Vector Control Flashcards
• Carrier of disease agents from one organism to another
Vector
*along with agent and environment
Presence of vectors result to what
higher discomfort, lower productivity, and eventually, death.
(see table of Major vector-borne diseases of human and associated etiological agents and arthropod vectors)
(see table of Major vector-borne diseases of human and associated etiological agents and arthropod vectors)
Type of vector serving as external carrier such as housefly carrying enteric organisms or Aedes spp. transmitting Dengue
Mechanical
T or F: mechanical vectors are not involved in life cycle of infectious agent
true
type of Vector which is PART of the life cycle of the infectious agent
Biological
Reservoir of the infectious agent
Factors affecting vector-borne diseases
- Population Migration
- International Travel and Commerce
- Land Use Change
- Microbial Adaptation and Resistance (drug resistance)
- Lack of Reliable Public Infrastructure Services
- Climate Change
[Factors affecting vector-borne diseases] What influences population migration?
war, environmental degradation, and regional conflicts
[Factors affecting vector-borne diseases] Aspect of population migration which increases access to habitats of vectors (i.e.: open sewers, water storage containers)
Rapid unchecked urbanization
[Factors affecting vector-borne diseases] Aspect of population migration which causes disease vectors to develop a preference for feeding solely on humans
Higher population density
[Factors affecting vector-borne diseases] This factor ensures the continual spread of disease vectors
International Travel and Commerce
• Seaports, airports and cemeteries are especially vulnerable
• The effects of global trade in food result in unhygienic food
production, handling and preparation
[Factors affecting vector-borne diseases] How do changes in land and water patterns such as deforestation affect disease vectors?
Additional breeding habitats due to water management practices (e.g. dam building, open irrigation canals & flooded rice fields, open sewer pits)
[Factors affecting vector-borne diseases] Lack of reliable public infrastructure services include
Lack of funds for sanitation, effective water management systems, and basic public health care
three factors which drive vector-borne diseases
Zoogeography (natural distribution of vector species)
Climate (major)
Man-made drivers
Man-made drivers of vector-borne diseases
modulate the distribution and include climate change, hydrological changes/irrigation dams, changed land use patterns and urbanization
Examples of vectors
A. Mosquitoes B. Flies C. Cockroaches D. Bedbugs E. Lice F. Rodents
T or F: It is important to know which type of mosquito is present to determine prevention and control of possible spread of disease and infection
true
Four stages of development of mosquitoes and flies
Egg
Larva
Pupa
Adult
During which stage of mosquito development that female mosquitoes require blood meal
in production of eggs
- to obtain protein in hemoglobin for laying eggs in water
- fertilized eggs require water for hatching
Stage of mosquito development wherein full grown larva does not feed and spends most of its time at the water surface
pupa
Stage of mosquito development wherein Anopheles larvae lie parallel to the water surface
Larva
® Culicine larvae hang at 450 angle to the water surface
Durng this stage, female mosquitoes bite and are usually the vector
adult
*males feed on plant juices
This is the basis of comparison between different types of mosquitoes
Biting Patterns and Preferred Habitats of Mosquitoes
subject to change with climate change
Biting Patterns and Preferred Habitats of ANOPHELES SP.
Biting patterns: Daytime Preferred habitats: Permanent water, partially shaded, clean running water Disease Importance: Malaria, Eastern US, Africa, Asia
Biting Patterns and Preferred Habitats of AEDES AEGYPTI
BP: Mainly daytime can bite at night (welllit areas)
PH: Artificial containers, clean stagnant water, indoors
DI: Yellow Fever, Dengue
Biting Patterns and Preferred Habitats of Culex sp.
BP: Night time
PH: Permanent, dirty water, indoors, outdoors
DI: Encephalitis, US
What are transmitted by the mosquito vector (Anopheles minimus flavirostris) in malaria?
plasmodium parasites
How many provinces in the Philippines are endemic of malaria?
80
- 22 are malaria free but latest data indicate that 27 provinces are now free
- 59 still with cases
- 7 with high number of cases
9th leading cause of morbidity in PH
Malaria
14 million at risk
Region with highest prevalenc of malaria
region iv-b (82%)
2nd: region xi
* 77% of reported cases from Palawan followed by Davao del Norte (7%) and Sultan Kudarat (6%)
Malarial parasite sp with widest distribution and cycle every 48 hours with common relapses
P. vivax
*P. falciparum and ovale also cycle every 48 hours
Characteristics of P. falciparum
• Most common in the Philippines; in tropical and subtropical regions • Causes cerebral malaria • rare relapses
Plasmodium which cycles every 72 hours and is widely distributed producing persistent infection
P. malariae
P. ovale is a rare species in?
africa and asia
(see table 4. Geographic distribution of Malaria in the Philippines)
(see table 4. Geographic distribution of Malaria in the Philippines)
Dengue, which usually occur only during the rainy season, but is now perennial throughout the year, and a major health problem in Asia-Pacific is caused by?
arbovirus
*transmitted by A. aegypti (day biting and also late afternoon)
producer of dengue vaccine (tetravalent; contains serotypes 1-4) in PH
Sanofi Pasteur
*for 9-45 y.o.
Serotypes of dengue common in PH
2 and 4
type of cycle in yellow fever (arbovirus; aedes)
jungle urban cycle
*Tropical and subtropical areas in America and Africa
mosquito vector transmitting encephalitis (not common in PH)
culex sp.
virus causing st. Louis encephalitis
flavivirus
virus causing Eastern Encephalitis
Togavirus
natural hosts of encephalitis
birds
*dead end hosts: horses and humans
A gravid fly female lays this much eggs
100-150
Flies are mechanical vectors for
typhoid fever, enteroviruses, parasitic worms
Flies (Family Tabanidae) are biological vectors for
tularemia and anthrax
Most important source for flies
household garbage
Family of cockroaches
Family Blattidae
life cycle of cockroaches (brown-banded house pests) and bedbugs
egg, nymph, adult
The ootheca/egg capsules of cockroaches contain this much eggs
14-37
Bedbug species
Climex lecturalis
- females lay 200 eggs per year
- nuisance and hypersensitivity reactions
Infestation with lice
Pediculosis
Lice are vectors for
endemic typhus, trench and relapsing fever
factors influencing distribution of lice
- Age
- Crowding
- Sex
- Method of closeting garments
- Race
- Family size
- Socioeconomic status
Roof rat
Rattus rattus
house mouse
Mus musculus
rodents are reservoirs for
leptospirosis
salmonellosis
ratbite fever
These are vector for plague, rickettsial pox and murine typhus
rodents
hosts for fleas and mites
Litter produced by mice each year
10-12 with 9-19 offpsrings each litter
T or F: rodents live within limited area/home range
true, within 100-150 feet
How are rodent’s senses well-developed?
- Keen sense of touch through vibrissae and tactile hairs
- Color blind
- No aversion to odors of man, traps, or baits
- Taste sense not as well developed
- good swimmers
Plague/Yersinia pestis is found in rodents how?
Xenopsylla cheopsis: oriental rat flea
Another organism transmitted from rodents to man by rat fleas
murine typhus (rickettsia typhi)
Mostly affected with rat bites
Children <5 years old are mostly affected
Vector surveillance should be done in order to?
determine species, seasonal variations and population densities (abundance)
one of the major breakthroughs in vector control
DDT (dichlorodiphenyltrichloroethane)
- 1940s
*expensive, resistance, side effects (POP, persists in envi and biomagnifies)
General vector control measures
- Reducing population density
- Reducing vector longevity or vectorial capacity through indoor residual spraying
- Ecology and biology
- Surveillance
- Personal or community protection
- In the pipeline: genetically engineered mosquitoes
- Changes in human habitation of behavior
[Vector control measure]
source reduction is carried out by
- Different forms of environmental management such as engineering, modification, manipulation
- Predator-prey systems
- Microbial toxins
- Chemical larviciding
- Chemical adulticiding (fogging)
[Vector control measures] What is the difference between environmental modification and manipulation?
- Environmental Modification o Improvement of water supply and storage o Proper solid waste management o Sanitation systems - Environmental Manipulation o Chemical application o Higher level than modification
[Vector control measures] Personal or community protection involves what
- Insecticide treated nets and materials (short and long lasting)
- Housing improvement
- Zooprophylaxis
- Vaccines
Vector control is affected by
- Advanced technology
- Modern pesticides
- Man’s ability to modify environmental conditions
Vector control will depend on the following
- Local ecology and behavior of the vector species, including its habitats, flight range, feeding preferences and seasons
- Local epidemiology of the disease (endemicity)
- Human activities such as irrigation and animal farming
- Socioeconomic conditions of affected communities
- Cultural context
- Feasibility of applying interventions in specific settings acceptable to the population
- Environmental change
During mosquito surveillance, adults are collected using what
aspirator (device made out of cloth schreening, rubber and glass tubing) or light traps
[Surveillance]
These are done to determine the extent of mosquito breeding leading to formulation and application of appropriate control measures
Larva surveys
How are larva surveys done?
- Placing the lip of the dipper under the water surface then pulling forward
- Counting and recording the larvae
- Some can be collected via a syringe and placed in vials for ID.
Early control programs include
- Screening of houses
- Use of mosquito nets (pesticide-impregnated)
- Drainage or filling of swamps and other water sources
examples of chemical control
- Insecticides – adulticides or larvicides
- Stomach and contact poisons and fumigants
- DDT (banned in some countries)
- Organophosphates – for protection of man and environment (banned in some countries)
These are factors affecting level of pesticides in food chains
- Amount of pesticide ingested (there may be residual pesticides in foods)
- Time period over which pesticides are ingested
- Pesticide-storage capability of animal
- Rate of detoxification and excretion
These are the usual organisms involved in biological controls
- small fishes which feed on larvae
- birds, bats and dragonflies eat adult mosquitoes
What are the disadvantages to HUMANS in doing biological control?
- Parasitic infestations
- Exposure to harmful toxins
- Allergic reactions
What are the disadvantages to ENVIRONMENT in doing biological control?
- Infestation or predation on beneficial organisms
- Displacement of beneficial organisms
- Interference with control program
Environmental modifications by humans include
filling, draining, coverage, reclamation or landfill of manmade and natural breeding sites
[Dengue Vector Surveillance and Control] Entomological indicator for dengue vector to assess risk of outbreaks involving percentage of water-holding containers infested with larvae or pupae
Container Index
[Dengue Vector Surveillance and Control] Entomological indicator involving number of positive containers per 100 houses inspected
Breteau index
[Dengue Vector Surveillance and Control] Entomological indicator involving percentage of houses infested with larvae
and/or pupae.
House index (HI)
DOH 4S Strategy against dengue
- Search and Destroy the breeding places of vectors
- Self-protection measures (don’t let yourself be bitten by mosquitoes)
- Seek early consultation (very critical especially in pediatric patients >3 days of high fever)
- Say “no” to indiscriminate fogging
How do ovilarvicidal traps work?
Works by trapping the eggs and larvae of Aedes aegypti in their laying site (can or cup) with active organic solution and killing them in the process before hatching and going to adult stage.
Component of DOST Mosquito OL trap which attract A. aegypti to lay and serve as trap for her eggs
Lawanit Puddle
[DOST Mosquito OL trap components] Dengue carrying female mosquitoes are attracted with color black. The cup holds the active solution for killing the eggs and larvae.
Black Color of Can or Cup
[DOST Mosquito OL trap components] makes OL solution that contains ovicidal and larvicidal with active components made from organic materials that attract and kills the eggs and larvae of dengue carrying mosquito.
OL Pellets and Water
(see control for other vectors)
(see control for other vectors)
“Opportunities for prevention of vector-borne disease in an age of change”
• Early detection of pathogen introduction due to travel and commerce
• Develop and disseminate vector control strategies and vaccines
• Improve water supply and sanitation
• Assure public health services
(Family planning, Health education, Immunization)
It is a rational decision-making process for the optimal use of resources for vector control which seeks to improve the efficacy, cost-effectiveness, ecological soundness and sustainability of disease-vector control
Integrated Vector Control Management (IVM)
Rationale behind IVM
Driving forces:
• The need to overcome challenges experienced with conventional single-intervention approaches to vector control
• Recent opportunities for promoting multi-sectoral approaches to human health
Five Key elements of global strategic framework for IVM
• Advocacy, social mobilization, regulatory control for public health and empowerment of communities
• Collaboration within the health sector and with other sectors though the optimal use of resources, planning, monitoring, and decision-making
• Integration of non-chemical and chemical vector control
methods, and integration with other disease control measures
• Evidence-based decision making guided by operational
research and entomological and epidemiological surveillance
and evaluation
• Development of adequate human resources, training and career structures at national and local level to promote capacity building and manage IVM programs
