MEDICAL ENTOMOLOGY
Dr. Cemile Bagkur
cemile.bagkur@neu.edu.tr
General characteristics of Arthropoda
• Bilateral symmetry
• Jointed appendages
• Hard exoskeleton
• Eyes compound or simple
• Digestive, vascular, excretory,
nervous systems present
• Reproduction; Seperate sexes,
sexual reproduction,
parthenogenesis.
Phylum Arthropoda
Class: Insecta Class: Arachnida
• Body division :Head, thorax & • Body division :Only one part
abdomen • No thorax & abdomen
• Thorax & abdomen segmentation
segmentation • No antenna
• One pair of antenna • 4 pairs of legs
• 3 pairs of legs • No wings
• 1,1or 2 wings • Acarina (Mites and Ticks)
• Hemimetabolic (Lice) • Araneida (Spiders)
• Holometabolic (Flea, Fly, Sand • Scorpionida (Scorpions)
fly, Tsetse, Mosquito)
• Hemi-metabolic development
(egg, nymphs and adults)
Lice
• Holo-metabolic development
(egg, larvae, pupa and
adults)Mosquito, flea…
Importance of arthropods
• Direct tissue invasion
• Envenomation
• Vesication (cause blister )
• Blood loss
• Transmission of disease
• Mechanical
• Biological
• Hypersensitivity reactions
• Psychological manifestations
Definitions
• Infestation:
• The reproduction, proliferation and maturation of the arthropods on the
body.
• Biological vector:
• Only proliferation Y. pestis in fleas
• Only development W. bancrofti in mosquitoes
• Proliferation and development Plasmodium spp. in mosquitoes
• Mechanical vector:
• Accidental transmission of disease Salmonella spp. by “house fly”
Class: Insecta
• Human Lice
• Head Louse Pediculus humanus capitis
• Pubic Louse Phthirus pubis
• Body Louse Pediculus humanus humanus
Head and Body Lice
• All species suck blood intermittently, which may cause unexplained dermatitis.
• Eggs, known as nits, are deposited on hair shafts or clothing, depending on the
species.
• Only P. humanus * transmits the agents of epidemic typhus, trench fever, and
relapsing fever.
• Infestations with both body and hair lice occur among people living in crowded
conditions who have little opportunity for bathing and laundering.
• Children of school age are at particular risk for acquiring head lice through the
sharing of caps, clothing and combs.
• Nits of head lice are deposited primarily on hair shafts, and those of body lice are
deposited on clothing.
Head and Body Lice
• Because objects such as hair casts, hair spray and fungal hair infection may
mimic nits, differentiation is important.
• Transmission occurs primarily through the sharing of infested clothing and
bedding because body lice tend to lay their eggs in clusters, especially
along seams or waistbands.
Pediculosis (Lice infestation)
• Itching
• Fever
• Allergic reaction
• Rash
• Headache
• Thickness of skin
• Body louse’s fecal material transmits
• Epidemic typhus (Ricketsia prowazeki)
• Trench (Quintana) fever (Bartonella quintana)
• Relapsing fever (Borrelia recurrentis)
Pubic Lice
• The pubic louse, Phthirus pubis, is distinctly different from the others.
• It is rounder, the abdomen is more crab-like, and the first pair of legs is
significantly smaller and more slender than the other pairs.
• Pubic lice and their nits are found primarily on pubic hairs but may
extend to the chest, armpit, and facial hair.
• Transmission occurs primarily during sexual intercourse.
• Treatment
• Mechanical (combing)
• Benzene hexachloride, pyrethrins, piperonyl butoxide
Fleas
• Small (1–2 mm), laterally compressed, wingless ectoparasites capable of
sucking blood.
• Long, muscular legs are adapted for jumping great distances.
• Infestations commonly occur with exposure to domestic animals and pets.
• Most common species are the dog flea (Ctenocephalides canis), the cat
flea (Ctenocephalides felis), and the human flea (Pulex irritans).
• Some individuals become highly sensitized to flea bites, whereas others
are unaffected.
• Cat and dog fleas are the usual intermediate hosts for the tapeworm D.
caninum and less frequently for H. diminuta and H. nana.
Fleas
Pulex irritans
Fleas
Fleas
• The Oriental rat flea, Xenopsylla cheopis, is an
extremely important species because it transmits the
plague bacillus and the agent of murine typhus.
• Tunga penetrans is found in both Central & South
America and Africa.
• The female flea attaches and embeds itself in the skin,
especially between the toes and under the toenails,
where it grows to the size of a small pea.
• After eggs are discharged, the flea dies, prompting an
inflammatory response and possible secondary Bubonic plague
bacterial infection.
Tungiasis
Bed Bug
• Cimex lectularius is reddish brown, dorsoventrally flattened, wingless insect (~5
mm).
• Fed especially at night on mammals.
• During daylight hours, they hide under mattresses, loose wallpaper and
floorboards.
• Although they are not known to transmit disease, bedbug bites may cause
painful symptoms, depending on an individual’s sensitivity to their saliva.
• Transient parasite
• Adult 4-5 mm
• Brown-grey coloured
• Live in wood-made material
• Cause edema, itching
Bed Bug
Bed Bug
Kissing Bug
• Kissing bugs (Triatoma, Rhodnius, Panstrongylus) black or brown.
• Transmit the agent of Chagas’ disease, T. cruzi, in the feces, which is
secondarily inoculated into the skin by the human host while
scratching.
Bees, Wasps, Beetles, Ants, Moths and Butterflies
• Hymenopterans are social insects that readily defend their nests when
disturbed.
• They may cause some allergic reactions even anaphylaxis.
• Some beetles may give a painful bite, exude vesicating fluids that cause
dermatitis or blister formation.
Flies, Mosquitoes and Midges
• Diptera are characterized by the presence of a single pair of membranous wings.
• Responsible for the greatest role of human disease through blood-sucking
activities, biological or mechanical transmission of infectious agents, and
direct tissue invasion by larval forms (myiasis).
• Cause local irritation or systemic reactions from sensitivity to the saliva and, in
some individuals, physical and psychological damage.
Flies, Mosquitoes and Midges
• Biological vector
• Malaria, filariasis and arboviral disease by mosquitoes
• Onchocerciasis by blackflies
• Leishmaniasis and bartonellosis by sand flies
• African trypanosomiasis by tsetse flies
• Mechanical vector
• Non-biting flies such as house flies, flesh flies and blow flies, which can easily
contaminate food.
Mosquito species
Diphtera (Flies)
Phlebotomus spp.
Prevention and Protection
• Avoidance of outdoor activity
during down and dusk can reduce
risk of exposure.
• Wearing long-sleeved shirts, long
pants and hats minimizes areas of
exposed skin.
• Repellents applied to open parts of
the body.
• Mosquito nets
• Chemical treatment of the
house/environment against adult and
larval mosquitoes.
Flies, Mosquitoes and Midges
• Myiasis may occur by flies in an accidental,
facultative, or obligatory way.
• Maggot Therapy
• Introduction of live, disinfected maggots
(fly larvae) into the non-healing skin and
soft tissue wound(s) of a human/animal
for the purpose of cleaning out the
necrotic (dead) tissue within a wound
(debridement) and disinfection.
• e.g. Lucilia sericata The green bottle
fly
Class: Arachnida
Scorpion and Spider
• Both have two body segments (cephalothorax and abdomen)
• Both are best known for their ability to inject poisonous venom.
• Toxicity to humans varies depending on the species; many elicit no more
reaction than that of a bee sting, but some are deadly (neurotoxin,
cardiotoxin, nephrotoxin, hemolytic toxin).
• Most spider bites cause only transitory irritation and pain, only widow
spiders (Latrodectus) are responsible for systemic arachnidism (neurotoxin
capable of producing weakness, myalgia, paralysis, convulsions, and,
occasionally, death).
• Spider Latrodectus variolus
• Scorpion Neurotoxic toxin
Spider and Scorpion
Latrodectus variolus (Black widow)
Ticks
• Have a fused cephalothorax and abdomen, as well as a characteristic
toothed hypostome for feeding.
• Tick development progresses through four stages: egg, larva, nymph,
and adult.
• Following hatching, a blood meal is required for progression to the
subsequent stage.
• Humans usually acquire ticks in grassy or brushy areas in close
proximity to the usual animal hosts.
Ticks
• All species are obligate blood-sucking ectoparasites and are important
vectors of viral, bacterial, and protozoal pathogens to humans and
domestic animals.
• May produce local tissue damage and blood loss.
• Species affecting humans include members of the family Ixodidae
(hard ticks) and Argasidae (soft ticks).
Ixodidea
Ticks
• Tick paralysis, a syndrome
caused by a neurotoxin
secreted by a tick’s salivary
glands that produces
ascending flaccid paralysis
and toxemia.
• Removal of the attached tick
usually results in resolution
of symptoms within hours to
days.
Tick paralysis
Woman's face paralysed after a tick burrowed in her ear
Ticks as “Vectors”
• Viral
• Tick – borne encephalitis
• Colorado tick fever
• Crimean – Congo hemorrhagic fever
• Ricketsial
• Tick typhus (Rickettsia rickettsi)
• Q fever (Coxiella burnetti)
• Bacterial & spirochetal
• Relapsing fever (Borrelia duttoni)
• Tularaemia (Francisella tularensis)
• Lyme disease (Borrelia burgdorferi)
• Protozoal
• Babesiosis
Removal of ticks
• DO
• DO NOT • Use a pair of pointed
• Panic tweezers
• Crush the tick's body • Cleanse bite site with
• Try to burn the tick off antiseptic before and after
• Apply petroleum jelly, nail removal
polish or any other • Wash hands afterwards
chemical (other than
antiseptic)
Mites
• Mites are arachnids of microscopic size (usually <1 mm) that are
widely distributed in the environment.
• Medically important species may attack humans directly, serve as
vectors for infectious disease, or cause dust allergies.
• Humans are commonly infested with both Demodex folliculorum
(mites of the sebaceous glands and hair follicles) and Demodex brevis,
the follicle mites, and Sarcoptes scabei, the itch or mange mite.
Demodex
• Follicle mites are minute (0.1–0.4 mm), elongate parasites with
stubby legs that can be recovered from hair follicles and sebaceous
glands.
• Their presence has been associated with various skin conditions, they
are commonly found in healthy individuals as well.
Demodex
Sarcoptes scabei
• Greater medical importance because of their ability to create serpiginous
tunnels through the upper layers of the epidermis.
• Transmitted through personal contact.
• Found primarily in the interdigital spaces and the flexor surfaces of the
wrists and forearms and less commonly in other areas, including the
breasts, buttocks, and external genitalia.
• Inflammation and intense itching result from the tunneling activity and
from the deposition of eggs and excreta.
• Clinical manifestations vary depending on the degree of sensitization to
the parasites and their products .
• Lesions often become secondarily infected.
Sarcoptes scabei
Sarcoptes scabei
Sarcoptes scabei
• Generalized dermatitis occurring in the presence of thousands of mites, typically
in elderly or immunocompromised individuals, is known as crusted or
Norwegian scabies.
• The diagnosis is made by placing skin scrapings collected from tunneled areas
in 20% potassium hydroxide or mineral oil for clearing and examining under the
microscope.
• 1% gamma benzene hexachloride (kills both eggs and mites) or 10%
crotaminton for in infants, children, pregnant women.
Other mites
• House mites (Dermatophagoides ) responsible of “house - dust”
allergy.
• Trombiculid mites are vectors of Tsutsugamushi disease (scrub
typhus) by R. tsutsugamushi.
Thank you for listening…
