Medical and Veterinary Entomology Lecture
Terminology
Disease: An abnormal condition that impairs bodily function associated with certain symptoms and signs. Does not always involve a pathogen.
Pathogen: disease-causing organism
Host: an organism that harbors another organism.
Vector: an organism that transmits a pathogen from a reservoir to a host. To be a vector (mosquito) the one carrying the pathogen (malaria) must be a different species to the one carrying the pathogen (human).
Insects that cause diseases
The insect causes disease but there is NO pathogen involved.
Pediculosis
The infestation of lice in the head, body, or pubic hair. The lice are specialized to human hosts. The saliva of the louse causes an allergic reaction that results in itching. The itching results in sores on the skin.
Scabies
A disease caused by a mite, Sarcoptes scabiel, that is specialized to human hosts. Mites are not an insect but a type of arachnid. These microscopic mites burrow under the skin. Their droppings are what results in itchy rashes of the skin. Itching can worsen at night due to the increase in body temperature. It is most commonly spread between adults through sexual contact. However, it can spread between family members through normal physical contact.
Myiasis
(Diptera: Calliphoridae, Sacrophagidae, Muscidae)
An infection of blowfly larvae that feed on the living tissue of humans and livestock. Blowfly larvae that infects livestock is an economical problem. A method of control in certain species of blowfly is called the sterile-male technique (SIT). Where sterile males are introduced to a population to lower the success in mating with females.
Insects as Vectors of Disease-Causing Pathogens
Modes of Pathogen Transfer
Mechanical Transfer
Pathogens do not replicate in the vector. The vector picks it up and then transfers it over to a host. Within the host, replication begins.
Biological Transfer
Propagative: pathogens replicate within the vector.
Cyclodevelopmental: Pathogen undergoes development but doesn't reproduce within the vector.
Cyclopropagative: Pathogen undergoes development and replication within the vector.
Biological Transfer: Single Cycle
human-to-vector-to-human.
Insect picks up the pathogen from human A. Pathogen undergoes some sort of development or replication within the insect vector. Insect vector then goes on to pass pathogen to human B.
Possible to eliminate in humans since it moves from human to vector to human.
Biological Transfer: Secondary Cycle/Zoonotic
human to vector to human OR animal.
animal to vector to human.
Animal hosts are called reservoirs.
Harder to eliminate in humans because of more variability for implantation. Can be moved through multiple species of vectors. Then it is able to be implanted in both humans and animals.