Ectoparasites Causing Human Diseases PDF

Ectoparasites causing human diseases Name: Dr. Faten Alhemrany Designation: Assistant Professor Department: Microbiology Department Ectoparasites/ Microbiology Learning Objectives Knowledge & understanding Discuss properties, pathogenesis, clinical find...

Ectoparasites causing human diseases Name: Dr. Faten Alhemrany Designation: Assistant Professor Department: Microbiology Department Ectoparasites/ Microbiology Learning Objectives Knowledge & understanding Discuss properties, pathogenesis, clinical findings and laboratory diagnosis of ectoparasites causing human diseases  Ectoparasites: are parasites that are found either on the skin or only in the superficial layers of the skin.  All ectoparasites are arthropods. jointedlegs rigidexternalcoverning  Arthropods are invertebrates with a chitinous exoskeleton. The ectoparasites that cause human disease fall into two main categories: botharepartofarthropods a 1. Insects: six-legged arthropods such as lice, flies, and bedbugs. spairs 2. Arachnids: eight-legged arthropods such as mites, ticks, and spiders 4pairs  Many arthropods are vectors that transmit the organisms causing important infectious diseases such as female anopheles mosquito of malaria.  However, in this lecture, the arthropods will be discussed not as vectors, but causes of the disease themselves. Insects jl eggedarthropods sit Lice t Ye leurai Disease: Pediculosis Pediculosis is caused by two species of lice: 1. Pediculus humanus: head louse and body louse 2. Phthirus pubis: (pubic louse) primarily affects the genital area but the axilla and eyebrows can be involved as well. Pediculus humanus has two subspeciestypes  Pediculus humanus capitus (head louse) that primarily affects the scalp.  Pediculus humanus corporis (body louse) that primarily affects the trunk. Important Properties Lice are easily visible, being roughly 2 to 4 mm long. with naked eye They have six legs armed with claws by which they attach to the hair and 3pairs skin. Pediculus has an elongated body, whereas Phthirus has a short body and resembles a crab, and hence its nickname, the crab louse. Nits are the eggs of the louse and are typically found attached to the hair shaft. Nits are white and can be seen with the naked eye. Nits of the body louse are often attached to the fibers of clothing.  Last Tidy June Pediculus Phthirus Life cycle Transmission Head lice are transmitted primarily by fomites such as hats, combs, and towels. These are especially common in school children. Body lice live primarily on clothing and are transmitted either by clothing or by personal contact. Body lice leave the clothing when they require a blood meal. Pubic lice are transmitted primarily by sexual contact. Widespread infestations of body lice occur when personal hygiene is poor, e.g., during wartime or in crowded refugee camps. Note that: The body louse is the vector for several human pathogens, notably Rickettsia prowazekii, the cause of epidemic typhus, whereas the head louse and the pubic louse are not vectors of human disease. Pathogenesis  Adult lice bite and feed on blood in this process they inject saliva into the skin, which induces a hypersensitivity reaction and as a consequence pruritus. itching Clinical Findings  Pruritus is the main symptom for all types of infection.  Excoriations may result from scratching and secondary offskin wearing bacterial infections may occur.  In Pediculosis capitis, the adult lice are often difficult to head see, but the nits are easily visualized. writeeggs  In Pediculosis corporis, the adult lice are primarily in the body clothing rather than on the body.  In Pediculosis pubis, the adult lice and nits can be seen attached to the pubic hair. as sittingto Laboratory Diagnosis The laboratory is not involved in diagnosis. its mainlyclinical Nits fluoresce under ultraviolet light of a Wood’s lamp, which can glowishine eggs be used to screen the hair of large numbers of people. likeinschools Flies Disease: Myiasis Myiasis is caused by the larvae of many species of flies. Fly larvae are also known as maggots. Botflies are the most known to cause myiasis. mmmmm Important Properties The flies that cause myiasis are found worldwide and infest many animals as well as humans. Transmission The precise route of transmission varies depending on the species of fly: The adult fly deposits eggs in a wound and the egg hatches to produce the larva. The fly deposits eggs in the nostrils, the conjunctiva, or on the lips. The fly deposits eggs on unbroken skin and the larva invades the skin. dietinvastion Dermatobia is especially interesting in that it deposits eggs on a mosquito. When the mosquito bites a human, the warmth of the skin induces the egg to hatch and the larva enters the skin at the site of the mosquito bite. Pathogenesis The presence of the larva in tissue induces an inflammatory response. larT Clinical Findings lossofsensation diabetic The characteristic lesion is a painful, erythematous papule resembling a furuncle. The lesion may also be pruritic. itching larvae The larvae can often be seen. Some patients report a sense of movement within the lesion. Cutaneous myiasis is the most common form but ocular, intestinal, genitourinary, and cerebral forms occur. analopeningmost with common children Laboratory Diagnosis clinical The laboratory is not involved in diagnosis. fidaded Bedbugs III J Important Properties species Cimex lectularius has an oval, brownish body and is as about 5 mm long. Bedbugs reside in mattresses and in the crevices of hidden parts wooden beds (can be seen by naked eyes). At night, they emerge to take a blood meal from sleeping humans. Clinical Findings The main symptom of a bedbug bite is a pruritic wheals caused by a Red mark swollen hypersensitivity reaction to proteins in the bug saliva. The bite of a bedbug is not known to transmit any human disease.orinfection Laboratory Diagnosis clinical The laboratory is not involved in diagnosis. mggesto Bedbug hifTY.geArget exposed uneased Kite Arachnids SW arthropods eightingegged Mites Disease  Scabies and it is caused by the "itch" mite, Sarcoptes scabiei.  It is not a vector for other human pathogens. Important Properties The adult female Sarcoptes mite is approximately 0.4 mm in length, with a rounded body and o.si eight short legs. 4pairs Transmission  It is transmitted by personal contact or by fomites such as clothing, especially under unhygienic conditions, e.g., in the homeless and during wartime. Pathogenesis  The mite is located within the stratum corneum of the epidermis.superficiallayer ofskin  The pruritic lesions result from a delayed hypersensitivity reaction to the feces of the mite. T.EE tegg i EEEeEn pressure Clinical Findings no agegroup all congetaffected 1. In immunocompetent people  The typical lesions are either tracks or papules that are very pruritic. itchy  The most common sites are the hands, wrists, axillary folds, and genitals. Fathers between  Areas of the body where clothing is tight, such as along the belt line, are often involved. areas buttocksback.ec pressure  The itching is typically worse at night. 2. In immunocompromised individuals  Extensive crusted dermatitis (Norwegian scabies) can occur.  These patients may be infested with thousands of mites with little or no pruritus. a isaio skinwornoes n.ie  Excoriations may become infected with Staphylococcus aureus or Streptococcus pyogenes, resulting in pyoderma. Bacterium Skinpfction Laboratory Diagnosis Microscopic examination of skin scrapings reveals the mites, their eggs, or fecal pellets. Ticks Disease  Tick paralysis.  Vector of diseases: rickettsial, spirochaetal, viral, bacterial and protozoal diseases  Ticks are commonly found in grassy woodland areas and are attracted by carbon dioxide and warmth from humans. Important Properties and Transmission Female ticks require a blood meal for maturation of their eggs, and hence it is the female that causes tick paralysis as well as serves as the vector of diseases. A tick attaches to human skin by means of its proboscis.mouthpart Pathogenesis  Paralysis is mediated by a neurotoxin that blocks acetyl choline release at the neuromuscular junction—an action similar to botulinum toxin. EEE  The toxin is made in the salivary gland of the tick. The tick must remain attached for at least 4 days prior to the onset of symptoms. Clinical Findings An ascending paralysis resembling Guillain-Barre syndrome occurs. startinlegascendupwards The paralysis is symmetrical and can ascend from the legs to the head within several hours. Respiratory failure and death can occur. main risk Recovery typically occurs within 24 hours of removal of the tick. The tick is often found at the hairline at the back of the neck or near the ear. Children younger than 8 years are most often affected.asthey tarty play stayingrassywood Laboratory Diagnosis clinical The laboratory is not involved in diagnosis. hairline mother 4 pair oflegs mouth attachby mouthpart partisamshedded Spiders  Two species of spiders cause most of the significant disease: 1. The black widow spider (Latrodectus mactans). to morphologicallydifferent 2. The brown recluse spider (Loxosceles reclusa). The black widow spider is about 1 cm in length with characteristic orange-red hourglass on its ventral surface. The brown recluse spider is also about 1 cm in length, but has a characteristic violin-shaped marking on its back. 1 I Black widow spider Brown recluse spider Neurotoxic Disease Dermonecrotic Disease dermonic The bite of the black widow spider causes neurologic The bite of the brown recluse spider causes tissue symptoms primarily. necrosis symptoms primarily. Within an hour after the bite, pain and numbness The necrosis is due to proteolytic enzymes in the spread from the site. toxincontain venom. Severe pain and spasms in the extremities and Bites are initially itchy painless, followed by abdominal pain occur. neurological vesicles then hemorrhagic bullae. Fever, chills, sweats, vomiting, and other assist The lesion ulcerates, becomes necrotic, and may constitutional symptoms can occur.dianhee not heal for weeks to months. In contrast to the bite of the brown recluse spider, tissue necrosis does not occur. nonceration Most patients recover in several days but some, mainly children, die. Case scenario : Case problem : Summary Discuss properties, pathogenesis, clinical findings and laboratory diagnosis of : 1. Lice 2. Flies insects 3. Bedbugs 4. Mites 5. Ticks arachinds 6. Spiders References 1. Levinson W: Review of Medical Microbiology & Immunology, 14th Ed 2. Amboss.com Thank You