This tendency, for a cow, say, over a human, or the other way around, has implications for disease transmission and for mosquito control. Scientists have been looking into this and a genetic basis for the different biting behavioural patterns for mosquitoes has been identified.
The new research, from University of California (Davis), has found that mosquitoes are more likely to feed on cattle than on humans provided they possess a specific chromosomal rearrangement in their genome. Significantly this genetic make-up lowers the chances of the mosquitoes transmitting the malaria parasite. This is because the rates of malaria transmission are dependent upon whether mosquitoes bite humans or animals.
To demonstrate this, the science group examined whether the genetic basis to host choice with the Anopheles arabiensis mosquito (a key vector for malaria in East Africa). Understanding the biology and behavior of Anopheles mosquitoes can help understand how malaria is transmitted, and can aid in designing appropriate control strategies. Taking this line of research, the scientists sequenced the genomes of 23 human-fed and 25 cattle-fed mosquitoes taken from the Kilobero Valley in Tanzania. Here different genetic components were identified.
According to lead researcher Dr. Bradley Main: “Whether there is a genetic basis to feeding preferences in mosquitoes has long been debated.” He then adds that the debate is now over for the researchers located the gene region associated with cattle feeding, which is a chromosomal rearrangement called the 3Ra inversion. These findings provide support that the inversion in An. arabiensis is linked to cattle feeding, although further research will be required to verify this.
From this discovery, Dr. Main explains: “using a population genomics approach, we have established an association between human feeding and a specific chromosomal rearrangement in the major east African malaria vector.”
The researchers have identified specific genes that affect the genetic trait. From this Dr. Main thinks that genetics can be used to track mosquito behaviour, and that this information can be used to improve local control strategies.
Beyond trending, the knowledge could also be used to aid the genetic modification of mosquitoes to make the disease carrying species prefer cattle over people. This is a somewhat controversial idea.
The process of modifying the insects involves a method called “gene drive” (which has been discussed in an earlier Essential Science column). This technology consists of inserting modified genes into an organism. Not all scientists are keen on this approach, fearing that it could lead to the elimination of an entire species and could have ecological consequences, such as cross-species gene transfer. In addition, there is no internationally agreed regulatory framework to track the release of the modified mosquitoes. An alternative approach involves harnessing genetic sequencing technology to track the evolution of different viruses (as was done previously with Ebola viruses).
The research has been published in the journal PLOS Genetics. The research paper is headed “The Genetic Basis of Host Preference and Resting Behavior in the Major African Malaria Vector, Anopheles arabiensi.”
This article is part of Digital Journal’s regular Essential Science columns. Each week we explore a topical and important scientific issue. Last week we looked at a new type of bacteria that can cause an anthrax-like disease together with some cases from Africa. The week before we considered how building surfaces as complex as insect wings has inspired research into light scattering, techniques that might shine a spotlight on the assessing the development of Alzheimer’s disease early.