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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)
Black Deer Fly Chrysops
Glossina - The Tsetse Fly
• Day feeders, attracted to moving objects.
• Both males and females feed on blood.
• Larviparous giving birth to larvae ready to pupate. The larva is deposited in loose, dry soil, and soon completes development.
• Attracted to chemicals found in human sweat (1st column, 580)
Glossina - The Tsetse Fly
• Important vectors of Trypanosoma gambiense and T. rhodiense, causative agents for African Sleeping Sickness
• Glossina morsitans is one example of many
African Sleeping Sickness
• Caused by Trypanosoma gambiense and T. rhodiense.– T. gambiense causes a chronic form that is found
in west central and central Africa.• Attacks CNS, often fatal
• Wild animals do not serve as reservoir hosts
– T. rhodiense causes an acute form in east central and central Africa.
– Wild animals serve as reservoir hosts.
Muscidae
• Musca domestica - the house fly – Why is it so important? – Synarthropy - close relationship with man -
frequent table and outhouse.– A male and female fly inApril. All flies survive
and reproduce offspring. How many flies in August?
– 1.9 X10 20 in August (cover the surface of the earth 47 feet deep)
Myiasis
• Infestation of tissue with maggots
• Cochliomyia hominovorax (primary screw worm) is the most important producer of human and domesticated animal myiasis.
• Eradicated in U.S. by releasing of sterile male flies.
• Female flies only mate once, if mate with sterile male, will not mate again.
Medically Important Arachnids
• The ticks and the mites– General statements
• Ticks and mites are important because they cause harm to animals they infest and because they are important vectors for other diseases.
• Ticks are ectodermal parasites of vertebrate hosts during larval, nymphal and adult stages
• Mites are found on the skin or in the respiratory system or other organs of hosts.
Medically Important Ticks and Mites
– Morphology• Segmentation is reduced externally.
• Anterior gnathostoma or capitulum (jawed mouth or head) and idiosoma which makes up the body of the organism
• The capitulum consists of feeting apendages surrounding the mouth. Chelicera or pincher like feeding structures are characteristic
• Usually contain 4 pair of legs although some mites have less than 4 pair of functioning legs.
Order Ixodida: the ticks
• Several ways they are important to man– Exsanguination - excessive loss of blood – Dermatosis - breakdown of dermal tissue– Paralysis - Paralysis resulting from secretions
of the tick. Reversed when tick is removed.– Otoacariasis - Infestation of the ear with ticks– Transmitters of other pathogenic organisms.
One, Two, and Three Host Ticks
Ixodidae (hard ticks) and Argasidae (soft ticks)
Family Ixodidae – Hard ticks
• Characteristics of hard ticks– Capitulum is terminal and can be seen from the
dorsal view– Scutum is present and eyes when present are on
the scutum– Pedipalps are rigid and not leg like– Marked sexual dimorphorism– Posterior margin of opisthosoma may be
divided into sclerites called festoons
Scutum
Family Ixodidae – Hard ticks
• The family of hard ticks is divided into three subfamilies.
• Subfamily Ixodinae with the single genus Ixodes• Subfamily Amblyominae containing Amblyomma,
Haemaphysalis, Aponomma and Dermacentor.• Subfamily Rhipicephalinae containing
Rhipicphalus, Anocentor, Hytalomma, Boophilus, and Margaropus
Dermacentor variabilis
• American Dog Tick• Principal vector of
Rocky Mountain Spotted Fever
• Causes tick paralysis and transmits tularemia
• Family Ixodidae - hard tick
Dermacentor andersoni
• Rocky Mountain Wood Tick
• Vector for several diseases in man.
Amblyomma americanum
• Lone Star Tick• Wide variety of hosts• Transmits Rocky
Mountain Spotted Fever and Tularemia
• Family Ixodidae - hard
Ixodes scapularis
• Blacklegged tick• Common In Eastern
U.S.• Family Ixodidae –
hard tick
Rhipicephalus sanguineus
• Brown Dog Tick• Transmits East Coast
Fever in Cattle• Family Ixodidae –
hard tick
Other ticks
• Ixodes dammini - important vector for Lyme disease. Caused by spirochaete Borrelia burgdorferi
• Boophilus annulatus - American cattle tick. Transmits Texas Cattle Fever. First evidence of arthropod as a vector
Family Argasidae – the soft ticks
• Characteristics– Capitulum is subterminal and can not be seen from the
dorsal view– No festoons or scutum– Sexual dimorphorism is slight– Pedipalps are freely articulated and leg like– Other characteristics see text page 614 second column – There are 5 genera of Soft ticks – Argas, Ornithodoros, Otobius, Nothoaspis, and
Antricola
Scutum
Otobius megnini
• Spinose ear tick• Soft tick belonging to
the FamilyArgasidae• May be found in ears• Adults do not feed
Argas persicus
• Poultry tick• Soft tick belonging to
the family Argasidae• Can be very
destructive to fowl.
Mites
• Dermanyssus gallinae the chicken mites - Nocturnal feeders that will aggressively feed on humans can cause severe dermititis.
• Dermadox folliculorum - hair follicle mite of humans (fig 40.9, page 617)
• Family Trombiculidae - the chigger mites• Sarcoptes scabiei - the itch mite causes
sarcoptic mange or scabies.
Dermodex folliculorum
• Human hair follicle mite
• 20 % of people under 20 are infected and nearly 100 % of older people.
Sarcoptes scabiei
• Sarcoptic mange or scabies mite.
• Skin parasites of homoiotherms. What are homoiotherms?
• 7 year itch or Norwegian Itch, or scabies.
• May see it.
Dermanyssus gallinae
• Chicken Mite • Very destructive to
chickens• Can be very painful to
humans.