Research Council (CSIC), the University of Granada (UGR) in Spain and the Nature Research Centre in Lithuania.

The reviewed studies, which monitored the presence of avian malaria parasites in mosquitoes captured in the wild, showed a very low infection rate. This suggests that, although this fly is capable of interacting with these parasites, its role as a transmitter of them in nature is limited. “We suggest that this is probably due to its tendency to feed mainly on the blood of mammals, and not so much on birds,” explains Jesús Veiga, a CSIC researcher at the EBD and first author of the study. However, the number of studies exploring this possibility is limited and, on a global scale, they have only been carried out in a few countries in the current distribution area of ​​this invasive mosquito.

Tiger mosquito (Aedes albopictus). (Photo: James Gathany/CDC)

On the other hand, this work also reviewed the studies that specifically analysed the development of avian malaria parasites, of the Plasmodium genus, in the laboratory, where a great variability was found depending on the species of parasite involved. While species such as Plasmodium vaughani and Plasmodium circumflexum do not seem to be able to develop in the tiger mosquito, others such as Plasmodium gallinaceum can complete their development and even be transmitted effectively from one bird to another. Plasmodium gallinaceum significantly affects poultry and causes serious economic losses due to the mortality of untreated birds, the loss of meat quality and the reduction in egg production. Therefore, special attention must be paid to the presence of the tiger mosquito in these environments.

“However, the results obtained so far are limited to a small number of species and genetic lineages of avian Plasmodium, which limits the conclusions that can be obtained regarding the role of this invasive mosquito species in the circulation of avian malaria,” warns Veiga. “This,” adds the researcher, “is especially relevant considering that there are more than 50 morphospecies and 1,500 genetic lineages of avian Plasmodium.” Exploring a greater number of species of these parasites in the tiger mosquito is therefore essential to predict how their introduction into new ecosystems can affect the epidemiology of avian malaria in nature.

The review is titled “Literature Review on the Role of the Invasive Aedes albopictus in the Transmission of Avian Malaria Parasites”. It has been published in the academic journal Animals. (Source: EBD / CSIC)