Triatomine control Flashcards
Classification
Family - Reduviidae, subfamily - Triatominae
How many are blood feeds and how many are vectors
120 obligate vertbrate blood feeders
60 Chagas vectors in South America
Three genera of importance
Rhodnius, panstrongylus, triatoma
Why can T. infestans outcompete other species?
Short lifecycle, ingests more blood, can outcompete other species in the domestic environment
Treatment of Chagas
Nifurtimox and Benznidazole. Adverse effects are worse in adults.
Acute and chronic phase symptoms
Acute: romana’s, sign, fever, lymphadenopathy
Chronic: cardiomyopathy and gastrointestinal abnormalities
Chagas transmission by triatomines.
T. cruzi enter host via eyes/mucous membranes/abraded skin.
Insects ingest during feed and infected for life.
Parasites develop in gut 9-17 days. Infective metacyclic in hindgut.
Efficient vectors are those defecating whilst feeding up to 25 minutes.
Up to 50% of bugs in 70% of houses are infected.
Key facts about triatomine life cycle
Females lay up to 600 eggs in lifetime, all stages blood feed, larval to adult 6 months to 2 years, adults can survive without feed 3-4 months
Detecting triatomine transmission
Search for bugs/egg cases/faecal stains on walls of home and peri-domestic area
Nymphs - wingless therefore indicate infestation
Chagoma-Romanas sign in residents
Gomez-Nunez boxes
Factors influencing human transmission
Bugs domesticated Early defaecation Bugs infest poor housing/thatched roofs, esp when domestic animals live in close association Rodent/possum entering domestic cycle Rhodnius - palm fronds Bedding and furniture Adults fly
Triatomine zoonoses
Sylvatic - opossums/armadillos/rodent]
domestic - dogs/cats/rats
Benefits of domestication for triatomines
Protection against climatic extremes
Protection against some predators
Food - rich/constant
Drawbacks for humans living with triatomines
Nuisance
Blood loss
T. cruzi risk
Genetic consequences of triatomine domestication
Selection of individuals of greatest energetic efficiency.
Tendency to genetic monomorphy in each population
Tendency to low genetic variability within each population
CONSEQUENCES - body size reduction, evolution of resistance less likely
Although there is extensive morphological variation within species - species plasticity
Goubiere et al. Are all vector species a mix of partially recognised species?
Extensive morphological variation, species plasticity. Genetic studies show reduction in species. Highly adapted to ecological niches. Hybrids selected against.
Triatomines spraying
Residual spraying = 3 treatments/ year $25. DDT resistance (malaria spraying is effective)
Improve housing
Separate animals and humans
What responses are there to the reinfestation problem?
Technical - develop formulations of longer residual action
Strategic - eliminate the source population
Southern cone initiative success
Brazil 2000 - 10/12 endemic states free of vector and transmission
Chile 1983-1999 - 96% reduction house reinfestation. Child incidence from 5.4 to 1.05%. Chile is freee
Other countries that have eliminated or interrupted transmission.
Elimination 1953 costa rice. Central america free of R. prolixus. Interuption transmission 2008 guatemala, 2009 el salvador, 2010 nicaragua and honduras
Operational strategy towards elimination
Attack phase requiring mass intervention, vigilance phase only requires selective intervention
Cimex and Chagas
High prevalence Chagas in homes and that. Mice can harbour (bidirectional transmission)
