Medical Entomology PDF

10/9/2024 Medical Entomology Medical Entomology This is a branch of In other words, medical entomology which deals entomology is the medical with arthropods which science directly co...

10/9/2024 Medical Entomology Medical Entomology This is a branch of In other words, medical entomology which deals entomology is the medical with arthropods which science directly concerned affects the health and well- with vectors that affects being of man and human and animal health. vertebrate animals. 1  10/9/2024 Characteristics features of class insecta Life cycle (Developmental Stages) of Insects Complete (Complex) Metamorphosis This is a specialization in which the life history is divided into four distinct parts: The egg. The larva or feeding stage. The pupa, a quiescent (fasting) transformation stage. The adult or reproductive stage. Egg → Larva → Pupa → Adult Incomplete (Gradual) Metamorphosis There is a gradual change from one stage to the next stage until the young or nymph, reaches the adult stage. Lice and bugs are examples of the gradual metamorphosis type. Egg → Nymph → Adult. 2  10/9/2024 There are three organisms that medical entomologist must be familiar with:_ Host Medical Entomology Insect vector Pathogen I. Pathogen :_ Basically microorganisms ( Bacteria , viruses or fungi) that are capable of causing diseases. 3  10/9/2024 Pathogens also include harmful parasites, such as ( Protozoans and Nematodes) II. Insect vector living agents which transmit or help to transmit disease from infected person to a healthy person. Ex:_  Female Anopheles mosquito transmits malaria 4  10/9/2024 III. Host :_ Organism that is infected with or bearing a pathogenic or non pathogenic organism. Some diseases may include a single host; however, other may include multiple hosts species.  Reservoir host:_ Organism that maintain the infective stage when active transmission doesn’t occur. Ex:- human populations is a reservoir host for malaria Two classes of Hosts Primary host Secondary host Primary host:- The host in which the pathogenic organism reaches sexual maturity and sexual reproduction occurs. Secondary host:- In which the asexual reproduction of the parasitic organism occurs. 5  10/9/2024 Ex:_ In Malaria disease Pathogen : Plasmodium sp. (protoazoan) Vector: female Anopheles mosquito. Host : primary host: mosquito secondary host: Human Found in every type of habitat in all regions. Feed on a wide variety of plant or animal. 6  10/9/2024 Insects are related to public health by two ways Indirect Direct effects effects Annoyance Insects as vectors and Envenomization hosts of pathogenic organisms Allergic reactions Entomophobia Parasitoses Arthropods as Direct Causes of Disease Parasitoses 1. Ectoparasitoses Arthropod bloodfeeding, burrowing, crawling, or scraping at and just beneath the skin surface. Ex: Ticks, fleas and sucking lice Reactions can include dermatoses, allergic reactions, and loss of efficiency and productivity. 2. Endoparasitoses Some arthropods invade tissues or body cavities of vertebrate hosts. One example is the "chigoe" or "chigger" flea. When the invasion is by fly maggots, the condition is called myiasis. 7  10/9/2024 Allergic reactions Most animals have physiological mechanisms that defend against the introduction of foreign, or nonself, substances. A foreign substance that results in the production of antibodies by the animal is called an antigen. Antigens that produce unusually strong defensive reactions in animals are called allergens and the conditions in animals are allergies. These hypersensitive reactions often are associated with adverse symptoms such as itching, redness, swelling and rash. Repeated exposure to the same antigen usually causes allergy. In some hypersensitive individuals, fragments of arthropod integument may be allergenic. A small mite and Cockroaches can cause serious allergies in humans. Mosquito bites can result in allergic reactions to some people because they inject salivary fluids containing antigens. Envenomization This is the introduction of venom or other toxins by arthropods through stinging or biting. Toxins substances often are proteins that cause poisonous reactions in other animals. Ex. Wasps, bees and spiders are arthropods that produce venom. Entomophobia Certain people may develop a psychopathic condition that is manifested by a strong sense of being infested by arthropods. This condition may be accompanied by actual symptoms such as skin rash, redness, abrasions and secondary infections. 8  10/9/2024 Annoyance Arthropods can cause considerable discomfort and annoyance to people and other animals merely by their presence and normal activities, even when they produce no serious physical harm. Ex:-flies, wasps, midges, mosquitoes and black flies. Indirect Effects The primary indirect effect of medical and veterinary insects is disease transmission. Transmission of infectious disease may be: a. Horizontal transmission, which consists of the spread of infection from one person to another by direct contact and fecal contamination. b. Vertical transmission, mother to infant in the birth canal. 9  10/9/2024 There are three mechanisms of infectious disease transmission: Mechanical transmission. Biological transmission. Hereditary transmission. Mechanical transmission Mechanical transmission is the transfer of a pathogen from an infectious source to a susceptible host by a vector, without any reproduction or developmental changes in the pathogen. Insect transport pathogen on its body parts ( tarsus, hairs, spines and setae) Ex:- Typhoid can be transmitt mechanically by cockroach. 10  10/9/2024 Biological transmission In which the pathogen either reproduces, undergoes developmental changes, or both in the vector. There are three types of biological transmission: Propagative transmission. Developmental transmission. Cyclopropagative transmission. A. Propagative transmission In which pathogens are carried internally and multiplies inside insect body. Ex: plague and typhus transmission by flea 11  10/9/2024 B. Cyclo-developmental transmission In which pathogen undergoes developmental changes ( change in pathogen life cycle), and doesn't multiply inside the body of the insect vector. Ex: microfilaria within culex mosquito C. Cyclopropagative transmission In which the pathogen must develop and also undergoes multiplication inside the vector. Ex: malaria in the female anopheles mosquito. 12