Medical Entomology MEDICAL IMPORTANCE OF ARTHROPODS

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

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

Scabies

LICE Pediculus humanus (P. h. corporis): body louse Pediculus h. capitis: head louse Morphology: 2 -3 mm 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.

LICE Louse(singular) , Lice (pleural) Pediculus humanus

Pediculus humanus

The American Heritage® Dictionary of the English Language : 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.

Life cycle of the head louse ( Pediculus humanus capitis )

Nits of Pediculus humanus • Pediculus humanus

Phthirus pubis (pubic louse or crab louse) Smaller than Pediculus. (about 2 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.

Myiasis Classification: 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

Ophthamomyiasis

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

Bed bugs (Cimex lectularius)

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)

Scorpions • 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).

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 dengue fever, Rift Valley Fever Lice Body louse: vector for: Relapsing fever, typhus and trench fever. ﺍﻟﻘﻤﻞ Fleas Ticks ﺍﻟﺒﺮﺍﻏﻴﺚ Aedes: yellow fever, Rat flea is vector for plague due to Yersinia pestis. Soft ticks , some are vestors for : Borrela duttoni Hard ticks Include vectors for Babesiosis (protozoa), Q fever, and Rocky mountain spotted fever : ﺍﻟﻘﺮﺍﺩ Tse tse fly (Glossina) ﺫﺑﺎﺑﺔ ﺍﻟﺘﺴﻲ Vector for African Trynanosomiasis (African sleeping sickness) Black fly (Simulium) ﺍﻟﺬﺑﺎﺑﺔ ﺍﻟﺴﻮﺩﺍﺀ Vector for Onchocerca (river blindness) Sand fly (Phlebotomus) ﺍﻟﺮﻣﻞ Vectors for leishmania and sandfly fever virus. Cyclops ﺫﺑﺎﺑﺔ Vector for Dracunculus medinensis

HOUSE FLY World-wide distribution Body with 3 visible parts, Musca domestica 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

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. Rat flea Pulex irritans :

Fleas Rat flea

TICKS Body 1 segment 4 pairs of legs no antennae no wings Soft ticks: Hard Ticks: Vector for: Relapsing fever • Babesiosis, • Q fever, Rocky Mountain spotted 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)