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
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
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
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
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.
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
- First major outbreak in the US 1999 – Queens, NY
- 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
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)
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
- Most have known inexpensive preventative measures or treatments
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.
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?
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.
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
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
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
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
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
- Can limit the ability
- 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
- Bacillus thuringiensis israelensis (Bti)
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
- “Hair of the dog” came from rabies
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.
- Repeated infection leads to progressive scarring of the eyelid and mechanical damage to the cornea
- 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)
- If left untreated, the infection eventually causes the eyelid to turn inwards
- 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%
- Infection may remain dormant for decades
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
- Both male and females take blood meals
- 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
- Using traps
