Vector-host interactions in disease transmission.
Tick-borne spirochetes include borreliae that cause Lyme disease and relapsing fever in humans. They survive in a triangle of parasitic interactions between the spirochete and its vertebrate host, the spirochete and its tick vector, and the host and the tick. Until recently, the significance of vector-host interactions in the transmission of arthropod-borne disease agents has been overlooked. However, there is now compelling evidence that the pharmacological activity of tick saliva can have a profound effect on pathogen transmission both from infected tick to uninfected host, and from infected host to uninfected tick. The salivary glands of ticks provide a pharmacopoeia of anti-inflammatory, anti-haemostatic and anti-immune molecules. These include bioactive proteins that control histamine, bind immunoglobulins, and inhibit the alternative complement cascade. The effect of these molecules is to provide a privileged site at the tick-host interface in which borreliae and other tick-borne pathogens are sheltered from the normal innate and acquired host immune mechanisms that combat infections. Understanding the key events at the tick vector-host interface, that promote spirochete infection and transmission, will provide a better understanding of the epidemiology and ecology of these important human pathogens.
Nuttall
P A
PA
CEH Institute of Virology and Environmental Microbiology, Oxford, UK. pan@ceh.ac.uk
Paesen
G C
GC
Lawrie
C H
CH
Wang
H
H
D000818:Animals; D001898:Borrelia / Q000145:classification*; D001899:Borrelia Infections / Q000276:immunology* / Q000635:transmission*; D006801:Humans; D007303:Insect Vectors; D008193:Lyme Disease / Q000635:transmission*; D012061:Relapsing Fever / Q000635:transmission*; D017282:Tick-Borne Diseases / Q000635:transmission*; D013987:Ticks / Q000382:microbiology*