BIOL 3P64 Lecture Notes - Lecture 13: Salivary Gland, Midgut, Lyme Disease
5 May 2018
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Lecture 13: Detrimental Insects-Animal Pests
o Many animal pests consists of parasite that live on (or in) the bodies of animals
o Additionally, some are capable of vectoring animal diseases
▪ Some can affect humans as well
o Effects caused by animal parasites
▪ Physical damage, behavioural alterations, physiological changes, death
o Examples of insects considered animal pests
▪ Siphonaptera: the fleas
▪ Diptera: the flies
• Suborder Mematocera (the long horned flies) consitaisn a lare number of giting insects that transmiitt
disease (mosquitoes, blackflies)
• Cayptratae: other animal affecting flies, i.e botflies and stable flies
▪ Hemiptera: ture bugs i.e. bed bugs
▪ Other non-insect arthropods
• Subclass Acari: ticks and mites
o Notes on vectors
▪ 2 main types of disease vectors
• Mechanical: organism that just transfers a disease from one host to another, facilitating spread
o No deveoplment or reprdocution within the vector
o Simple transportation form one palce to another
• Biological vector: organism in which the disease reproduces and develops
o Life cycle of the disease is reliant upon the vector
▪ Biological vectors: the barriers to infection ***two important limiting factors***
• In order for an insect to be a successful biological vector, the disease infecting it must be able to pass
two main barriers to infection
• First barrier: Midgut wall
o Disease must be able to escape through the midgut wall to escape digestion and excretion
o Allows it to access the haemolymph, so that it can reproduce and spread throughout the body
• Second barrier: Salivary gland wall
o Disease must be able to penetrate the wall of the salivary glands
o Allows it to spread to additional hosts when the insect feeds
▪ Detection of virus/disease in different parts of the body indicate what barriers have been passed
• Disease found in midgut: insect is able to ingest the disease agent
• Disease found in the wings/legs: disease has passed the 1 st barrier to infection (midgut wall)
o Generally, extremities/appendages used for this purpose
o Processed separately from midgut and head
o Disease found in salivary glands: disease has passed the 2 nd barrier to infection
▪ At this point, it’s very likely that the insect is a capable vector for the disease in
question
o Examples
▪ Class Archnida: subclass Acari: Order Parasitiformes
• Suborder Ixodida
• Not insects but still important biting arthropods worth learning about
• Small parasitic organisms that feed on animal and human blood
o Distendible abdomen
o Piercing mouthparts
▪ Chelicerae
• Ghost Moose
o Not a different moose species
o Rather, a moose that is suffering from extensive tick damage
o Numerous ticks attach to the moose and feed on the blood
o Moose attempts to remove ticks, and removes its own hair instead
o Getting worse with shorter, milder winters
▪ Ticks are also vectors for numerous diseases
• Lyme disease: Bacterial agent
find more resources at oneclass.com
find more resources at oneclass.com
o Borrelia sp.
o Infects dogs, as well as humans
o Can cause mild symptoms, but also some cases of paralysis and kidney effects
• Rocky mountain spotted fever: Bacterial agent
o Rickettsia rickettsii
o Infects dogs and large mammals
o Hemorrhaging
o Possible blood clotting, which can lead to death
o Biting Midges
▪ Nematoceran (longhorned) flies
• Order: Diptera: Family Ceratopogonidae
• Extremely small flies, commonly called “no-see-ums” or punkies
o They can walk through a screen door hole with ease
• Roughly 6000 species worldwide
o 600 in North America
• Most feed on invertabrates (i.e. Insect haemolyymph)
o But some genera feed on vertebrate hosts
• His thesis focus
▪ Main biting midge genus for disease transmission is Culicoides
• Culicoides species transmit a number of harmful viruses throughout the world
• 2 mm in size, maximum
• Bite many livestock animals, wild ruminants, and humans
▪ Bluetongue Virus
• Culicoides sonorensis is the primary vector for Bluetongue Virus (BTV) in North America
• It cannot transfer from host to host without aid
• Bluetongue infects farm livestock
o Outbreaks in Europe previously caused thousands of sheep deaths, from infection and
slaughter for containment
• Sheep, goats, and deer most susceptible
o Hemorrhaging
o Swollen, cyanotic (blue) tongue
o Breathing issues
o Kneewalking
o Possibly death
• Does NOT infect humans!
▪ Bluetongue Virus Infection
• Culicoides bites infected host
• Virus penetrates through peritrophic membrane and moves through midgut cells
o 1 st barrier to infection is the midgut
• Virus propagates within the haemolymph and organs
• Eventually moves to the salivary gland
o 2 nd barrier to infection is gland
• BTV enters gland and leaves during feeding
o Infection of new host
• Culicoides and BTV
o Before 2013, C. sonorensis only known in the USA and BC/Alberta
o However...I managed to find it in Ontario in summer 2013
o BTV was isolated in ON for the first time in 2015
▪ EHDV: August 2017
• Epixootic hemorrhagic disease virus
▪ Botflies (not BUTT-flies)
• Order Diptera: Family Oestridae
o NOT a Nematocera (Suborder Calyptratae instead)
o Commonly also called warble flies
• Usually rather large, hairy flies that have severely reduced mouthparts in the adult form
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
In order for an insect to be a successful biological vector, the disease infecting it must be able to pass two main barriers to infection. First barrier: midgut wall: disease must be able to escape through the midgut wall to escape digestion and excretion, allows it to access the haemolymph, so that it can reproduce and spread throughout the body. Disease must be able to penetrate the wall of the salivary glands. Disease found in salivary glands: disease has passed the 2 nd barrier to infection. Not a different moose species: rather, a moose that is suffering from extensive tick damage, moose attempts to remove ticks, and removes its own hair instead, getting worse with shorter, milder winters. Numerous ticks attach to the moose and feed on the blood: ticks are also vectors for numerous diseases. Can cause mild symptoms, but also some cases of paralysis and kidney effects. Bite many livestock animals, wild ruminants, and humans: bluetongue virus.
