week 2 Flashcards
environmental factors that affect malaria epidemiology
temp, season, dams, migration, deforestation, urbanization
how does urbanization affect malaria
creates breeding sites
increases entomological inoculation rate
vectkrs become more tolerant of xenobiotics
advantages of IVM
improves efficacy, cost effective, sustainable, preserve efficacy of existing tools, reduce evolution of IR
limits of IVM
cost, technical capacities, human resources, political will
what methods of control can be used in cities
LSM (few fixed and findable): habitat modification of manipulation, biological control (predatory larvivorous fish), larviciding
house improvements
limits of LSM as a control
short residual effect, needs repeating often. toxicity for non-target species, labour and financial constraints
what are the impacts of infection on a mosquito
DAMAGE- to tissues, midgut, increased susceptibility to other infections
DEPLETION- lower concs of aa in haemolymp, midguts use more glucose
BEHAVIOUR- decreases apyrase(enzyme catalyses hydrolysis of atp) activity, more time feeding
SURVIVAL (filariasis infection) FECUNDITY (malaria)
what is involved in the insect innate immune response
- physiochemical barrier- cuticle and peritrophic matrix
- cellular defense- hemocytes (would healing, phagocytosis, encapsulation)
- Humoral response- antomicrobial peptides, melanin
what insecticide products contain and active ingredient as well as pyrethroid, and can be used on nets
chlorfenapyr
pyriproxyfen
main mosquito resistance mechanisms
behavioural avoidance
cuticular resistance
target site mutates
metabolic resistancce
main kdr mutations in the sodium channel
L1014F L1014S
how do OPs and carbamates work
phosphorylate or carabamate active site serine of AchE
IR operational resistance definition
the selection of a heritable characteristic in an insect population that results in the repeated failure of an insecticide product to provide the intended level of control when used as recommended
loss of susceptibility/ developing resistance definition
the development of an ability to tolerate doses that would prove lethal to a majority of individuals in a normal population of the same species
issues with current insecticides
only 4 used in irs, with two modes of action , therefore resistance increasing
only pyrethrpids used on nets- resistance seen
with IR increasing what alternatives for vector control are there
- spatial insecticides
- attractive toxic sugar baits
- microbial insecticides- bacillus used for control of aquatic insects like similum, aedes and culex
what is temephos
OP larvicide to treat water infected with mosqs midges black fly larvaee
major resistance development factors
application freq popn isolation rate of reproduction persistence of effect dosage
define cross resistance
the mechanisms expressed may resist more than one insecticide
define multiple resistance
an insect expresses more than one resistance mechanism
what are the different ways to manage resistance in IRS
- single formulation containing 2+ insecticides
- fine-scale mosaic- application of diff MoA insecticides against the same popn eg. using 2 diff moa insecticides in diff dwellings in same village. mosqs likely to come into contact with a second insecticide if they survive exposure to first, reducing selection pressure for both insecticides
- rotate insectidies with diff MoA over time
monitoring of vector susceptibility objectives
- baseline data collection at start of a programme in order to inform planning and insecticide choice
- monitor susceptibility over time and compare with baseline
- detection of resistance so management can be introduced
what is LC50
conc of compound required to kill 50% popn
what is resistance ratio
LC50 resistant popn / LC50 susceptible popn
describe the steps taken in a resistance monitoring programme
- field collection of bloodfed adults/larvae
- species identification
- rear to F1 generation and/or larvae to adults
- WHO/CDC susceptibility testes
- kdr RT-PCR or sporozoite rate (gives idea of impact of resistance on epidemiology)
how to manage IR
- reserve class of insecticide for vector control and exclude from agri and household use
- ensure insecticide is applied properly and at the correct dose
- use dose that kills heterozygote partially resistant vectors
- mix compounds with diff MoA
- rotations or mosaics of insecticides
define urbanization
increased movement and settlement of population from rural to urban settings
why might people move from rural to urban settings?
better jobs, education, health care, absence of electricity and water supply, drought, terrorism conflict, armed gangs
what is unplanned urbanization?
to develop an area without planning infrastructure which is unhygienic and unhealthy for the settlement. can lead to over crowding, slums and development of activities favouring vector breeding sites
what are the drivers of infectious disease outbreaks in cities?
- unplanned urbanization- creates suitable habitats for vectors and rats
- poor housing- local transmission
- travel- dissemination of diseases
- overcrowding slums- transmission, bad hygiene practices
LF was traditionally a rural disease but now urban, why?
Unplanned urbanization- lack of sanitation - Culex vector lives in polluted water and latrines
what endogenous factors of the mosquito affect malaria epidemiology
density longevity species feeding preference vectorial competency vectorial capacity immunity
what endogenous factors of plasmodium affect malaria epidemiology
density
stage of development
compatibility
virulence
what endogenous factors of man affect malaria epidemiology
age
immunity
genetic
sex
what exogenous (environmental) factors affect malaria epidemiology?
temperature season dams migration deforestation migration
advantages of IVM
improves efficacy, cost effectiveness, sustainability, preserve efficacy of existing tools, reduce evolution of IRS
limits of ivm
cost, technical capacities
name two common kdr mutations
L1014F L1014S
how do you manage IR in the field
monitor resistance in field popn
determine the extent of resistance
adjust insecticide used
what mechanisms of resistance are seen in insects
metabolic
target site
reduced penetration
behavioural
alternative methods for killing adult mosqs?
house improvements-eave tubes, insecticide treated material
insecticide treated clothing
lethal host-mimicking traps (animals treated with insecticide)
toxic sugar baits
LSM
what different vector sampling methods are there
HLC Net traps CDC light traps barrier screens# electrocuting traps immature traps
when choosing a sampling method what should you consider
prevalence vector vector behaviour- how will it interact with the trap? biting rate changes over time every sampling method has some bias
