SPHU 1020- Cell, Individual, and Community. Cropley week 6
SPHU 1020- Cell, Individual, and Community. Cropley week 6 SPHU 1020
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This 14 page Class Notes was uploaded by Claire Jacob on Saturday February 20, 2016. The Class Notes belongs to SPHU 1020 at Tulane University taught by Dickey-Cropley, Lorelei in Summer 2015. Since its upload, it has received 14 views. For similar materials see Cell, Individual & The Community in Public Health at Tulane University.
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Date Created: 02/20/16
More NTDs week 6 Trichinellosis ● caused by Trichinella spiralis ● transmitted via eating raw or undercooked pork or wild game (bear, boar, seal, walrus, etc.) infected with cysts ● Digestive juices dissolve hard covering of ingested cysts and worms emerge in small intestine ● adult females lay eggs that develop into larvae, which migrate through blood and lymphatics to form cysts in muscles ● wild animals serve as a reservoir ● Distribution ○ infection occurs worldwide where raw or undercooked pork products are consumed ○ incidence markedly declined in US, with 72 cases (31 from eating wild game) from 1997 to 2001 ■ US now prohibits feeding offal, raw meat and uncooked garbage to pigs, contributing to the incidence decline ● s/s: ○ early: 12 days include N/V, diarrhea, vomiting, fatigue, and fever ■ mild cases have flulike symptoms that go undiagnosed Dracunculiasis: guinea worm ● found in African communities lacking clean drinking water ● transmission: ingest water containing larvaeinfected copepods ○ ingested larvae penetrate stomach and intestinal wall and enter abdominal cavity where they mature into adult worms ○ migrate to foot or leg, blister forms, and then burrow out of the foot Guinea worm eradication? ● prevention based on teaching villagers to filter copepods from their drinking water ● Guinea worm disease set to become 2nd human disease in history, after smallpox, to be eradicated, 1st parasite disease to be eradicated and 1st disease to be eradicated without use of a vaccine or medicine ● 3.5 million cases in 1986 to 126 in 2014, this year, 22 incidences ● Main initiative of Carter Center and Bill and Melinda Gates Foundation working with CDC, WHO, etc. Lymphatic filariasis ‘elephantiasis’ ● Primary causative agent Filarial nematode: Wucheraria bancrof ● 250 million humans affected; widely spread in tropical and subtropical countries ● route of transmission ○ transmitted to humans by mosquitos ○ transmission depends on 2 issues: ■ availability of vectors ■ presence of a population of people to infect the vector ○ called Biological Transmission because part of its life cycle is completed whilst in the mosquito ● clinical disease ○ early s/s: fever ○ later: elephantiasis (common, but incorrect word: elephantitis) ○ late complication of filariasis ○ lymphangitis (enlargement of limbs, scrotum, breasts, or vulva with dermal hypertrophy and verrucous changes ○ lymphadenitis (femoral, inguinal, auxiliary nodes) ● DX, TX, Prevention and Control ○ DX: made on clinical grounds ■ using blood films ■ use of sentinel sites ○ TX/ prevention: ■ antiinflammatory agents ■ diethylcarbamazine (DEC), antihelminthic drugs: ivermectine, albendizole, doxycycline Onchocerciasis ● River Blindness ● endemic in 30 countries in subsaharan Africa and 6 in Americas ● 6.5 million infected, 770,000 blind or severely visually impaired ○ in small villages, nearly all past age of 40 are blind, presenting serious obstacle to socioeconomic development ● transmission: ○ black fly ■ breeds in fastflowing waters and streams ○ fly bite deposits larvae under skin, which mature into adult worms (forming skin nodules) that produce millions of microfilariae that migrate through the body ● s/s: ○ rashes, intense itching, and skin depigmentation; invasion of cornea causes blindness ● DX/TX: no blood test ● skin nodules diagnostic; surgical removal of nodules reduces the number of microfilariae produced Schistosomiasis ● >200 million people infected; prevalence increasing ● widely distributed throughout Africa, S america and some parts of Asia; distribution increasing with migration ● Epidemiology and risk factors ○ source of infections: humans and mammals (esp. cattle) ○ Route of transmission: transmission occurs in freshwater where larval stage of schistoma come in contact with and penetrates human skin ○ 3 factors: ■ method of disposal of human excreta ■ presence of snail intermediate host ■ contact (via swimming, bathing, etc) ● acute: early systemic circulation of schistosomules fever, enlargement and tenderness of liver, dysentery ● late stage: eggs trapped in tissues or embolizing to liver hepatic fibrosis, portal… ● prevention: treat patients and domestic animal at the same time ○ avoid infected water Control and elimination of helminths: Public Health Perspective ● economic development ● greater access to medical care ○ easily treat w/worm meds but need repeated tx ○ mass treatment of infected schoolaged population ● health education programs ○ proper disposal of fecal material ○ cook veg grown in soil with feces ● vaccines to provide protection from infection and reinfection Investment in NTD control has high rates of economic return ● major approach to control is through mass drug administration of antihelminthic drugs or “deworming drugs” Comprehensive propoor strategy to integrate programs for either control or eliminate NTDs: 7 for 4 ● 7 NTDs could be controlled/ eliminated using 4 existing drugs ○ 3 currently donating by Merck and Company, GlaxoSmithKline and Pfizer; praziquantel available at relatively low cost ● each drug has overlapping specificity so that multiple NTDs concurrently targeted ● 4 drug regimen also targets ectoparasites such as scabies, pediculosis, tungiasis, etc… Sites of Action of the Antihelminthic Drugs Drug Distribution Program Barriers ● logistical considerations ○ remote, rural areas in tropical developing countries ○ specific temperatures and physical conditions for transport and storage ● health infrastructure ○ resourcepoor settings ○ includes training medical support personnel ● poverty restraint Major Neglected Tropical Diseases (NTDs) caused by protozoa/viruses ● diseases caused by protozoa ● they are vectorborne diseases Biology of Protozoans ● Eucaryotic microorganisms ● worldwide distribution ● relatively few are human pathogens ● many have complicated life cycle ○ encystation forms dormant cysts ○ excystation to trophosite ● classified on the basis of the means of locomotion Chagas’ disease *all info in powerpoint* ● American trypanosomiasis Chagas in the United States ● disease exists almost exclusively as a zoonosis Chagas disease s/s ● 1st few weeks symptom free ● fever, fatigue, body aches, h/a, rash, loss of appetite, diarrhea, N/V ● mild enlargement of liver or spleen, swollen glands, local swelling where the parasite entered the body ● classic sign of acute chagas disease in Romaña’s sign: swelling of the eyelids on side of face near the bite wound ● causes heart problems later in life Treatment: Benznidazole ● antiparasitic medication; almost 100% effective killing parasite during acute stage ● important to be diagnosed early and then treated Leishmaniasis ● caused by flagellated protozoan Leishmania ○ endemic in most tropical and subtropical areas ○ transmission: by bite of female sandflies ○ they are phagocytosed and differentiate and multiply within host macrophages ○ biological transmission ○ 3 human manifestations; ■ determined by parasite species, geographic location, and host immune response ■ visceral leishmaniasis has close to a 100% mortality rate; parasites invade liver and spleen ● s/s: fever, weight loss, anemia, and protrusion of abdomen ■ mucocutaneous leishmaniasis parasites invade skin and mucous membranes, destroying nose, mouth, and throat ■ Cutaneous leishmaniasis results in mild to disfiguring skin lesions on exposed parts of the body, particularly the face, arms, and legs ○ prevention ■ interruption of transmission by reducing vector Sandfly population ■ prevent sandfly bites: ● PPM: Personal Protective Measures: insecticide treated nets (DEET) Arthropodborne Diseases ● called arboviruses ● with a single exception (Colorado tick fever), they are transmitted by mosquitos ○ arbovirus transmission cycle Dengue ● dengue fever ○ can be caused by four strains of this RNA virus ○ mosquito vector Aedes aegypti ■ rarely, Aedes albopictus ○ epidemics recorded in 1700s in Asia, Africa, and North America ○ dengue virus infections may be debilitating but are usually self limiting; recovery occurs in about 10 days ○ “breakbone disease” ● Dengue Hemorrhagic Fever ○ Early s/s: flulike, making early dx difficult ○ hemorrhages occur in the skin, gums, and other body parts ○ shock may develop, requiring immediate treatment to prevent death, and, even with intensive treatment, the fatality rate is 40% ○ DX requires virus isolation or detection of specific antibodies ○ no vaccines against dengue infection Encephalitiscausing Arboviruses ● West Nile fever, eastern equine encephalitis, western equine encephalitis, st. louis encephalitis, and colorado tick fever ● all are RNA viruses ● humans are not reservoirs… we are a deadend host for the viruses West Nile Virus ● birds can be reservoirs ● think that it entered through NYC ○ infected human ○ smuggling birds ● endemic in Louisiana ● humans are mostly getting it through mosquito bites ● disease in humans ○ incubation 2 to 14 days ○ many WNV infections are asymptomatic ○ West Nile fever ■ most common form ■ resembles influenza ■ most infections resolve in 2 to 6 days ■ persistent fatigue can occur ● occurs rarely ○ diagnosis ■ spinal taps ○ tx ■ no specific treatment available ■ just supportive measures Morbidity/ Mortality ● Tropical diseases do not occur in isolation. In most countries of Subsaharan ● coinfection with tropical diseases adversely affects the natural history and progression of HIV/AIDS, tuberculosis and malaria ● several studies point to the increasing severity of clinical malaria that results from helminth coinfection ● other studies link helminth coinfections with increased susceptibility to HIV/AIDs or worsening progression of HIV ● in addition to HIV/AIDS, one major tropical diseases in Africa, namely visceral leishmaniasis is an opportunistic disease… so it’s common in people with suppressed immune systems One of the biggest problems with these diseases in Anemia ● most important of the leading comorbidity conditions Textbook Notes pp. 243247, 285, 315, 291292, 304310 Plague (aka the Black Death) ● the term “plague” is used in a general sense to describe an explosive outbreak with a high death rate ● causation: Yersinia pestis ○ one of the most virulent bacteria known→ only takes one bacillus to establish infection ● Medieval Europe was beleaguered by Y. pestis from 13471351 ○ fleas carrying the plague bacillus transmitted it to humans ○ appx ⅓ of europe’s pop (25 million people) died of the plague in four years ■ as many as 800 people died each day in Paris ○ the bodies were piled up and fed on by rats, resulting in even more infected rats whose fleas spread the disease ● Plague is considered a reemerging infection because of its increase throughout the world→ resurfaced in 1994 in Surat, India. several hundred people were infected and about 50 died ● In the US, sporadic cases occur, particularly in the southwest because of contact with infected rodents ● Plague is a zoonosis; over 200 species of mammals, primarily rodents, serve as reservoirs… rat fleas are usually the vectors ● s/s: ○ Bubonic Plague: ■ the bacilli localize in the lymph nodes, causing them to swell to the size of eggs, called buboes. hard, red, and painful ■ the bacilli invade the bloodstream, liver, lungs, and other sites ■ hemorrhages occur under the skin and the dried blood turns black (the Black Death) ■ mortality rate in untreated cases is over 50% ○ Pneumonic Plague: ■ individuals with the bubonic form develop pneumonia and transmit the bacteria to others by coughing and through saliva ■ the bacteria invade the lungs which become filled with a frothy, bloody fluid ■ nearly 100% fatal without early detection and treatment ○ Septicemic plague ■ a third form of the disease; it results from the spread f infection from the lungs to others parts of the body ■ 100% fatal ● disease control aims to interrupt transmission between reservoirs and humans Ehrlichiosis ● Ehrlichiosis is an emerging tickborne infection, similar to Lyme disease, caused by a gramnegative intracellular bacillus ● the ticks may be moving from dogs to humans ● human monocytic ehrlichiosis ○ causation: Ehrlichia chaffeensis ● human anaplasmosis ○ causation: Anaplasma phagocytophilum ● both types have similar s/s ○ fever, headache, general malaise, and in some cases, a rash ● vector: deer and dog tick Arthropodborne Diseases Dengue Fever ● aka breakbone fever ● four dengue viruses carried by Aedes aegypti and Aedes albopictus ● although the disease is debilitating, recovery occurs in about ten days ● Dengue hemorrhagic fever is a serious and potentially fatal infection caused by a dengue virus strain different from the one causing the initial infection ○ hemorrhages occur in the skin, gums, and other areas within the body. shock may develop ○ even with medical treatment, 40% fatality rate ● no immunization so best prevention is insectcontrol ● s/s: ○ early characteristics are flulike Yellow Fever ● aka yellow jack ● causation: RNA virus transmitted by A. aegypti ○ bites by day and breeds in standing water ● the largest epidemic in the US was in NOLA in 1853, resulting in a death toll of 7,849 ● s/s: ○ fever, bloody nose, headache, nausea, muscle pain, (black) vomiting, and jaundice (discoloration of skin and eyes. yellow) ○ in about a week, the infected individual is either dead or in the process of recovery ● immunization has been available since 1950 with live, attenuated viruses EncephalitisCausing Arboviruses ● common arboviruses in US: ○ West Nile Fever, eastern equine encephalitis, western equine encephalitis, St. Louis encephalitis, and Colorado tick fever ● humans do not serve as reservoir hosts… we’re dead end hosts ○ viruses cycle between wild animals, primarily birds and mosquitos ● When the virus invades the spinal cord, the meninges (wrappings around the spinal cord and brain) become inflamed, possibly resulting in a coma, convulsions, tremors, paralysis, memory deficits, and permanent brain damage West Nile Fever ● West Nile Virus ○ carried by the same mosquito that transmits St. Louis encephalitis ● prevention: mosquito control measures ○ mosquito spraying abatement measures along with onset of cooler temperatures break the cycle ● outbreak in New York→ probably came in a bird or mosquito imported on a jet aircraft ● worldwide, most cases are children and young adults Protozoan Diseases Biology of Protozoans ● unicellular ○ no cellular specialization and differentiation allowing for sharing of functions ● have a cell membrane, membranebound nucleus, and other membranebound organelles within the cytoplasm ● most protozoans are heterotrophic and aerobic. many ingest food particles by phagocytosis; the particles are then enclosed within food vacuoles in which digestion takes place ● Encystation allows for outside survival and is a process resulting in a dormant resting stage cyst surrounded by a thick capsule ● Excystation to the trophozoite form (the reproductive and feeding stage) occurs after ingestion of the cyst by a host. ● Asexual reproduction by binary fission is most common ○ a primitive form of sexual reproduction, called conjugation, occurs in some protozoans and allows for the direct exchange of genetic material during physical contact of mating pairs ● most are freeliving and constitute a sizable portion of plankton ● classified on their mechanism of locomotion: ○ sarcodina, mastigophora, ciliata, and sporozoa Foodborne and Waterborne Diseases Giardiasis ● a common protozoan intestinal infection in the United States acquired by drinking contaminated water ● causation: the flagellated Girardia lamblia ● dubbed “hiker’s diarrhea” and “beaver fever” ● one of the most common waterborne human diseases in the United States ● life cycle: ○ after excystation of the cysts to the vegetative and multiplying trophozoites, attachment to the lining of the intestine occurs by means of sucking disks ○ the parasites feed on mucous secretions and undergo reproduction, resulting in large populations ● s/s: ○ diarrhea, abdominal pain, and large amounts of gas ○ symptoms usually appear about two weeks after infection and may last six weeks or longer ● transmission: swallowing contaminated water ○ parasite is resistant to the chlorine ○ as few as ten cysts are enough to establish giardiasis ○ contaminated environmental surfaces and persontoperson contact by the fecaloral route ○ fecally contaminated food Arthropodborne Diseases Trypanosomiasis ● aka sleeping sickness ● West African trypanosomiasis is caused by Trypanosoma brucei gambiense ● East African trypanosomiasis is caused by Trypanosoma brucei rhodesiense ● transmitted by the bite of infected tsetse flies ● life cycle: ○ tsetse fly takes a blood meal from an infected reservoir host: wild animals, domestic animals, or human ○ the trypanosomes multiply and migrate from the gut of the fly to the salivary glands, where further development takes place ○ the fly bites a human and a red chancre (sore) develops at the site, and from there the parasites move into the blood, spinal fluid, lymph nodes, and brain ● s/s: ○ early: fever, fatigue, swollen lymph nodes and aching muscles and joints ○ late: the trypanosomes invade the brain and cause personality changes, progressive confusion, difficulty in walking, and altered sleep patterns ■ sleeping for long periods of the day (“sleeping sickness”), accompanied by insomnia at night is common ○ if left untreated: death occurs within a few months to several years after infection ● antigenic variation→ they change their “coats” as a defensive virulence strategy resulting in evasion of the host’s immune defense mechanisms ● Trypanosoma cruzi is the causative agent of American trypanosomiasis, aka Chagas Disease ○ wild animals serve as reservoirs ○ the vector is a triatomid insect, the “kissing bug” ■ defecates as it bites, causing itching and scratching, resulting in inoculation of the trypanosomes into the skin ○ can also be spread by blood transfusion and by organ transplantation ○ occurs in Mexico and Central and South America where an estimated 8 to 11million are infected ○ s/s: ■ causes slow, widespread tissue damage, particularly to the heart, causing it to enlarge and impairing its function, leading to heart failure ■ death occurs within 30 years of infection if the disease is untreated Leishmaniasis ● caused by several species of Leishmania ● endemic in many tropical and subtropical areas ● transmission: bite of female sand flies that become infected while taking blood from wild and domestic animal reservoir hosts ● Life cycle: ○ when an infected sand fly bites a human, the parasites enter the skin and are engulfed by cells called macrophages ○ the parasites multiply and are released when a microphage bursts ● 3 human manifestations determined by particular species, the geographic location, and the host immune response ○ Visceral leishmaniasis (aka kalaazar) ■ the most severe form with close to a 100% mortality rate ■ parasites invade the liver and spleen and cause characteristic symptoms, including irregular bouts of fever, weakness, weight loss, anemia, and protrusion of the abdomen due to the swelling of the spleen and liver ○ Mucocutaneous leishmaniasis (aka espundia) ■ parasites invade the skin and mucous membranes, causing destruction of the nose, mouth, and throat ○ Cutaneous leishmaniasis (aka Baghdad boil and tropical boil) ■ results in mild disfiguring skin lesions, primarily on exposed parts of the body, particularly the face, arms, and legs
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