Medical Entomology in Brief

Medical Entomology in Brief

Dr. Alfatih Saifudinn Aljafari Assistant professor of Parasitology

College of Medicine- Al Jouf University

Aim and objectives

• Aim: – To bring attention to medical entomology as important

biomedical science

• Objective: – By the end of this presentation, audience could be

able to: • Understand the scope of Medical Entomology • Know medically important arthropods • Understand the basic of pathogen transmission dynamic •

Medical Entomology in Brief- Dr. Aljafari (CME- January 2019)

In this presentation

• Introduction

• Classification of arthropods

• Examples of medical and public health important species

• Insect Ethology

• Dynamic of disease transmission

• Other application of entomology


Definition

• Entomology: – The branch of zoology concerned with the study of insects.

• Medical Entomology: – Branch of Biomedical sciences concerned with “ArthrobodsIn the past

the term "insect" was more vague, and historically the definition of entomology included the study of terrestrial animals in other arthropod groups or other phyla, such, as arachnids, myriapods, earthworms, land snails, and slugs. This wider meaning may still be encountered in informal use.

• At some 1.3 million described species, insects account for more

than two-thirds of all known organisms, date back some 400 million years, and have many kinds of interactions with humans and other forms of life on earth


Arthropods and Human

• Transmission of infectious agents

• Allergy

• Injury

• Inflammation

• Agricultural damage

• Termites

• Honey

• Silk

Medical Entomology in Brief- Dr. Aljafari

(CME- January 2019)

Phylum Arthropods

• Hard exoskeleton, segmented bodies, jointed appendages

• Nearly one million species identified so far, mostly insects

• The exoskeleton, or cuticle, is composed of chitin.

• Acute senses include simple and compound eyes, brains, and many ganglia.

• Arthropods use pheromones to communicate.

• They have open circulatory systems, complete digestive system, and efficient means of wastes excretion by Malpighian tubes.

• Arthropods reproduce sexually, but some exhibit parthenogenesis.


300 million years old fossil with full body impression

Insect perfectly preserved in amber


Science for every insect

• Coleopterology - beetles • Dipterology - flies • Odonatology - dragonflies and damselflies • Hemipterology - true bugs • Isopterology - termites • Lepidopterology - moths and butterflies • Melittology (or Apiology) - bees • Myrmecology - ants • Orthopterology - grasshoppers, crickets, etc. • Trichopterology - caddis flies • Vespology - Social wasps


Phylum: Arthropoda

Sub-Phylum: Chelicerata

Class: Arachnida/Octapoda; e.g., Spider, Mites and Ticks

Sub-Phylum: Mandibulata (Antennata)

Class: Crustacea; two pairs of antennae. e.g. Crayfish, Crabs, lobsters, shrimps

Class: Myriapoda

Sub-class: Chilopoda; e.g. Centipedes Sub-class: Diplopoda; e.g. Millipedes

Class: Insecta/Hexapoda

Sub-class: Apterygota (4 Orders) Sub-class: Pterygota (27 Orders)


Class Arachnida

• A typical adult arachnid has two distinct body regions: Cephalothorax and abdomen. – Ticks and mites have only one body segment.

• Cephalothorax, bears 4 pairs of legs; a pair of chelicerae that are; a pair of pedipalps and simple eyes.

• They have no antennae and no wings. • large abdomen with no external gills or locomotor organs.

– Excretion by Malpighian tubules. – Respiration by book lungs and trachea.

• Spiders, mites, ticks, scorpions.


Hottentotta tamulus Poisonous (neurotoxin)

Black widow (Latrodectus mactans) Poisonous

Sarcoptes scabiei -Lays its eggs in dermal layer -Severe itching - Causing (Sarcoptic mange) OR Scabies

Examples Arachinds of medically important for Human


Bacterial

Lyme disease Borrelia burgdorferi Ixodes species

Relapsing fever Borrelia hermsii Ornithodoros species

Rocky Mountain spotted fever Rickettsia rickettsii Dermacentor variabilis

Viral

Tick-borne encephalitis (TBEV) Ixodes species

Protozoan

Babesiosis Babesia microti Ixodes species

Toxin

Tick paralysis Toxins Dermacentor andersoni

Ixodes species

Dermacentor Ornithodoros


Class Crustacea

• Most crustaceans are aquatic and use gills for gas exchange.

• 2 pairs of antennae for sensing.

• Mandibles for crushing food that move side to side.

• Eyes are located on movable stalks.

• Many have five pairs of walking legs used for seizing prey and cleaning other appendages.

• First pair is often modified into strong claws.

Water flea (cyclops)

Transmission of Guinea warm (Dracunculus medinensis)


Class Insecta

• A typical adult insect has three distinct body regions: head, thorax and abdomen.

• head, which bears one pair of compound eyes, one pair of unbranched antennae and paired mouthparts.

• the thorax, which is composed of three segments each bears a pair of legs, in many groups the second and third segments each bear a pair of wings.

• the abdomen, segments and having mating organ. – Excretion by Malpighian tubules; – respiration by pipe-like tracheae, exoskeleton or by gill; – digestion by tubular digestive tract; – blood circulation by open circulatory system; – reproduction by paired reproductive organs. – Muscular system, nervous systems also present.


Subclasses of Insecta

• Apterygota – Wingless – One pair or more than one pair of appendages present in front

of genital opening – Mandible is attached into a specific position of head capsule – Moulting continuous after sexual maturity.

• Pterygota

– Winged or secondarily wingless insects – No appendage present in front of genital opening – Mandible is attached into two specific position of head capsule – Sexually matured adults do not moult.


English (common) Scientific Order عربي

Ant Hymenoptera النمل

Bee Hymenoptera النحل

Butterfly Lepidoptera الفراش

Grasshoppers Orthoptera الجراد

Fly Diptera الذباب

Mosquito Diptera البعوض

Louse (lice) Phthiraptera القمل

termite Isoptera دابة الأرض

spider Arachnida العنكبوت

There are more than 31 different orders of insects in the class Hexapoda, sixteen of which are considered of economic importance to agriculturists. Among them (according to Holly Quran)


Phthiraptera

Diptera

Head Louse: -Transmission of Typhus

Siphonaptera

Rat flea (Xenopsylla cheopis) Transmission of Yersinia pestis Cause of Pleaque

Sand fly Transmission of Leishmania

Tsetse fly (Glossina) Treansmission of African Trypanosomiasis

Blackfly Transmission of Onchocerca volvulus The cause of (river blindness)

Deer fly (Crysops) Transmission of Loa loa Hemiptera

Tritomine bug (kissing bug) Transmission of American trypanosomiasis


• Chikungunya • Dengue fever • Lymphatic filariasis • Rift Valley fever • Yellow fever • Zika

• Malaria • Lymphatic filariasis

• Japanese encephalitis • Lymphatic filariasis • West Nile fever


Ethology

• Circadian rhythm

• Feeding preference

• Host preference

• Ambience and humidity

• CO2 vs O: Female mosquitoes have nerve cells called cpA neurons that have a receptor to detect carbon dioxide.


Vector-borne diseases

• Vector-borne diseases are human illnesses caused by parasites, viruses and bacteria that are transmitted by arthropods and snails.

• The major vector-borne diseases, together, account for around 17% of all infectious diseases

• Every year there are more than 700 000 deaths from diseases

Medical Entomology in Brief- Dr. Aljafari

(CME- January 2019)

Arboviruses

•Arthropod-borne viruses are viruses that can be

transmitted to man by arthropod vectors. The WHO

definition is as follows

•“Viruses maintained in nature principally, or to an important extent,

through biological transmission between susceptible vertebrate hosts by

haematophagus arthropods or through transovarian and possibly venereal

transmission in arthropods.”


Dynamic of pathogen transmission

• Feeding habits: – Most of insect biological vectors are Heamtophagous

• Periodicity – Nocturnal – Diurnal – Sub periodic

• Host preferences: – Zoophilic – Anthopophilic – Zoonotic

• Type of transmission: – Biological – Mechanical – Vertical and transstadial


Feeding habits: Most of insect biological vectors are Heamtophagous

Periodicity Nocturnal Diurnal Sub periodic

Host preferences: Zoophilic Anthopophilic Zoonotic

Type of transmission: Biological Mechanical Vertical and transstadial


Dynamic of pathogen transmission

• Complex demographic, environmental and social factors. – Global travel and trade,

– unplanned urbanization and

– environmental challenges such as climate change • Changes in agricultural practices due to variation in temperature

and rainfall can affect the transmission of vector-borne diseases

– Factors affecting pathogen transmission, making transmission season longer or more intense or causing diseases to emerge in countries where they were previously unknown.


A. Africanus

A. bromeliae

Rural cycle


Yellow fever transmission zone in Africa Aedes mosquito habitat


Forensic entomology

• The scientific study of the invasion of the succession pattern of arthropods with their developmental stages of different species found on the decomposed cadavers during legal investigations

• Identification of insects at various stages of their life cycle, such as eggs, larva, and adults.

• Collection and preservation of insects as evidence.

• Determining an estimate for the postmortem interval or PMI (the time between death and the discovery of the body) using factors such as insect evidence, weather conditions, location and condition of the body, etc.


Histerid beetles Predator of fly eggs

~ 10 days

Ham & Checkered Beetles (Cleridae)

Predator of flies & beetles;

also feed on dead tissue

~15 days

Skin Beetles (Dermestidae)

Feed on dried skin & tissues

~20 days


Myiasis

• Myiasis is an infestation of the skin by developing larvae (maggots) of a variety of fly species within the arthropod order Diptera .

• Worldwide, the most common flies that cause the human infestation are:

– Dermatobia hominis (human botfly)

– and Cordylobia anthropophaga (tumbu fly).


Control and prevention

• Nets

• Insecticides

• Repellants

• Natural enemies

• Sterilization


• Karl von Frisch

• winner of the 1973 Nobel Prize in Physiology or Medicine (ethology of bees)


Medical Entomology in Brief

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