Vector Transmitted Diseases Summary

Vector Transmitted Diseases

• Intended Learning Outcomes:

  • Understand life cycles and transmission of Dengue virus and Borrelia burgdorferi.

  • Comprehend disease control measures based on vector transmission routes.

  • Know diagnosis and treatment strategies for Dengue fever and Lyme disease.

Global Perspective

• 17% of infections, 700,000 deaths per year from vector-borne diseases.

• Dengue fever affects 96 million people annually, causing 20,000 deaths.

• Lyme disease is prevalent in temperate regions including the UK.

• Climate change, urbanization, and globalization exacerbate emerging diseases.

Dengue Virus

• Classification: Flavivirus, 50 nm particle, ssRNA +ve sense.

• Infects humans and Aedes mosquitos.

• Transmission Cycle:

  • Mosquito bites infected person, replicates in human cells, spreads via saliva.

• Symptoms of Dengue Fever: Flu-like symptoms appear 4-10 days post-bite, lasting 2-7 days.

  • Severe cases may lead to shock and are more common with repeat infections.

Detection and Treatment of Dengue

• Diagnosis via RT-PCR or ELISA for antibodies.

• No antiviral treatment; supportive care reduces mortality in severe cases.

• Preventive measures focus on mosquito control.

Acquired Immunity in Dengue

• Four distinct serotypes (DENV-1 to DENV-4).

• Repeat infections increase risk of severe dengue due to antibody-dependent enhancement.

• Vaccines: Dengvaxia licensed in 2015 for those previously infected, Q-Denga licensed in 2022.

Lyme Disease

• Causative Agent: Borrelia burgdorferi, transmitted by Ixodes ticks.

• Stages of Infection:

  • Local infection at tick bite (bullseye lesion).

  • Disseminated infection with flu-like symptoms.

  • Chronic symptoms post-bacteremia.

• Diagnosis: Blood tests for antibodies may yield false negatives/positives.

• Treatment: Antimicrobial drugs (doxycycline, amoxicillin) effective early; prevention through tick avoidance.

• No vaccine available.