Intoduction: Medical Entomology

Medical Entomology

• study of insects, insect-borne disease, and other associated problems that affect humans and public health

Medical entomology is devoted to?

Devoted to understanding, preventing and controlling arthropod-borne disease, which are mostly classified as “Zoonoses”

• “Zoon”- animals, and “nosos/noson”- illness/diseases

Zoonosis

Disease or infection that is transmissible from animals to human (anthropozoonosis) or from humans to animals (zooanthroponosis)

Medical entomology: subdivisions

1. Public health entomology- study of arthropods and human health

2. Veterinary entomology- study of arthropod and their effects on pets, livestock, and wildlife

Anthropoids act as (.)

• organisms that live at the expense of their host

Parasites

• protozoans, helminths, arthropods

Organisms whose presence in another organisms has potential to cause disease

Pathogens

• viruses, fungi, bacteria

Role of Arthropods: Direct causes of disease

1. Ectoparasitoses

2. Endoparasitoses

3. Envenomozation

4. Allergic reactions

5. Delusory parasitosis

6. Food contaminants

7. As vectors of pathogenic microorganisms

8. As intermediate hosts of disease pathogen

Ectoparasitoses

Diseases caused by various kinds of contact (blood feeding/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

• “Chigoe” or “chigger” flea- female of which becomes embedded as a result of swelling of the hosts tissues surrounding the feeding site

• Myiasis- caused by infestation of Diptera fly larvae (maggots)

Envenomization

Introduction of venom (defensive purposed or to kill prey) or other toxins (proteins that cause poisonous reactions) by arthropods through stinging or biting

• wasps (mastoparan), bees (melittin) and spider (e.g neurotoxin) produce venom

Allergic reactions

Physiological mechanisms that define 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, low bp, narrow airways= block breathing, nausea and vomiting

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)

• result of self-inflicted scratching or unwise application of fluids causing skin rash, redness and abrasions

• Annoyance, fear of arthropods, formicophilia

Entomophobia

Fear of insects

Arachnophobia

Fear of spiders and other arachnids

Acarophobia

Fear of mites and ticks

Formicophilia

Unusual human psychosexual disorder

• self-induces sexuoerotic arousal and orgasm when ants, cockroaches or other small are allowed to crawl, creep or nibble on the body, notably the genitalia, perinatal area, or nipples

Vector

Agent by which pathogen is transmitted from one host to another

• arthropods carry and transmit infectious pathogens directly or indirectly from an infected animal to a human or from an infected human to another human

• E.g via biting of mosquitoes, or tsetse flies

Patrick Manson

Showed that mosquito Culex pipiens fatigans is a vector of Wuchereria bancrofti, the causative agent of filariasis

Theobald Smith & Frederick L. Kilbourne

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

Carlos Findlay

Yellow fever mosquito, Aedes aegypti, was the vector of this virus

Walter Reed

Proved A. Aegypti to be the principal vector of yellow fever virus

David Bruce

Demonstrated that tsetse fly Glossina palpalis transmit, during blood feeding, the trypanosomes that cause African tyrpanosomiasis

Howard Taylor ricketts

Rocky Mountins wood tick, Dermacentor andersoni, is a vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever

F. Percival Mackie

Showed that human body lice are vectors of Borrelia recurrentis

Carlos Chagas

Demonstrated transmission of the agent that causes African trypanosomiasis