6 - Vector Control

• Vector Control is a key topic in Environmental and Occupational Health.

Vector Control Defined

• Involves vectors, which are carriers of disease agents that spread diseases from one organism to another, continuing the disease life cycle.

Types of Vectors

• Mechanical Vectors: Microorganisms attach to the vector's appendages and spread physically, like a housefly carrying enteric organisms.
• Biological Vectors: The vector is part of the microorganism's life cycle and facilitates entry from one body to another, such as Anopheles mosquitoes for malaria, with biting as the action that facilitates the entry.

Impact of Vectors

• The presence of vectors increases disease, death, and discomfort while decreasing productivity.
• Disease impact on workers can have socio-economic consequences.
• Vector-borne diseases account for ~17% of the global burden of communicable diseases, causing 700,000 deaths yearly

Vector-Borne Diseases (VBDs)

• Illnesses are caused by parasites, viruses, or bacteria transmitted by vectors.
• The Philippines still has a high cases, yet vector control is a possible solution.

Examples of Vector-Borne Diseases in the Philippines

• Mosquitoes transmit Chikungunya, Dengue, Japanese encephalitis, Lymphatic Filariasis, Malaria, and Zika virus.
• Snails transmit Schistosomiasis, which is endemic in certain areas of Visayas.

Global Examples of Vector-Borne Diseases

• Mosquitoes transmit Yellow Fever, Rift Valley Fever, and West Nile Fever.
• Triatomine bugs transmit Chagas Disease.
• Ticks transmit Lyme Disease, Tick-borne Encephalitis, and Typhus.
• Sandflies transmit Leishmaniases.
• Mites and lice transmit Rickettsialpox and Typhus.
• Flies transmit Onchocerciasis and Human African Trypanosomiasis.
• Fleas transmit Murine Typhus and Plaque.

Key Global Facts on VBDs (2020)

• Affect poorer populations in degraded environments and unfavorable housing conditions.
• Over 3.9 billion people in over 128 countries risk contracting dengue, with ~96 million yearly cases.
• Malaria causes >400,000 yearly deaths, mostly in children under 5.
• Other diseases like Chagas, leishmaniasis, and schistosomiasis affect hundreds of millions.
• All VBDs are preventable with strategic vector control and interventions.

Factors Influencing VBDs

• Population Migration: Driven by war, environmental degradation, and regional conflicts.
• International Travel and Commerce: They facilitate disease vector spread, making seaports, airports, and cemeteries especially vulnerable.
• Land Use Change: Includes industrialization disrupts natural habitats.
• Microbial Adaptation and Resistance: Antibiotic use causes microbial adaptation and resistance and unrationalized use of antibiotics is a global problem.

Vector-Borne Diseases & Climate

• Global climate change increases mosquitoes due to warmer climates and rainfall, and vectors develop adaptive behaviors.
• In 2020, ~17% of the global communicable disease burden, caused 700,000 deaths annually.

Key Issues Influencing Vector-Borne Diseases

• Zoogeography involves the natural distribution of vector species.
• Population: 80% of the world's population is at risk of one or more vector-borne diseases.
• Climate: Man-made global climate change, hydrological changes (irrigation, dams), changed land use patterns, and urbanization are included.

Population Migration & Urbanization

• Rapid unchecked urbanization causes vectors to access habitats like sewers and stagnant water.
• Higher job opportunities increase migration to urban areas, increasing number of people can create preferential feeding for solely on humans by vectors.
• Events that degrades environment will force more people to rely vectors or humans for nourishment.

Land Use Changes

• Space is a problem especially in the urban area, natural habitats are disrupted by space and industrialization.
• Poor water management leads to more vector habitats and breeding sites like: dam building, open irrigation canals, flooded rice fields, and open sewer pits.

Lack of Public Infrastructure

• Insufficient funds sanitation facilities, effective water management, and basic public health care.
• Unavailability of public health programs and mosquito controls for Dengue, Malaria.

Climate Change Impact

• Global climate change increases disease associated mosquitoes because they become resistant.
• Dengue became an all year-round problem, temperature and rainfall increases cases, and vectors develop adaptive behaviors by changing in breeding sites, feeding patterns.

Vector Control Methods

• Vector control is affected by advanced tech, modern pesticides, and man's ability to modify environmental conditions and surveillance and will show in patterns of breeding and survival and control measures.

Mosquito Vectors & Diseases

• Aedes carry Chikungunya, Dengue, Lymphatic Filariasis, Rift Valley Fever, Yellow Fever, and Zika (all viruses or parasites).
• Anopheles carry Lymphatic Filariasis (parasite) and Malaria (parasite).

Stages of Development

• Mosquitoes go through 4 stages: egg, larva, pupa, and adult with fertilized eggs needing water to hatch.

Mosquito Control

• Temperature influences rearing, survival, longevity, gonotrophic cycle length, adult body size.
• Climate change does not uniformly increase burden of VBDs, but change will occur.

Malaria

• Malaria incidence in the Philippines is decreasing.
• Factors of plasmodium are vivax, falciparum, malariae, and ovale.
• Fever is the most common symptom of malaria.

Dengue

• Dengue cases are high in the Philippines but decreased over time.
• Dengue is caused by arbovirus and carried by Aedes aegypti mosquitoes
• Aedes Lay eggs in clear, stagnant water, and can be distinguished by the stripes on its body.

Vector Control Measures

• Essential because effective vaccines or drugs aren't always available, so the vector is controlled.
• Involves local ecology and behavior of the vector species, including its habitats, flight range, feeding preferences and seasons, along with climate change..

Chemical Control for Mosquitoes

• Insecticides target adults (adulticides) or larvae (larvicides).
• Can be stomach or contact poisons.

Biological Control for Mosquitoes

• Small fishes feed on larvae, and birds, bats, and dragonflies eat adult mosquitoes.

Environmental Control

• The most-used practical control with Mosquito breeding sites coming from man-made sources like water containers and natural settings.
• Focuses on Long-lasting physical shape, reliability in water and sanitation.

Dengue Control

• Focuses on 4S strategy against Dengue to Search and Destroy Breeding Places, Self-Protection Measures, Seek Early Consultation, Say "NO" to indiscriminate fogging.

Vector Surveillance

• Employs indicators to assess the risk of outbreaks, like the House Index, Container Index, and Breteau Index.

Environmental Management

• Seeks change envrionment for prevent propagation and human contact by destroying non-essential containers, environmental modiciation includes filling, draining, coverage, reclamation or landfill.

Integrated Vector Control Management

• Rational and Improves efficacy, cost-effectiveness, ecological for sustainability.