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Vectors and infection
The Apollo-SV definition of 'infection' is: A reproduction of a pathogen organism of a particular biological taxon in a tissue of a host organism from another taxon.
A key question arose: are vectors infected?
The answer depends on the particular pathogen / vector species combination.
Mosquitoes are infected by the pathogens involved in malaria, Chikungunya, and Dengue.
Mosquitoes are indeed infected by the malaria parasite. See: http://www.malariavaccine.org/malvac-lifecycle.php
When a mosquito bites an infected human, it ingests the gametocytes, which develop further into mature sex cells called gametes. The fertilized female gametes develop into actively moving ookinetes that burrow through the mosquito's midgut wall and form oocysts on the exterior surface. Inside the oocyst, thousands of active sporozoites develop. The oocyst eventually bursts, releasing sporozoites into the body cavity that travel to the mosquito's salivary glands...
CHIKV virus enters, and is capable of replicating in, the cells of its mosquito vectors.
- Solignat M, Gay B, Higgs S, Briant L, Devaux C. Replication cycle of chikungunya: A re-emerging arbovirus. Virology. 2009;393(2):183-197. doi:10.1016/j.virol.2009.07.024.
- Weaver S, Lecuit M. Chikungunya Virus and the Global Spread of a Mosquito-Borne Disease. NEJM 2015; http://www.nejm.org/doi/full/10.1056/NEJMra1406035
Dengue virus infects mosquito midgut (enters midgut cells and replicates) and spreads to salivary glands over a period of 8-12 days:
WHO/TDR. Dengue guidelines for diagnosis, treatment, prevention and control. New edition. Geneva, World Health Organization, 2009.