Arthropod Part 3

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.