Pthirus pubis - Pubic or Crab Louse: Pthirus pubis - Pubic or Crab Louse


Pig Louse : Pig Louse


Hemiptera - the true bugs: 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: 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: 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.


Reduviidae - The Assassin Bugs : 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.


Reduviidae - The Assassin Bugs : 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: Reduviidae - Kissing Bugs Rhodnius prolixus Triatoma infestans


Chagus Disease: 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.


Slide10: 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.


Slide11: 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.


Siphonaptera - the fleas: 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: 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: 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.


Types of Fleas: 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).


Some Important Fleas: 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: 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: 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)


Ctenocephalides felis (cat flea): Ctenocephalides felis (cat flea)


Pulex irritans - the Human Flea : Pulex irritans - the Human Flea


Xenopsylla cheopis - oriental rat flea: Xenopsylla cheopis - oriental rat flea


‘Tunga penetrans: ‘Tunga penetrans


Fleas as Vectors: 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.


Three Types of Plague: 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.


Murine Typhus: 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 Songer’s Webpage at http://microvet.arizona.edu/Courses/MIC420/lecture_notes/yersinia/yersinia_p_history.html: Following info from Dr. Glenn Songer’s 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


Black Death Pandemic - From Asia to Europe on the Silk Road: 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, Armenia Moved via the trade routes to Europe


The Black Plague: 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: The Black Death


Great Plague of London - 1665: 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 Rosies A Pocket Full Of Posies Ashes, Ashes, All Fall Down"


Prevention of Diseases Carried by Fleas : 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: 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)


Family Psychodidae - Subfamily Phlebotominae - Phlebotomus: 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. Carrion=s 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: 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.


Some Important Mosquitos: 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: 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: Anopheles feeding on person


Mosquito Control: 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: Mosquito eating fish


Culex pipiens Male: Culex pipiens Male


Aedes aegypti - yellow fever mosquito: Aedes aegypti - yellow fever mosquito


Culex pipiens and Anopheles punctipennis: Culex pipiens and Anopheles punctipennis


Simulidae: Simulidae 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: Simulium larva


Tabanidae: 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.


Tabanidae: 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)


Black Deer Fly Chrysops: Black Deer Fly Chrysops