Pthirus pubis Pubic or Crab Louse

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Pthirus pubis - Pubic or Crab Louse
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Pig Louse
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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

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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

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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
  places.

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Reduviidae - The Assassin Bugs

• The assassin bugs - most feed on other insects.
• One Subfamily Triatominae contain important
  vectors of Trypanosoma cruzi which causes Chagus
  disease.
• 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.

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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. .

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Reduviidae - Kissing Bugs

• Rhodnius prolixus Triatoma infestans
  

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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.

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Pathogenesis of Chagus Disease

• Acute phase - most common in children under 5
  years
• 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.

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Epidemiology

• 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
  disease.

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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

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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.

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Siphonaptera - the fleas

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

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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
  fowl.
• Chigoe (Tunga penetrans) buries under skin on
  feet and hands - (see fig 37.12).

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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

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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.

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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)
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Pulex irritans - the Human Flea
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Xenopsylla cheopis - oriental rat flea
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Tunga penetrans
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Fleas as Vectors

• Plague
• Commonly known as the black death
• Caused by bacterium Yersinia pestis (Pasturella
  pestis)
• 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.

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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
  cases.
• 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.

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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.

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Following info from Dr. Glenn Songers Webpage at
http//microvet.arizona.edu/Courses/MIC420/lecture
_notes/yersinia/yersinia_p_history.html

• 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
  world
• 10,000 deaths per day at peak in Byzantium
  lasted 50 years, killed 100 x 106 people

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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
  proximity
• First use of "Black Death" probably because of
  severe cyanosis in terminal plague victims.
• China, India, Syria, ArmeniaMoved via the trade
  routes to Europe

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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)

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The Black Death
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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"

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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.

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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
  equilibrium
• Have complete or Holometabolous development (egg,
  larvae, pupae, adult)

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Family Psychodidae - Subfamily Phlebotominae -
Phlebotomus

• 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.

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Culicidae - Mosquitos

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

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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).

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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.

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Anopheles feeding on person
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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.

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Mosquito eating fish
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Culex pipiens Male
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Aedes aegypti - yellow fever mosquito
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Culex pipiens and Anopheles punctipennis
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Simulidae

• Black flies, buffalo nats
• Immature stages aquatic found in cold rapid
  flowing streams.
• Transmitts Onchocerca volvolus which causes river
  blindness among other things

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Simulium larva
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Tabanidae

• 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.

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Tabanidae

• 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)

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Black Deer Fly Chrysops