1.B - how do physical/climactic factors affect disease patterns and outbreaks? Flashcards
what are the physical/climactic factors that determine disease distribution and patterns?
- temperature (e.g. Malaria needs heat and flu season = cold weather)
- geographical barriers (mountains, sea, deserts = slows down spread)
- precipitation/water sources (mosquitoes need stagnant water sources to breed.)
how is BILHARZIA distributed?
- commonly found throughout Africa, the Caribbean, the Middle East and Asia.
- schistomiasis affects almost 240 mill worldwide
- mainly occurs in marginalised communities w/ no access to clean drinking water/adequate sanitation
- prevalent in tropical/subtropical. if rainfall is low and temps are high habitats will dry out
- at least 90% of those requiring treatment for Bilharzia live in Africa
- deaths are estimated globally at 12,000/year
physical or seasonal factors that influence the distribution of BILHARZIA
- they live in fresh water
- if rainfall is low and temp is high, many snail habitats will dry out, decreasing the annual period in which temp is possible for snails to be active
- in south central africa, Bilharzia is very high in spring, and fewest in winter during the heavy rains.
- known as a “disease of poverty”, both resulting from and contribuitng to lower socio-economic conditions in the areas where it is endemic.
synoptic links for BILHARZIA
- experts say the Malawi govt is to blame - insisting the lake is free of Bilharzia, so anxious it is to preserve its reputation and flow of tourists.
- irrigation practices associated with the infection for 6000yrs. Piped water systems have ↑ snail habitats and human water contact
- climate change may alter the geographical distribution by affecting the sustainability of freshwater bodies.
how is DENGUE FEVER distributed?
- spread in tropical and subtropical areas
- mosquito is a vector
- common during June to December monsoon season, when mosquitoes thrive in stagnant water.
physical or seasonal factors that influence the distribution of DENGUE FEVER
- common June-Dec monsoon season (seasonality). climate is favourable for breeding of Aedes mosquitoes
- altitude - needs to be at 1000m above sea level. if high altitude, too cold for mosquitoes
- precipitation - mosquitoes breed in stagnant water
- need hot temps to live.
synoptic links for DENGUE FEVER
- water cycle has a direct impact on breeding and development of mosquitoes as they flourish and breed in stagnant water
- climate change affects water cycle increasing evaporation due to sea level rise
- ↑ temp - subtropical and tropical temps. causing places higher in latitude to also be affected
how is MALARIA IN ETHIOPIA distributed?
- caused by parasite that commonly infects a certain type of mosquitoe that feeds on humans
- in 2021 nearly 1/2 the world’s population at risk of Malaria
- WHO Africa region home to 95% of malaria cases and 96% of malaria deaths
- children under 5 accounted for about 80% of all malaria deaths
- highest transmission found in Africa south of Sahara and parts of Oceania e.g. Papua new guinea
- 52% of ethiopians are at risk of infection
physical or seasonal factors that influence the distribution of MALARIA IN ETHOPIA
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human influences:
> deforestation = breeding grounds
> building dams = stagnant water and breeding grounds - people living below 2000m of altitude are at great risk of contracting
- mosquitoes not adapted for 2000m+ climate. temp too low.
synoptic links for MALARIA IN ETHIOPIA
- in temperate areas, e.g. western europe and USA, economic development and public health measures have succeeded in eliminating malaria.
- human travel and migration = spread of disease into diff continents
- water cycle: stagnant water acts as breeding ground. if there is too much water breeding sites can be washed away.
SEASONALITY OF DISEASE - distribution
- INFLUENZA IN THE UK
- in autumn there is flu season due to changes in lifestyle
- people are indoors more meaning neighbourhood effect is higher = higher rates of transmission of contagious, airborne diseases - results in spikes in infection rates (same for COVID)
physical or seasonal factors that influence the distribution of SEASONALITY OF DISEASE
- monsoon rains e.g. Malaria in Uganda, Dengue in Chad
- heavy rains cause ↑ in stores of water = more mosquitoes breeding = massive outbreaks of disease e.g. Malaria/dengue fever
SEASONALITY OF DISEASE - synoptic links
PLACE
- only really occurs in places at higher latitudes (e.g. not in the tropics)
- can be lessened by good education/healthcare initiatives e.g. flujabs in ACs
- only places susceptible to mosquito borne diseases will be affected. however more developed places will be able to overcome this with education programmes
(e.g. use bed nets during rainy season/good healthcare)
what are the conditions that support the spread of zoonotic diseases?
- when movement of infected wild animals is unrestricted by physical barriers (or in the case of domestic animals, political boundaries)
- controls on the movement of diseased domestic animals w/in countries = ineffective
- urbanisation creates suitable habitats for animals such as foxes, racoons and skunks
- vaccination of pets + domestic livestock is sparse
- limited control w/in urban areas of feral dogs, cats, pigeons etc.
- hygiene + sanitation are poor; drinking water is contaminated by animal faeces, blood and saliva
- man-made habitats (e.g. pools/ponds) encourage vectors to breed
- prolongued contact between humans + animals - e.g. poultry farms and avian flu, cattle farming.
