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Pthirus pubis Pubic or Crab Louse


Nocturnal feed on hosts while they sleep (bed bugs), painful bite disrupts sleep ... Insect defecates when feeds. ... Sudden appearance in winter of 1346-1347 ... – PowerPoint PPT presentation

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Title: Pthirus pubis Pubic or Crab Louse

Pthirus pubis - Pubic or Crab Louse
Pig Louse
Hemiptera - the true bugs
  • Some 55,000 species
  • Hemielytra type of wing. Anterior half is
    leathery while the posterior portion is
    membranous. Some are wingless

Cimex lectularius - the bed bug
  • Cosmopolitan - in the temperate zones
  • Not a major transmitter of human pathogens.
    Mechanically transmit Hepatitis B virus and
    source of much misery to man.
  • Can live without food for as long as 18 months (4
    months is common)
  • Nocturnal feed on hosts while they sleep (bed
    bugs), painful bite disrupts sleep

Cimex lectularius - the bed bug
  • Dorsoventrally flattened - allows them to hide in
    tight places, cracks, under loose materials, in
    thatch houses.
  • Control is use of insecticides and remove hiding

Reduviidae - The Assassin Bugs
  • The assassin bugs - most feed on other insects.
  • One Subfamily Triatominae contain important
    vectors of Trypanosoma cruzi which causes Chagus
  • Called Kissing bugs often bite on tender parts
    of the body (lips) and have a bite that does not
    hurt while feeding. Hurts sometime later.

Reduviidae - The Assassin Bugs
  • The most common vectors of T. cruzi are
    Panstrongylus megistus, Triatoma infestans, and
    Rhodnius prolixus
  • Dogs, cats, rodents are important reservoir hosts
    in the urban setting and in the Sylvantic cycle
    the opossum is very important. .

Reduviidae - Kissing Bugs
  • Rhodnius prolixus Triatoma infestans

Chagus Disease
  • Caused by the protozoan Trypanosoma cruzi.
  • Develops in the posterior of the insect infective
    forms passed out in insect feces.
  • Insect defecates when feeds.
  • Feces with infected forms rubbed into break in
    skin or into membranes of eyes.

Pathogenesis of Chagus Disease
  • Acute phase - most common in children under 5
  • Romana's sign
  • Pseudocysts can form in almost any tissue Heart
    muscle ganglion cells are very susceptible and up
    to 80 of them may be destroyed.
  • Death may occur within 3-4 weeks after infection.

  • Reduviidae bugs are the most important link to
    human transmission
  • wild mammals may serve as reservoir hosts, dogs
    and cats are more important reservoirs for human

Siphonaptera - the fleas
  • The combined effects of Nero and Kubla Khan, of
    Napoleon and Hitler, all the Popes, all the
    Pharoahs, and all the incumbents of the Ottoman
    throne are as a fuff of smoke against the typhoon
    blast of fleas rabages through the ages.
  • Quote by B. Lehane

Siphonaptera - the fleas
  • Important in the transmission of many organisms
    especially the the plague.
  • Morphology - see figures page 554-555. These
    will used in lab to identify fleas.
  • Jumping mechanism -
  • Can jump more than 100 times body length.
  • Resulin is a specialized protein that releases
    97 of its stored energy.

Siphonaptera - the fleas
  • In general, fleas lack significant host
  • Most fleas do have preferred hosts.
  • Fleas are grouped as to how much time they spend
    on the host.

Types of Fleas
  • Spend little time on host (feeding) spend most of
    time in nest. Some rodent fleas.
  • Spend most of time on host but can transfer from
    host to host. Most fleas.
  • Sticktight flea attaches permanently to skin of
  • Chigoe (Tunga penetrans) buries under skin on
    feet and hands - (see fig 37.12).

Some Important Fleas
  • Nosopsyllus fasciatus - northern rat flea -
    Usually not considered an important plague vector
    because it seldom bites man.
  • Pulex irritans - the human flea - see page 557.
    Is not host specific and commonly appears on dogs
    (80 of fleas on dogs were Pulex irritans in
    Georgia study). Can transmit plague

Some Important Fleas
  • Echidnophaga gallinacea is the sticktight flea of
    poultry. Buries its mouthparts under the skin
    and remains attached.
  • Ctenocephalides canis and C. felis are the dog
    and cat fleas. Often bite humans. Can be
    distinguished from other fleas by the presence of
    genal ctenidium with more than 5 teeth.

Some Important Fleas
  • Xenopsylla cheopis - The oriental or tropical rat
    flea - most important vector for plaque and
    murine typhus
  • Tunga penetrans (chigoe, jigger, chigger, chique,
    sand flea) commonly penetrates the skin around
    the base of nails on feet and hands. (See fig
    37.12, page 560)

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Ctenocephalides felis (cat flea)
Pulex irritans - the Human Flea
Xenopsylla cheopis - oriental rat flea
Tunga penetrans
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Fleas as Vectors
  • Plague
  • Commonly known as the black death
  • Caused by bacterium Yersinia pestis (Pasturella
  • Releases toxins that act on the mitochondrial
    membranes inhibiting uptake of ions and thus
    normal functioning of the cellular respiration.
  • Primarily a disease of rodents. Infected flea
    bites man and he becomes infected.

Three Types of Plague
  • Bubonic - primary plague in epidemics,
    demonstrates buboes (large swollen areas in lymph
    nodes of the groin area or armpits (see fig
    37.13, page 561). Fatal in 25-50 of untreated
  • Pneumonic plague involves heavy infection of
    lungs. Is highly contagious and can be spread by
    breathing, coughing. Often fatal
  • Primary septicemic - generalized blood infection.
    Is often fatal.

Murine Typhus
  • Murine typhus
  • Endemic or flea-borne typhus caused by Rickettsia
    mooseri (prowazekii).
  • Usually rather mild in humans fever, head and
    body aches, and rash of 14 days or so duration.
  • Xenopsylla cheopis is most important vector.

Following info from Dr. Glenn Songers Webpage at
  • History of the Plaque- problem since early
    recorded history- Justinian Pandemic 6th century
  • Began 540 A.D. in Egypt, spread to Alexandria
    then on to Palestine, and to the rest of the
  • 10,000 deaths per day at peak in Byzantium
    lasted 50 years, killed 100 x 106 people

Black Death Pandemic - From Asia to Europe on the
Silk Road
  • 14th century social conditions poor, rat
    population high, rats and humans lived in close
  • First use of "Black Death" probably because of
    severe cyanosis in terminal plague victims.
  • China, India, Syria, ArmeniaMoved via the trade
    routes to Europe

The Black Plague
  • Probably first use of biological weapons bodies
    of plague victims catapulted into enemy camp.
  • Sudden appearance in winter of 1346-1347 in
    Europe- suspect black rat (Rattus rattus) and
    its flea Xenopsylla cheopsis. Throughout 14th
    century, upto 55 million died. (1/3 population)

The Black Death
Great Plague of London - 1665
  • Began 1664 - "Just before Christmas
  • Peak mortality 7000/week Total mortality of
    100,000 (Total population 500,000) Not isolated
    to London or England
  • May have given rise to children's rhyme
  • "Ring Around The RosiesA Pocket Full Of
    PosiesAshes, Ashes, All Fall Down"

Prevention of Diseases Carried by Fleas
  • Control of fleas - Use of insecticides and light
    traps that attract fleas.
  • General sanitation
  • Conditions conducive to high rat and flea
    populations and human overcrowding contribute to
    plague outbreaks.

Diptera - the Flies
  • More members of this group are involved in the
    transmission of pathogens than any other
    Arthropod group.
  • General features
  • These organisms have two wings (Diptera) and a
    second pair of halters which function in
  • Have complete or Holometabolous development (egg,
    larvae, pupae, adult)

Family Psychodidae - Subfamily Phlebotominae -
  • The sand flies
  • Weak flies that can fly only short distances and
    can not fly when wind is blowing.
  • Transmits Leishmania causing Kala azar disease
    and tropical sore.
  • Carrions disease (Oroya fever). Caused by the
    bacterium Bartonella bacilliformis. It is a
    visceral form that causes muscle and joint pains,
    anemia, jaundice, and is sometime fatal.

Culicidae - Mosquitos
  • Mosquitos are the most Important insect vectors
    of human disease?
  • Have scales on the wing veins and posterior
  • Have an elongate proboscis
  • Life cycle includes eggs, larvae (wiggler) pupa
    (tumbler), and adult.
  • Larval forms use siphon tube to breath.

Some Important Mosquitos
  • Culex tarsalis - main vector of western equine
    encephalitis (WEE) and St. Louis encephalitis
  • Culex pipiens - are important vectors for
    filarial worms (Wucheria bancrofti and
    Dirofilaria immitis).
  • Aedes aegypti - the yellow fever mosquito - also
    dengue, (breakbone fever).

Anopheles sp
  • At rest, the head, thorax, and abdomen form a
    straight line. When they feed, there is a sharp
    angle toward the host
  • Vectors for Plasmodium falciparium, the most
    important of the human malarias
  • Female Anopheles mosquitos are the vectors
    Anopheles freeborni is a common example.

Anopheles feeding on person
Mosquito Control
  • Control of mosquitos comes from two major methods
  • Destruction of breeding sites - drainage of
    swamps, changing water levels, removal of trash
    (cans, tires, etc.) Mud puddles in Honduras.
  • Destruction of the organism - Insecticides,
    Gambusia (mosquito larvae eating fish), oil on
    the water.

Mosquito eating fish
Culex pipiens Male
Aedes aegypti - yellow fever mosquito
Culex pipiens and Anopheles punctipennis
  • Black flies, buffalo nats
  • Immature stages aquatic found in cold rapid
    flowing streams.
  • Transmitts Onchocerca volvolus which causes river
    blindness among other things

Simulium larva
  • Transmitts Trypanosoma evansi which causes surra
    in horses, cattle, dogs, etc.
  • The deer fly, Chrysops is important in
    transmission of Loa loa - the African eye worm.
  • Often cause significant blood loss.

  • Tabanids as transmitters of pathogens.
  • Anautogeny - must have blood meal for development
    of eggs
  • Telmophagy feeding habit - pool of blood that can
    receive pathogenic organisms.
  • Large blood meals (feed for long time)
  • Intermediate feeding (from organism to organism)

Black Deer Fly Chrysops