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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:
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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
HOUSE FLY Musca domestica 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
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.: • Nasopharyngeal (i.e., relating to or affecting nose and pharynx) cavities of herbivorous mammals, • Cutaneous and subcutaneous tissues, Facultative :larvae developing in decomposing organic materials or the necrotic tissues of living animals
Myiasis - Larva of human botfly, Dermatobia hominis, manually expressed from furuncle
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.
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.
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
Fleas Rat flea
LICE Pediculus humanus humanus (P.h.corporis):body louse Pediculus h. capitis:head louse Morphology: 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.
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.
Treatment of Lice infestation; • Removal and decontamination of clotheses 50 C, dry cleaning • Application of preparations containing permethrin • Removal of nits by fine comb
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. The other species of bed bugs feed on bats and certain birds.
Triatomid bug , vector of Chagas disease( American trypanosomiasis)
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 .
TICKS Body 1 segment 4 pairs of legs no antennae no wings Hard Ticks: Babesiosis, Q fever, Rocky Mountain spotted fever Soft ticks: 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
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.
