Medical Entomology

MEDICAL IMPORTANCE OF ARTHROPODS

• 1)As aetiologic agents (causes) of diseases.– Tissue damage– Induction of hypersensitivity reactions. – Injection of poisons– Entomophobia (acarophobia)

• 2) As vectors of diseases: • I: Mechanical transmission - simple carriage of

pathogens.• II: Biological transmission:

– - cyclical – - propagative– - cyclopropagative

• III: Transovarian transmission

ARTHROPODS OF MEDICAL IMPORTANCE

Class Insecta ΕήθΤϟ Class Arachnida ΐ ϛΎϨόϟ

ΕΎϳήθϘϟClass Crustacea

Muscid flies:housefly,Tsetse fly

Myiasis-producing flies .

Scorpions ΏέΎϘόϟ Water flea (Cyclops)

Mosquitoes ν ϮόΒϟ: Anopheles, Aedes Culex

Spiders ΐ ϛΎϨόϟ

SandflyϞϣήϟΏΎΑΫ

(Phlebotomus) Ticks: ΩήϘϟ hard, soft

Black fly(Simulium) Mites α Ϯδϟ Fleas Κϴ ήΒϟϏ -Sarcoptes

scabiei,

Lice(Pediculus,Phthirus) ϞϤϘϟ

-dust mites

Bugs:Cimex,Triatoma ϖΒϟ Bees ϞΤϨϟ

Scabies Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

LICEPediculus humanus humanus (P.h.corporis): body lousePediculus h. capitis:head louseMorphology: 2-3mm long dorsoventrally flattened  Life Cycle : Head or body lice transferred by contact with infested person or clothes . Females deposit eggs on the hair (nits)Eggs hatch after 10 days -----nymphs-------maturation in 2 wks . Larvae and adults feed on human blood. Diagnosis: nits are visible by naked eye , they fluoresce under UV light (Wood’s lamp for screening).Pathology: Pedicolosis ,irritation and pruritus.Body louse is vector for Relpsing fever, Typhus & Trench fever. 

LICELouse(singular) , Lice (pleural)

Pediculus humanus

Pediculus humanus

lousy (louzy)adj. lous·i·er, lous·i·est ,lousi·ly adv. ,lousi·ness n.

1. Infested with lice.2. Extremely contemptible; nasty: a lousy trick.3. Very painful or unpleasant: a lousy headache.4. Inferior or worthless: a lousy play.

The American Heritage® Dictionary of the English Language :

Life cycle of the head louse

( Pediculus humanus capitis )

Nits of Pediculus humanus

• Pediculus humanus

Phthirus pubis

Phthirus pubis (pubic louse or crab louse)

Smaller than Pediculus. (about2 mm)

Infests pubic hair mainly.

Transmitted by direct contact with infested person or clothes.

Life cycle 30-40 days.Irritant , no disease transmission.

Phthirus pubis

Treatment of Lice infestation;

• Removal and decontamination of clotheses 50 C, dry cleaning

• Application of preparations containing permethrin

• Removal of nits by fine comb

Myiasis ((التدويد

Myasis: summary • Caused by a large number of flies. Common in rural

areas where people are in close contact with animals.• Eggs or first stage larvae are deposited on body

apertures, wounds or introduced into unbroken skin. Larvae develop causing tissue damage.

• Pathology and Clinical picture: depends on type of fly, location in body and number of maggots. Skin ulcer, aural, nasal or eye lesions.

• Diagnosis: by identification of maggot.• Treatment: surgical removal.

Obligatory : larvae normally develop within or on living tissues of vertebrates e.g.:

(a) Nasopharyngeal (i.e., relating to or affecting nose and pharynx) cavities of herbivorous mammals,

(b) Cutaneous and subcutaneous tissues,

Facultative :larvae developing in decomposing organic materials or the necrotic tissues of living animals

Myiasis

Classification:

Ophthamomyiasis

- Larva of human botfly, Dermatobia hominis, manually expressed from furuncle

Myiasis

Bed bugs

(Cimex lectularius)

Bed Bug, small, flat, oval bloodsucking insect, with a reddish-brown color, reduced wings, and an unpleasant odor.

The common bed bug infests houses, particularly beds. It hides during the day and feeds at night, sucking the blood of humans and other mammals. Two to four generations are produced yearly, depending on the temperature and the food supply.

Bed bugs (Cimex lectularius)

Bed bugs (Cimex lectularius)

• Highly venomous• Thick-tail scorpions

(family Buthidae). They have thick tails and thin pincers.

Scorpions

Non-venomous • Thin-tail scorpions

(families Scorpionidae, Ischnuridae). They have thin tails and broad, well developed pincers.

Scorpions

Local scorpions in KSA include :

The yellow scorpions (Leiurus quinquestriatus),

The black scorpion (Androctonus crassicauda).

Scorpions

This is a preparation containing the F(ab')2 fraction of the immunoglobulins raised against scorpion venoms. The antivenom is prepared by hyperimmunizing healthy horses using gradually increasing doses of local scorpion venoms and immunomodulators .

Bee stings

BEES 

Venoms of bees are a mixture of enzymes and several polypeptides some of which are pharmacologically active e.g. histamine or neurotoxic. Some people are hypersensitive to venoms and suffer anaphylactic reaction , death might result in 1 hour.

Latrodectus hasseltii (The Red-back Spider):

This spider is commonly found outdoors and around human habitation. It's often called The Red-back spider.

A bite from a hasseltii is highly venomous.

Hobo or Brown Recluse Spider:

A venomous bite from a can cause severe necrotic arachnidism results from envenomation (venom poisoning). It occurs due to the venom's ability to clot blood that results in an area of tissue receiving inadequate blood flow and thus dying secondary to oxygen starvation.

Important arthropod vectors for human diseases

House fly (Musca domestica) Mechanical transmission of many viruses, bacteria and parasites.

Mosquitoes البعوض Anopheles :malaria filariasis Culex: filariasis, viruses Aedes: yellow fever, dengue fever, Rift Valley Fever

Lice القمل Body louse: vector for: Relapsing fever, typhus and trench fever.

Fleas البراغيث Rat flea is vector for plague due to Yersinia pestis.

Ticks القراد Soft ticks , some are vestors for : Borrela duttoni Hard ticks Include vectors for Babesiosis (protozoa), Q fever, and Rocky mountain spotted fever :

Tse tse fly (Glossina) التسي ذبابة Vector for African Trynanosomiasis (African sleeping sickness)

Black fly (Simulium) السوداء ا لذبابة Vector for Onchocerca (river blindness)

Sand fly (Phlebotomus) ذبابة

الرملVectors for leishmania and sandfly fever virus.

Cyclops Vector for Dracunculus medinensis

World-wide distribution

Body with 3 visible parts,

3 pairs of legs

1 pair of visible wings.

Retracted mouth parts

Breeds in soil and dirt

Not a blood sucker.

Mechanical transmission of many diseases : viruses, bacteria and parasites

HOUSE FLY

Musca domestica

Mosquitoes :

Cosmopolitan , more than 3000 species.

Larval and pupal stages always aquatic

Mouth parts in female adapted to piercing and sucking blood.

Genus and species distinguished by morphology of adult and deveopmetal stages.

Anopheles stephensi

Phlebotomus ( sand fly

Phlebotomus ( sand fly

Simulium damnosum (black fly)

Vector of Onchocerciasis ( river blindness)

Black in colour with hump back and short strong legs.

Short antennae and short strong mouth parts.

Breed in fast running stream of water , rich in Oxygen .

Diurnal activity.

Vector of river blindness (onchocerciasis).

Tse tse fly (Glossina spp)

Breeds in forests of central Africa.

Body with 3 visible parts,

3 pairs of legs

1 pair of visible wings.

Mouth parts well developed

for sucking blood.

Vector of African sleeping sickness.

Cyclops : vector for Dracunculus medinensis

Fleas

Wingless ,brown, laterally flattened, 3 pairs of well developed legs for jumping

 

Diseases:

Xenopsylla cheopis- rat flea:plgue, murine typhus.

Pulex irritans : Rat flea

Rat flea

Fleas

TICKS Body 1 segment 4 pairs of legs

no antennae no wings

Hard Ticks:

Vector for:

•Babesiosis,

•Q fever, Rocky Mountain spotted fever

Soft ticks:

Vector for:

Relapsing fever

• Brown Dog Ticks • A. Engorged Female • B. Female • C. Male

• Black-Legged Ticks (Deer Ticks) • D. Larvae • E. Nymphs • F. Males • G. Females • H. Engorged Female

Triatomid bug , vector of Chagas disease( American trypanosomiasis)