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Infectious Disease Epi > Class 9- Vector Borne Diseases > Flashcards

Class 9- Vector Borne Diseases Flashcards

1
Q

Factors linked w/ Emergence of VBDs

A
  • Increased ease and frequency of global travel
  • Rapid urbanization resulting in slums with high density populations
  • Profusion of nonbiodegradable containers
  • Public health infrastructure has degraded
    • Less emphasis on vector control
  • Environmental influences
    • Building of large dams
    • Deforestation and changes in land use
    • Introduction of new virus amplifying hosts
    • Climate change
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2
Q

Influence of climate change on VBD

A
  • Warmer temperatures allow
    • vector to survive in areas that were previously too cold
    • Speeds up virus replication in mosquito gut
      • Mosquito becomes infectious faster
    • Increases speed of pupae development and adult maturation
      • Faster the adult matures – sooner it will take a blood meal
    • Can cause changes in migratory pathways of viremic hosts
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3
Q

Dengue Epidemiology

A
  • 4 dengue subtype viruses
    • Life long immunity to exposed subtype
    • Risk of Dengue Hemorrhagic fever increases with subsequent exposures!
  • Originated in monkeys and independently jumped to humans in Africa or South East Asia 100-800 years ago
  • Transmitted by the Aedes mosquito
  • Estimates 50-100 million infections each year
    • 500,000 DHF cases
    • 22,000 deaths
      • mostly in children
  • Vaccine would need to be a tetravalent vaccine
    • Means it prevents all four virus subtypes
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4
Q

Dengue Fever Clinical Presentation

A
  • Reservoir- Transmitted principally by the Aedes aegypti mosquito
    • Bites during daylight hours.
  • Route- Monkeys act as a reservoir host in west Africa and south-east Asia.
    • There is no direct person-to-person transmission.
  • Dengue Fever (aka break-bone fever)
    • High-grade fever, chills, headache, and pain behind the eyes
    • Severe body aches
  • Dengue Hemorrhagic Fever (DHF)
    • Bleeding appears as tiny spots of blood on the skin, gums, larger patches of blood under the skin, low blood pressure, hepatomegaly, seizures, encephalopathy, and liver damage
    • Symptoms are followed by a shock-like state
  • There is no cure!
    • Requires close monitoring and IV fluids
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5
Q

Aedes albopictus- the Tiger Mosquito

A
  • Secondary spreader for Dengue Fever
  • Species spread to the Western Hemisphere as a result of the international trade in used tires.
    • The United States imports millions of tires from Asia, for remanufacturing purposes.
    • Tiger mosquitoes are closely associated with used tires, which are used as a preferable site for ovaposition
    • It is likely that tires imported to Houston, Texas from Japan in 1985 brought tiger mosquitoes to the United States.
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6
Q

West Nile Virus background

A
  • First isolated in 1937 in the West Nile district of Uganda
    • First major outbreak in the US 1999 – Queens, NY
      • Thought to have been imported from Israel
  • Humans are incidental hosts
    • Play little to no role in maintain cycle of transmission
  • Viremic reservoirs are key contributing factor to outbreaks
  • Can be transmitted by multiple mosquito genuses
    • Culex mosquito is primary vector
    • Assisted in spread across the US
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7
Q

West Nile Disease/Clincal Profile

A
  • Reservoir – Birds (passerines, crows, and magpies)
  • Route – mosquito bites, (reports of cases through blood transfusion and organ transplant)
  • Incubation – 3-14 days
  • Symptoms – fever, headache, body ache, fatigue, back pain,
  • Communicability- not applicable (although someone can check communicable disease manual and double check)
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8
Q

Neglected Tropical Diseases Overview

A
  • Why are called “neglected” tropical diseases
    • They don’t receive the same attention as fatal infectious diseases
    • They disproportionately impact “neglected” populations
      • Infectious diseases that are disproportionately endemic in developing countries
      • Often restricted to poor, marginalized sections of the population.
    • Neglected financially…
      • Most have known inexpensive preventative measures or treatments
        • not always available to those at the highest risk.
        • Impact the lives of over a billion people worldwide and threaten the health of millions more.
          • Tend to have low mortality rates
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9
Q

NTD at the Community Level

A
  • Neglected tropical diseases such as leprosy, lymphatic filariasis and leishmaniasis are feared and the source of strong social stigma and prejudice.
    • As a result, these diseases are often hidden – out of sight, poorly documented and silent.
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10
Q

NTD Neglected at a National Level

A
  • Neglected tropical diseases tend to be hidden below the radar screens of health services and politicians because they afflict populations that are often marginalized, with little political voice.
  • How do you prioritize NTDs when compared to HIV, Malaria, TB, and acute respiratory infections?
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11
Q

NTD Neglected at an International Level

A
  • Neglected tropical diseases do not travel easily and thus do not pose an immediate threat to western society.
  • The development of new diagnostic tools has been under-funded largely because neglected tropical diseases do not represent a significant market.
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12
Q

NTDs targeted for elimination Globally

A
  • Group 1 Diseases
    • Chagas
    • Lymphatic filariasis
    • Onchocerciasis
    • Rabies transmitted by dogs
    • Neonatal tetanus
    • Trachoma
    • Leprosy
    • Malaria
    • Plague
  • Group 2 Diseases
    • Schistosomiasis
    • Soil-transmitted helminthiasis
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13
Q

Guinea Worm

A
  • Causative agent- Dracunculus medinensis
  • Transmission: ingestion of unfiltered water containing infected copepods
  • Prevention: Drink filtered water
    • Intervention: Individual pipe like filters to drink from
  • Guinea worm disease is in the process of being erradicated
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14
Q

What are the risk factors NTDs?

A
  • Living in endemic regions
  • Insufficient access to clean drinking water
  • Lack of sanitation infrastructure
  • Poor housing quality/exposure to vectors
  • Inadequate education
  • Limited access to health services
  • Poverty
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15
Q

Epidemiology of LF

A
  • An estimated 120 million people in tropical and subtropical areas have lymphatic filariasis
    • ~25 million men have genital form of disease (most commonly hydrocele)
    • ~15 million people, mostly women, have elephantiasis of the leg
  • Lymphatic Filariasis (LF) and Onchocerciasis are responsible for the loss of an estimated 6.3 million Disability-adjusted life years (DALYs)
    • 1 DALY is thought of as one lost year of “Healthy Life”
  • Over 400 million at risk for LF
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16
Q

Lymphatic Filariasis cause and vector

A
  • Lymphatic Filariasis
    • Caused by Nematode infection (roundworms)
    • Vector
      • the mosquito
17
Q

Clinical Manifestation of LF

A
  • Tends to cause
    • Lymphodema (swollen limbs)
    • Hydrocoele (swollen testes)
      • Can limit the ability
        to walk
  • Social stigma
  • Albendazole
    • $.05-.10 per person per year
18
Q

Environmental control of NTD

A
  • Reduce standing water
  • Reduce vegetation or organic material in standing water
  • Change the salinity of the water
  • Lay polystyrene beads on top of the brackish water in the pit latrine
    • Inhibiting the vectors ability to lay eggs
19
Q

Biological control of NTD

A
  • Bacterial insecticides
    • Bacillus thuringiensis israelensis (Bti)
      • Larva have trouble digesting food after exposure
    • Larvivarous fish
      • Used to control Anopheles mosquitoes
    • Juvenile Turtles, Trachemys scripta
      • Control Aedes aegypti in cement laundry tanks, Honduras
20
Q

Behavioral changes to limit mosquito exposure

A
  • Avoid peak biting hours (varies by vector)
  • Apply repellant (DEET)
  • Sleep under insecticide treated bed nets (ITNs)
  • Avoid wearing dark clothing
  • Mosquitoes are attracted to body heat, carbon dioxide, and movement
    • Flailing your arms around to slap mosquitoes, might only make the situation worse…
21
Q

Onchocerciasis epidemiology

A
  • Estimated 37 million individuals have onchocerciasis
    • 270,000 are blind (River Blindness)
    • 500,000 suffer some form of visual impairment
    • 100 million at risk of Onchocerciasis
  • Transmitted by female black flies
22
Q

Where do black flies lay eggs?

A
  • Fast moving rivers
    • The river transports food and oxygen to them constantly
23
Q

Clinical Manifestations of Onchocerciasis

A
  • Mainly comes in the form of dermatitis
  • Ocular onchocerciasis- leads to keratitis or hardening of the sclera (whites of eyes
    • (1 in 72 cases)
    • No reported cases of blindness in Latin America since 1995
  • Social stigma associated with disease
  • Pathologies caused mainly by microfilaria and inflammatory response of Wolbachia bacteria
24
Q

Schistosomiasis Epidemiology

A
  • Schistosomiasis ranks second only to malaria as the most common parasitic disease.
  • 240 million people in as many as 78 countries
  • 700 million at risk
    • 85% of all cases are in Africa
    • Estimated 25 million people live at risk in the Americas
  • ​​Cercariae (free-swimming larval stage in which a parasitic fluke) are released into water through human fecal matter and urine.
    • School aged children are at most risk due to time spent swimming and bathing in contaminated water
25
Q

Clinical Manifestation of Schistosomiasis

A
  • Hepatitis, splenomegaly (enlarged spleen), pulmonary shistosomiasis
    • Chronic infection can damage the liver, intestine, spleen, lungs, and bladder.
  • Treated annually with a single dose of 2.5 tablets of praziquantel ($.08 per tablet)
26
Q

Rabies Epidemiology

A
  • Over 50,000 death annually
    • Africa and asia most effected
  • Transmission through bite from infected mamal (virus is in saliva)
    • 99.99% fatality rate.
    • Interventions must focus on prevention
      • Human cases have been reduced by 90% over the past 20 years
  • 90% of rabies exposures globally come from dogs
    • “Hair of the dog” came from rabies
      • people used to rub the hair of the dog that bit them on the wound
27
Q

Trachoma Epidemiology

A
  • Estimated 50 million people live in risk areas in Latin America and the Caribbean
    • 7,000 cases identified (mainly in Brazil)
    • Almost eliminated in Mexico
  • More prominent in areas of water shortage, numerous flies, & crowded living conditions
28
Q

Clinical Manifestation of Trachoma

A
  • Leading infectious cause of blindness
    • Repeated infection leads to progressive scarring of the eyelid and mechanical damage to the cornea
      • Infection in children leads to blindness later in life.
  • Chlamydia trachomatis
    • Spreads through contact with eye discharge
    • Transmitted through eye seeking flies
      • If left untreated, the infection eventually causes the eyelid to turn inwards
        • Eyelashes rub on the eyeball causing intense pain and scarring of the front of the eye (ultimately leads to irreversible blindness)
    • Children at highest risk of exposure
      • Child to child transmission
      • Fly to child transmission
        • Malnourished children unable to swat flies away
29
Q

WHO SAFE strategy for Trachoma

A
  • S- Surgical component
  • A- Antibiotics
  • F- Facial cleanliness
  • E- Environmental improvement
    • controlling fly population
30
Q

Soil-transmitted helminthes (STH) Epidemiology

A
  • Commonly known as intestinal worms
    • Most common infection worldwide
    • Infects over 1 billion people
  • Caused by ingestion of eggs from contaminated soil or active penetration by larvae (hookworms)
  • Most common in Africa, Asia and South America
31
Q

Clinical Manifestation of STH

A
  • Wide range of symptoms including intestinal blockage, anemia, protein deficiency, painful passage of stool
  • Treated with the anthelmintic albendazole
    • (Cost $0.02-.03 cents per dose)
    • Also reduces risk of LF
32
Q

Chagas Epidemiology

A
  • 8 to 11 million people are infected.
  • Individuals living in rural areas are at greatest risk for acquiring infection.
  • Chronic Chagas
    • ​Infection may remain dormant for decades
      • Can kill you!
    • Average life time risk of developing chronic chagas complications is about 30%
33
Q

Chagas Transmission

A
  • Transmitted by infected triatomines (kissing bugs)
  • Infection can also occur:
    • Vertically
    • Contaminated blood products
    • Infected organ transplant
    • Lab accident
    • Contaminated food or drink (rare)
  • The triatomine bug thrives under poor housing conditions
    • (mud walls, thatched roofs)
    • Falls from the ceiling and uses exhaled CO2 to track your mouth
  • Individuals living in rural areas are at greatest risk for acquiring infection.
    • Public health efforts aimed at preventing transmission have decreased the number of newly infected people and completely halted vectorborne transmission in some areas.
34
Q

Sleeping sickness epidemiology

A
  • Over 95 % of cases of human infection occur in Tanzania, Uganda, Malawi, and Zambia
  • Disease has been better controlled recently
    • 7,000-10,000 CASES ANNUALLY.
  • Transmitted by the Tsetse fly
    • Both male and females take blood meals
      • However, females take blood meals more often before oviposition
  • Cattle are effected as well
35
Q

Sleeping Sickness Clinical Manifestation

A
  • East African Sleeping Sickness
    • Fever, headache, muscle pain, enlarged lymph nodes, and rash.
    • After a few weeks parasite will invade the central nervous system.
    • Death usually occurs within months.
    • Most reported cases are East African
  • West African sleeping sickness
    • Milder symptoms
    • CNS damage usually occurs after 1-2 years
    • Most often kills in about 3 years if left untreated
36
Q

The Tsetse fly

A
  • Opportunistic feeders
  • Gives birth to one egg at a time.
    • Can live up to 3 months and produce 31 generations
  • Principal control method- reduce vector population
    • Using traps
      • Flies attracted to the blue and black colors

Infectious Disease Epi (11 decks)

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