Votýpka J., Svobodová M. & Volf P. (2002) Development of avian trypanosomes in mosquitoes. Abstract in The Journal of Eukaryotic Microbiology 49 (2): 10 A (No.40).
ISSN 1066-5234, IF 1,739
ABSTRACT. Parasitic flagellates of the genera Trypanosoma and Leishmania have
a two-host life cycle and alternate between vertebrate and insect hosts. Transmission
of the parasite into the insect vector is due to uptake of flagellates with
peripheral blood. However, transmission to the vertebrate host may occur in
several ways, for example, by inoculation with insect saliva or contamination
with insect feces. The location of parasites in the insect digestive tract or
in the salivary glands is critical to the mechanism of transmission to the vertebrate
host. Avian trypanosomes (strain CUL1, which originates from naturally infected
Culex pipiens pipiens) were used to infect laboratory reared female mosquitoes
(Culex pipiens quinquefasciatus). Infected mosquitoes (16 days post infection)
were dissected and heavy infections of trypanosomes were found in the division
between the foregut and the thoracic midgut. The other parts of the digestive
tract including salivary glands were parasite-free. Semithin and thin cross-sections
of the fore part of the alimentary tract containing trypanosomes were analyzed
by light and electron microscopy, respectively. The parasites observed were
in close contact with chitin in the cuticular lining of the stomodeal valve
only; the region of epithelium covered by microvilli was not colonized. The
adhesion of the parasite to this cuticle-lined region occurs by the formation
of zonal hemidesmosome-like plaques at the extremities of the expanded flagella
of epimastigote. The high number of trypanosomes in the anterior part of the
thoracic midgut creates a plug, which could result in the regurgitation of flagellates
into the vertebrate host with a backflow of ingested blood during sucking. Additionally,
some damage to the chitin layer or impairment of the stomodeal valve motility
could help such a transmission process. The development of avian trypanosomes
in mosquitoes is similar to that of the leishmanias in sand flies and therefore
could represent a new model for the investigation of host-parasite relationships