Mosquitoes that have a midgut infection barrier means that viruses cannot establish an infection within the midgut. This can be due to genetic factors, such as a lack of expression of receptors on cells, or non-genetic factors such as microbiome density and composition.

Mosquito Midgut Infection Barrier

The midgut escape barrier stops dissemination of the virus across the basal lamina. The escape barrier is related to the thickness of the basal lamina, as a thicker basal lamina means a harder crossing for the virus, thus it is retained in the midgut.

Mosquito Midgut Escape Barrier

The vector competence of mosquitoes depends on the virus' ability to cross several physical barriers and antiviral responses within the mosquito:
- Midgut infection barrier
- Midgut escape barrier
- Salivary gland infection barrier
- Salivary gland escape barrier
- RNA interference

University of California, Davis

Mosquitoes are one of the most important vectors of arboviruses. Common viruses transmitted by mosquitoes: dengue, zika, yellow fever, chikungunya, and many others. 

Mosquitoes and Emerging Pathogens

Rückert, Claudia, and Gregory D Ebel. “How Do Virus-Mosquito Interactions Lead to Viral Emergence?” Trends in Parasitology, U.S. National Library of Medicine, Apr. 2018, www.ncbi.nlm.nih.gov/pubmed/29305089. 

How do virus-mosquito interactions lead to viral emergence?

Mosquito Vector Competence

When a mosquito is taking a blood meal, it is possible to also ingest an arbovirus from an infected individual. The virus travels through the feeding tube, infects the midgut epithelium, and replicates in the midgut before entering the basal lamina and disseminate throughout the body. Then, the virus is able to infect the salivary gland, where it can be released into the saliva and infect the next host when the mosquito is taking another blood meal.

Mosquito Blood Feeding Mechanism 

The vectorial capacity of mosquitoes is mostly influenced by these variables:
- extrinsic incubation period
- probability of mosquito daily survival
- probability of a host being fed upon

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