Medical Arachnoenthomology

Plan of lecture  Phylum Arthropoda: general characteristic, classification, medical importance.  Crustaceans as intermediate hosts of helminthes.  Class Arachnida: general characteristic, classification, medical importance.  General characteristics, classification of class Insecta.  Order Anoplura (lice). Morphology, medical importance, methods of control.  Order Siphonaptera (fleas). Morphology, medical importance, methods of control.  General characteristics, classification, medical importance of order Diptera.  Anopheles, Aedes, and Culex mosquitoes and their role in transmission of infections.

 Three-fourth of all animal species belong to the Phylum Arthropoda. The name “arthropod” comes from two Greek words, arthros, jointed, and podes, feet.  All members of the Phylum Arthropoda share the following characteristics:  1. Arthropods have jointed appendages.  2. The arthropod body is segmented.  3. Arthropods have an exoskeleton.  4. Arthropods have a ventral nervous system, an open circulatory system, a digestive system, and specialized sensory receptors.

Phylum Arthropoda includes 3 classes of medical importance: 1.Class Crustacea: cyclops, crabs. 2. Class Arachnida (Octapoda): scorpions, spiders, ticks and mites. 3.Class Insecta (Hexapoda): mosquitoes, flies, bugs, lice, fleas.

Class Crustacea Most crustaceans have Most crustaceans have  two pairs of antennae,  three pairs of chewing appendages,  various numbers of pairs of legs.  Crustaceans differ from the insects in that they have legs on their abdomen as well as on their thorax.  Medical importance: Cyclopes are intermediate hosts of the fish tapeworm (Diphyllobothrium latum) and Dracunculus medinensis.

Class Arachnida.  The Class Arachnida is a group of more than 100,000 species, including spiders, scorpions, ticks, and mites.  Most arachnids are adapted to kill prey with poison glands, stingers, or fangs.  Arachnids have a body that is divided into a cephalothorax and an abdomen.  Attached to the cephalothorax are 4 pairs of legs, a pair of chelicerae, and a pair of appendages called pedipalps. The pedipalps aid in chewing; in some species pedipalps are specialized to perform other functions. The pedipalps aid in chewing; in some species pedipalps are specialized to perform other functions. Arachnids undergo incomplete metamorphosis.

Class Arachnida includes 3 orders of medical importance: Order Scorpiones. Order Araneae (spiders) Order Acari (ticks and mites).

5 Interesting Facts about Scorpions  Scorpions live everywhere but the Arctic and Antarctic  Male and female scorpions find each other by vibration, scent, or touch. Then they dance together for half an hour or more.  Females often eat the males when they are done with the dance.  Scorpions have 8 legs and 2 claws.  The bigger the claws are, the less venom it has.

Diet   Small rodents   insects  Clawed feet  25 types can harm/kill man  Alive before the dinosaurs

-Scorpions have greatly enlarged pedipalps, which they hold in a forward position. - They also have a large stinger on the last segment of the abdomen. Pathogenicity. The local symptoms of bite include severe pain, inflammation and swelling. Muscular spasm and convulsions can occur in severe cases. Fatal outcome is caused by respiratory failure, pulmonary edema and shock. Control: spraying of insecticides. Scorpions differ from spiders in two ways:

Spiders are not a “bug”  Spiders are not insects they are part of a group called Arachnid  There are more than 30,000 different species of spiders

Arachnophobia  Arachnophobia is the fear of spiders  This is the number one fear of Americans today  Although most spiders are harmless and helpful to our lives This spider has a venomous bite that causes serious wounds

Spiders  There are about 35,000 named species of spiders (order Araneae).  These animals play a major role in all terrestrial ecosystems.  Spiders hunt their prey or catch it in webs.

Spider Eyes  Most spiders have either six or eight eyes  Even so they cannot see far away  They use the hair on their bodies as sensors to feel their way around and to tell when other animals are near

Order Acari  Most mites are small, less than 1 mm long,  the adult length from 100 nm to 2 cm.  the cephalothorax and abdomen are fused into an unsegmented ovoid body.  Respiration occurs either by means of tracheae or directly through the exoskeleton.  They are found in virtually every terrestrial, freshwater, and shallow marine habitat known and feed on fungi, plants, and animals; they act as predators and as internal and external parasites of both invertebrates and vertebrates.

Sarcoptidae “Scabies Mites”  Sarcoptes scabiei Also called the “itch mite” of humans Not Vectors of any disease.  Morphology: male (0,2 mm) is smaller than female (0,4 mm).  Body is oval, convex dorsally and flat ventrally.

Sarcoptes scabiei (itch mite) Mouthparts: a)rudimentary hypostome without teeth. b)chelicerae end in pincer-like structures. c)pedipalps are short and 3- segmented. The whole cycle takes about 2 weeks.

Distribution  Worldwide  All races and socioeconomic classes  All climates  300 million cases annually!

 Burrowing initially occurs in thinner skin of the body.  Bend of knee and elbow.  Webbing between fingers and folds of the wrist.  Genitalia and buttocks.  Breasts. Behavior

Scabies Rash

Life cycle

Transmission Spread by ovigerous female mites through:  Personal (prolonged close) contact  Occasionally by infested sheets (rare).  Touching or shaking hands (unlikely).  Sexual activity.  Among children (outbreaks).  Mites can survive up to 24 hours off host.

Diagnosis is made by -itching of affected surfaces at night -specific lesions - finding of the parasite in the tunnels by a needle. Control is provided by Control is provided by - proper treatment of infected persons - sterilization of clothes and bedding - personal cleanliness. Diagnosis

Ticks Ticks Ticks are blood-feeding ectoparasites (parasites that occur on the surface of their host). Ticks are divided into hard-bodied ticks (family Ixodidae) and soft-bodied ticks (family Argasidae)

TICK LIFE CYCLE

-female ticks lay eggs. - Larvae hatch, feed on blood and then drop to the ground. - Larvae molt into nymphs. - Nymphs feed on blood and molt into adults. - Adult male and female feed on blood. -Life cycle takes several months (1-2 years in some species). Life cycle:

Anatomy of IXODES ticks

Size

Female Deer Tick Male Deer Tick Crawling

Female Deer Tick Larvae

Ticks  Medical importance.  - Mechanical injury by the bite.  - Tick paralysis: progressive flaccidity due to a failure of acetylcholine liberation in the neuromuscular junction. Tick’s toxin produces a block in the motor nerve fibers. The toxin is elaborated by the tick’s ovaries and is secreted by salivary glands.  Vectors of diseases:  -hard-bodied ticks (Ixodidae) are carriers of rickettsial, spirochaetal, viral, bacterial, and protozoan diseases.  soft-bodied ticks (Ornithodorus) are vectors of endemic relapsing fever (caused by Borrelia duttoni) and Q-fever.  Control of ticks:  Repair of cracks.  Insecticide spraying on floors and cracks.  Infested animals are dusted by insecticide agents or dipped in special solution.  In endemic areas: wear light-colored, tightly woven slacks and a long sleeved shirt; spray clothing with an insect repellant containing N,N- diethyltoluamide

Insects Insects have three body sections:  the head, thorax, and abdomen;  three pairs of legs, all attached to the thorax;  one pair of antennae.  they may have one or two pairs of wings.  The mouthparts of insects are elaborate. There are two principal kinds of metamorphosis in insects: simple and complete.

Insects  Class Insecta is divided into 4 orders of medical importance:  1. Order Anoplura (lice).  2. Order Siphonaptera (fleas).  3. Order Hemiptera (bugs).  4. Order Diptera (mosquitoes and flies).

Order Anoplura (lice)  Order Anoplura (lice). Body is flattened dorso-ventrally.  Lice are wingless insects with short legs.  Order Anoplura displays incomplete metamorphosis. Head louse  Morphology (Pediculus humanus):  Adult louse is 2-5 mm in size, male is smaller than female.  Body is divided into head, thorax and abdomen.

The head louse found on humans is specific to people. It can’t be contracted from the family dog, cat or any other animal. Mammals and birds can have lice but they are species specific.  These are insects that CANNOT jump or fly.  Their method of movement relies on 6 legs, each of which ends in a claw which can grasp human hair.

Lice  Life cycle.  - Female louse lays about 10 eggs daily.  Eggs are cemented to hairs or to fibers of clothes.  Eggs hatch in about one week.  Nymphs feed on blood and pass through 4 instars.  Adult louse emerges in about two weeks.  Disease transmission (body louse). 1.Epidemic typhus caused by Rickettsia provaceki, Trench fever. Epidemic relapsing fever

Transmission of Head Lice  Host-to-host (direct contact from someone who is infested)  By wearing infested clothing (hats, scarves, coats, hair ribbons etc.)  By using infested combs, or brushes  By lying on a bed, couch or carpet that has recently been in contact with an infested person.

 Head Lice are NOT known to transmit pathogens (germs). They are a nuisance but NOT a health hazard.  Lice don’t mount expeditions, striking off to find new heads. They are obligate human parasites, their goal is to stay on the head where they presently live!!!!!

About 2500 species, most parasites of mammals only approx. 100 species on birds Temporary obligate parasites, blood-feeding exclusively as adults Most fleas of medical and veterinary importance are not host species-specific increases the potential for acquisition and transmission of pathogens Order Siphonaptera (fleas)

Flea Life Cycle

Flea eggs

Adult fleas

Important Flea Species Xenopsylla cheopis (Oriental rat flea) - primary urban plague vector Pulex irritans (human flea) - occasional epidemic plague vector Ctenocephalides felis, C. canis, - cat and dog flea - primary pest species Tunga penetrans – sand flea (chigoe)

Parasitic Flies Class Hexapoda Order Diptera

Flies - Diptera  The key distinguishing adult structure : two wings.  All Flies are Holometabolous (having a complex metamorphosis  i.e. egg, larvae pupa, and adult)

One of Great Adaptations of of Flies - The Habitat of larval stage  The habitat of the larval stage is basically “aquatic or semi-aquatic,” and they have adapted to live in very, very “challenging” environments. Allows them to invade Dead and Living tissues

Diptera – Flies as parasites  Ectoparasites 1.Adults are free living but blood feeding with the larvae stages aquatic or in moist semi-aquatic habitats. (Nematocera and Brachycera)

Diptera – Flies as parasites 2.Adults ectoparasites (or blood feeding) but larvae develop within female and essentially pupate after emerging from mother (Glossina, Hippoboscidae)

Diptera – Flies as parasites  Endoparasites 3.Adults free living but larvae are internal or partially internal (flesh feeding) parasites of vertebrates (Oestrus, Gasterophilus, Cochliomyia hominovorax) Gasterophilus intestinalis

Myiasis Defined The invasion of organs and tissues of humans or other vertebrate animals with dipterous larvae, which for at least a period feed upon the living or dead tissue or, in the case of intestinal myiasis, on the host’s ingested food.

Metallic Flies  Cochliomyia hominivorax

Lucilia spp. Calliphora spp.

Musca domestica. Housefly is a medium-sized fly, mm in length; the female is generally slightly larger than the male. Distribution: cosmopolitan. Morphology. Adult fly has a gray color. Body is divided into head, thorax, and abdomen. Life cycle. 1. Eggs are laid into masses of decaying organic substances, garbage, refuse or manure. 2. Larvae hatch in 6-24 hours and feed on organic matter. 3. They molt 2 times giving 3 larval stages. 4. The third larva pupates inside the larval skin. 5. The adult emerges after a few days.The whole cycle takes about one week.

House fly 4 dark stripes 4th vein angled Red eyes  Breeding media  Garbage  Decaying fruit or vegetables  Decaying meat  Human or animal feces  Grass clippings

Medical importance 1. Indirect mechanical transmission of microorganisms (as typhoid, poliomyelitis and bacillary dysentery), eggs of helminthes and cysts of protozoa. 2. Accidental myasis. Control 1.Sanitary disposal of refuses, garbage and manure (breeding media) by dumping, burning or application of insecticides. 2.Control of adult flies by screening or space spraying of insecticides.

Mosquitoes  Bloodfeeding - only females take blood  Males and females feed on plant sugars  Gonotrophic cycle - feed, egg development, oviposition (half-gravid, gravid)  Egg biology - oviposition location, type of egg, desiccation resistance, diapause  Larval biology - aquatic, spiracle for breathing, filter- feeders, some cannibalistic, variable habitats

Eggs – 3 strategies  Singly on water surface  Anopheles  Singly in a pile, on moist substrates  Aedes/Ochlerotatus  Form of a raft, on water surface  Culex  Culiseta Differences between Anopheles and Culex.

Larval Stage – Growth Stage  Larval instars (4)  Aquatic, Filter feeders  Respiration Anopheles

Pupa – Lighter than water  Non-feeding  Respiration AnophelineCulicine Pupal Stage Comparison

Mosquito Pupa and Larvae

Mosquito Emerging from Pupal Exuvia

Adults Adults Anopheline Culicine Adult Stage Comparison Emergence Mating Feeding

Aedes aegypti Anopheles Culex

Thank you for attention !