LEC-1 - Introduction to Medical Entomology PDF

12 out of the 21 NTDs are caused by parasites OUTLINE 11 out of the 21 NTDs are endemic in the Philippines ○ 8 out of the 11 endemic NTDs are caused by I. MEDICAL...

12 out of the 21 NTDs are caused by parasites OUTLINE 11 out of the 21 NTDs are endemic in the Philippines ○ 8 out of the 11 endemic NTDs are caused by I. MEDICAL III. ARTHROPODS AND arthropods ENTOMOLOGY HUMAN HEALTH Three are mosquito-borne diseases: Dengue, A. Aim A. As Disease Chikungunya, and Lymphatic Filariasis B. Scope Transmitters Other diseases are caused by species of bugs or C. Neglected Tropical B. As Direct Agents of mites Disease Disease and II. ARTHROPODS Discomfort Table 1. 21 Neglected Tropical Diseases A. Characteristics C. As Intermediate B. Classes Hosts of Parasite Buruli Ulcer Mycetoma C. Morphology IV. REVIEW QUESTIONS D. Metamorphosis Chagas Disease (Kissing bug) Onchocerciasis (Black fly) Dengue (Mosquito) Rabies SOURCES Bertuso, A.G. (2024). PH 177 Introduction to Medical Chikungunya (Mosquito) Scabies (Mite) Entomology. Dracunculiasis Schistosomiasis MEDICAL ENTOMOLOGY Echinococcosis Soil-Transmitted Helminths Also called public health entomology Defined as the science dealing with the relation of insects, Foodborne Trematodiases Snakebite Envenoming arachnids, and other arthropods to the causation of pathological conditions in man or to the transmission of African Sleeping Sickness Taeniasis and Cysticercosis organisms responsible for such pathological conditions (Tsetse fly) Includes scientific research or investigation on the behavior, ecology, and epidemiology of arthropod disease vectors Leishmaniasis (Sandfly) Trachoma Deals with arthropods causing injury and diseases to humans and animals Leprosy Yaws ○ Veterinary entomology is included in this category because many animal diseases can become a human Lymphatic Filariasis (Mosquito) health threat Note: Red → NTDs caused by an arthropod AIM Ultimately aims for the prevention, and if possible, the ARTHROPODS eradication of human and animal diseases related to 85% of Animal Kingdom arthropod transmission and causation Organisms belonging to Phylum Arthropoda ○ “You can eradicate the disease but not the insect” Coined from the Greek words arthro (jointed) and poda ○ Disease can be eradicated by interrupting (legs) transmission. CHARACTERISTICS SCOPE Bilaterally symmetrical, elongated body subdivided into Includes the knowledge of arthropod: somites ○ Biology → e.g. life cycle ○ Somites → distinct segments/ body divisions ○ Behavior → basis of strategy on attack towards Has paired, jointed appendages eradication Majority have a chitinous exoskeleton covering their body ○ Ecology → relationship of organism to environment ○ Chitin → polysaccharide resistant to dessication ○ Control One of the distinguishing characteristics: having a haemocoel (a greatly reduced general body cavity) NEGLECTED TROPICAL DISEASE ○ Coelom → body cavity Well-developed head, usually with compound eyes but may also have simple eyes called ocelli ○ Compound eyes → used to see the outline or shape of the image ○ Ocelli → makes them see the actual image Figure 1. Parasites and neglected tropical diseases (NTDs): Global burden of NTDs. PH172: Helminthology & Parasitology | TEAM A: ALFORJA, LISTA PURA 1 of 5  CLASSES MORPHOLOGY There are thirteen (13) classes of Arthropods Depending on the arthropod class, there may be 2+ somites Five of which are medically important, including: Arthropods may be classified according to their: For this course, we will be focusing on the following classes: ○ Body segments (i.e., somites) and characteristic appendages (e.g., wings, mouthparts, and antenna) ○ Type of metamorphosis 1 Class Chilipoda → Each body segment has 1 pair of legs → Centipede 2 Class Diplopoda → Each body segment has 2 pairs of legs → Millipede Figure 2. Arthropod Morphology Note: Instead of using the word mouth, in entomology, we use 3 Class Crustacea “mouthparts” → 5 or more pairs of legs Information retrieved from BSPH 2024 Tagmata → Alimango, Alimasag, ○ Refers to the generalized body divisions Talangka ○ Head, thorax, abdomen Head ○ Eye Compound eye Simple eye → Ocelli ○ Mouthparts 4 Class Arachnida Feeding structures fused together Thorax → 4 pairs of legs ○ Prothorax Non-winged part; where prothoracic leg → Spiders, Mites, Ticks, ○ Mesothorax Scorpions First pair of wings; where mesothoracic leg ○ Metathorax → Only Mites and Ticks Second pair of wings; where metathoracic leg are vectors of diseases. Abdomen ○ No legs ○ Ovipositor 5 Class Insecta METAMORPHOSIS Process by which the organism undergoes extremely rapid → 3 pairs of legs physical changes sometime after birth ○ What changes specifically? → form, function, structure → Most numerous class Typically required for sexual maturity Three Types of Metamorphosis: → Also known as ○ Ametabolous Hexapoda ○ Hemimetabolous ○ Holometabolous 6 Class Pentastomida → Without legs in adult → 2 pairs of legs in larva → Now extinct Figure 3. Three Types of Metamorphosis PH172: Helminthology & Parasitology | TEAM A: ALFORJA, LISTA, PURA 2 of 5  CYCLO-PROPAGATIVE NOTES Examples from the figure above: Pathogenic agents undergo propagation and development ○ Ametabolous → silverfish inside the arthropod’s body and then multiply in the process ○ Hemimetabolous → cockroach Example: ○ Holometabolous → housefly ○ In malaria, anopheles mosquito with Plasmodium First image per type of metamorphosis → egg (if falciparum ametabolous, holometabolous), ootheca (if ○ In Chagas disease, kissing bug with Trypanosoma cruzi cockroach/hemimetabolous) (BSPH 2023 Trans) Second and third images per type of metamorphosis → immature forms PROPAGATIVE Fourth image per type of metamorphosis → mature forms Agents undergo no cyclical changes but multiply in the process Example: AMETABOLOUS ○ In bubonic plague, flea with Yersinia pestis Type of growth or life cycle in insects in which there is a slight or no metamorphosis, only a gradual increase in CYCLO-DEVELOPMENTAL size Agents undergo developmental changes but do not Present only in primitive wingless insects multiply Example/s: Silverfish Example: ○ Aka Thysanura ○ In filariasis, mosquito with microfilaria ○ Allergenic → do not touch ○ These are the insects that can be found inside old books MECHANICAL VECTORS Transmit pathogens by: HEMIMETABOLOUS ○ Oral secretions Incomplete metamorphosis ○ Contaminated external surfaces of their body From the Greek words hemi (half), meta (change), bole (to Agents do not enter the arthropod’s body throw) ○ Do not undergo multiplication nor development inside Do not have pupal stage Examples: Some parts of the body change during metamorphosis, only ○ More than 100 pathogens associated with housefly partially modified as they mature and may cause diseases in humans and animals ○ As they molt, wings develop. Housefly bringing Salmonella in its mouth parts then Example/s: Cockroaches, grasshoppers, and dragonflies dislodged into the food ○ Cockroaches have filthy habits of eating while HOLOMETABOLOUS defecating A type of growth or life cycle where a larva completely Considered both mechanical vector and allergen changes its body plan to become an adult ○ Flies as transmitters of pathogens and cause direct injury From the Greek words holo (complete/whole), meta, bole; by invading tissues (myiasis) (BSPH 2023 Trans) hence, holometabolous means “completely or wholly changing” Example/s: ○ Butterflies: Eggs → caterpillar → chrysalis → butterfly Transformation is so swift and complete that the insect must spin a cocoon or enter the pupation stage and stay dormant for weeks while its body undergoes radical changes ○ Houseflies: Eggs → larva → pupa → adult ARTHROPODS AND HUMAN HEALTH As disease transmitters As direct causes As intermediate hosts AS DISEASE TRANSMITTERS BIOLOGICAL VECTORS Acquire pathogenic agents (parasites) in the act of blood Figure 4. Examples of common flies. feeding Agents undergo multiplication, propagation, and AS DIRECT CAUSES OF DISEASE OR DISCOMFORT development inside the arthropod’s body After which, transmit to humans GENERAL FORMS Common examples: ENTOMOPHOBIA ○ Mosquitoes Entomophobia (including delusory parasitosis, acarophobia, ○ Fleas and parasitic dermatophobia) ○ Kissing bugs ○ Experience delusions and see insects even though Types of biological transmission: there are none ○ Cyclo-propagative ○ Example: Delusory parasitosis → Some affected humans ○ Propagative see larva coming out of their eyes and skin, but ○ Cyclo-developmental microscopic examination only show dead skin cells ○ Cannot be corrected by reasoning, persuasion, nor logical argument ○ More common in educated and people with rich backgrounds PH172: Helminthology & Parasitology | TEAM A: ALFORJA, LISTA, PURA 3 of 5  ANNOYANCE ○ Acetylcholine → lower blood pressure and cause Insects as pests paralysis to the direct dural lesion Nuisance especially since they reproduce quickly Stinger from Centruroides spp. (one of the most venomous species of scorpions) injects the venom with sulfhydryl ACCIDENTAL INJURY TO SENSE ORGANS groups ○ Sulfhydryl → produce hemolytic and neurotoxic effects Cockroaches (or insects) may damage eyes with symptoms: ENVONIMIZATION Immediate sharp pain Numbness Inclusive of allergies Itching of nose, mouth and throat Biting → centipedes, spiders, ticks, ants Excessive salivation Sting → ants (hantik) Two recorded venomous spiders: Urticating hairs of caterpillars (higad) ○ Latrodectus hasselti (black widow spider) Vesicating fluids of blister beetles (substances from abdomen ○ Loxosceles geometricus (brown recluse spider) that feels very hot) Aeroallergens; house dust mites; cockroaches CANTHARIASIS Caused by blister beetle DERMATOSIS Due to fleas, bugs, lice, dipterans (e.g. midges, mosquitoes) ○ Midges that hover above your hair and bite in late afternoon ○ Suspected to carry Hepatitis B MYIASIS Infestation of live maggots in tissue Caused by fleshfly (Sarcophaga), latrine fly, blowfly Female flies deposit to pus → development to maggots Most cases reported in PGH are cancer patients Figure 5. Examples of venomous arthropods. Three forms: ○ Accidental (Pseudomyiasis): Caused by flies that have ARTHROPODS AS ALLERGENS no requirement or preference of development in a host. As contact allergens or blistering insect allergens through Eggs may be deposited accidentally in oral openings their setae (urticating hair) ○ Semi-specific (Secondary): Caused by facultative or Example: Caterpillar of moths, butterfly wings, or feces of opportunistic parasitic flies that usually develop in cockroaches (has allergen that causes asthma) decaying organic matter. Can also deposit in living tissue Poisonous secretions (e.g. Green bottle fly, blue bottle fly) ○ Histaminic substances from urticating hairs (ie., may ○ Specific (Primary): Caused by flies whose larvae are cause redness, inflammation, and urticarial wheals with obligate parasites of living tissues associated pain) ○ Proteinaceous substances ECTOPARASITES ○ Water soluble protein pytic enzyme Parasites that live on the outside of its host Insect hair on clothing → widespread dermatitis, imitating Needs blood to develop/metamorphosize a mechanical injury (i.e. red blotches appear quickly and Fleas are one of the most important arthropods causing injury develop into red ridges of rash because of setae which can to humans through their bites or lesions embed on the skin of humans or animals) Biting pattern: Allergens can also be ingested, having adverse effects on ○ Lesions arranged in a zigzag line humans: ○ Dull red spots may persist long after the active lesions ○ Ingestant Allergens have cleared Eating or unintentionally swallowing allergenic Most common human parasitic fleas: insect material ○ Pulex irritans (transmitted the Bubonic plague) Despite proficient methods of production and ○ Ctenocephalides canis storage, trace amounts of insect material still find ○ Ctenocephalides felis their way into our food ○ Xenopsylla cheopis ○ Insect Allergy ○ Tunga penetrans Result of ingesting small quantities of insect material in food over a lifetime VENOMOUS ARTHROPODS Include bees, wasps, ants, moths and butterflies, centipedes, millipedes, scorpions (Centruroides spp.), and spiders Arthropods that: ○ bite (e.g. black widow spider) ○ sting ○ secrete substances that triggers allergies (e.g. millipedes secretes oil that can have a burning sensation on skin) Bees (e.g. honeybees and bumblebees) inject toxins using their stinger located at the tip of their abdomen ○ Toxins: Melittin, hyaluronidase, phospholipase A, histamine Figure 6. Caterpillar seta ○ Cause local and general toxicity and allergy to humans Wasps (e.g. hornet and yellowjacket) inject same venom components of bees plus acetylcholine PH172: Helminthology & Parasitology | TEAM A: ALFORJA, LISTA, PURA 4 of 5  INSECTS AS FOOD-BORNE HEALTH HAZARDS REVIEW QUESTIONS Hazard Analysis Critical Control Points (HACCP) classifies 1. Which is not a general characteristic of arthropods? insects or arthropods as food-borne health hazards a. All have bilateral symmetry. b. They have a reduced body cavity called the haemocoel. PHYSICAL HAZARD c. They have an endoskeleton that is chitinous. Ingestion of body parts of insects d. All are segmented into somites. Example: Cockroach legs/body parts may cause respiratory 2. TRUE OR FALSE. Only ticks and mites are the illnesses disease-carrying vectors from Class Arachnida. 3. Which is the correct pair? BIOLOGICAL HAZARD a. Insecta: 6 legs b. Diplopoda: 2 legs Passive vectors or carriers of pathogens c. Crustacea: 8 legs Example: Cockroaches may harbor numerous nematodes, d. Chilopoda: 2 legs which can infect humans 4. In which type of metamorphosis do insects undergo a CHEMICAL HAZARD complete change in body form during development, including distinct larval and pupal stages? Allergens (e.g. chitin in exoskeleton) a. Hemimetabolous metamorphosis Insect venom (e.g. alcohols, carbon acids, phenols, b. Ametabolous metamorphosis aldehydes, steroids, etc.) c. Holometabolous metamorphosis Insect products (e.g. iron, selenium, zinc) d. Gradual metamorphosis Processing contaminants (e.g. polycyclic aromatic 5. TRUE OR FALSE. Plasmodium falciparum multiply only hydrocarbons) and not develop in the Anopheles’ body, so it is an example of cyclo-propogative. FEEDING SUBSTRATES 6. This is a disease caused by the blister bee. Environmental contaminants capable of bioaccumulation a. Myiasis Example: heavy metals, selenium, dioxins, and b. Cantharsis organochlorines c. Toxicosis d. Dermatosis 7. What is the correct description of Pseudomyiasis? a. This is caused by obligate parasites of the human tissues. b. This has no specific development in a specific host. c. These are caused by parasitic flies in dead and already decaying organic material. d. None of the above 8. With their stingers, bees and wasps can cause the same toxic venomous toxins except for: a. Hyaluronidase b. Histamine c. Pytic enzyme d. Acetylcholine 9. Allergic reactions to arthropods are primarily triggered by: a. Salivary proteins b. Compound eyes c. Antennae d. Abdominal segmentation 10. What is a potential hazard associated with arthropods infesting stored food products in households? a. Transmission of infectious diseases b. Structural damage to buildings c. Contamination and spoilage of food d. Induction of allergic reactions ANSWER KEY 1. C, 2. TRUE, 3. A, 4. C, 5. FALSE, 6. B, 7. B, 8. D, 9. A, 10. C PH172: Helminthology & Parasitology | TEAM A: ALFORJA, LISTA, PURA 5 of 5