1 Medical Entomology

• Medical Entomology - study of insects, insect-borne diseases, and other associated problems that affect humans and public health
• Medical Entomology - controlling arthropod-borne diseases, which are mostly classified as “Zoonoses”: “Zoon” – animals, and “nosos/noson” – illness/diseases
• Zoonosis – disease or infection that is transmissible from animals to humans (‘anthropozoonosis’) or from humans to animals (‘zooanthroponosis’)
• Subdivisions of medical entomology:

  1. Public health entomology – study of arthropods and human health
  2. Veterinary entomology – study of arthropods and their effects on pets, livestock, and wildlife
• Role of Arthropods in Human & Animal Health

  1. Direct cause of disease
  2. As vectors of pathogenic microorganisms
  3. As intermediate hosts of disease pathogen
• Direct causes of disease - arthropods act as parasites
• Parasites - organisms that live at the expense of their hosts, (e.g. protozoans, helminths, arthropods)
• Pathogens – organisms whose presence in another organism has the potential to cause disease (e.g. viruses, fungi, bacteria)
• Ectoparasitoses – diseases caused by various kinds of contact (bloodfeeding/bloodsucking, burrowing, crawling, or scraping) between arthropods and the external body surfaces of hosts

  • E.g., bloodsucking (ticks, fleas, lice), burrowing (mites)
• Ectoparasitoses - Causes dermatoses, allergic reactions, loss of efficiency/productivity in humans; weight loss, lowered milk production in animals
• Endoparasitoses – invade tissues or body cavities of vertebrate hosts
• Ensoparasitoses:

  • “Chigoe" or "chigger“ flea - female of which becomes embedded as a result of swelling of host's tissues surrounding the feeding site
• Endoparasitoses:

  • Myiasis – caused by infestation of Diptera fly larvae (maggots)
• Envenomization – introduction of venom (defensive purposes or to kill prey) or other toxins (proteins that cause poisonous reactions) by arthropods through stinging or biting
• Wasps (mastoparan), bees(melittin) and spiders (e.g. neurotoxin) produce venom
• Allergic Reactions – physiological mechanisms that defend against the introduction of foreign, or nonself, substances
• Antigen - foreign substance that results in the production of antibodies
• Allergens - antigens that produce unusually strong defensive reactions causing allergies (condition)
• Hypersensitive reactions are associated with adverse symptoms such as itching, redness, swelling and rash
• Venoms of arthropods can act as allergens that cause anaphylaxis (fatal = shock, ↓BP, narrow airways = block breathing, nausea and vomiting)
• Allergic reactions

  • E.g., house dust mite, cockroaches, mosquito
• Delusory parasitosis – psychopathic condition manifested by strong sense of being infested by arthropods (but may not be the actual case)
• Delusory parasitosis - result of self-inflicted scratching or unwise application of fluids causing skin rash, redness and abrasions
• Annoyance – e.g. abundance, small size, or habit of flying into or around the eyes, ears, and nose, splatter on surfaces
• Fear of arthropods:

  • Entomophobia – fear of insects
  • Arachnophobia – fear of spiders and other arachnids
  • Acarophobia – fear of mites and ticks
• Fear of arthropods - reflect unusual severe psychological response, more-than- normal fear often resorting to excessive or obsessive measures to control the problem (e.g., overtreatment of themselves or their homes with insecticides and other chemical compounds)
• Formicophilia – unusual human psychosexual disorder
• Formicophilia - self-induced sexuoerotic arousal and orgasm when ants, cockroaches, or other small are allowed to crawl, creep, or nibble on the body, notably, the genitalia, perianal area, or nipples
• Food Contaminants – house fly on food regurgitates pathogen-contaminated fluids before or during feeding, also may defecate with potential pathogens, then subsequent consumption leads to the transmission of pathogens to humans or other animals
• Food Contaminants - integument of household pests (e.g., flies, cockroaches) can serve as a contact source of pathogens that may be readily transferred to food items
• Vector – agent by which pathogen is transmitted from one host to another
• As Vectors of Pathogenic Microorganisms

  • Arthropods carry and transmit infectious pathogens directly or indirectly from an infected animal to a human or from an infected human to another human
• As Vectors of Pathogenic Microorganisms

  • E.g., via biting of mosquitoes, or tsetse flies
• As Intermediate Hosts of Disease Pathogen - larval fleas that live in the bedding of dogs and cats ingest eggs of the tapeworm, then become infected when they ingest the biting adult fleas
• Patrick Manson - showed that mosquito Culex pipiens fatigans is a vector of Wuchereria bancrofti, the causative agent of filariasis
• Theobald Smith & Frederick L. Kilbourn - implicated cattle tick, Rhipicephalus annulatus, as a vector of Babesia bigemina, the causative agent of Texas cattle fever (bovine babesiosis)
• Ronald Ross - demonstrated the role of mosquitoes as vectors of avian malarial parasites from diseased to healthy sparrows
• Giovani Battista Grassi - described cyclical development of malarial

  parasites in anopheline mosquitoes
• Paul Louis Simond - showed that fleas are vectors of the bacterium Yersinia pestis that causes plague
• Josiah Nott - published circumstantial evidence that mosquitoes were involved in the transmission of yellow fever virus to humans