View source for 31. Epidemiology and prevention of haematogenic and lymphogenic infections

Vector-borne diseases

* Infections transmitted by the bite of infected arthropods like:
** Flies
*** Sleeping sickness
** Mosquitoes
*** Malaria
*** Yellow fever
*** Zika
*** Dengue fever
*** West Nile fever
** Ticks
*** Lyme disease
*** Tick-borne encephalitis
*** Q fever
*** Tularaemia
** Lice
** Fleas
*** The plague
* The infection can be located inside the vector or outside
* Arthropods are cold-blooded and are therefore very sensitive to changes in the climate
** Climate change changes their habitat -> can make areas previously spared from these diseases become affected
* Prevention
** Protective clothing
** Insect repellant
** Regularly examine the skin for ticks
** Avoid endemic areas
** Remove ticks safely
** Insect nets

Lyme disease

* Borrelia burgdorferi, afzelii and garinii
* Epidemiology
** Endemic in most of Europe, most in central and eastern European countries
* Transmission
** By bite of the ''Ixodes'' tick
* Reservoir
** Many small mammals
** Ground-feeding birds
* Symptoms
** Target-shaped rash (erythema migrans)
** Myocarditis
** Neuroborreliosis
** Lyme arthritis
* Prevention
** No vaccine
** Avoiding tick bites
** Early removal of attached ticks

Tick-borne encephalitis

* An arbovirus (= transmitted by arthopod) and a flavivirus (= the genus it belongs to)
* Epidemiology
** Endemic in areas of Europe and Asia
** Most cases occur during the summer
* Transmission
** By bite of the Ixodes tick
* Reservoir
** Small rodents
* Clinical features
** Few infected people get sick
** Illness is worst in elderly
** Neurological symptoms, sometimes permanent
* Prevention
** Vaccine exists
** Avoiding tick bites
** Early removal of attached ticks

Malaria

* Parasites of the genus plasmodium
** Plasmodium falciparum – most severe
** Plasmodium ovale
** Plasmodium vivax
* Epidemiology
** Most cases are in Africa, especially Nigeria and Congo
** Major cause of death in developing countries
* Transmission
** By mosquitoes (Anopheles species)
** Entomologic inoculation rate = how many infectious mosquitoes bites per person per year
*** A measure of transmission intensity
*** High if above 50
*** The higher the EIR, the greater the burden of malaria
** Rarely by blood transfusion, needle sharing, etc.
* Reservoir
** No animal reservoir
** Only lives in humans
* Risk groups for severe disease
** Pregnant women
** Children and infants
** HIV infected
* Prevention
** Chemoprophylaxis:
*** For travellers to malaria endemic countries
*** For high-risk residents of endemic countries
** Kill mosquitoes
** Insect nets
** Clothes that cover the body
** Mosquito repellent
* Vaccine
** Name: RTS,S
** Very recent (2019)
** Against plasmodium falciparum

Crimean-Congo haemorrhagic fever (CCHF)

* CCHF virus, a type of nairovirus
* Endemic in Africa, Balkans, Middle East, Asia
* Transmission by tick
* Symptoms
** Up to 80% lethality
** Fever
** Diffuse bleeding
*** Diarrhoea
*** Petechiae

Tick-borne relapsing fever

* Caused by several spirochaetes
* Transmission by tick
* Symptoms
** Relapsing fever
** Headache

West Nile virus

* A flavivirus
* Epidemiology
** Originated from Africa, now present worldwide
* Reservoir
** Birds
* Transmission
** Mosquitoes
* Symptoms
** Often asymptomatic
** Most commonly mild infection flu-like symptoms and rash
** Rarely meningitis or encephalitis
* Prevention
** Protect against mosquito bites

Japanese encephalitis

* Japanese encephalitis virus
* Epidemiology
** Main cause of viral encephalitis in many parts of Asia
* Reservoir: birds
* Transmission by mosquitoes
* Symptoms
** Often asymptomatic
** Rarely encephalitis and neurological sequelae
* Vaccine exists

Zika virus

* A flavivirus
* Transmission by mosquito
* Symptoms
** Often asymptomatic
** Congenital zika causes CNS malformations
* Prevention
** Protect against bites

Yellow fever

* Yellow fever virus, a flavivirus
* Transmission by mosquito
* Occurs in Sub-Saharan Africa and South America
* Infants and children are at highest risk
* Clinical features
** Most patients experience mild symptoms
** 15% develop serious disease
*** Haematemesis
*** Bloody diarrhoea
*** Jaundice
*** Organ failure
* Prevention
** Vaccine
*** Reccomended for those travelling to or living in areas with yellow fever transmission
** Protection against mosquito bites

Lymphatic filariasis

* Also called elephantiasis
* Filarial parasites transmitted to humans through mosquitoes
* Causes severe lymphoedema

[[Category:Public health 4 - Preventive medicine]]