Arthropod A

ARTHROPODAAbundo, John DavidAlmazan, Alyssa PilarVelasco, James Samuel

External Characteristics

•chitinous exoskeleton and appendages•body divided into head, thorax, and

abdomen•elaborate mouthparts for sucking,

chewing, and biting

Medical Importance

•Transmit parasites and bacteria, causing disease▫Modes of Transmission

mechanical biological

•External parasites

MEDICALLY IMPORTANT ARTHROPODSslides in stockroom

Cyclops

•small, aquatic copepod•free-living•no carapace•antennae•median eye•one pair of maxillae•five pairs of swimming legs

Cyclops

•intermediate hosts of:▫Diphyllobothrium latum▫Dracunculus medinensis▫Gnatosthoma▫Spirometra

Spider

•body: cephalothorax and abdomen;prosoma constricted from opisthosoma

•no antenna•4 pairs of appendages•1 pair of chelicerae having hollow fangs

(opening of poison glands•gonads open near base of abdomen

Spider

REPRODUCTION•eggs in masses protected by coccoon•molting of immature spiders

FEEDING•carnivorous/cannibalistic• insert fangs into victims’ bodies to render

helpless/kill, then suck out nourishing juices

ENVENOMATION (ARACHNIDISM)•Spiders defend themselves by attacking

and injecting toxin in skin•due to nonhemolytic neurotoxin•Systemic - caused by

▫tropical tarantulas▫widow spiders ▫wandering spiders▫wolf spiders

Systemic Arachnidism: Symptoms•Sharp pain at site of bite•Redness and swelling later on•Intense burning and aching•Dizziness, leg weakness and tremors,

abdominal cramps•dull pain in chest, back, and abdominal

muscles, all of which contract spastically; board-like rigidity

•hypertension, profuse cold sweating, nausea, vomiting, severe headache, moderate rise in temperature, constipation, acute urinary retention, reduced heartbeat and feeble pulse, cyanosis, anxiety, labored breathing and speech, insomnia, restlessness with light stupor. convulsions in children

•at times complete prostration, shock, or delirium

Systemic Arachnidism

DIAGNOSIS•two small red spots at site of bite•history of possible exposure; clinical signs

and symptomsTREATMENT

•local anesthetic, or analgesic (parenteral administration of diazepam)

•intravenous infusion and hydrocortisone•hot baths and intravenous injection of

Systemic Arachnidism

•Neostigmine•Intramuscular administration of antivenin

(for black widow bites)

ENVENOMATION (ARACHNIDISM)•Necrotic – caused by

▫Loxosceles sp., commonly L. reclusa (brown recluse spider)

Necrotic Arachnidism: Symptoms•Severe, sharp pain at site of bite, which

immediately becomes swollen and ischemic

•Small amount and low potency venoms:mild systemic reaction and scarlatiniform

rash

Necrotic Arachnidism

•Considerable amount and high potency: viscerocutaneous effectsON FACE

•Eye injury appears as puffy, thick, reddened wheal with a necrotic center that shuts eye; swollen area becomes violet in color, then blackens and dries; area sloughs after cutaneous necrosis, leaving a deep granular center; slow healing with deep disfigurement and scar tissue

ON LIMBS•Separation of superficial skin layers from

deeper tissue to form vesicles or blebs•Upper limb: extensive deep necrosis into

deep muscle; sloughing

•SYSTEMIC REACTIONS: hemolytic anemia, hemoglobinuria, hematuria, jaundice, fever, sensorial involvement within 6-24 hrs after bite (HIGH MORTALITY RATE)

Necrotic Arachnidism

DIAGNOSIS•characteristic necrotic lesions, along with

history of exposureTREATMENT

•no specific chemotherapeutics•administration of corticosteroids

True Lice

•small, crawling,wingless insect

•distinct head, thorax, andabdomen

•dorsoventrally compressed•1 pair of antennae•1-clawed tarsi•sucking mouthparts• legs adapted for clinging to hairs and

fibers

True Lice

•produce pediculosis, an irritating dermatitis

•can transmit the causative agents of specific diseases

Pediculus humanus capitis

•The head louse feeds on blood several times daily and resides close to the scalp to maintain its body temperature.

Pediculus humanus capitis

•It has a simple life cycle:

Pediculus humanus capitis • Head lice infestations can be asymptomatic, particularly

with a first infestation or when an infestation is light. Itching (“pruritus”) is the most common symptom of head lice infestation and is caused by an allergic reaction to louse bites. It may take 4-6 weeks for itching to appear the first time a person has head lice.

• Other symptoms may include: ▫ a tickling feeling or a sensation of something moving in

the hair;▫ irritability and sleeplessness; and▫ sores on the head caused by scratching. These sores

caused by scratching can sometimes become infected with bacteria normally found on a person’s skin

Pediculus humanus capitis

•Head lice are not known to transmit any disease and therefore are not considered a health hazard.

DIAGNOSIS•Finding a live nymph or adult louse on the

scalp or hair of a person•Finding nits attached firmly within 1/4

inch of the base of hair shafts (frequently behind the ears and near the back of the neck)

TREATMENT•Pyrethrins •Permethrin lotion 1%•Malathion lotion 0.5%;•Lindane shampoo 1%;

Pediculus humanus corporis

•lice live and lay eggs on clothing and only move to the skin to feed

•known to spread disease▫typhus ▫louse-borne relapsing fever▫trench fever▫Salmonellosis

Pediculus humanus corporis

•roseate elevated papule at site of bite, with intense pruritus; scarring of skin with parallel stripes, and bronzing with pigment; inflammatory reaction

Pediculus humanus corporis

DIAGNOSIS•Finding eggs and crawling lice in the

seams of clothing (or on the skin).TREATMENT

•Improving the personal hygiene of the infested person

•Pediculicide

Haematopinus suis

•Largest louse speciescommonly associated withdomestic animals

•It is found most frequently in the folds of skin behind the ears and between the legs

•Blood-sucking activity results in much irritation and discomfort to swine.

•Pediculosis is manifest by pruritus and dermal irritation with resultant scratching, rubbing, and biting of infested areas

•A generally unthrifty appearance, rough coat, and lowered production in farm animals are common

•In severe infestations, there may be loss of hair and local scarification

•Extreme infestation with sucking lice can cause anemia

•Sucking lice cause small wounds that may become infected. The constant crawling and piercing or biting of the skin causes nervousness in hosts

DIAGNOSIS•Hog lice usually move more slowly and

are found with mouthparts embedded in the skin

TREATMENT•Spraying with coumaphos, malathion,

methoxychlor, permethrin, tetrachlorvinphos, lindane, phosmet, amitraz, and fenvalerate

Cimex lectularius (Bedbugs)

•Blood sucking species•Habits

▫Feed at night on humans and small mammals

▫Conceal in crevices of wooden bedsteads or under loose wallpaper

▫Easily transported in clothing and baggage▫Emit a characteristic odor

Cimex lectularius (Bedbugs)•Morphology• Oval, dosoventrally

flattened, chestnut-brown bodies• Pyramidal head bears

compound eyes, slender antennae, specialized mouthparts in a long proboscis• Each of the 3 thoracic

segments bears a pair of legs that terminate in a pair of simple claws

Cimex lectularius (Bedbugs)

Cimex lectularius (Bedbugs)•Clinical Manifestations

▫Bite of the bedbug produces red itching wheals and bullae

▫Some persons show little or no reaction▫Others may manifest allergic symptoms

with generalized urticaria and even asthma▫Role in transmission of human disease is

minimal; may act as a mechanical carrier but is not a proved biologic vector of human diseases

Cimex lectularius (Bedbugs)•Treatment

▫Irritation and itching of bites may be relieved by ammonia, spirits of camphor, menthol-phenol paste, or calamine lotion

•Control▫Repair of cracked plaster and wallpaper▫Apply 5% DDT solution in kerosene, 0.1%

Lindane oil solution, or 1% malathion solution to floors, walls, furniture, and mattresses

Order Acarina(Ticks and Mites)•Includes many parasites and vectors of

diseases of humans and lower animals•Mouth parts and their base, the

capitulum, are attached to the anterior portion of the body by a movable hinge

•Sexes are separate

Ticks vs Mites Parasitic Ticks

• Larger Size• Leathery body• Exposed armed hypostome• Presence of a pair of

spiracles• Nearly all are capable of

biting human beings

Parasitic Mites

• Much smaller• No leathery covering• Hypostome is unarmed• Spiracles present on the

idiosoma of some mites• Only some cause direct

injury to people or transmit human diseases

Dermacentor variabilis (Dogtick)•Hard tick•Morphology

▫Reddish or mahogany-brown cephalothorax and abdomen are fused into an oval body with four pairs of 6-segmented legs

▫Capitulum (false head) consists of basis capituli, of taxonomic value, and mouth parts comprising hypostome (anchors to host), chelicerae (cutting organs for insertion of hypostome), and pedipalps (support)

Dermacentor variabilis (Dogtick)•Clinical Manifestations

1. Mechanical injury Produces inflammatory reaction, with local

hyperemia2. Tick paralysis

Caused by neurotoxins produced by tick’s salivary glands. Symptoms include: weakness in both legs which progresses to paralysis and may ascend to arms, legs, and head. Respiratory paralysis may lead to death

3. Transmission of human diseases Rocky mountain spotted fever, Lyme

disease, tularemia

Dermacentor variabilis (Dogtick)•Treatment

▫Removal from skin by gentle traction after applying chloroform, ether, or alcohol* Care should be taken not to break of the

capitulum in the wound- Paralysis, if present, subsides after removal

of tick

Sarcoptes scabiei (Mange Mites)

• Morphology▫ Small, oval, dorally

convex, ventrally flattened eyeless mite

▫ Male: 200 to 250 µ▫ Female: 330 to 450 µ▫ Mouth parts consist of

toothed chelicerae, 3-jointed conical pedipalps, and hypostome

▫ 4 pairs of legs

Sarcoptes scabiei (Mange Mites)•Scabies

▫Sites are interdigital spaces, flexor surfaces of the wrists and forearms, elbows, back, and genitalia

▫Lesions appear as slightly reddish elevated tracts in skin

▫Intense itching aggravated by warmth and perspiration causes scratching which spreads infestation and irritates lesions

▫Diagnosis: obtaining mite from its burrow with a needle

▫Transmitted by personal contact

Sarcoptes scabiei (Mange Mites)•Treatment

▫Application of Kwell after a hot, soapy bath

•Control▫Treatment of infected individuals,

sterilization of garments and bedding, and personal cleanliness

MOSQUITOES

Anopheles, Aedes, Culex

Morphology:• Have Elongated mouth parts;– females – adapted for piercing and sucking blood, consist of

grooves lower labium, the upper labrum-epipharynx, the hypopharynx, the styletlike mandibles, and the serrated maxillae. The maxillary palps are slender and hairy

– Males – weak mouth parts unable to penetrate human skin, relegated to a vegetarian diet – plant juices. Maxillary palps are long and ornamented like the antennae with tufts of hair( gives a plumed appearance. Salivary glands are located in the prothorax.

• Long, 15 –jointed antennae; males - pulmose, females – pilose• Characteristic wing venation, with scales• Roughly spherical head is almost covered by a pair of compound eyes

that nearly meet• Rigid thorax, covered by a dorsal scutum; bears 3 pairs of long,

slender legs

Aedes (A. aegypti) Culex (C. pipiens)

Anopheles (A. stephensi)

Difference between Culex and Anopheles: EGGSCULEX

• Eggs are laid vertically in clusters.

• Rafts are formed.• Egg cigar-shaped• Egg without lateral air float.• Usually 200-400 eggs in dirty

water.

ANOPHELES

• Egg are laid horizontally singly.• Rafts are not formed.• Egg boat-shaped.• Egg with lateral air floats.• usually 40-100 eggs are laid in

fresh and clean water.

CULEX ANOPHELES

LARVACULEX

• Bottom feeder.• The head hangs downwards at

an angle with the surface.• Without paimate hairs.• Long conical respiratory siphon.

ANOPHELES

• Surface feeder.• The head lies horizontally

parallel to the surface of water.• With palmate hairs on the

abdomen.• Respiratory siphon absent (=

exceedingly short)

CULEX ANOPHELES

PUPA

CULEX

• Pupa colorless• Respiratory trumpet long.• No palmate hairs.

ANOPHELES

• Pupa green in color.• Respiratory trumpet short.• With palmate hairs.

CULEX ANOPHELES

CULEX PUPA (C. annulirostris)

Clinical Manifestation

• Bites from Mosquitoes (female) causes itching and swelling

• Others have little irritation, redness

Treatment

• Calamine lotions• Cortisone creams– Basically anti itching creams or lotions

FLEAS

Ctenophalides canis, C. felis

Morphology

• Fleas are small, brown, wingless insects, 2.0 – 2.5 mm, with laterally compressed bodies. The small head may bear eyes and combs; all have antennae and suctorial mouth parts. Each segment of the three-segmented thorax bears a pair of powerful legs terminating in two curved claws.

C. canis

male female

Clinical Manifestation• Flea infestations can be not only annoying for both animals and humans but

also very dangerous. Problems caused by fleas may range from mild to severe itching and discomfort to skin problems and infections. Anemia may also result from flea bites in extreme circumstances. Furthermore, fleas can transmit tapeworms and diseases to pets.

• When fleas bite humans they may develop an itching rash with small bumps that may bleed. This rash is usually located on the armpit or fold of a joint such as the elbow, knee, or ankle. When the area is pressed, it turns white.

• When dogs are troubled by fleas they scratch and bite themselves especially in areas such as the head, neck, and around the tail. Fleas normally concentrate in such areas. This incessant scratching and biting may cause the dog's skin to become red and inflamed.

• Flea allergy dermatitis is developed by those dogs allergic to flea saliva. In this case, the symptoms previously mentioned are more pronounced. Because of compulsive scratching and biting, the dog may lose hair, get bald spots, exhibit hot spots due to extreme irritation, and develop infections that result in smelly skin

Treatment• To effectively get rid of fleas and flea eggs, one should treat not only

dogs but also the household and exterior regions to eliminate eggs from bedding, grass, floor, furniture and other areas.

• Treatment should be given as soon as signs of fleas appear and repeated regularly. Delays in treating the infestation may lead to flea-transmitted diseases.

• Once-a-month topical products are the most commonly used products to kill parasite infestations. They are normally applied on the back of the pet and their advantage is that they also provide protection from further infestations. Sprays come in the form of aerosols and pump bottles and they are meant to be applied on all parts of the pet. Dips and rinses are also available but they are not as common as the other such products because they are ones of the most unsafe for the health of the pet.

• Avermectin