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Unformatted text preview: Unit 15 in Entomology  Unit 15: medical entomology.  The objectives in this unit are to describe the different types of medically related effects caused by arthropods, both direct and indirect, to define the terms associated with disease transmission, and to describe the general characteristics of the seven diseases covered, including the vector, where in the world it is a problem, the disease symptoms, how it is treated and controlled, and the type of disease.  Arthropods and insects, in particular, cause many medically related effects. Directly they can cause dermatitis and allergic reactions. But indirectly they can pass on diseases that can be debilitating and sometimes fatal. Throughout history, arthropods and insects have affected and infected mankind and animals with everything from minor afflictions to major diseases that have caused catastrophic epidemics. In this unit we will investigate the interaction of arthropods and insects with animals and mankind through direct and indirect means, as well as reviewing their use as forensic evidence. Please read your textbook readings to familiarize yourself with the terms associated with medical entomology.  Well begin our discussion with some direct host reactions to arthropods. Some direct effects, such as pain and suffering, are difficult to measure, but some quantifiable, economic effects include mechanical reactions (including dermatosis, dermatitis and itching), exsanguination (which is the loss of blood or annoyance), myiasis (which is where dipterous larvae invade the living tissue), toxins and paralysis (including envenomization), allergic reactions (which leads to anaphylaxis), and entomophobia (which is the psychological fear of insects). Let's take a look at each of these direct effects in more detail.  Mechanical reactions: one causative agent of a mechanical, itching, reaction is a mite infestation. One mite, in particular, is the agent of scabies in humans and sarcoptic mange in other animals. The scabies mite is an obligate parasite, meaning it must feed on a host in order to complete its lifecycle. After mating, the female mite will burrow under the skin and lay her eggs. She secretes substances that trigger an allergic reaction in the host that results in painful itching. This mite can be passed through close contact between hosts and can live for 36 hours outside of the host. Sarcoptic mange found in animals is basically the same as that in humans. Most animals, including cattle, pigs, horses, and dogs, experience the same dermatitis, leading to weight and hair loss. Mange mites have been recovered and described from different animals, but it is unclear if the mites are species specific. Some mites show a preference for a certain species of host, but the specificity of the host is not absolute. The photos below show a dog infected with mange mites and on the right is a picture of the Sarcoptes mange mite....
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- Spring '08