Arthropods

Phylum arthropoda

largest and most varied PHYLUM in the animal kingdom

• at least 1.1M species

1. bilateral

2. segmented

3. complete

4. separate (usually)

5. trachea (air tubes), book lungs

Arthropoda

1. symmetry

2. segmentation

3. digestive system

4. sex

5. respiration (2)

branching tracheal tubes

• open to surface via spiracles

• in insects and spiders with hard tegument

• open to surface through ____

spiracles

pores in exoskeleton

Trachea

• connect to spiracles

• carry oxygen to the body cells

book lungs

• pigment: hemocyanin

• in some spiders

• thin sheets of respiratory tissue

• exchange oxygen with a respiratory pigment ____ in blood

1. Class insecta (mosquitoes, flies, cockroaches)

2. Order Acarina (ticks, mites)

1. Class + 3

2. Order + 2

1. biological

2. mechanical

2 kinds of vectors

Biological vector

Vector that acquire pathogenic agents in the act of blood feeding.

• multiplication → development → infectious

Mechanical vectors

Vectors that transmit pathogens by way of their oral secretions (vomitus of flies) and the contaminated external surfaces of their body (feet, wings)

• mere contaminators

vomitus of flies

vector: oral secretion sample

feet, wings

vector: external body surface

Direct harm

Type of harm:

• annoyance

• venom stings (can cause death)

Class insecta

considered the largest group approx.70% of the phylum

• most important medically

1. head

2. thorax (chest)

3. abdomen (stomach)

Class Insecta 3 major regions

1. 1 PAIR antennae

2. 2 PAIRS of wings

3. 3 PAIRS of legs (6 legs total)

4. compound eyes

4 characteristics of class insecta

chewing

mouthparts of beetles, cockroaches

piercing, sucking

mouthparts of mosquitoes, bugs

lapping and sponging

mouthparts of flies

1. Prosoma (cephalothorax)

2. Opisthosoma (abdomen)

Class Arachnida (2) major regions

1. 4 PAIRS of walking legs (adults) (8 total)

2. NO antennae

3. NO wings

Class Arachnida (3) characteristics

1. Order Scorpionida (scorpions)

2. Order Araneida (spiders)

3. Order Acarina (mites, ticks)

(3) Arachnid Orders Med Important

• Order — arachnids

Order Scorpionida

• Pincers on the 1st set of appendages (pedipalps)

• Long tail with stinger

• Four pairs of legs

pedipalps

appendages of class arachnids

Order Scorpionida

1. IMPT: sting humans

2. hemolytic venom causes a painful swelling at the site of the sting

3. neurotoxic venom may produce numbness at the sting site, profuse sweating, salivation and nausea.

Order Scorpionida

If the victim is alive for 3 hours after

the sting, survival is capable

Order Araneida

• slender waist (pedicel)

• chelicerae on 1st set of appendages = injects venom

1. Lactrodectus (black widow spider)

2. Loxosceles (brown widow spider)

(2) dangerous Araneida species

black widow

• mature female is deep black

• gagambang gubat

black widow spider

bite can cause light swelling and two tiny red spots may

appear, with local redness at the point of attack

Loxosceles

genus of venomous spiders

Loxosceles

• venom produces necrotic lesions in the tissues

• venom is carried by the bloodstream causing red blood

  cell destruction

Mites and Ticks

• round or oval

• dorsoventrally depressed forms

• head, thorax, and abdomen fused together

• no visible segments

Sarcoptes scabei (itch mite)

Whitish and disc shaped, flattened ventrally

• with common name

peg-like protuberances, few bristles

Dorsally, the mite is covered with numerous small peg-like

_____ and a few ____

Sarcoptes scabei (itch mite)

Legs are short and stubby, divided into five ring-like segments

S. scabei

trasnfer via direct contact and to a limited extent from undergarments or soiled beddings

15-20 minutes

how much time for S. scabei to transmit person-person

11

The average number of adult female Sarcoptes found on a person is about

Scabies

• caused by S. scabei

• galis-aso

• contagious

• Note: Female mite favors places on the body where

  the skin is wrinkled (wrists, elbows, feet, between fingers)

Ticks

parasitologically significant

• vectors of diseases

• transmitting pathogens like protozoa, bacteria, and viruses

1. Order copepoda (cyclops: freshwater crustacea)

2. Order decapoda (macrocrustaceans, crabs, lobsters, shrimps)

(2) Tick orders of Med IMPT in Class Crustacea

• with examples

Order Copepoda (cyclops)

• Body: cephalothorax and

  abdomen

• 6 pairs appendages on head

• 5 pairs appendages on anterior thoracic trunk region

Copepods

Intermediate host for Dracunculus medinensis (Dracunculasis)

• human parasite

Dracunculus medinensis

• Infective: L3

• MOI: drink unfiltered water

human parasite carried by copepods

• with infective stage and MOI

Class Diplopoda (millipedes)

2 pairs of legs per segment

Class diplopoda/millipedes

• Most feed on decaying matter.

• Some species can eject cyanide (poison)

millipedes

Secretions ooze from the small pores arranged

along its sides and produce dermatitis and severe

itchiness in humans

Millipedes

In chickens, it can cause permanent blindness.

• rarely enter houses

Class Chilopoda (Centipedes)

• 1 pair of legs per segment

• move rapidly, often under logs, some in homes

• can bite

• poison claws (modifiied 1st pair of legs)

Centipedes

have poison claws (modifiied 1st pair of legs)

Centipedes

• most are harmless (since only few have fangs strong enough to penetrate the human skin

• mostly bite in self-defense

• amt of venom introduced depend on size

Class Insecta — Order Diptera

3 pairs of legs (Class — Order)

Class insecta — order diptera

they carry Mosquito-borne diseases:

a. Malaria

b. Filaria

c. Dengue

d. Japanese Encephalitis

1. Malaria

2. Filaria

3. Dengue

4. Japanese encephalitis

Mosquito-borne diseases (4)

1. Anopheline mosquitoes

2. Culicine mosquitoes

(2) important divisions or tribes of mosquito vectors:

Anopheline mosquitoes

tribe/division

• consisting of Genus Anopheles, which are vectors of human malaria and human filariasis

Culicine mosquitoes

tribe/division

• vectors of dengue, Japanese encephalitis and human filariasis, which includes the genera Aedes, Culex and Mansonia

1. Anopheline — Anopheles — malaria, human filariasis

2. Culicine — Aedes, Culex, Mansonia — Japanese encephalitis, human filariasis

Tribe — Genus — Disease

type of antennae

Class insecta — order diptera

• Differentiation of sexes is based on

1. Male: plumose or bushy

2. Females: pinnose or less bushy

(2) types of antennae in class insecta — order diptera

Anopheles flavirostris

most important vector of

malaria in the Philippines

A. flavirostris

Wings usually dark or with one pale spot present

A. flavirostris

At rest, the body forms an angle nearly vertical with the surface (head, thorax, and abdomen are in a straight line

Mansonia bonneae

vector for brugian filariasis

Mansonia bonneae

1. ADULT: light to dark brown in

   color light yellow to golden in

   color

2. LEGS: pale markings

3. WINGS: white and dark broad

   scales

lymphatic vessels

M. bonneae

• The parasite reach the _____ where they develop

  into adult worms

1. Aedes egypti (urban dengue)

2. Aedes albopictis (rural dengue)

(2) vectors of dengue in PH

Aedes egypti (urban dengue)

• tiger mosquito

• black or dense brown

• White scales forming on the

  thorax & legs

• Tip of the abdomen is usually

  pointed

Aedes albopictus (rural dengue)

adults are relatively small and show a black and white pattern due to the presence of white/silver scale patches against a black background on the legs and other parts of the body