Arthropod-Borne Diseases F2023 PDF

LEARNING OUTCOMES: 3-1-2-1-1 CATEGORIZE ARTHROPOD-BORNE DISEASES, CONCLUDE AND SUGGEST THE APPROPRIATE CONTROL MEASURES. Chapter 22, 23 ARTHROPODS THAT TRANSMIT DISEASE  Ticks, mosquitoes, fleas and biting flies  Transmission usually by biting INFECTIONS  Viral (arboviruses)……………….(CN...

LEARNING OUTCOMES: 3-1-2-1-1 CATEGORIZE ARTHROPOD-BORNE DISEASES, CONCLUDE AND SUGGEST THE APPROPRIATE CONTROL MEASURES. Chapter 22, 23 ARTHROPODS THAT TRANSMIT DISEASE  Ticks, mosquitoes, fleas and biting flies  Transmission usually by biting INFECTIONS  Viral (arboviruses)……………….(CNS)  West Nile, Encephalitic viruses  Bacterial……………………(CVS)  Ricketsia ricketsii, Borrelia burgdorferi, Yersinia pestis  Parasites………………….(CVS)  Malaria ARTHROPOD-BORNE VIRUS (ARBOVIRAL ENCEPHALITIS)  Organism: arbovirus  Mode of transmission: mosquito-borne viruses Reservoir: birds, horses, rodents and mammals  Seasonal occurrence: summer months  Symptoms: fever, headache, and altered mental status ranging from confusion to coma  Control:………?  Types of Arboviral encephalitis: Disease Pathogen Mosquito Reservoir Epidemiology Mortal (vector) ity Western WEE virus Culex Birds Severe disease, 5% Equine (Togavirus) frequent Encephalitis Aedes Horses neurological damage, especially in Culiseta Small infants mammals Eastern EEE virus More severe than > 30% Equine (Togavirus) WEE, affects Rodents mostly young Encephalitis children and Large younger adults St.Louis SLE virus mammals Mostly urban 20% Encephalitis (Flavivirus) outbreaks, affects mainly adults over 40 California CE virus Affects mostly 4-18 1% Encephalitis (Bunyavirus) year age groups in rural or suburban areas. About 10% have neurological damage West Nile WN virus Most cases 4-18% Encephalitis (Flavivirus) asymptomatic. Symptoms vary from mild to severe  PLAGUE  Organism: Yersinia pestis, gram-negative bacilli  Mode of transmission: rat flea bite (Xenopsylla cheopis)  Pathogenesis:……………..? o Virulence factor: its resistance to phagocytosis. PLAGUE- CONT’D  Forms of plague: 1- Bubonic plague (buboes): enlargement of the lymph nodes of the groins, fever, malaise and headache - It is the most common form - Mortality rate: 50-75  PLAGUE- CONT’D Forms of plague: 2- Septicemic plague: Bacterial endotoxins cause disseminated intravascular coagulation (DIC). Signs include: - Bleeding under the skin or from the mouth, or nose - Blackened skin, especially on the nose, fingers, and toes - Belly pain, diarrhea, vomiting, and shock  PLAGUE- CONT’D Forms of plague: 3- Pneumonic plague: - Mortality rate: 100%, unless the disease is discovered within the first 12-15 hrs of the onset of fever -Pneumonic plague is very contagious because can spread by airborne droplets - Cough, sometimes with blood - Shortness of breath PLAGUE- CONT’D  Laboratory diagnosis: - Isolation of bacteria - Direct detection of the capsular antigen within 15 minutes (blood and other body fluids)  Treatment: streptomycin and tetracycline  Prophylaxis: vaccine, (To whom?) ???????????????????????? State true or false:  Mortality rate of WEE is 30%  WNE affects mainly adults over 40 years  Yersinia pestis is Gram positive bacilli  In plaque, the vector is house fly  Mortality rate of bubonic plaque is 10%  Septicemic plaque is the most common form  The animal reservoir of plaque is dear LYME DISEASE (LYME BORRILIOSIS)  Causative organism: Borrelia burgdorferi - Spirochete - Obligate Intracellular pathogen EPIDEMIOLOGY  It was first diagnosed as rheumatoid arthritis, was reported near the city of Lyme, Connecticut  Seasonal occurrence: summer months  Mode of transmission: by Ixodes species ticks (mainly deer ticks) – Tick borne disease  Mammalian reservoirs: mice and deer LIFE CYCLE  Field mice:  Dear:  Ticks: feed three times during its life cycle; - First and second feeding are on field mice - Third feeding is on a dear  Human: become infected by the nymph stage of the tick ………. LIFE CYCLE  Human: become infected by the nymph stage of the tick which feed on infected mice with B.burgdorferi. The ticks usually attaches from grass - They don’t feed for the first 24 hrs and usually requires 2-3 days of attachment before transmission of bacteria and infection occur  Occurrence: 1% of tick bites result in Lyme disease LIFE CYCLE Deer tick eating STAGES OF LYME DISEASE (SYMPTOMS)  First stage: - First week: erythema migrans (outwardly expanding rash) / bulls-eye appearance - A couple of weeks: Flu-like symptoms too and the rash fades - Antibiotic taken during this interval is very effective ( the best treatable stage) LYME DISEASE SYMPTOMS  Second stage: Dissemination: days to weeks - Bulls-eye rash appear at other sites of the body - Heart palpitation, also pain in muscles, joints and tendons, and strong headache - Neurological symptoms: facial paralysis, memory loss, meningitis and encephalitis may occur LYME DISEASE SYMPTOMS  Third Stage: Persistent infections  Chronic arthritis for years  Cognitive impairment, weakness, pain in joints (especially the knees), fatigue  Can end up with permanent damage DIAGNOSIS AND TREATMENT  Clinical diagnosis: depends on its symptoms  Laboratory diagnosis: ELISA, IFA, both should be confirmed by Western blot test  Treatment: streptomycin and tetracycline are effective even in the later stages TYPHUS  Causative organism: Rickettsias, gram negative pleomorphic bacteria that are obligatory intracellular parasites of eukaryotes - Rickettsias, which are spread by arthropod vectors, infect mostly the endothelial cells of the vascular system and multiply within them - The resulting inflammation causes local blockage and rupture of the small blood vessels TYPHUS Epidemic typhus: R.prowazaki Pediculus H.C. Endemic typhus: R.Typhi Xenopsyla cheopis Rocky mountain spotted fever: R.Ricketssia Tick TYPHUS – CONT’D  Three forms of typhus: 1- Epidemic typhus - Symptoms: high and prolonged fever lasts for 2 weeks. Small red spots caused by subcutaneous hemorrhage is characteristic (erythematous maculopapular rash) - Mortality rate: high if untreated - Treatment: tetracycline and chloramphenicol - Control: …………………………………? 2- Endemic typhus - Less sever than epidemic typhus - Mortality rate: less than 5% - Control: …………………..? 3- ROCKY MOUNTAIN SPOTTED FEVER  Organism: caused by Rickettsia rickettsii  Tick borne disease LIFE CYCLE OF ROCKY MOUNTAIN SPOTTED FEVER Symptoms: Fever, nausea, severe headaches, muscle pain. Macular rash mistaken for measles. It often appears on palms and soles Mortality rate: 3-20% if untreated Diagnosis: serological tests, but don’t become positive until late in the illness Treatment: tetracycline and chloramphenicol ????????????  State true or false:  Lyme disease occurs mostly in winter  Field-mice is considered a dead-end in Lyme disease  Dear is the most important animal reservoir in Lyme disease  Chronic arthritis is characteristics of 2nd stage of Lyme disease  Epidemic typhus is called murine-borne typhus  Endemic typhus is more sever than epidemic  Macular rash is characteristic of epidemic typhus