A Short Primer on Arthropods of Medical Importance

What Just Bit Me?

Rosmarie Kelly, PhD MPHPublic Health Entomologist

GDPH – 2 Peachtree St NWAtlanta, GA 30303

404-657-2912 (w)404-408-1207 (c)

rmkelly@dhr.state.ga.usrpk8@cdc.gov

http://health.state.ga.us/epi/zvbd/http://www.Gamosquito.org

2

3

First, some background info…

What is Entomology?

- the branch of zoology that deals with the study of insects

• the study of insects that carry diseases• may also deal with other arthropods that carry

disease (ticks & mites)• may deal with insects & other arthropods that

are considered pests by humans

A Public Health Entomologist works in the realm of public health

4

What is Medical Entomology?

5

1. an annoying or troublesome person, animal, or thing; nuisance.2. an insect or other small animal that harms or destroys garden plants, trees, etc.3. a deadly epidemic disease, especially a plague; pestilence.

What is a pest?

Arthropods that are considered pests by humans are primarily found in 2 classes:

• Arachnida – spiders, ticks, mites• Insecta – the insects

6

7

We define pests in terms of our own standards of good and bad -- standards that are often based largely on aesthetics, economics, and personal welfare, and shaped by cultural bias and personal experiences.

A "pest" is defined as any organism that causes annoyance or injury to human beings, human possessions, or human interests.

The injury may be physical (bites and stings), medical (causing illness or disease), or economic (monetary loss to goods or property). Injury may arise directly from the pest itself, or may develop indirectly as a result of the actions or behavior of the pest.

8

The species we regard as pests usually affect us in one or more of the following ways:• They are an annoyance or

nuisance• They endanger human health

or safety• They threaten the welfare of

useful plants or domestic animals

• They damage stored products or structural materials

In reality, many of the insects and other arthropods we label as pests are essential

components of our natural ecosystem.

9

Out of the 800,000 - 1,000,000 species of insects that have been described so far, not more than 1,000 (about 1/10 of 1%) can be regarded as serious pests, and less than 10,000 (about 1%) are even occasional or sporadic pests.

10

Aesthetic pests cause no damage and inflict no injury.

They may be annoying, unsightly, or disruptive (like chirping crickets that keep you awake at night, or dance flies that swarm around your head in the spring), but their presence will cause no injury or financial liability.

An insect is most likely to be regarded as an aesthetic pest when it inadvertently invades a home or business establishment.

11

Agricultural pests

• Of all the insect species now living on earth, at least half of them (400,000 - 500,000) feed directly on the tissues of living plants.– Herbivores with chewing mouthparts consume a

plant directly.– Plant tissue is also damaged by herbivores with

piercing-sucking mouthparts. • Many insects that feed on plants also serve as

vectors of plant diseases.

12

Pests of Medical Importance

It is impossible to measure the full impact of insects and other arthropods on human health and welfare.

• These organisms have the capacity to inflict injury, disease, discomfort, or distress.

• They can be a direct cause of illness, pain, and suffering through bites and stings, infested wounds, or allergic reactions.

• They feed on blood or body tissues and they may transmit deadly pathogens or parasites.

Economic losses associated with these pests are borne not only by the affected individuals and their families, but also by human society in general. • Losses include not only the direct costs of medicine and health care, but also

indirect costs resulting from stress, absenteeism, and reduced productivity. • These are costs that are not easy to measure in dollars and cents.

13

Many of the Medically Important Arthropods are Hematophagous (they feed on blood)

14

All of the arthropods that can pierce human skin havemouthparts that are especially adapted for piercing, cutting, or burrowing.

These include:• Diptera (mosquitoes, black flies, horse flies, deer flies,

stable flies, sand flies, and various biting midges)• Hemiptera (bed bugs, assassin bugs, water bugs) • Thysanoptera (thrips)• Phthiraptera (sucking lice)• Siphonaptera (fleas)• the class Arachnida (spiders, mites, and ticks)

15

Although the amount of blood taken by each insect may be quite small, the cumulative effects of blood feeding by large populations of hematophagous insects can be life-threatening.

Salivary enzymes and other compounds, such as anti-coagulants, anesthetics, and vasodilators also may be injected by the mouthparts during feeding.

The localized reaction to an insect bite (pain, swelling, redness, etc.) is usually a physiological (inflammatory) response to these injected compounds.

16

Contrary to popular belief (and the internet), you can not reliably tell what bit you by looking at the bite.

Identification of the source of the bite is important in order to determine whether to seek emergency medical attention, call your doctor, or treat the bite at home.

The best way to do this is to see what bit you.

17

What is a primer?

An old-fashioned school book that contains very basic facts about a subject.

1. An elementary textbook for teaching children to read.2. A book that covers the basic elements of a subject.

A Short Primer on Arthropods of Medical Importance

And now to the topic at hand…

18

ARTHROPODA is for:

All insects are arthropods but not all arthropods are insects!

19

What is an arthropod?

The arthropods constitute over 90% of the animal kingdom and are classified in the phylum Arthropoda.

They are distinguished from other animals by:• an exoskeleton (a skeleton

on the outside of the body)

• body divided into distinct parts

• jointed legs and appendages

• May have wings and antennae

• bilateral symmetry (both sides of the body are the same)

20

BUGSB is for:Another truism: all bugs are insects; not all insects are bugs.

A “bug” is one of the 35000 or so species in the order Hemiptera.

Many bugs are considered a nuisance, especially in agriculture.

Some bugs are pests of medical importance because they transmit diseases.

21

Hemipterans have piercing-sucking mouthparts

Hemipterans feed on a variety of liquids, including blood.

22Bed Bugs

female male

What is that!

nymph

eggs

23

Female bed bugs deposit 3 to 8 eggs at a time; a total of 200-500 eggs can be produced by one female over her 10 month life span.

The eggs hatch in 4-12 days.

Bed bugs go through 5 nymphal stages before reaching maturity. This usually takes 35-48 days.

LIFE CYCLE

Reactions to Bites

The bite of a bed bug is painless. Common allergic reactions include the development of large welts that are accompanied by itching and inflammation. The welts usually subside to red spots but can last for several days. Blister-like eruptions have been reported in association with multiple bed bug bites and anaphylaxis may occur in patients with severe allergies.

24

25

C is for:

COLEOPTERA (beetles and weevils), the largest order in the class Insecta.

26

What is that!

Blister beetles receive their common name from the ability of their hemolymph to produce blistering on contact with human skin.

Hemolymph is often exuded copiously by reflexive bleeding when an adult beetle is pressed or rubbed.

Blisters commonly occur on the neck and arms, as the result of exposure to adult beetles attracted to outdoor lights at night.

27

D is for:• Diptera, the true flies

Flies are insects. Diptera means two wings; di = two, ptera = wings. The hind pair of wings are reduced to a couple of knob-like balance organs.

28

What is that?Psorophora ciliata (shaggy-legged gallinipper)

This is the largest blood sucking mosquito in the US. The larvae are large and are predacious upon other larvae. The adult inflicts a painful bite.

Larval habitat: flooded fields, temporary ground pools, and ditches.Adult habitat: fields and yardsBiting activity: Anytime of the day when disturbed.Flight range: 1-2 miles

29

What is that!Myiasis is the infestation of the organs or tissues of host animals by the larval stages of dipterous flies, usually known as maggots or grubs.

The fly larvae feed directly on the host's necrotic or living tissue. The hosts are usually mammals, occasionally birds and, less commonly, amphibians or reptiles.

TYPES• dermal, sub-dermal or cutaneous (creeping)• nasopharyngeal• ocular• intestinal/enteric or urinogenital • open wounds - traumatic • boil-like, the lesion is termed furuncular • bloodsucking myiasis - sanguinivorous

30

Medical Myiasis• Not all flies associated with myiasis are deleterious or otherwise

a nuisance to their vertebrate hosts. • Some species of Calliphoridae (blowflies) have been observed

on infected wounds since the mid-1500’s. • History:

– Ambroise Paré (1509-1590), the chief surgeon to Charles IX and Henri III, discovered in 1557 during the battle of St. Quentin that maggots often infested pus-forming wounds.

– In 1829, Baron Dominic Larrey the chief surgeon to Napoleon found that these infestations prevented infection and hastened healing.

• Today, these beneficial maggots serve as an adjunct to modern medicine rather than solely as a last resort.

• They are used to treat several maladies including the foot wounds of diabetic patients.

31

Disease Transmission

Mosquitoes are estimated to transmit disease to more than 700 million people annually in Africa, South America, Central America, Mexico and much of Asia with millions of resulting deaths.

In Europe, Russia, Greenland, Canada, the United States, Australia, New Zealand, Japan and other temperate and developed countries, mosquito bites are now mostly an irritating nuisance; but still cause some deaths each year.

32

HYMENOPTERA

sting and bite

H is for:

Insects - ants, bees, wasps, hornets

33

Hymenoptera • The best defense against hymenoptera is to avoid them

• When ants, bees, wasps, or hornets attack, run!

• Pain, redness & swelling are normal at the sting site

• Anyone with >15-25 stings should seek medical attention

34

35

What is that!

The European hornet, Vespa crabro, is the largest of the European eusocial wasp.

The queen measures 25 to 50 mm (1–2 in) long; males and workers are smaller.

European hornets are attracted to lights at night…

36

What is that!The velvet ant, or cow

killer, is a wasp. Females are wingless and

covered with dense hair. The males have wings.

37

Africanized Honey Bees

• “Killer Bees”• Originally brought to

South America from southern Africa in 1956 (crossbreeding program)

• Areas of colonization: every Latin American country except Chile; Arizona; New Mexico; Nevada; Texas; California; Mississippi; Florida; … and Georgia???

38

I is for:

• Insect– 3 body parts– 6 legs– 1 pair antennae– 0, 1, or 2 pairs of

wings

Remember, all insects are arthropods but not all arthropods are insects!

Growth & Development

• MetamorphosisGradual – adults & nymphs

usually eat the same food and live in the same habitat

Complex – adults & larvae eat different foods and live in different habitats

• Molt to increase size

39

40

L is for:• Lepidoptera, the moths and butterflies

– Lepidoptera are insects.– The name Lepidoptera, derived from the

Greek words "lepido" for scale and "ptera" for wings, refers to the flattened hairs (scales) that cover the body and wings of most adults.

– Although many Lepidoptera are valued for their beauty, and a few are useful in commerce, the larvae of these insects are probably more destructive to agricultural crops and forest trees than any other group of insects.

41

Urticating (irritating) Caterpillars

• Urticating hairs can be of two distinct types– Envenomating hairs

• Tubular • Hold venom

– Non-envenomating hairs• Fragile• Irritating

• Contact - wheals and widespread rashes that can be accompanied by a burning sensation

42

What is it!

Moths in the genus Calyptra are sometimes known as vampire moths, a colorful name referring to the ability of at least some species to pierce mammalian flesh and feed on blood.

43

M is for:

• Mites – small arthropods that can infest animals, plants, and stored foods and include important disease vectors

• Mites are wingless, lack antennae and are flat or round bodied

• Adults have eight legs, although the first immature stage has only six legs

• All members have piercing-sucking mouthparts

44

Chiggers

• Chiggers are the juvenile form (larvae) of a mite in the family Trombiculidae.

• Chiggers are barely visible to the naked eye (their length is less than 1/150th of an inch).

• They are red in color and are most easily seen when clustered in groups on the skin.

• The juvenile form has six legs; the (harmless) nymphal and adult mites have eight legs.

• They do not suck blood but cut into the skin, inject skin-digesting saliva and suck up the liquefied skin

45

Scabies

• Very small & rarely seen

• They burrow into the skin

• Reaction: initially, little irritation; after about a month, a rash appears

• Common bite areas: skin between the fingers, bend of the elbow & knee, penis, breasts, and shoulder blades

46

P is for:

• Phthiraptera, the lice – small, wingless, parasitic insects

47

Head Lice (Pediculosis)• Infestation of the hair on the scalp by Pediculus

humanus capitus, or the human head louse• Live by biting and sucking blood from the scalp• Problem common in schools and institutions• 6-12 million people worldwide are infested each

year• Three forms of lice: nit, nymph, and adult

www.headlice.org

48

What bit me!

Phthirus pubis – crab louse

49

S is for:• Siphonaptera, the fleas

– Fleas are insects– As adults, all fleas are blood-sucking external parasites– In addition to their irritating bites, fleas may also transmit

pathogens that cause disease in humans and other animals

– Cat and dog fleas are intermediate hosts for a tapeworm (Dipylidium caninum) that infects dogs, cats, and humans

• Ever heard of the plague?

50

The Black Death (1347 – 1350)The Black Death came in three forms. All forms were caused by a bacterium called Yersinia pestis. In some cities, as many as 800 people died every day.

• bubonic plague was the most commonly seen form of the Black Death (mortality rate was 30-75%)

• pneumonic plague was the second most commonly seen form of the Black Death (mortality rate was 90-95%)

• septicemic plague was the most rare form of all (mortality was close to 100%)

The economy was probably hit the hardest of all the aspects of Europe. The biggest problem was that valuable artisan skills disappeared when large numbers of the working class died. This eventually lead to a change in the society structure.

51

T is for:• Ticks

– Ticks are arthropods, like spiders.– Two families of ticks, Ixodidae (hard ticks) and

Argasidae (soft ticks), are important to humans because of the diseases or illnesses they can transmit or cause.

• Ticks are the leading vectors of diseases to humans in the United States, second only to mosquitoes worldwide.

52

Don’t Do This to Remove a Tick

• Put vaseline on it• Put fingernail polish over it• Put mineral oil on it• Drench it with whiskey, wine, or

other alcoholic beverages• Stick a lit match on it (or a

recently extinguished match)• Especially do not combine the

above flammable materials with the match treatment!

53

Resources• http://www.cals.ncsu.edu/course/ent425/text18/pestintro.html• http://www.emedicinehealth.com/ticks/article_em.htm• http://emedicine.medscape.com/article/769067-overview• http://www.crcpress.com/product/isbn/9780849385391 • http://www.agius.com/hew/resource/arthrop.htm• http://www.who.or.id/eng/contents/aceh/wsh/books/evc/evc-02.pdf • http://lancaster.unl.edu/pest/resources/medspider006.shtml• http://www.medicinenet.com/chiggers_bites/article.htm• http://www.cdc.gov• http://health.state.ga.us/epi/zvbd/

And many, many more. Be careful though. There is a lot of mis-information out there.

Take a Disease and History class if you ever get a chance.

54

"There was an old lady who swallowed a spider that wiggled and jiggled and tickled inside her. She swallowed the spider to catch the fly. I don't know why she swallowed the fly. Perhaps she'll die."

Insects and Arthropods in Poetry and Folklore

The lighter side…

55

ANY QUESTIONS?